# Let's have a discussion : "Archer's Paradox"



## GEREP (May 6, 2003)

With all the tuning discussions lately, there seems to be some confusion about the term *"Archer's Paradox."* 

I thought it might be good to have a discussion about what *"Archers Paradox"* is, why it exists, and what it does, and does not mean.

First of all, let's look at a couple definitions:

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_*"The term archer's paradox refers to the phenomenon of an arrow traveling in the direction it is pointed at at full draw, when it seems that the arrow would need to pass through the starting position it was in before being drawn, where it was pointed to the side of the target. The bending of the arrow (around the bow), when released, is the explanation of the paradox and should not be confused with the paradox itself. Flexing of the arrow when shot from a modern 'centre shot' bow is still present and is caused by a variety of factors, mainly the way the string is deflected from the fingers as the arrow is loosed."*_

http://en.wikipedia.org/wiki/Archer's_paradox


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In more laymen's terms:

_*"Layperson "logic" dictates that a straight and balanced arrow must be shot straight at a target in order to hit it. In reality, the arrow must be aimed OFF of the target by a traditional archer in order to hit the target. You do not point the arrow at the target, this is THE paradox. 

The term "Archer's Paradox" was coined by Dr. Robert P. Elmer, a well-known archery author in the 1930s. His observations were confirmed by others who used high speed photography to scrutinize the behavior of an arrow upon release by the archer to answer a paradoxical situation. 

His concern was the question as to why an arrow will succeed in hitting a target even though the arrow is placed at an angle to the side of the target prior to shooting. It is actually pointing away, off of the target to the side away from the bow. 

From appearances when properly placed on the bow of a right-handed archer, the arrow should strike well to the left of the target as it travels in a direct path to the target. It does not. This is a paradoxical situation! (And is also present for left-handed archers, only to the opposite/right side of the target.)"*_

http://www.texasarchery.org/Documents/ArchersParadox/Archersparadox.htm


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So, first of all, we must understand that arrows *flex* and arrows *bend*. Arrows don't *"paradox,"* nor are they ever *"in paradox,"* nor are there *"paradoxical forces"* in terms of what is happening when an arrow is released. 

Archers *"Paradox"* (which actually means *"contradiction,"*) is actually the *phenomenon* that exists when an arrow that is pointed away from a target, actually ends up hitting that target. That is the *"paradox"* or the apparent *"contradiction."* 

It is because the arrow *flexes*, or *bends* (for a variety of reasons to be discussed later), that the arrow that appeared to be aimed in the wrong direction actually ends up hitting where it us supposed to. This is the *"paradox"* or apparent *"contradiction."* 









Notice that the arrow in the first illustration, sitting next to a riser (blue dot) is pointed away from the intended target. One would think that the arrow, when released, would continue to travel on the same line, and eventually hit left (for a right hand shooter) of where intended. Hence the *"paradox,"* or in terms of this discussion, the *"Archers Paradox."*

More a little bit later on what actually *causes* an arrow to *flex* or *bend.*

KPC


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## Arron (Nov 18, 2012)




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## JINKSTER (Mar 19, 2011)

First?...let's analyze the word...

*par·a·dox
ˈparəˌdäks/
noun
noun: paradox; plural noun: paradoxes

a statement or proposition that, despite sound (or apparently sound) reasoning from acceptable premises, leads to a conclusion that seems senseless, logically unacceptable, or self-contradictory.

"a potentially serious conflict between quantum mechanics and the general theory of relativity known as the information paradox"


a seemingly absurd or self-contradictory statement or proposition that when investigated or explained may prove to be well founded or true.
"in a paradox, he has discovered that stepping back from his job has increased the rewards he gleans from it"
synonyms:	contradiction, contradiction in terms, self-contradiction, inconsistency, incongruity; More
oxymoron;
conflict, anomaly;
enigma, puzzle, mystery, conundrum
"the paradox of war is that you have to kill people in order to stop people from killing each other"

a situation, person, or thing that combines contradictory features or qualities.
"the mingling of deciduous trees with elements of desert flora forms a fascinating ecological paradox"*

and now that that's out of the way?...the shaft is too!..(so to speak) :laugh:

Provided of course there is enough point weight to cause enough compression and deflection of the properly spined shaft as the nock leaves the string and whips to the outboard side effectively clearing the riser wall as it passes it.

Other forces involved include (but are not limited too)...

1. How clean the archers release is.

2. Nock too String fitment.

and?...

3. String Torque.

all I got...L8R, Bill. :cool2:


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## Castmaster (May 2, 2013)

My understanding of the archer's paradox is that the arrow corrects itself after leaving the bow and bending around the riser. But by what you are saying there is also another correction that happens internally in the mind that corrects the aiming of the arrow to accommodate the erratic arrow flight. 






Oh the music is the best in this video


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## GEREP (May 6, 2003)

OK, so what causes an arrow to flex?

We've seen it suggested that the linear (in line) force of the string pushing the arrow actually cause the shaft to bend. This isn't really the case. If the forces were perfectly "linear" from the start, the arrow wouldn't flex at all. It is because the force is *NOT* linear, that the flexing happens. When the string rolls off the fingers, it first moves *laterally* before moving forward. It is this *lateral* (not linear) movement that causes the arrow to bend, or flex. 

In the attached high speed video, you will see what happens when the string rolls off the fingers laterally, causing the initial flex of the arrow shaft.






Now, the stiffer the shaft, the less flex there will be, and the more flexible the shaft, the more flex there will be. This is where matching the stiffness of the arrow shaft, with the weight and design of the bow (amount the riser is cut to, or past the centerline of the bow), and how much the arrow NEEDS to flex in order to bend around the riser without excessive contact.

A riser that it cut well past center will require less flex of the arrow in order to bend around the riser, and therefore eliminating excessive contact.

KPC


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## Easykeeper (Jan 2, 2003)

Good thread, thanks for starting it GE...:thumbs_up

Even if the force applied to the arrow from the string is perfectly linear (no fingers, mechanical release, precise centershot, well tuned arrow), there will still be deflection in the arrow although it will be less than anything experienced by finger shooters. Since there is no such thing as an infinitely stiff shaft it will bend and dissipate some of the energy until the inertia of the point weight is overcome even if you could achieve a perfectly linear force applied exactly inline with the arrow. The oscillation induced continues but dissipates as the arrow goes downrange.

This is a good read on arrow flight. It's a little mathy but not too bad. The issue of arrow flight is very complex; I understand just enough to know how much I _don't_ know...:wink:

http://www.ocf.berkeley.edu/~archery/wp-content/uploads/2011/08/KNSU-paper-by-Lieu-version4.pdf


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## Sanford (Jan 26, 2009)

I would add that speed of arrow is irrelevant to the process of the flex, as it's all in the forces present at the point of release by hand and arrow mass at the moment of release (Moment of Inertia). The arrow's mass is relevant to arrow speed, but even if the arrow didn't move, the flex is the flex. This point seems to confuse some folks when it comes to BH tuning, where lower BH increases arrow speed but lowers flex in arrow. Ferguson even devotes a section of his book to this misunderstanding on tuning.


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## Castmaster (May 2, 2013)

I like to think the arrow bends to my will; but I ask it very nicely.


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## JINKSTER (Mar 19, 2011)

GEREP said:


> OK, so what causes an arrow to flex?
> 
> We've seen it suggested that the linear (in line) force of the string pushing the arrow actually cause the shaft to bend. This isn't really the case. If the forces were perfectly "linear" from the start, the arrow wouldn't flex at all. It is because the force is *NOT* linear, that the flexing happens. When the string rolls off the fingers, it first moves *laterally* before moving forward. It is this *lateral* (not linear) movement that causes the arrow to bend, or flex.
> 
> ...


Very good depiction and description Kev...I've pretty much knew the forces at work here but what you're slo-mo vid there did was to show me "Just How Much" lateral string movement is involved...in my mind?...I was picturing about 1/4th of that in the vid...and since we're discussing this?...please allow me to open up a huge can-o-worms here...as to what happens when..."A Controlled Pluck"....is involved...and/or..."The Effects of Point Weight"...cause you know my history...buying bow after bow going lower and lower in poundage found me always having an excess of stiffly spined arrows...which I dealt with by adding more point weight...an in some dire sessions?...I found myself actually "ADAPTING/MODIFYING" my release to accommodate cleaner arrow flight...and I may have even been compenstaing with a bit of bowhand torque...and in some extreme instnces (in days gone by) maybe even "Throwing the bow out of the way" at-the-shot..but still managed to achieve clean arrow flight and get the point to the mark....with grossly stiff arrows...interesting stuff here.


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## gjlama94 (Oct 11, 2013)

GEREP said:


> OK, so what causes an arrow to flex?
> 
> We've seen it suggested that the linear (in line) force of the string pushing the arrow actually cause the shaft to bend. This isn't really the case. If the forces were perfectly "linear" from the start, the arrow wouldn't flex at all. It is because the force is *NOT* linear, that the flexing happens. When the string rolls off the fingers, it first moves *laterally* before moving forward. It is this *lateral* (not linear) movement that causes the arrow to bend, or flex.


This is incorrect. The arrow would bend regardless of finger roll. This comes back to the limitations of the physical propeties of the arrow. One if which would be a lack of infinite stiffness so the acceleration provided by the force of the string could be instantly applied to the tip of the arrow.

The arrow bends because upon release, the rear of the arrow is actually accelerating faster than the front of the arrow. The inertia of the arrow tip contributes to the tip more slowly acclerating. The result is the bending of the arrow shaft until the two (rear of arrow and tip of arrow) are in equilibrium. (This is why more weight in the tip bends the arrow more.) Once the arrow tip comes up to speed, the arrow begins to oscillate back and forth and its the first oscillation that provides the clearance around the riser. Once the arrow stops oscillating, the tip and rear are in perfect equilibrium.

Finger roll adds torque to the arrow, meaning the arrow starts to spin like a helicopter. We call it fishtailing.

Also, the same process happens in reverse when the arrow strikes a target. The tail wagging after it hits is the result.


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## GEREP (May 6, 2003)

As to the flex of the arrow, the less lateral movement of the string (as is experienced when it rolls off the fingers) the less flex or bending of the arrow there is going to be.

When you look at a mechanically released arrow, notice how little arrow flex or bending there is. This is because the force actually *IS* more linear, and not moving laterally first.






As a matter of fact, with a mechanically released arrow, what shaft flex there is, is often "up and down" as opposed to side to side. This is caused by vertical forces caused by vertical nock travel, (a function of cam timing, among other things, a discussion for a different day) instead of lateral forces caused by the string rolling off the fingers.

In a *PERFECT* world, if the force of the string were to actually *BE* 100% linear to the arrow, there would be no flex at all, regardless of the point weight. Unfortunately, you cannot eliminate lateral or vertical movement totally, you can only minimize it.

KPC


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## JINKSTER (Mar 19, 2011)

GEREP said:


> Unfortunately, you cannot eliminate lateral or vertical movement totally, you can only minimize it.
> 
> KPC


and then "compensate for it"...mechanically....or?...


"intuitively".


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## Easykeeper (Jan 2, 2003)

GEREP said:


> As to the flex of the arrow, the less lateral movement of the string (as is experienced when it rolls off the fingers) the less flex or bending of the arrow there is going to be.
> 
> When you look at a mechanically released arrow, notice how little arrow flex or bending there is. This is because the force actually *IS* more linear, and not moving laterally first.
> 
> ...


I agree with everything except the bold line. Until an infinitely stiff shaft is developed there will still be bending even if the applied load were perfectly inline with the shaft; gjlama described it better than I did earlier. The arrow shaft is basically a loaded column and behaves according to the same principles as any other column under load. There is no such thing as an infinitely stiff column, at least as far as I know.


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## GEREP (May 6, 2003)

gjlama94 said:


> Also, the same process happens in reverse when the arrow strikes a target. The tail wagging after it hits is the result.


This is incorrect. The tail wagging is a result of the arrow not entering the target *absolutely perfectly* square. It's the exact reverse of the what happens when a string pushes an arrow, instead of a target stopping one. If the force is not 100% linear, the arrow is going to shed energy either vertically or laterally. Having said that, an arrow will never be either pushed or stopped 100% perfectly square so it is a moot point.

What needs to be known is that movement, either lateral or vertical is what causes the bending of the arrow. Forward force exacerbates the flex, but does not cause it. The more force the more flex, either on the acceleration end or deceleration end, but force does not initially cause the flex. It is force that is not perfectly *"linear"* that causes the flex.

KPC

KPC


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## Rick Barbee (Jan 16, 2013)

I'm not going to go into what paradox is, or isn't. Gerep & others have covered it quite well.

What I will add is this:

A finger shooter trying to eliminate paradox from their arrow will generally wind up
with one, or both of the following - (1) an arrow that is way to stiff for the bow,
and/or (2) a loose/release that is uncontrollable, twitchy, and difficult to repeat.

Paradox really is your friend IF you learn how to use it. 

Rick


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## grapplemonkey (Nov 2, 2005)

JINKSTER said:


> and then "compensate for it"...mechanically....or?...
> 
> 
> "intuitively".


No... humans just aren't designed that way. Hence us not being able to shoot like a Hooter.... release aids and all.


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## JINKSTER (Mar 19, 2011)

grapplemonkey said:


> No... humans just aren't designed that way. Hence us not being able to shoot like a Hooter.... release aids and all.


You miss-interpreted my meaning...by "mechanical" I meant..."tuning"...such as strike-plate modification...be it thicker or thinner...or addressing point weight...or shaft length....i.e. "Mechanical Compensation".

and something tells me I may have just encountered...."Instinctive Arguing" :laugh:


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## Sanford (Jan 26, 2009)

The compensation is called fletch. Instinctive or not has nothing to do with tune. If the tune is bad enough fletch can't get a straight flight, every target distance is off the path but save one.


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## grapplemonkey (Nov 2, 2005)

Sanford said:


> The compensation is called fletch.


Good answer and great movie.


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## GEREP (May 6, 2003)

Rick Barbee said:


> I'm not going to go into what paradox is, or isn't. Gerep & others have covered it quite well.
> 
> What I will add is this:
> 
> ...


Rick:

I hate to be a jerk, but this is why I started this thread in the first place. 

Arrows don't paradox, nor are they ever "in paradox." They flex, they bend, they oscillate, they noodle, etc.

The "archers paradox" refers only to the contradiction between where an arrow is pointed and where it impacts.

It would be like saying that when an arrow bends, it is *"in contradiction."*

It's actually quite simple to "eliminate" archers paradox.

My rig is setup and performs well that way. My arrow and string are in linear alignment, and are pointed directly at the target. Therefore, no paradox. No contradiction between where the arrow is pointed and where it impacts.









No, it doesn't eliminate the flex, or the bending of the arrow, but that is completely different than *"Archers Paradox."*

KPC


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## grapplemonkey (Nov 2, 2005)

We've been duped people... I call bait-n-switch here. For me this didn't play out to be a discussion... I just got taught something I thought I already knew.


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## JINKSTER (Mar 19, 2011)

GEREP said:


> Rick:
> 
> I hate to be a jerk, but this is why I started this thread in the first place.
> 
> ...


But Kev...even though your Titan II riser is a "cut well past center" riser...are you saying you've achieved zero lateral movement at release as the string comes off your fingers?


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## grapplemonkey (Nov 2, 2005)

JINKSTER said:


> But Kev...even though your Titan II riser is a "cut well past center" riser...are you saying you've achieved zero lateral movement at release as the string comes off your fingers?


His last line Bill... "No, it doesn't eliminate the flex, or the bending of the arrow, but that is completely different than "Archers Paradox.""

I had to go back and reread his first post... head slapping moment ensued.


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## GEREP (May 6, 2003)

JINKSTER said:


> But Kev...even though your Titan II riser is a "cut well past center" riser...are you saying you've achieved zero lateral movement at release as the string comes off your fingers?


Not at all. Not even remotely close. 

I eliminated the *"paradox,"* or the *"contradiction"* between where the arrow is pointed and where it impacts. All is in linear alignment. A riser cut past center and a stiffer than normal arrow shaft allows for it.

There is no way I can eliminate the lateral movement of the string coming off my fingers...BUT that's not what *"archer's paradox"* is.

Hence the point of the discussion.

:wink:

KPC


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## Rick Barbee (Jan 16, 2013)

I don't think you're a jerk Kevin, and I'll give you that because you are correct, 
but what most folks think of when the word paradox is mentioned in archery is the flexing of the shaft,

so

replace paradox with flex in my statement, and it still holds true. 

You've achieved good alignment of the arrow to where it is pointing.
I usually do also, even off the shelf, but we as finger shooters will never completely eliminate the
flex of the shaft, or even greatly reduce it without creating other insurmountable problems.

Rick


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## GEREP (May 6, 2003)

grapplemonkey said:


> We've been duped people... I call bait-n-switch here. For me this didn't play out to be a discussion... I just got taught something I thought I already knew.





grapplemonkey said:


> His last line Bill... "No, it doesn't eliminate the flex, or the bending of the arrow, but that is completely different than "Archers Paradox.""
> 
> I had to go back and reread his first post... head slapping moment ensued.



Still think you've been duped?

KPC


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## grapplemonkey (Nov 2, 2005)

GEREP said:


> Still think you've been duped?
> 
> KPC


Yes... and happily might I add. You do know it'll take some time for this to sink in for some folks right?


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## Rick Barbee (Jan 16, 2013)

GEREP said:


> Still think you've been duped?
> 
> KPC


You're a crafty feller.
Known that since our first encounter on the LW. 

Rick


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## GEREP (May 6, 2003)

Rick Barbee said:


> I don't think you're a jerk Kevin, and I'll give you that because you are correct,
> but what most folks think of when the word paradox is mentioned in archery is the flexing of the shaft,
> 
> so
> ...


Thanks Rick. I know you understood what I was getting at but I thought it necessary to be consistent in the discussion.

The reason I started this thread is because over the last few days, I have noticed a lot of confusion in regard to "archers paradox," arrow flex, center shot, and what the meanings are of each, and why they are important to understand. There have even been some fantastical, official sounding definitions thrown around that don't really mean anything, and are actually in contradiction to reality, and therefore in my opinion counterproductive.

If one doesn't understand the basic terminology, and everyone isn't on the same page as far as the concepts, how can anyone ever expect to learn anything, or work through their own tuning problem?

KPC


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## Rick Barbee (Jan 16, 2013)

Kevin, you're doing a FINE job. Carry on.
I'll be following, because I'm very interested to see where it goes from here. 

Rick


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## GEREP (May 6, 2003)

grapplemonkey said:


> Yes... and happily might I add. You do know it'll take some time for this to sink in for some folks right?


It will probably never sink in for some, but that's OK. 

I guess my concern is with the new folks that come here looking for advice and end up leaving more frustrated than they came.

This really isn't rocket science...at least the basic tuning part, but some people try to make it seem like you need a degree in physics and a Ouija board to get an arrow to fly straight.

KPC


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## Sanford (Jan 26, 2009)

It does seem common for many folks to refer to the action, the dynamics, as the "paradox" of the arrow. That does happen a lot with things becoming terms of art in language, when, even a noun can be made into a verb. We do it all the time with all types of stuff - when we say we xerox a copy for example. None of that should preclude knowing the base meaning, or purposeful use of the word, though.


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## Matt_Potter (Apr 13, 2010)

GEREP said:


> It will probably never sink in for some, but that's OK.
> 
> I guess my concern is with the new folks that come here looking for advice and end up leaving more frustrated than they came.
> 
> ...


I feel exactly the same way - problem is once bad info is out there it's out there for good and is libel to be found by some poor shlub doing a search. 

Matt


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## GEREP (May 6, 2003)

Easykeeper said:


> I agree with everything except the bold line. Until an infinitely stiff shaft is developed there will still be bending even if the applied load were perfectly inline with the shaft; gjlama described it better than I did earlier. *The arrow shaft is basically a loaded column and behaves according to the same principles as any other column under load.* There is no such thing as an infinitely stiff column, at least as far as I know.


I just noticed this Easy, so I thought I would/should respond.

I realize we're getting kind of far out into the weeds here, but I would disagree with your theory that *"the arrow shaft is basically a loaded column and behaves according to the same principles as any other column under load."*

You would think so, however the forces are not the same.

A column supporting an axial load is under stress from *both* ends.









An arrow only has force from one end, the string. So, if the force (srting) is *absolutely perfectly* linear to the column (arrow shaft), it will simply push the column forward. No flexing of the column will occur. Unfortunately, we will never have a situation where the force and the column are perfectly square so it's a matter of managing *how much* flex there is going to be.

In reality, what an arrow (column) actually experiences is what is called an *"eccentric load,"* which is a load or force upon the column (arrow shaft) that is not symmetrical with its central axis, therefore producing the bending. Why is it not symmetrical? Because of the lateral movement of the string rolling off the fingers before the force going forward. Is it *exacerbated* by a heavy tip, a weak shaft, a poor release, or a heavier draw weight? Yes. Is it caused by any of those things? No. 

The lateral movement of the string gets the whole ball rolling (or shaft bending as it were).

:wink:

KPC


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## Matt_Potter (Apr 13, 2010)

You want to really mess with your head throw string-walking into the the mix ;-)


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## JINKSTER (Mar 19, 2011)

GEREP said:


> Not at all. Not even remotely close.
> 
> I eliminated the *"paradox,"* or the *"contradiction"* between where the arrow is pointed and where it impacts. All is in linear alignment. A riser cut past center and a stiffer than normal arrow shaft allows for it.
> 
> ...


Interesting....so what is it?....the ability to come up with a combination of spine/length and point weight to effectively noodle a shaft around a riser that's not cut-past-center?....or are you saying that the lateral movement of the string coming off the fingers kicks the nock end into alignment to facilitate clearance and the flexing is just a product of the process?...or?...both?


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## grapplemonkey (Nov 2, 2005)

He explains what the archer's paradox in his first post.


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## JINKSTER (Mar 19, 2011)

grapplemonkey said:


> He explains what the archer's paradox in his first post.


He also entitled this thread..."Let's have a discussion"....and I'm obviously not the sharpest broad head in the box so this may take awhile. :laugh:

cause sometimes it's difficult to properly explain and convey what may or may not make sense pending a variety comprehension levels.


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## grapplemonkey (Nov 2, 2005)

Sanford said:


> It does seem common for many folks to refer to the action, the dynamics, as the "paradox" of the arrow. That does happen a lot with things becoming terms of art in language, when, even a noun can be made into a verb. We do it all the time with all types of stuff - when we say we xerox a copy for example. None of that should preclude knowing the base meaning, or purposeful use of the word, though.


This is the bane right here.


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## JINKSTER (Mar 19, 2011)

grapplemonkey said:


> This is the bane right here.


wow!.....

*bane
bān/
noun
noun: bane; plural noun: banes

a cause of great distress or annoyance.
"the bane of the decorator is the long, narrow hall"
synonyms:	scourge, plague, curse, blight, pest, nuisance, headache, nightmare, trial, hardship, cross to bear, burden, thorn in one's flesh/side, bitter pill, affliction, trouble, misery, woe, tribulation, misfortune, pain More
"scurvy was the bane of these seafarers"
archaic
something, typically poison, that causes death.*

strangely?...I feel empowered....buwhahahahahahah! :laugh:


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## Roger Savor Sr (Feb 16, 2014)

Kevin, great thread, and my skeptical mind isn't finding anything to disagree with, so I must concur. .......Oh, and if you think some may be confused here, then merely repost this on The Leatherwall and you'll see a brand of befuddledness like none you could have ever imagined.


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## grapplemonkey (Nov 2, 2005)

JINKSTER said:


> wow!.....
> 
> *bane
> bān/
> ...


And sorta rightfully so... I mean we've become so accustomed to think arrow flight when we hear paradox.


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## GEREP (May 6, 2003)

JINKSTER said:


> Interesting....so what is it?....the ability to come up with a combination of spine/length and point weight to effectively noodle a shaft around a riser that's not cut-past-center?....or are you saying that the lateral movement of the string coming off the fingers kicks the nock end into alignment to facilitate clearance and the flexing is just a product of the process?...or?...both?


In all honesty JINKS, I'm not sure what you're asking.

What is what? Archers Paradox? The definition is in my first post.

Flexing of the arrow has nothing to do with how much a riser is cut past center. It has to do with lateral movement caused by the string rolling off the fingers. A given arrow is going to flex the same whether or not it's shot from a riser cut past center or a longbow that has no sight window cut in it at all...if the weight (force) is the same and the lateral movement of the string (release) is the same, a given arrow is going to flex the same. 

The riser being cut past center simply allows for more clearance, and therefore a wider range of arrow spines that can fly properly from it.

The point of the thread is to help people understand that arrow flex (bend, oscillation, etc.) is completely different than "archers paradox".

While one is used to describe the effects of the other, they aren't the same.

Flex is flex. Bending is bending. Oscillation is oscillation. "Archers Paradox" is the *visual contradiction* between where an arrow appears to be aimed and where it actually ends up hitting.

Paradox is *not* the arrow flexing, bending, or oscillating.

KPC


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## Dave V (Aug 13, 2008)

> Flex is flex. Bending is bending. Oscillation is oscillation. "Archers Paradox" is the visual contradiction between where an arrow appears to be aimed and where it actually ends up hitting.


This is important enough that it deserves to be posted TWICE.


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## Sanford (Jan 26, 2009)

GEREP said:


> Flexing of the arrow has nothing to do with how much a riser is cut past center. It has to do with lateral movement caused by the string rolling off the fingers. A given arrow is going to flex the same whether or not it's shot from a riser cut past center or a longbow that has no sight window cut in it at all...if the weight (force) is the same and the lateral movement of the string (release) is the same, a given arrow is going to flex the same.
> 
> KPC


I would beg to differ, there. The amount of flex has everything to do with how much the window is cut. Without a fulcrum, the arrow won't bend from lateral movement, as it would just turn or rotate about its axis. 

The distance the wall (the fulcrum) is from string centerline determines how much lateral movement of the shaft is turned into bend. The farther from center, it gets less bend. That's why moving your strike plate out makes the arrow act stiffer and moving closer to centerline makes your arrow act weaker.


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## JINKSTER (Mar 19, 2011)

GEREP said:


> In all honesty JINKS, I'm not sure what you're asking.
> 
> What is what? Archers Paradox? The definition is in my first post.
> 
> ...


Well?...I get the dif your making..."bend/flex VS visual contradiction"...(although I do like to set my bows up so they hit where I look and believe I do this through proper tuning)....and maybe my thoughts are running a little deeper than you're willing to sink Kev so let me phrase the question another way...

are you saying that ultimately it's the lateral movement of the string coming off the fingers is what aligns the arrow despite the visual contradiction?

Because for me?...that "visual contradiction" gets dramatically reduced at full draw....and the arrow that appeared to be looking slightly like this...

\ 

at static looks like this...

|

to me at full draw.

on my cut-to-center bows.


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## gjlama94 (Oct 11, 2013)

One thing I'd like to throw out is the way tribes come up with there own lingo. In a technical sense, GEREP is absolutely correct. A paradox is the simultaneous existence of two contradictory things. And he has correctly identified what "archer's paradox" is in his first post.

But tribes tend to create their own languages, or better yet, lingo. One example is the computer hacker tribe who can have a completely coherent discussion within their tribe that's spoken in English, yet no one else would understand because of the liberal use of terms like "grok" and "ack" and references to stories only of interest to computer hackers.

I'd submit that the use of the word "paradox" by the archer tribe is in a similar vein. A sort of sub-language that only has meaning within the archer tribe. As such, is it really incorrect for tribe members to be using the term this way? Typically, a "tribal elder" would have to make that call.


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## JINKSTER (Mar 19, 2011)

gjlama94 said:


> One thing I'd like to throw out is the way tribes come up with there own lingo. In a technical sense, GEREP is absolutely correct. A paradox is the simultaneous existence of two contradictory things. And he has correctly identified what "archer's paradox" is in his first post.
> 
> But tribes tend to create their own languages, or better yet, lingo. One example is the computer hacker tribe who can have a completely coherent discussion within their tribe that's spoken in English, yet no one else would understand because of the liberal use of terms like "grok" and "ack" and references to stories only of interest to computer hackers.
> 
> I'd submit that the use of the word "paradox" by the archer tribe is in a similar vein. A sort of sub-language that only has meaning within the archer tribe. As such, is it really incorrect for tribe members to be using the term this way? Typically, a "tribal elder" would have to make that call.


Unless of course it's a full moon during _"DZEH"_ mating season.


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## BLACK WOLF (Aug 26, 2005)

GEREP said:


> If one doesn't understand the basic terminology, and everyone isn't on the same page as far as the concepts, how can anyone ever expect to learn anything, or work through their own tuning problem?


It definitely isn't just with with tuning issues. It carries over into aiming and form terminology also :wink: If nothing else...it should teach people to ask questions for clarity to help with better communication.

Good thread, Kev! :thumbs_up

Ray :shade:


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## GEREP (May 6, 2003)

Sanford said:


> I would beg to differ, there. The amount of flex has everything to do with how much the window is cut. Without a fulcrum, the arrow won't bend from lateral movement, as it would just spin at its axis.
> 
> The distance the wall (the fulcrum) is from string centerline determines how much lateral movement of the shaft is turned into bend. The farther from center, it gets less bend. That's why moving your strike plate out makes the arrow act stiffer and moving closer to centerline makes your arrow act weaker.


You can disagree, but I think you would be incorrect. Watch the following video.






You will see that the flex caused by the lateral string movement is not dependent on how much the window is cut. What the amount the window is cut WILL end up affecting is where the arrow ends up hitting, but the amount of flex is the amount of flex. 

If what you are saying was accurate, an arrow shot *with fingers* through a "shoot through" riser, or a whisker biscuit, or from a drop away rest, would have no fulcrum, therefore no flex. We both know that's not the case.

KPC


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## gjlama94 (Oct 11, 2013)

JINKSTER said:


> Unless of course it's a full moon during _"DZEH"_ mating season.


But of course...


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## Sanford (Jan 26, 2009)

GEREP said:


> You can disagree, but I think you would be incorrect. Watch the following video.
> 
> 
> 
> ...


Gerep, plain physics. Watch the arrow bend "into" the shelf wall (plunger) on first flex. Test it yourself. Set an arrow on the table with the end overhang. You can swing a 15lb sledge hammer across and against the nock and the arrow will just turn and spin. It needs an opposing force to bend - which is the bow held by the archer and that contact point being the wall on your bow. Reckon why those plungers are there to fine tune what is where on the side doesn't matter?  This isn't new stuff, it's explained in many tuning manuals as well.


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## GEREP (May 6, 2003)

JINKSTER said:


> are you saying that ultimately it's the lateral movement of the string coming off the fingers is what aligns the arrow despite the visual contradiction?
> 
> Because for me?...that "visual contradiction" gets dramatically reduced at full draw...


Yes, and no...kinda.

Ultimately, the lateral movement of the string is what causes the arrow to flex or bend. It doesn't necessarily "align" anything.

The "visual contradiction" does indeed appear to be reduced at full draw.










But it doesn't have anything to do with a riser cut past center or not. It has everything to do with the arrows position within that sight window, width of the strike plate, position of cushion plunger, etc. That's were *tuning* a specific shaft to a specific bow comes in. 

KPC


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## GEREP (May 6, 2003)

Sanford said:


> Gerep, plain physics. Watch the arrow bend "into" the shelf wall (plunger) on first flex. Test it yourself. Set an arrow on the table with the end overhang. You can swing a 15lb sledge hammer across and against the nock and the arrow will just turn and spin. It needs an opposing force to bend - which is the bow held by the archer and that contact point being the wall on your bow. Reckon why those plungers are there to fine tune what is where on the side doesn't matter?  This isn't new stuff, it's explained in many tuning manuals as well.


So are you saying that an arrow, shot by a finger release, through a shoot thru riser, with a drop away rest will not flex? If what you are saying is true, it can be no other way.

No fulcrum, no flex, right?

KPC


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## Hiram (Jul 31, 2013)

Rick Barbee said:


> I'm not going to go into what paradox is, or isn't. Gerep & others have covered it quite well.
> 
> What I will add is this:
> 
> ...


This works for me Rick,,we are both shooters more than we are talkers.


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## Hiram (Jul 31, 2013)

GEREP said:


> So are you saying that an arrow, shot by a finger release, through a shoot thru riser, with a drop away rest will not flex? If what you are saying is true, it can be no other way.
> 
> No fulcrum, no flex, right?
> 
> KPC


There has to be a direction for the arrow to start or there will be no consistency for a bending point along the line. No matter though,,the fingers will still distort the string as it clears the fingers. The fingers pushing the string away is what causes the Paradox. Release shooters tune with spring pressure on a prong rest in the vertical because the Paradox in vertical rather than horizontal. Yes,,the angle of deflection changes the spine of the arrow and the deflection. Less linear, less bend,,more inline, more bend. More bend, the bending points move further away from each other along the arrow length.


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## grapplemonkey (Nov 2, 2005)

Sanford said:


> Gerep, plain physics. Watch the arrow bend "into" the shelf wall (plunger) on first flex. Test it yourself. Set an arrow on the table with the end overhang. You can swing a 15lb sledge hammer across and against the nock and the arrow will just turn and spin. It needs an opposing force to bend - which is the bow held by the archer and that contact point being the wall on your bow. Reckon why those plungers are there to fine tune what is where on the side doesn't matter?  This isn't new stuff, it's explained in many tuning manuals as well.


I thought the opposing force was the arrow's point/head?


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## JINKSTER (Mar 19, 2011)

GEREP said:


> Yes, and no...kinda.
> 
> Ultimately, the lateral movement of the string is what causes the arrow to flex or bend. It doesn't necessarily "align" anything.
> 
> ...


Okay...it's official....I fully disagree...mainly because your last two sentences of....

*"But it doesn't have anything to do with a riser cut past center or not. It has everything to do with the arrows position within that sight window, width of the strike plate, position of cushion plunger, etc. That's were tuning a specific shaft to a specific bow comes in."*

Which are in direct contradiction unto themselves...because everything you mentioned within those two sentences....does....

"have everything to do with the arrows position within that sight window"

and that's a fact Jack! :laugh:

Kev....I'm starting to think that Titan II riser has spoiled you....it's been my experience that those cut past center metal risers allow for a far greater range of tune than do their cut-too-center wood counterparts which are far more critical and less forgiving to tuning (and form) errors where your Titan will in fact tune with a far greater range of arrow spine and point weight...since the arrow can be adjusted to center-shot and beyond.

is this where you're trying to go with this?...either way?...no need to respond I guess as none of this plays a role in my head as far as shooting goes...but thanks...it's been interesting.


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## Sanford (Jan 26, 2009)

grapplemonkey said:


> I thought the opposing force was the arrow's point/head?


That's a base, or minimal amount of moment of inertia. The more flex you are trying to induce, though, the more by other means you will need. That's the basis of tuning an arrow by strike plate. Which means, yes, and a big yes, that the strike plate position (centershot location) changes the amount of flex induced.


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## grapplemonkey (Nov 2, 2005)

From what I'm reading and seeing is there is no changing the amount of flex... we can only change when and where?

edit... well we can change the arrow's flex thru point weight our bow weight... but that's not what we're talking about right?


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## Sanford (Jan 26, 2009)

grapplemonkey said:


> From what I'm reading and seeing is there is no changing the amount of flex... we can only change when and where?


Changing the amount of flex is a tenet of tune. If you are not changing the amount of flex, you are not changing the cyclical dynamics of the arrow, which is the only way to eventually tune it to travel in a straight path relative to force direction.


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## GEREP (May 6, 2003)

Sanford said:


> That's a base, or minimal amount of moment of inertia. The more flex you are trying to induce, though, the more by other means you will need. That's the basis of tuning an arrow by strike plate. Which means, yes, and a big yes, that the strike plate position (centershot location) changes the amount of flex induced.


You haven't answered the question. If there is no sidep late at all, such as in the case of a drop away rest. or a shoot thru riser, (or both) are we to assume there will be not flex if shot with fingers?

The sideplate position only starts the arrow out in such a position that *with* the flex caused by the lateral movement of the string, it will end up going where you want it to go. A cushion plunger doesn't change flex, it absorbs the flex that has already been imparted on the arrow.

KPC


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## ranchoarcher (Sep 26, 2013)

Sanford made a valid point. The plunger to centershot position absolutely impacts the amount of arrow flex. If the shooter cranks it out all the way in either direction the arrow flight will change substantially demonstrating the plunger's affect on arrow flight. It's why they exist in the first place. If it were preferred to have an arrow on center shot, why are nearly all bows (except compound) built to have the arrow off center. It's needed to offset the finger string roll. No way around that unless a person has super fast fingers that can out run a bow string.


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## JINKSTER (Mar 19, 2011)

Sanford said:


> Changing the amount of flex is a tenet of tune. If you are not changing the amount of flex, you are not changing the cyclical dynamics of the arrow, which is the only way to eventually tune it to travel in a straight path relative to force direction.


Absolutely...Correct.

Something tells me we're all being led down a garden path here for personal amusement.


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## grapplemonkey (Nov 2, 2005)

I think we're not all discussing the same thing.


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## GEREP (May 6, 2003)

JINKSTER said:


> Which are in direct contradiction unto themselves...because everything you mentioned within those two sentences....does....
> 
> "have everything to do with the arrows position within that sight window"
> 
> and that's a fact Jack! :laugh:


Ummm...no its not. Go back and read what I said. You can have a riser that is cut 5" past center, but if your sideplate is 4 7/8" thick, it means nothing. It's the position of the arrow *within* the sight window, which is determined by the width of the sideplate, or the position of your plunger that matters.

KPC


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## grapplemonkey (Nov 2, 2005)

I'm thinking atlatl....


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## GEREP (May 6, 2003)

Very interesting discussion guys, but I have to go to a party. Will resume when I get back if it's still going.



KPC


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## Sanford (Jan 26, 2009)

grapplemonkey said:


> edit... well we can change the arrow's flex thru point weight our bow weight... but that's not what we're talking about right?


We were, but now were being asked to defend what is common knowledge in tuning a bow to an arrow!

There are other ways to induce more flex in the arrow from at the bow (or reduce in reverse process) than bow weight.

On Oly bows, there's a second plunger hole farther out. Some folks use that one, as it makes the distance between the strike and nock longer - longer distance in shaft between force and fulcrum = more bending.

Then, there's BH adjustment. That changes the angle of deflection at launch and to smaller degree, final draw weight (though I have seen some draw force curves that suggest this is minimal in reality). I chalk this one up more to deflection angle.

Then, there's moving the strike plate in or out - moving the arrow closer or farther from string deflection to change amount of bend the deflection can create.

These are all well known basic tuning methods, and each will induce/reduce the amount of dynamic spine (flexing) in the arrow.


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## GEREP (May 6, 2003)

Sanford said:


> Changing the amount of flex is a tenet of tune. If you are not changing the amount of flex, you are not changing the cyclical dynamics of the arrow, which is the only way to eventually tune it to travel in a straight path relative to force direction.


Not correct. You aren't changing the flex of the arrow, you are changing the way the bow reacts to the flex of the arrow. The only way to change the flex of the arrow is to either change the arrow itself, length, tip weight, etc., or change the force applied to it.

Everything else is tuning the bow to the arrow, not the arrow to the bow.

KPC


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## Sanford (Jan 26, 2009)

GEREP said:


> Not correct. You aren't changing the flex of the arrow, you are changing the way the bow reacts to the flex of the arrow. The only way to change the flex of the arrow is to either change the arrow itself, length, tip weight, etc., or change the force applied to it.
> 
> Everything else is tuning the bow to the arrow, not the arrow to the bow.
> 
> KPC


KPC, I don't even know where to begin with that! Sorry. The only way I know to change how the "bow reacts" to tuning in the arrow is by stabilization, which adds mass to reduce the moment of inertia in the bow, which again, goes to strike position.


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## DDSHOOTER (Aug 22, 2005)

KPC, there is a link. http://tradtalk.com/forums/showthread.php?t=46511
In that thread I came up with a factor in finding static front node for striker bottom/plunger location. However, as a fact were are looking for dynamic front node location.

Please keep in mine: really what matters, coming from top coaches, is how the rear node/nock clears the bow and how the nock leaves BH in terms of arrow straightforwardness. These factors determine a ok tune vs perfect tune for the shooter and bow/arrow combinations. 

Watch the first video of the longbow again.... this may make more sense. 

I agree with you on the misused terminology in traditional archery. It blows my mind sometimes. What really perplexing is when there become two meaning of which neither are correct.

Also, but not relating to this subject is nock travel due to imbalance in the limbs or string walking. Which is another one. Lol.
Dan


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## Hiram (Jul 31, 2013)

grapplemonkey said:


> I think we're not all discussing the same thing.


Your right Bro,,some of us are talking Bow mechanics and others are on hypothetical s.


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## Hiram (Jul 31, 2013)

GEREP said:


> Not correct. You aren't changing the flex of the arrow, you are changing the way the bow reacts to the flex of the arrow. The only way to change the flex of the arrow is to either change the arrow itself, length, tip weight, etc., or change the force applied to it.
> 
> Everything else is tuning the bow to the arrow, not the arrow to the bow.
> 
> KPC


To tune, You pay attention to how the arrow reacts to the Bow. and or change the Bow create the proper arrow reaction to achieve tune. This is usually a proprietary and individualistic endeavor due to individual inputs upon the Bow, draw length,release, etc.


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## Hiram (Jul 31, 2013)

Sanford said:


> We were, but now were being asked to defend what is common knowledge in tuning a bow to an arrow!
> 
> There are other ways to induce more flex in the arrow from at the bow (or reduce in reverse process) than bow weight.
> 
> ...



Good synopsis! Thanks for the discussion,,good week end to all and good shooting!


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## DDSHOOTER (Aug 22, 2005)

QUOTE=Easykeeper;1070183211]Good thread, thanks for starting it GE...:thumbs_up

This is a good read on arrow flight. It's a little mathy but not too bad. The issue of arrow flight is very complex; I understand just enough to know how much I _don't_ know...:wink:

http://www.ocf.berkeley.edu/~archery/wp-content/uploads/2011/08/KNSU-paper-by-Lieu-version4.pdf[/QUOTE]

Easy, thanks for the link. It have this setup at work. Good experiment. Once you have a good tune. Finding the natural frequency would be easier when changing arrows. OR
I wonder if .35 Hz/fps approximation is a good tune starting point?
Dan


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## GEREP (May 6, 2003)

Hiram said:


> The fingers pushing the string away is what *causes the Paradox*.


I guess some, no matter how many times it's explained, *still* won't get it.



Aside to Sanford:

You said...

_"Gerep, plain physics. Watch the arrow bend "into" the shelf wall (plunger) on first flex. Test it yourself. Set an arrow on the table with the end overhang. You can swing a 15lb sledge hammer across and against the nock and the arrow will just turn and spin. *It needs an opposing force to bend - which is the bow held by the archer and that contact point being the wall on your bow."*_

You still haven't answered my question. I'll ask it for the third time.

If the above statement is true, are you suggesting that if an arrow is shot buy fingers, through a "shoot thru riser" with a drop away rest, there will be no arrow flex? There is no "opposing force" on either side or underneath the arrow, so there is nothing to cause the arrow to flex, correct?

No fulcrum, no flex, right?

Next question:

If an arrow is shot in the above manner and it *does* flex, (which we both know it will) what is the *"opposing force"* causing it to bend? Remember, there is no wall on either side, no floor, no ceiling to act as that *"opposing force."* How can it flex?

KPC

KPC


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## Easykeeper (Jan 2, 2003)

DDSHOOTER said:


> QUOTE=Easykeeper;1070183211]Good thread, thanks for starting it GE...:thumbs_up
> 
> This is a good read on arrow flight. It's a little mathy but not too bad. The issue of arrow flight is very complex; I understand just enough to know how much I _don't_ know...:wink:
> 
> http://www.ocf.berkeley.edu/~archery/wp-content/uploads/2011/08/KNSU-paper-by-Lieu-version4.pdf


Easy, thanks for the link. It have this setup at work. Good experiment. Once you have a good tune. Finding the natural frequency would be easier when changing arrows. OR
I wonder if .35 Hz/fps approximation is a good tune starting point?
Dan[/QUOTE]

Makes sense to me, I averaged the four possible situations at the bottom of figure 13 and come up with 0.347 Hz/fps.


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## Sanford (Jan 26, 2009)

GEREP said:


> I guess some, no matter how many times it's explained, *still* won't get it.
> 
> 
> 
> ...


Never measured it in that situation, have you? There should be a slight amount of resistance in the pile, but laterally, that would be nill, as it's at the very end of the shaft that's being laterally turned. 

Lay an arrow on the table and try to bend it by pushing laterally on the nock - easy test of physics, there, as you see the arrow spin about where the pile is at and not the shaft bending in the middle  The forward motion of the arrow from a bow, coupled with that lateral deflection, creates a dynamic process. By having a strike, you have a place where in that dynamic process the arrow can't move laterally at the front as it is in the back - creating a bending condition, that again, is dynamic with forward motion.

There's an excellent diagram of the process on top of page 6 in the pdf link of D.K. Lieu's research which DDSHOOTER posted above.

Still, none of this has to do with the fact that tuning by moving out/in strike does in fact change the dynamic spine of the arrow - the degree of flex created. That's too basic a tuning parameter to argue.


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## Easykeeper (Jan 2, 2003)

GEREP said:


> I just noticed this Easy, so I thought I would/should respond.
> 
> I realize we're getting kind of far out into the weeds here, but I would disagree with your theory that *"the arrow shaft is basically a loaded column and behaves according to the same principles as any other column under load."*
> 
> ...


I agree you except for the first paragraph. 

Until the inertia of the mass on the front of the arrow (point) and the mass of the front part of the shaft is overcome there _is_ a force on the front of the arrow and it's working in opposition to the force applied to the string, exactly like the free body diagram you posted. The mass of the point and it's resisting force relative to the string is one of the main contributors to the initial flexing of the shaft. If it were not so changing the point weight wouldn't affect the tune.

Regardless of whether you model the shaft as a column or a beam, neither analysis will be complete without considering the other since it's a dynamic situation. I'd guess if you really wanted to model it correctly you would consider it a column at the moment of launch and a beam at some point in it's forward travel where the mass of the point has matched the velocity of the nock/string. 

And like you said, the initial flexing is influenced by tip weight, shaft spine, the shooters release, and draw weight. 

I'll add in the degree of centershot since that is what is determining the moment arm for the force applied to the shaft and point by the string; what you referred to as an eccentric load. Also the material of the side plate (soft/hard/springy...) or plunger tension has to be taken into account since that is the restoring force as mentioned in the link I posted. Since the shaft is applying a force to the strike plate or plunger, there must be an equal and opposite force.

Lateral movement of the string by the fingers is part of the equation, but only part. The whole equation is constantly changing with with time, the time it takes for the nock to leave the string, after that is a different model.


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## Sanford (Jan 26, 2009)

Easykeeper said:


> Lateral movement of the string by the fingers is part of the equation, but only part.


Bingo!


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## Matt_Potter (Apr 13, 2010)

You guys are going to hurt your brains - bare shaft at 25 - disengage brain - go shoot


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## GEREP (May 6, 2003)

How about if I give you a hint Sanford. 

There *is* an opposing force, it has everything to do with physics, and nothing whatsoever to do with a strike plate, center shot, or plunger position.

It's as basic as the principle that states that an object at rest tends to stay at rest, and the resistance it has when something else is trying to propel it into motion. 

Strike plate, center shot, or plunger position actually alter or affect the dynamic spine of the arrow. They do affect how the bow *handles* the dynamic spine of a given arrow but the dynamic spine is a function of 4 things. Stiffness of the shaft, length of the arrow, weight of the tip, and the force of the bow.

Apparently, things aren't as basic as you might have thought.

By the way, your arrow on the side of a table analogy doesn't work, unless of course you can hit it with something traveling 130 -150 mph.

Here is a very good article for you to read. See if it might change your mind.

http://www.huntersfriend.com/carbon_arrows/hunting_arrows_selection_guide_chapter_3.htm

It's the most easy to understand article on arrow spine, both static and dynamic, that I have come across.

KPC


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## grapplemonkey (Nov 2, 2005)

Are we still talking about the posted topic?


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## Easykeeper (Jan 2, 2003)

Matt_Potter said:


> You guys are going to hurt your brains - bare shaft at 25 - disengage brain - go shoot


I wish there was a thank-you function on this sight, and yes I see the irony in me posting that...:wink:


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## GEREP (May 6, 2003)

Easykeeper said:


> Lateral movement of the string by the fingers is part of the equation, but only part.


You're absolutely correct Easy. The other parts of the equation are shaft stiffness, shaft length, tip weight, and bow force or acceleration.

The amount of centershot has an impact on how the arrow ends up flying, but NOT how much it flexes.

KPC


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## GEREP (May 6, 2003)

grapplemonkey said:


> Are we still talking about the posted topic?


No, but it's related.



KPC


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## grapplemonkey (Nov 2, 2005)

Why did we go off tangent?


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## Sanford (Jan 26, 2009)

GEREP said:


> The amount of centershot has an impact on how the arrow ends up flying, but NOT how much it flexes.
> 
> KPC


Sorry, it changes more about the amount of flex than how the arrow flies (direction), that's the "paradox" we tune around. But, research papers on arrow dynamics and tuning manuals aside, carry on with your explanations of the process.


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## grapplemonkey (Nov 2, 2005)

I think that the starting position of the tip/head could affect the flex but that would only happen at an extreme... no?


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## grapplemonkey (Nov 2, 2005)

There is only so much give at a certain amount of force... unless the forces change the flex should not... unless like I said above... the arrow is at an extreme angle which would cause lost energy?


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## Sanford (Jan 26, 2009)

grapplemonkey said:


> There is only so much give at a certain amount of force... unless the forces change the flex should not... unless like I said above... the arrow is at an extreme angle which would cause lost energy?


If the flex didn't change, the tune would not change. The flexing, or cycle rate, of the arrow DURING FLIGHT is what determines the ultimate path of the arrow and not where the tip is pointed at launch.


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## DDSHOOTER (Aug 22, 2005)

GEREP said:


> You're absolutely correct Easy. The other parts of the equation are shaft stiffness, shaft length, tip weight, and bow force or acceleration.
> 
> The amount of centershot has an impact on how the arrow ends up flying, but NOT how much it flexes.
> 
> KPC


Don't forget bow string weight, nock and fetching weight. 

The tip and nock are called anti-nodes. 

However, they have the most lateral movements once they leave the string. 

The front and rear nodes say straight to the target during the whole flight process. Went on the string the tip is the opposing the string and nock. 

The arrow bends inward if it is to stiff and outwards if it is weak. The ideal applicant will be the sweet spot when the arrow is straight as it leave the string and tails outwards a few milliseconds past the rest.

Finally, the rest is the launcher/dampening. Which can help in the tuning process with a plunger and POI

Dan


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## ranchoarcher (Sep 26, 2013)

This is why Wikipedia should not be considered the authority on any subject. It contradicts itself in the next paragraph. http://en.wikipedia.org/wiki/Archer's_paradox 

_The term was first used by E.J. Rendtroff in 1913,[1] and as understanding was gained about the arrow flexing out of the way of the bow as it is shot, (as first filmed by Clarence N Hickman http://www.archeryhalloffame.com/Hickman.html )[2][3] and then experiencing oscillating back-and-forth bending as it travels toward the target,[4] this dynamic flexing has incorrectly become a common usage of the term, causing a good deal of misunderstanding by *those only familiar with modern target bows, which being 'centre shot' do not actually show any paradoxical behaviour as the arrow is always pointing visually along its line of flight.*[5][6][7] _

Modern target bows, assuming they are talking about Oly bows, are not shot center shot. That we all know. It might be true that the term archers paradox has been hijacked and expanded to include the result of the paradox. Without actually reading all the referenced material it's open to debate what encompasses the original definition. Language police aside, so long as the shooter understands the concept and basic mechanics I think it a good thing to further the understanding and appreciation of the endeavor.


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## Nekekal (Dec 25, 2012)

I, as a relatively new archer, found this mostly very interesting. I have been struggling with center cut importance and why some people suggest building out the strike plate. From a physics point of view it makes no sense. It seems that you want the arrow as close to center as possible.

Yes, I know that the arrow is going to bend and from a large number of slow motion videos on the net it continues to oscillate all the way down to impact. That makes sense too. It is a dampened system and will oscillate until dampened out. 

To try to understand this I tried shooting my recurve with a release. I think it was called a "caliper release" and was activated by a trigger. Sometimes it worked well, sometimes not. And at the end of the day I had some serious feather cuts on my strike plate. My conclusion was that the mechanical release caused unpredictable flexing and some were towards the riser, some away. This seems to agree with some of what has been said here. I.e. The arrow will flex and the fingers get it going in the right direction.

I am still confused about the desirability of being at center where there is no paradox, you point to where you want to hit and just control flexing to the minimum needed for the feathers. Or to have a generous offset and let paradox happen via generous flexing.

I am not sure I completely buy that a completely linear force on the end of a noodle will not induce some flex especially with a heavy weight on the tip.

Thanks for the discussion.


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## Bender (Dec 6, 2006)

I have known about and understood the distinctions and definitions that GEREP is making for years, (decades?) Some time ago I was involved in a discussion here in which I made this very same distinction. A member here, noted author and "Olympic" coach informed me in no uncertain terms that by common usage the definition of "archer's paradox" has changed to actually refer directly to the initial flex of the arrow and its subsequent oscillations. By making the distinctions I was mindlessly following an archaic usage and was therefore of sub-normal intelligence, and did not know the subject and had nothing of value to say.

Its funny how the times have changed as some folks have come to realize that it is possible to think for themselves and a few have even dared to rebel against the tyranny of the self proclaimed guru and expert.


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## Sanford (Jan 26, 2009)

Bender, really. It upsets you that bad? Well, guess what? There's really no "instinct" in instinctive aiming, either.


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## grapplemonkey (Nov 2, 2005)

I'm thinking atlatl...


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## GEREP (May 6, 2003)

Sanford said:


> If the flex didn't change, the tune would not change. The flexing, or cycle rate, of the arrow DURING FLIGHT is what determines the ultimate path of the arrow and not where the tip is pointed at launch.


Whether you realize it, or are willing to admit it, you are actually supporting my argument. If you bothered to read the article that I linked (did you?) you will see that there are really only 4 ways to actually alter, or change the dynamic spine of an arrow. You can change tip weight, you can change the stiffness of the arrow shaft, you can change the length of the arrow shaft, you can change the amount of force or acceleration there is pushing said arrow. Having said that, a given arrow shaft, of a given length, with a given tip weight, shot with a given amount of force, is going to flex at a given amount. You can change things on the bow in order to absorb some of that flex, or alter the flight path, but you aren't changing the underlying amount of flex at the moment of release. It's baked in the cake.

If I change the tires on my car, it will affect how my car handles, corners, and rides, but it will not affect the horsepower or torque. It only affects how those things are handled.

Noise and vibration are a function of a bow shedding energy. By installing string silencers, limb savers, or a strap on quiver, am I changing the actual amount of energy the bow itself is shedding, or am I just providing something to absorb it?

----------------------------------------

At the end of the day, we can argue until we are all blue in the face but, the purpose of this thread was to actually discuss *"Archers Paradox,"* what it *is* and more importantly what it *isn't.* What we can or can't do in terms of tuning, to manage an arrows flex, isn't really the point. 

In a small way, it was also an attempt to encourage people to question some of the things they've heard for years, or decades, even by some of the so called experts. Tuning guides are full of things that simply are not true, or at least no longer true. 

I can show you tuning guides or so called experts that call the flex of the arrow *"paradox." * 

I can show you tuning guides that say that you must shoot cock feather out if you are shooting off the shelf. 

I can even show you tuning guides and some so called experts that will tell you that you need to have a "channel" between the rug and side plate for the lower hen feather to pass through. (and regardless of how you feel about flex, if you watch any video of a properly tuned bow/arrow combination, you'll plainly see that the lower hen feather is nowhere near the "channel" supposedly provided to accept it. 

I can show you where some so called experts insisted that carbon arrows were a different animal, and in order to get them to fly from a traditional bow, you must massively front load them.

I can show you where tuning guides and so called experts insist that you can't get an ILF bow "hunting quiet." There's just too many moving parts. Too many bells, whistles, and screws to ever get quiet.

I can show you tuning guides and so called experts that will insist that the ILF system cannot be used on risers shorter than 19" or so, or it will somehow result in catastrophic limb failure. 

I can show you where tuning guides and so called experts insist that shooting 3 under will require a nock point 3/4" above level.

I can even show you where a well known hunting expert claims that a two blade broadhead should be oriented vertically on your arrow, so it can more easily between the ribs of deer. 

What's my point? And what's the point of the entire thread.

First of all, if we are going to help each other, beginners, intermediate, or advanced, we really should understand what basic terms mean, and forget about trying to impress people with made up crap definitions of things that don't exist. It only further confuses those that don't actually realize that they are made up crap definitions of things that don't exist.

Second, question conventional wisdom. Just because you read it somewhere, by some so called expert, doesn't mean it's accurate. I can assure you, that two blade broadheads really will pass between the ribs of a deer...even if they are oriented horizontally on an arrow shaft. :wink:

Lastly, *TEST THINGS FOR YOURSELF!!* A lot of times you are going to prove that the tuning guides and so called experts were right, but at least you are going to understand why, as it pertains to your specific setup. However, sometimes, you are going to prove conventional wisdom wrong, your own experience will benefit from it, and you'll understand why.

Now, I'm going to go shoot the same rig I've been shooting for the last 8 years or so. It's a 17" ILF riser, shot literally tens of thousands of times, with arrows that some experts would say are too light, with not one catastrophic limb failure. I shoot cock feather in, three under, and my nock point is only 3/8 above level. I even have my arrow lined up almost perfectly with the string and *in spite of all this*, I get excellent arrow flight with arrows that are supposed to be too stiff for my setup, and I don't even have an anvil screwed into the front end. 

*Have fun and experiment.* Be willing to *NOT* be right. I just found out the other day that my alignment isn't perfect and it might be affecting my bow arm movement. I intend to work on that. Had I not read a *fantastic* thread by Matt Potter about teaching kids to shoot, and being willing to go to the trouble (thanks Kelli) of examining my own form and alignment, I might have never known what I was doing. 

KPC


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## JINKSTER (Mar 19, 2011)

GEREP said:


> What's my point? And what's the point of the entire thread.
> 
> First of all, if we are going to help each other, beginners, intermediate, or advanced, we really should understand what basic terms mean, and forget about trying to impress people with made up crap definitions of things that don't exist. It only further confuses those that don't actually realize that they are made up crap definitions of things that don't exist.
> 
> ...


Now I FULLY agree! 

Great Post Kev! :thumbs_up


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## Live In a Park (Apr 1, 2012)

Great thread, GEREP. I was confused by descriptions of the paradox as some kind of movement. Your posted definition of the paradox makes it clear. Thanks!

One tiny point about the force applied to a column: If the force is applied *perfectly* in line with the axis of the column, it will compress, not flex. Since perfect never occurs (exaggeration intended), we must learn to love the flex even if we try to minimize it.

And that's how you kill a great thread.


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## GEREP (May 6, 2003)

Live In a Park said:


> Great thread, GEREP. I was confused by descriptions of the paradox as some kind of movement. Your posted definition of the paradox makes it clear. Thanks!
> 
> One tiny point about the force applied to a column: If the force is applied *perfectly* in line with the axis of the column, it will compress, not flex. Since perfect never occurs (exaggeration intended), we must learn to love the flex even if we try to minimize it.


It has been a good discussion, glad you learned something. I know I learned a few new things when doing a little research.

As to your other point, I thought I addressed that...



GEREP said:


> An arrow only has force from one end, the string. So, if the force (srting) is *absolutely perfectly* linear to the column (arrow shaft), it will simply push the column forward. No flexing of the column will occur. Unfortunately, we will never have a situation where the force and the column are perfectly square so it's a matter of managing *how much* flex there is going to be.


In reality, even with an arrow, there *is* force at both ends... the weight of the tip at rest, and the force of the string accelerating forward. However, let me ask you a question. I would think, and I'm only guessing here, that in order for compression to be the *only* thing happening, not only would the force have to be perfectly in line with the axis of the column, but the force would have to be equal at both ends. In the case of an arrow being shot, the force at one end is massively different. So even if you could have the force be in perfect alignment with the axis of the column (arrow) would the massive difference between forces at the ends cause it to flex anyway?

KPC


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## Sanford (Jan 26, 2009)

Gerep, I think you are getting there in understanding. Assuming the deflection is constant, or should be with a consistent archer, ANYTHING you do to change dynamic spine (flex) is done via energy absorption. That includes point weight, shaft length, etc...

But, as to being only four way to change dynamic spine? There are many more:

This is from TradTech Titan Manual:

If your bare shaft (or broadhead) strikes to the left of the group, it is coming out stiff (nock to the
right) and can be remedied as such; decrease the spring tension on your cushion plunger, move your
centershot/shelf strike plate in toward the bow, increase bow weight or brace height, decrease you
bow string strands/weight, or increase your insert/field point/broadhead weight. (weights must match)
If your bare shaft (or broadhead) impacts to the right of the group, it is coming out weak (nock to
the left). To correct, increase the spring tension on your cushion plunger, move your centershot/shelf
strike plate out away from the bow, decrease bow weight, shorten your arrow’s length, lower bow
weight or brace height, increase bow string strands/weight, or decrease your inserts/field point/
broadhead weight.
When your bare shaft (or broadhead) impacts with or very near your group at this distance, your bow
is on its way to being finely tuned. For finer tuning, repeat this test at or beyond 20 yards if you are
comfortable shooting at farther distances; small variations can be seen & corrected at these distances.
If you make the above corrections and your bare shaft (or broadhead) is still more than 6” from your
group to the left (stiff) or to the right (weak), y
ou will need to make modifications in your set-up or
choice of arrows or broadheads.
If your bareshaft impacts with your fletched arrows, but your fletched arrows do not fly or group well,
wiggling or minnowing in flight (especially with broadheads), then fletching clearance is likely the
culprit. On an elevated rest, turn the arrow nock to orient the fletching for better clearance; when
shooting off the shelf, reverse nock your arrow with the cock feather in toward the bow; this will keep
your bottom hen feather from striking your shelf and causing the poor arrow flight and accuracy.
***Other variables that all effect dynamic arrow spine:*
The material, type and we
ight of your bowstring;
A softer B50 Dacron Polyester string will creep
and elongate on the shot more, making the arrow slower, reacting stiffer than Dyneema or Spectra
based materials like FastFlight, TS Plus, D75, ’02, 8125 or DF’97. High Performance blends using
Dyneema and Vectran will have virtually no creep and will weaken arrow spine over B50 or Dyneema
alone. These materials may be 1-3 fps slower than Dyneema alone and are known as Excel, Ultra-Cam,
450Plus, 452X. A traditional Flemish Twist string using two or three twisted bundles is softer and will
“uncoil” slightly resulting in a stiffer arrow than an Endless Loop bowstring with loop and end
servings. Adding weight to your bowstring makes your arrows react stiffer. Remember this when
choosing nocking point and serving type, number of strands, silencers, etc. A lighter string weakens
arrow spine and increases speed.
Brace Height:
This has a great effect on arrow spine, speed, bow noise and vibration. It is best to
shoot your bow where it is quietest and most pleasant to shoot, but keep in mind that a ½ to ¾ “
change in brace height can have the same effect as 25 grains of point weight.
Adding Weight to the Arrow: Adding a lengthwise weight tube will very slightly stiffen the arrow spine,
while adding weight only at the back of the arrow will substantially stiffen the dynamic spine just as
weight at the front insert or point end will weaken the arrow’s spine.

The physics are, no matter, you cannot change flex and say flex is the same. It always starts the same, but depending on the influences of opposing forces, arrow or bow, it can be made to change in dynamics.


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## rattus58 (Jul 9, 2007)

GEREP said:


> With all the tuning discussions lately, there seems to be some confusion about the term *"Archer's Paradox."*
> 
> I thought it might be good to have a discussion about what *"Archers Paradox"* is, why it exists, and what it does, and does not mean.
> 
> ...


Sorta like kentucky windage as dictated by arrow flexibility, assuming gravity is removed from the equation... which of course its not, and you have a similar "paradox" with trajectory don't you... :grin:


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## GEREP (May 6, 2003)

Sanford said:


> Gerep, I think you are getting there in understanding. Assuming the deflection is constant, or should be with a consistent archer, ANYTHING you do to change dynamic spine (flex) is done via energy absorption. That includes point weight, shaft length, etc...
> 
> But, as to being only four way to change dynamic spine? There are many more:
> 
> ...


That's funny Sanford. I've gotten it all along, and have not changed what I've been saying. It's other's that seem to be coming around to what I've been saying all along.

Those things that you point out in the TT owners manual (changing string and brace height) all change the amount of *force* applied to the arrow. It all falls in line with the 4 things that change dynamic spine.

tip weight
arrow length
arrow stiffness
bow output (force)

Nothing new here Sanford.

KPC


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## Sanford (Jan 26, 2009)

GEREP said:


> That's funny Sanford. I've gotten it all along, and have not changed what I've been saying. It's other's that seem to be coming around to what I've been saying all along.
> 
> Those things that you point out in the TT owners manual (changing string and brace height) all change the amount of *force* applied to the arrow. It all falls in line with the 4 things that change dynamic spine.
> 
> ...


Well, at least you can now see and agree that moving the strike plate, as the manual suggests, changes the force applied by moving the arrow away from or in to the deflection. I just picked the TT manual because that's a bow you can relate to, but it's nothing new, either.


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## Live In a Park (Apr 1, 2012)

GEREP said:


> In reality, even with an arrow, there *is* force at both ends... the weight of the tip at rest, and the force of the string accelerating forward. However, let me ask you a question. I would think, and I'm only guessing here, that in order for compression to be the *only* thing happening, not only would the force have to be perfectly in line with the axis of the column, but the force would have to be equal at both ends. In the case of an arrow being shot, the force at one end is massively different. So even if you could have the force be in perfect alignment with the axis of the column (arrow) would the massive difference between forces at the ends cause it to flex anyway?
> 
> KPC


The only massive force is at the nock end. The tiny "force" of the arrow is, as you pointed out, "an object at rest tends to stay at rest." The column will compress, but given the normal materials it will be very, very miniscule, probably all in the nock. If there is no force vector other than perfectly through the axis (and the materials are uniform), all that happens is compression. (Love a good physics discussion!)


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## GEREP (May 6, 2003)

Sanford said:


> Well, at least you can now see and agree that moving the strike plate, as the manual suggests, changes the force applied by moving the arrow away from or in to the deflection. I just picked the TT manual because that's a bow you can relate to, but it's nothing new, either.


You might want to go back and read that again Sanford. Maybe even a couple times. Maybe then, even you will see that there is a difference between actually *changing* the dynamic spine and *compensating* for the flex that you have. 

_*"If your bare shaft (or broadhead) strikes to the left of the group, it is coming out stiff (nock to the
right) and can be remedied as such; decrease the spring tension on your cushion plunger, move your
centershot/shelf strike plate in toward the bow, increase bow weight or brace height, decrease you
bow string strands/weight, or increase your insert/field point/broadhead weight*. (weights must match)
If your bare shaft (or broadhead) impacts to the right of the group, it is coming out weak (nock to
the left). To correct, increase the spring tension on your cushion plunger, move your centershot/shelf
strike plate out away from the bow, decrease bow weight, shorten your arrow’s length, lower bow
weight or brace height, increase bow string strands/weight, or decrease your inserts/field point/
broadhead weight."_

If you look very closely at what is being said here, and of course if you don't have an agenda, you will notice that there are a number of things listed, in this case for an arrow that is impacting too far to the left.

Three of the things actually *change* *the flex of the arrow*. Those are:

1. Increase bow weight or brace height. This *increases* the amount of force applied to the arrow, *increasing* the amount of flex. 

2. Decrease your bow string strands/weight. This also slightly *increases* the amount of force applied to the arrow, *increasing* the amount of flex,

3. Increase your insert/field point/broadhead weight. This slightly *increases* the amount of resistance to the force being applied to the arrow, *increasing* the amount of flex.

The two things that you seem to be hanging on to for dear life, which are decrease the spring tension on your cushion plunger, or moving your
centershot/shelf strike plate in toward the bow, *does nothing to increase or decrease the amount of flex*, it only *compensates* for the amount of flex that the arrow already has, and therefore allows the arrow (in this case, a shaft that is too stiff) to impact more to the right. Let me repeat. *You have done nothing to change the flex of the arrow,* you have just provided more space, laterally, for it to do what it's doing anyway. You have in effect, moved your arrow to the right, to compensate for an arrow that is hitting left.

Its like a right hand golfer that has a slice. You can set up and aim to the left, therefore compensating for the flight path of a ball that is slicing. It will indeed make the ball go where you want it to go, but you have done *NOTHING* to correct (change) the slice. You've simply made the slice that you already have playable.

Nothing different here. You can either *CHANGE* the amount of flex, *OR* you can adjust your centershot to make the flex that you already have playable.

KPC


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## GEREP (May 6, 2003)

Live In a Park said:


> The only massive force is at the nock end. The tiny "force" of the arrow is, as you pointed out, "an object at rest tends to stay at rest." The column will compress, but given the normal materials it will be very, very miniscule, probably all in the nock. If there is no force vector other than perfectly through the axis (and the materials are uniform), all that happens is compression. (Love a good physics discussion!)


Ha...I HATED physics. 

So, we can conclude that because the string rolling off the fingers forces the string to move laterally, it guarantees that the force will not be perfectly aligned through the axis if the arrow. Therefore you will, without a doubt, experience flexion, regardless of degree of centershot one's sight window might have. If you want to actually *alter* the flex, you will either have to better align the string (force) to the axis of the arrow (such as with a mechanical release), alter the force applied(to one end of the arrow shaft or the other), or alter the stiffness of the arrow shaft itself, correct?

KPC


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## Sanford (Jan 26, 2009)

GEREP said:


> Ha...I HATED physics.
> 
> So, we can conclude that because the string rolling off the fingers forces the string to move laterally, it guarantees that the force will not be perfectly aligned through the axis if the arrow. Therefore you will, without a doubt, experience flexion, regardless of degree of centershot one's sight window might have. If you want to actually *alter* the flex, you will either have to better align the string (force) to the axis of the arrow (such as with a mechanical release), alter the force applied(to one end of the arrow shaft or the other), or alter the stiffness of the arrow shaft itself, correct?
> 
> KPC


No, by the very degree the angle of shaft is to the loads at both ends, which induces bend, bend is altered by altering the strike position, or angle of the shaft by moving the front away from or in to the load centerline. You are contradicting yourself when you say the angle (not perfectly aligned) is good for one dynamic but has no effect on another.


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## drifter410 (May 7, 2010)

well if your new at tuning and you were confused before now your well.


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## GEREP (May 6, 2003)

Sanford said:


> No, by the very degree the angle of shaft is to the loads at both ends, which induces bend, bend is altered by altering the strike position, or angle of the shaft by moving the front away from or in to the load centerline. You are contradicting yourself when you say the angle (not perfectly aligned) is good for one dynamic but has no effect on another.


Right. And when a drive aimed at the left rough, ends up in the middle of the fairway, I guess you've *altered* your slice. 

By the way, I don't remember ever saying that one thing was good for one dynamic and has no effect on the other. What I said was that one thing *changes* the dynamic and one thing *compensates* for it.

But hey, don't let the facts get in the way of a good story. You're on a roll.



KPC


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## rmccutchan (Mar 29, 2014)

If I am understanding all of this correctly, this would be referring to something like parallax error, like in old cameras where the viewfinder is on top of the camera? You don't actually take a picture of what you see in the viewfinder since the lens is on a different plane, so you have to learn how to adjust the angle at which you shoot, which is why SLR cameras were invented. Is this correct?


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## GEREP (May 6, 2003)

rmccutchan said:


> If I am understanding all of this correctly, this would be referring to something like parallax error, like in old cameras where the viewfinder is on top of the camera? You don't actually take a picture of what you see in the viewfinder since the lens is on a different plane, so you have to learn how to adjust the angle at which you shoot, which is why SLR cameras were invented. Is this correct?


Actually, not really. 

From what I know, a *parallax error* is actually an error in the way something seems to appear. In other words, an object appears to be in a position that it is not.

*"Archer's paradox"* is the contradiction between where an arrow *actually is* pointed, and where it *actually does* impact.

Having said that, a parallax could actually create a paradox, but I'm not sure the reverse can also be true.



KPC


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## BLACK WOLF (Aug 26, 2005)

Newton "For every action, there is an equal and opposite reaction." :wink:

Ray :shade:


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## Sanford (Jan 26, 2009)

GEREP said:


> What I said was that one thing *changes* the dynamic and one thing *compensates* for it.
> 
> But hey, don't let the facts get in the way of a good story. You're on a roll.
> 
> ...


Compensate what? Tuning is changing the cycle rate, or initial bend to match initial force, to clear the riser properly and fly straight. If it's not changing the bend, it's not changing the cycling. The facts are in the tuning manuals you say are incorrect. The facts are in that posted paper by a PhD researcher and fellow archer, but I guess incorrect as well. The facts are that it's crazy that something as well known as changing centershot, which has a direct change on dynamic spine, is now incorrect and without anything supporting the reason everyone else is wrong.

Personally, I've been down the path with you before on other issues, so changing your view is not a concern. The ones who are learning tune need the correct info, though.


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## GEREP (May 6, 2003)

Sanford said:


> *Compensate what? * Tuning is changing the cycle rate, or initial bend to match initial force, to clear the riser properly and fly straight. If it's not changing the bend, it's not changing the cycling. The facts are in the tuning manuals you say are incorrect. *The facts are in that posted paper by a PhD researcher and fellow archer, but I guess incorrect as well.* The facts are that it's crazy that something as well known as changing centershot, which has a direct change on dynamic spine, is now incorrect and without anything supporting the reason everyone else is wrong.
> 
> Personally, I've been down the path with you before on other issues, so changing your view is not a concern. The ones who are learning tune need the correct info, though.


I know how badly you need to "win" this conversation Sanford, after all, I'm familiar with your path also.

Interestingly enough, I'm *NOT* disagreeing with what was stated in the paper you referenced. I'm actually *agreeing* with it. It's just that you're apparently not understanding what you are reading.

Let's take a look at what he actually says.

_"*If however the stiffness of the plunger button is correctly chosen to compensate for the deflection error caused by the fingers upon release,* the arrow would be aligned to the path of the center-of-mass, the bare shafts would group with the vaned shafts and the equipment would be tuned."_

I've read that paper thoroughly Sanford, and contrary to what you keep saying, and what you keep hoping for, nowhere does it what you are insisting that it says. 

_*The mechanics of arrow deformation at the instant of release is illustrated in Figure 9. The tail of the arrow is deflected sideways by the fingers. The amount and the repeatability of the deflection is determined by the skill of the archer. The sideways deflection and the load from the bowstring in a direction along the shaft causes the shaft to buckle slightly. The amount of buckling depends on the flexural stiffness of the shaft, the amount of any mass pile at the tip or tail, and (to a lesser extent) the mass of the shaft itself....

...The deformation of the arrow upon release creates the same effect as depressing the plunger button in altering the flight path of the arrow by changing the path of its center-of-mass. The compliance of the arrow can thus be added to the compliance of the plunger button in much the same way as would be springs in series. If their combination is overly stiff, the tail of the arrow initially will leave the bow oriented to the right of trajectory of the arrow center-of-mass (for a right-hand release) and the bare shafts will group to the left of the vaned shafts. The two groups can be forced to merge by reducing the flexural stiffness of the arrow, or the plunger button, or both.*_

As referenced above, there a number of instances where the Dr. describes ways to *alter the flex* of the arrow, however adjusting centershot and plunger position/stiffness aren't included in them. However, he does also mention several times that these can be used to *compensate for* or *alter the flight path of * an arrow that is *already* flexing. 

Which is of course what I have been saying all along.

KPC


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## Sanford (Jan 26, 2009)

Yep, GEREP, that's how a plunger changes tune, by changing the relationship of tip to center of force, or center of mass as he describes. In manual methods, old school, we set it by thickness of side plate and it's fixed in position. He's saying "compensation" from the plunger, not compensation in centershot location. The dynamic spine changes. Same thing.


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## GEREP (May 6, 2003)

http://www.eastonarchery.com/uploads/downloads/Tuning_Guide/Tuning_Guide.pdf

Here is an good guide for you to read Sanford. 

It's a lengthy read but they're saying the same thing the Dr. is saying, only in easier to understand terms. Page 2 and 3 clearly explain (pictures included) that plunger position, plunger tension, and centershot are all used to position the arrow in such a way that when the arrow leaves the bow, the nodes are in line with the target. They don't do anything to alter the flex of the arrow, it's just to make sure that when the arrow does flex, the nodes are in direct alignment to the target.

If you can find where they suggest that adjusting centershot in any way affects or alters the actual flex of the arrow, I'd sure like to see it.

Just out of curiosity, what do you do for a living, or if retired, what was your previous profession?

KPC


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## chetduggan (May 12, 2014)

Wow, boring Sunday night and I just read this entire thread. Not sure if I'm over stimulated or what, but as I started to doze off it occurred to me; I wonder if there is such a thing as "Target Paradox"? Does the deer say, " hahaha he'll never hit me, he's not aiming right". THWACK! "Oh ****!"


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## Hiram (Jul 31, 2013)

Pretty much what everyone has tried to tell you in this whole thread! Pretty much for the sake of argument or other meaningless ventures to twist the english language around some like my Mother in Law,,Funny actually,,


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## Hiram (Jul 31, 2013)

BLACK WOLF said:


> Newton "For every action, there is an equal and opposite reaction." :wink:
> 
> Ray :shade:


Hey RAY,,Was it Murphy that showed up dressed informally?,,,good Sunday to you and I totally agree!:cocktail:


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## GEREP (May 6, 2003)

BLACK WOLF said:


> Newton "For every action, there is an equal and opposite reaction." :wink:
> 
> Ray :shade:


Actually Ray, While I agree that *Newton's Third Law of Motion* is indeed at play here, it applies more to personalities than the subject at hand. In other words, when one person (me, in this case) says one thing, there are others (who will remain nameless) that will argue the exact opposite...no matter what. In this case, I suspect Newton was right. :wink:

In terms of the discussion topic, I think *Newton's Second Law of Motion* is more applicable.

_*"The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object."*_

-----------------------------------------------------------

Now, having said that, a lot of people don't know this but *Isaac Newton* had a brother by the name of *Fig.*

While *Fig Newton* probably wasn't as smart as his brother, he had a number of rather profound theories also.

_*"The number of moronic statements uttered tends to be in direct proportion to alcohol consumed."*_

_*"The wronger one is, the louder he gets."*_

_*"Profanity is the effort of a feeble brain to express itself forcibly"*_

Actually, I know the first two are Fig's, but I think that last one might be *Spencer Kimball's.*

:wink:

KPC


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## BLACK WOLF (Aug 26, 2005)

You forgot the most important one of all.....It's ALL about the G.A.P. :wink:

ALL of life's mysteries are hidden within the acronym :wink:

Ray :shade:


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## Sanford (Jan 26, 2009)

The problem we have is that Newton was way before the discovery of a new force, "compensation", where an arrow can change tune without it's dynamic spine being altered, which previously required a change in force acting on it to get the same result.


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## GEREP (May 6, 2003)

Sanford said:


> The problem we have is that Newton was way before the discovery of a new force, "compensation", where an arrow can change tune without it's dynamic spine being altered, which previously required a change in force acting on it to get the same result.


Did you find anything in the *Easton Arrow Tuning and Maintenance Guide* that suggests that adjusting centershot in any way affects or alters the actual flex of the arrow? If you did, I'd sure like to see it.

Maybe it's that you just don't think Easton knows anything about arrow tuning, or maybe you don't realize that you can change the tune of a *system* without changing the action of every *component* within that system, or maybe you are just interested at this point of deflecting attention.

*HEY LOOK...THERE'S A SQUIRREL!!*

KPC


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## Sanford (Jan 26, 2009)

GEREP said:


> Did you find anything in the *Easton Arrow Tuning and Maintenance Guide* that suggests that adjusting centershot in any way affects or alters the actual flex of the arrow? If you did, I'd sure like to see it.
> 
> Maybe it's that you just don't think Easton knows anything about arrow tuning, or maybe you don't realize that you can change the tune of a *system* without changing the action of every *component* within that system, or maybe you are just interested at this point of deflecting attention.
> 
> ...


Nice diversion and funny, but let's help folks who are looking for answers understand more about tuning and stay on common ground. 

Way back, I asked about compensation you mentioned. Maybe more in order is a description of how compensation differs from altering the forces acting on an arrow during its launch, since we all have common ground that the tune does change when we move centershot location.

The arrow's tune is ultimately in the arrow alone, when it's alone. It's the forces acting on it to change its tune, or not, we are talking about.

If as you say, the dynamic spine is set in the arrow only, and doesn't change its flex with centershot, then barring a clearance issue, it then wouldn't matter to centershot what bow we shot it from, it would fly straight and be in tune across bows. We know from tuning that ain't how it works.


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## GEREP (May 6, 2003)

Sanford said:


> Nice diversion and funny, but let's help folks who are looking for answers understand more about tuning and stay on common ground.
> 
> Way back, I asked about compensation you mentioned. Maybe more in order is a description of how compensation differs from altering the forces acting on an arrow during its launch, since we all have common ground that the tune does change when we move centershot location.
> 
> The arrow's tune is ultimately in the arrow alone, when it's alone. It's the forces acting on it to change its tune, or not, we are talking about.



Yes, in the same way that a sliced golf ball aimed at the rough ends up in the fairway. Once it leaves the clubface, it's "alone," but the action of the ball has not changed. It's still slicing just like it always has, you've just compensated for it.

An arrow is going to flex, just like it always has. By adjusting centershot (or making sure that the nodes line up with the target) you are just compensating for where it ends up.

KPC


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## Sanford (Jan 26, 2009)

Gerep, it's the changing of the flex that makes the nodes line up and stay in line during flight. By adjusting centershot, you are changing and altering that flex. That's the whole basis of the Archer's Paradox, the arrow is aligned one way but follows the path from the the point to the target. Flex, dynamic action of the arrow, is the answer to the paradox. If not, x# amount of draw weight on x-amount of dynamic spine of arrow would solve the paradox for any alignment.


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## BLACK WOLF (Aug 26, 2005)

If an archer is compensating for something...they are basically changing or modifying something...and for every action, there will be an equal and opposite reaction :wink:

Ray :shade:


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## GEREP (May 6, 2003)

Sanford said:


> Gerep, it's the changing of the flex that makes the nodes line up and stay in line during flight. By adjusting centershot, you are changing and altering that flex.


I'll let you take that one up with Easton. Apparently they don't know as much as you. I'm sure they'll very much appreciate you schooling them on that.

I'm done with this one, unless of course anyone has anything substantive to add.

KPC


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## Sanford (Jan 26, 2009)

Gerep, all that Easton was telling you was that for a fingershot bow, the arrow is set outboard of string center (diagram of doing so with a centershot bow using fingers), and that for a release shot bow it's set on string center. We already know that principle from many discussion here on minimal string/arrow alignment. The node alignment, or tune, is not dependent to centershot, or close center, though, as it's part of tune on many bows with many different degrees cut to center. There's nothing to take up with Easton, as they are correct in there description and advice.


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## GEREP (May 6, 2003)

Sanford said:


> Gerep, all that Easton was telling you was that for a fingershot bow, the arrow is set outboard of string center (diagram of doing so with a centershot bow using fingers), and that for a release shot bow it's set on string center. We already know that principle from many discussion here on minimal string/arrow alignment. The node alignment, or tune, is not dependent to centershot, or close center, though, as it's part of tune on many bows with many different degrees cut to center. There's nothing to take up with Easton, as they are correct in there description and advice.


Riiiight.










So let's see, for a recurve shot with fingers (RF), in this example, if the nodes don't line up, it's because the arrow *"is out too far."* Why? Because of an *"incorrect arrow rest position."*

Gosh, I wonder how one would correct an incorrect arrow rest position, that has the arrow out too far?

Hmmmmm...

KPC


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## Sanford (Jan 26, 2009)

If the arrow is going to flex the same amount either way, unless it's striking the rest on exit, what does it matter how you align it to make the arrow go straight- no change in flex from strike position should be no change in flex? Right? We're not worried about the aim point, we're wanting a straight flight path to the aim point.

Somehow, you seem to be telling us that the starting point of the head has a bearing on the ending point of the tail during a flex. That sounds familiar.


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## GEREP (May 6, 2003)

Sanford said:


> If the arrow is going to *flex the same* amount either way, unless it's striking the rest on exit, what does it matter *how you align* it to make the arrow go straight- no change in flex from strike position should be no change in flex? Right?











Same slice (flex), different alignment (rest position).

Not rocket science.

Have a nice evening Sanford.

*FORE!!*

KPC


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## Nekekal (Dec 25, 2012)

So, do we want to align with center or not? The bickering has me confused. It still seems to me from the physics, and given the arrow is going to flex from being driven off by the fingers that what a person wants is center shot with an arrow just flexible enough to clear the riser. The nodes would be in alignment, as would probably the stars.


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## DDSHOOTER (Aug 22, 2005)

Here, I going to throw this in: copied from IBO Trad Rules.

"c. No stabilizers, counterbalances, or weights of any kind may be attached or built into the bow,
except a quiver clearly designed to hold arrows. Arrows shall be shot off the hand or shelf of the riser
only. An arrow side plate (if used) may only extend one (1) inch above the arrow. *No soft materials that
will assist or affect the paradox of the arrow may be used to build up the shelf or strike plate of the riser.
Archers may use a hard material on the shelf or on the side of the riser under a hair or leather strip that
does not exceed 1/8” thickness.* The shelf may not be built up in a manner that will give the archer an
advantage in terms of feather or vane clearance. The intent is that the shelf meets the side of the riser
(strike plate) so the built-up shelf may not be a pyramid that provides clearance and separation from the
bow riser. Recurve archers will shoot from the orange stake."

Now why would you want to assist or affect Paradox?
or
Could their meaning be that soft material will dampen the effects of arrow Flexion. Also, why limit the hard materal to only 1/8" under the soft material". Some riser are cut past center shot would not make it back past center shot, let alone one shaft if you use Axis or some other small shaft. Larger shaft only. They didn't say that did they? Why wouldn't you want the front Node of the arrow to be directed towards the target? Does Easton know this? Maybe that's not the Traditional way. Making thing harder than they should be. They said no rest? no shoot thru, no shoot around, no dropaway, no SS launger Blade. These things have little effect on the arrow flexion.
Dan


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## Hiram (Jul 31, 2013)

I'm not confused at all, everybody knows NOT to argue with your mother in law,,you can NEVER win! lol


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## GEREP (May 6, 2003)

Hiram said:


> I'm not confused at all, everybody knows NOT to argue with your mother in law,,you can NEVER win! lol


Come on Sam, don't talk about Sanford that way.

First of all, he's kinda sensitive, and second, it's not nice to mock your mother-in-law.



KPC


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## GEREP (May 6, 2003)

Dan:

First of all, the 1/8" limit is for the hair or leather strip. The "hard material" can be as thick as you want it to be.

The reason they have the rule about the "soft material" is they don't want an overly soft sideplate to act as a cushion plunger (which is of course illegal in the trad classes)

KPC


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## DDSHOOTER (Aug 22, 2005)

GEREP said:


> Dan:
> 
> First of all, the 1/8" limit is for the hair or leather strip. The "hard material" can be as thick as you want it to be.
> 
> ...


That's not how I read it.

KPC, you know I have my Titan setup like yours, furniture padding. And if I remember right you were told it was illegal.
Dan


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## Sanford (Jan 26, 2009)

DDSHOOTER said:


> Now why would you want to assist or affect Paradox?
> or
> Could their meaning be that soft material will dampen the effects of arrow Flexion. Also, why limit the hard materal to only 1/8" under the soft material". Some riser are cut past center shot would not make it back past center shot, let alone one shaft if you use Axis or some other small shaft. Larger shaft only. They didn't say that did they? Why wouldn't you want the front Node of the arrow to be directed towards the target? Does Easton know this? Maybe that's not the Traditional way. Making thing harder than they should be. They said no rest? no shoot thru, no shoot around, no dropaway, no SS launger Blade. These things have little effect on the arrow flexion.
> Dan


The strike plate is the load bearing surface that along with the inertia of the pile, create the bend from forward force of the string and limbs. The amount of string deflection sets the offset in force at the tail end from the opposing force (strike and pile) at the front end. The deflection and column loading work in tandem. Move the front end either way and you affect the column loading.

Now, why would you want to assist this. It's because the deflection is supposed to be the constant, but we as humans are not constantly consistent, so having a compensating force, soft material or plunger action, within a fixed force, the strike, creates a buffer to the human error in deflection.


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## DDSHOOTER (Aug 22, 2005)

Sanford said:


> The strike plate is the load bearing surface that along with the inertia of the pile, create the bend from forward force of the string and limbs. The amount of string deflection sets the offset in force at the tail end from the opposing force (strike and pile) at the front end. The deflection and column loading work in tandem. Move the front end either way and you affect the column loading.
> 
> Now, why would you want to assist this. It's because the deflection is supposed to be the constant, but we as humans are not constantly consistent, so having a compensating force, soft material or plunger action, within a fixed force, the strike, creates a buffer to the human error in deflection.


Good argument, but I can shoot off a Dropaway or launcher plate with fingers. I have the dropway on the compound right now. 
Dan


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## Sanford (Jan 26, 2009)

DDSHOOTER said:


> Good argument, but I can shoot off a Dropaway or launcher plate with fingers. I have the dropway on the compound right now.
> Dan


Sure! The explanation I posted was just the classical, textbook science behind the dynamics. Not all involved, as there are many more, just the basics. 

BTW, it came right from the citations that made up the Wikipedia article Gerep posted, but don't tell him.  Now, that being said, what we can achieve or get away with is not conditioned on that, either.


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## GEREP (May 6, 2003)

DDSHOOTER said:


> That's not how I read it.


There are two parts of the sentence Dan. The 1/8" thickness apples to the hair or leather strip.


"Archers may use a hard material on the shelf or on the side of the riser *under a hair or leather strip that
does not exceed 1/8” thickness."*




DDSHOOTER said:


> KPC, you know I have my Titan setup like yours, furniture padding. And if I remember right you were told it was illegal.
> Dan


Actually, no. Mine is legal for IBO *"combined"* events. What it isn't legal for is IBO *"trad only"* events.

It is my understanding that would even be legal for *"trad only"* events if...

The pads were no more than 1/8" thick.

There is NO space between the shelf pad and the side plate pad.

I guess it depends whether an official would consider a felt pad softer than something like leather or Bear hair. 


Here is what it says for each type of event.

*IBO combined events:

"The shelf may be built up and the side plate may be built out with a hard material that has a minimal consistency of wood. The shelf and side plate may be covered with a softer material that is no thicker than 1/8 inch. TRD archers will shoot from the orange stake."*


*IBO Trad only events:

"No soft materials that will assist or affect the paradox of the arrow may be used to build up the shelf or strike plate of the riser. Archers may use a hard material on the shelf or on the side of the riser under a hair or leather strip that does not exceed 1/8” thickness. The shelf may not be built up in a manner that will give the archer an advantage in terms of feather or vane clearance. The intent is that the shelf meets the side of the riser (strike plate) so the built-up shelf may not be a pyramid that provides clearance and separation from the bow riser."*

If you ask me, the difference between events makes no sense. They should just decide on what they want, keep in consistent between both events, and be done with it.

But they don't ask me...nor should they.

KPC


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## GEREP (May 6, 2003)

Sanford said:


> The strike plate is the load bearing surface that along with the inertia of the pile, create the bend from forward force of the string and limbs. The amount of string deflection sets the offset in force at the tail end from the opposing force (strike and pile) at the front end.





DDSHOOTER said:


> Good argument, but I can shoot off a Dropaway or launcher plate with fingers. I have the dropway on the compound right now.
> Dan


Bingo Dan. No matter how many times Sanford says that the strike plate creates the opposing force that causes the arrow to flex, he still cannot explain then, why a finger shot arrow, shot off a drop away rest, *still flexes.* 

It's just a mystery I guess, either that or it's just part of that thing they call "trad mojo."

:wink:

KPC


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## Mo0se (Sep 24, 2002)

Matt_Potter said:


> You guys are going to hurt your brains - bare shaft at 25 - disengage brain - go shoot


Yes :thumbs_up


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## DDSHOOTER (Aug 22, 2005)

GEREP said:


> Bingo Dan. No matter how many times Sanford says that the strike plate creates the opposing force that causes the arrow to flex, he still cannot explain then, why a finger shot arrow, shot off a drop away rest, *still flexes.*
> 
> It's just a mystery I guess, either that or it's just part of that thing they call "trad mojo."
> 
> ...


We know feather clearance is not a problem because of paradox. If you bare shaft tune correctly the front and rear of the arrow will clear the riser.

Also, Sanford is only half right.

The other part that both of you miss is why come I can shoot off the lizard tongue rest. It has no side plate. The reason being is the front dynamic node. Remember it and the rear doesn't move in respect to the target. The shaft bends around these points. Which means the shaft can be shot at center shot with finger no side force. Now if the launcher is forward or back of that point the lateral finger pressure will force the anti-nodes in the opposite direction.
Dan


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## grapplemonkey (Nov 2, 2005)

DDSHOOTER said:


> We know feather clearance is not a problem because of paradox. If you bare shaft tune correctly the front and rear of the arrow will clear the riser.
> 
> Also, Sanford is only half right.
> 
> ...


Kev actually touches on that in one of his replies.


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## GEREP (May 6, 2003)

DDSHOOTER said:


> The other part that both of you miss is why come I can shoot off the lizard tongue rest. It has no side plate. The reason being is the front dynamic node. Remember it and the rear doesn't move in respect to the target. The shaft bends around these points. Which means the shaft can be shot at center shot with finger no side force. Now if the launcher is forward or back of that point the lateral finger pressure will force the anti-nodes in the opposite direction.
> Dan











Dan:

That's what this illustration from the Easton guide is in reference to.

This illustrates *"incorrect arrow rest position,"* which causes the front and rear nodes to be out of alignment with the target. The front node is *"out to far"* in relation the rear node, which is of course fixed by the string. The only way to correct this problem is to adjust the centershot, bringing the front node in alignment with the rear node. This can be achieved by using a thinner side plate, or adjusting the plunger. (not the tension of the plunger, but the position)

KPC


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## Sanford (Jan 26, 2009)

DDSHOOTER said:


> The other part that both of you miss is why come I can shoot off the lizard tongue rest. It has no side plate. The reason being is the front dynamic node. Remember it and the rear doesn't move in respect to the target. The shaft bends around these points. Which means the shaft can be shot at center shot with finger no side force. Now if the launcher is forward or back of that point the lateral finger pressure will force the anti-nodes in the opposite direction.
> Dan


Dan, that makes sense in the inertial support at the front, and it should mean you are tuning from a condition not unlike with a mechanical release, since you are on center with the shaft. I can see your explanation. 

I would suspect you have a good release at the fingers as well. Also, if it is with your compound, the string deflection is minimized some by the take-up of string by the cam and wheels sucking the string back in and no limb deflection that long limb bows have. Not saying impossible under conditions with a recurve, though. 

IOW, with a perfect shaft selection, excellent release, and minimizing string deflection, the difference between your finger shot and a mechanical release are showing near the same, which is a testament to your shooting and shaft selection as well.


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## GEREP (May 6, 2003)

Dan:

This is kind of a crude and out of proportion, but using Easton's illustration this shows what I am referring to.









If the black represents the sideplate, and the blue represents the riser, you can see how adjusting the thickness of the sideplate will bring the nodes more in alignment to the target. 

The arrow is gong to flex the same due to the lateral movement of the string off the fingers, but by adjusting the centershot (bringing the nodes in alignment), you are going to change the flight path of that arrow. Yes, you've *"tuned"* the system, but you really haven't changed the *flex* of the arrow. It's going to go through it's same oscillations, it's just that by re-aligning the shaft from the start, you change the flight path of that arrow, oscillations and all.

Now, having said that, this doesn't mean the flight is now going to be perfect. If the arrow is still too stiff or weak, you might have to go to a heavier/lighter point, lighter/heavier string, higher/lower brace height, etc. This *WILL* change the *flex* of the arrow because you are changing the force applied to it. Either from the back end (acclelleration) or from the front end (weight/resistance).

Depending on how the riser is cut, you may never get to a position where the nodes are perfectly aligned to start with. This is going to be the case with pretty much all risers that aren't cut past center. This is where pretty much all the "tuning" is going to have to be done with the arrow and not with the bow. This is what I was referring to when I was talking about tuning the arrow to the bow, or tuning the bow to the arrow.

For example, on many older style longbows, or recurves that aren't even cut *to* center, there aren't many, if any adjustments to be made on the bow, unless of course you want to break out the rasp. You are going to pretty much have to do *all* your "tuning" with the arrow. Spine, tip weight, arrow length, etc. In other words, you tune the arrow to the bow.

KPC


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## gjlama94 (Oct 11, 2013)

GEREP said:


> Bingo Dan. No matter how many times Sanford says that the strike plate creates the opposing force that causes the arrow to flex, he still cannot explain then, why a finger shot arrow, shot off a drop away rest, *still flexes.*
> 
> It's just a mystery I guess, either that or it's just part of that thing they call "trad mojo."
> 
> ...


Do you know how the drop works practically speaking?

The drop away feature is for fletching clearance. What do you think that implies regarding it's ability to provide an opposing force to flex the arrow?

Remember, we are dealing with the real world, not a theoretical one where the rest drops instantaneously upon arrow loose.


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## GEREP (May 6, 2003)

gjlama94 said:


> What do you think that implies regarding it's ability to provide an opposing force to flex the arrow?


While I'm quite certain other(s) will disagree, my opinion is that it doesn't apply any opposing force at all. It's just too flexible. It's only there to position the arrow for launch.






If this arrow was shot with fingers, it would flex laterally, just like any other arrow shot with fingers.

KPC


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## gjlama94 (Oct 11, 2013)

Also, regarding arrow compression and the angle of the arrow with regards to the string...

If you lay the arrow so it is perpendicular to the string force, I think we can agree that no compression along the length of the shaft takes place.

Now, orient the arrow so it is 45 degrees to the force of the string. Roughly half the string force goes towards compressing the arrow along it's length.

Now, align the arrow with the steing force and we have 100% of the string force working to compress the arrow.

Shouldn't be hard to see that building out the rest, or pushing out the plunger will change the angle between the arrow and the string force.

Practically speaking, how big an affect does it have? Probably not a lot. I won't say that its none, perhaps thr effect is only detectable with increased skill.


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## gjlama94 (Oct 11, 2013)

GEREP said:


> While I'm quite certain other(s) will disagree, my opinion is that it doesn't apply any opposing force at all. It's just too flexible. It's only there to position the arrow for launch.
> 
> 
> 
> ...


Think that video pretty conclusively demonstrates there is plenty of opposing force. If there wasn't, the arrow would have pushed it down.

If you watch, you can see the arrow has flexed away from the rest when it begins to drop, just in time for the fletchings to zip by untouched.


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## GEREP (May 6, 2003)

gjlama94 said:


> Practically speaking, how big an affect does it have?


Practically? I'd say virtually none. In the *grossly exaggerated* scenario that you describe, yes. However, in the minute degrees that we are talking about, not to mention the inherent inconsistencies of a human being drawing and releasing an arrow...even with a mechanical release, it would likely be impossible to even measure. *Certainly* not with a finger release.

On a computer program maybe. Even with the best of the best of the best archers, not very likely. If we could duplicate what happens on a computer program or a calculus equation, everyone in the Olympics would be tied for first place.

:wink:

KPC


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## Sanford (Jan 26, 2009)

gjlama94 said:


> Practically speaking, how big an affect does it have? Probably not a lot. I won't say that its none, perhaps thr effect is only detectable with increased skill.


There are two main players, well, many more, but two main ones. Here's from the actual research on that issue just on the second:

“The *second cause* of the bending of the arrow is related to the *width of
the rigid middle part of the bow*, called the grip or handle. When we 
Consider a classical bow in fully drawn position, the arrow will *form a
small angle* with the median plane of the bow. After release this angle increases 
swiftly because the distance between nock and grip decreases swiftly.

Then again by inertia the arrow will bend. The bending resulting from
The two mentioned causes is increased by the large *longi-tudinal force* exerted by the string on the nock. 

This force has a *buckling effect* on the arrow.”

_1 Journal of Engineering Mathematics 31 (4):285-306 (1997)_

I would add that the angle decreasing rapidly is only for a brief period, because as the arrow flexs back the other way, it comes away from the strike position.

And, to note: Before we got off into centershot bows, we were discussing Archer's Paradox, which relates to a non-centershot condition. The derail on different dynamics made for a good disussion, but never really changed the original dynamics under discussion.


----------



## GEREP (May 6, 2003)

gjlama94 said:


> Think that video pretty conclusively demonstrates there is plenty of opposing force. If there wasn't, the arrow would have pushed it down.
> 
> If you watch, you can see the arrow has flexed away from the rest when it begins to drop, just in time for the fletchings to zip by untouched.


Really? Watch what happens when that rest simply falls against the riser. Watch how it contorts when it makes contact with the shelf. If it is flexible enough to contort, pretty much under it's own weight, do you really think it is stiff enough to remain rigid at the moment of release, if there was any down force against it?

KPC


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## GEREP (May 6, 2003)

Sanford said:


> There are two main players, well, many more, but two main ones. Here's from the actual research on that issue just on the second:
> 
> “The *second cause* of the bending of the arrow is related to the *width of
> the rigid middle part of the bow*, called the grip or handle. When we
> ...


Would you mind posting the *"first cause"* so we can read it in context. 

I tried to download your sourse, but my computer doesn't support the file.

Thank you

KPC


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## Sanford (Jan 26, 2009)

GEREP said:


> Would you mind posting the *"first cause"* so we can read it in context.
> 
> I tried to download your sourse, but my computer doesn't support the file.
> 
> ...


Gerep, the first cause is the inertial bending from lateral deflection. That begins the offset. Inertial bending is going to happen, just in slight amounts, horizontally or linear. We can only speculate the amount, given variable conditions of arrow and bow. 

Key, is this last sentence: "The *two* mentioned causes *is increased* by the *large longi-tudinal force* exerted by the string on the nock." 

Inertial bending, either vector, cannot explain the full amount of bending needed except in center or close-center conditions.

Not sure why it won't download for you. It's in PDF. 

It's one of the citations that made up that Wikipedia info you posted in your first post. Check the bottom citation page for the link.


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## GEREP (May 6, 2003)

I'll have to check it out later...have to see a client.

Believe it or not, some things do take precedence.

KPC


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## gjlama94 (Oct 11, 2013)

GEREP said:


> Really? Watch what happens when that rest simply falls against the riser. Watch how it contorts when it makes contact with the shelf. If it is flexible enough to contort, pretty much under it's own weight, do you really think it is stiff enough to remain rigid at the moment of release, if there was any down force against it?
> 
> KPC


If the rest isn't stiff enough to support the downward presdure from the arrow, why doesn't it drop immediately rather than after 3/4 of the arrow has passed over it AND after the arrow flexes away from it.

If the rest was that flimsy, it could never stay up that long- the arrow should push it down if your contention is accurate.

Doesn't matter what the rest does AFTER it goes down and strikes the shelf.


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## DDSHOOTER (Aug 22, 2005)

If it to stiff it will bounce. If it to weak. Well you get the picture. If it launches were it's neither then it does matter that much unless your at or near the two extremes.

The video is not just showing you have describe it also show the bow nock travel and in some case cam lean. I wish I could find, like the one with the long bow in the beginning of the thread, were a release shooter shoot a weak and extra stiff shafts.

Kev, you have a point about the striker being out to far. Maybe that it what IBO is trying to do? Or someone else? The point is paradox, my mind, is not a good thing to have and this day and age it's a relic term.
Dan


----------



## Sanford (Jan 26, 2009)

gjlama94 said:


> If the rest isn't stiff enough to support the downward presdure from the arrow, why doesn't it drop immediately rather than after 3/4 of the arrow has passed over it AND after the arrow flexes away from it.
> 
> If the rest was that flimsy, it could never stay up that long- the arrow should push it down if your contention is accurate.
> 
> Doesn't matter what the rest does AFTER it goes down and strikes the shelf.


Here's a good article by Larry Wise on that situation with drop-aways on compounds. The paragraph on "arrow rest considerations" is the meat: http://arrowtrademagazine.com/articles/sept_12/Sept2012-DynamicArrowSpine.pdf

"The arrow touches the arrow rest for some amount of time during its forward
flight. This means the rest affects arrow bending and recovery, *making the rest a
rather important part of the dynamic spine equation*."


----------



## GEREP (May 6, 2003)

gjlama94 said:


> If the rest isn't stiff enough to support the downward presdure from the arrow, why doesn't it drop immediately rather than after 3/4 of the arrow has passed over it AND after the arrow flexes away from it.
> 
> If the rest was that flimsy, it could never stay up that long- the arrow should push it down if your contention is accurate.
> 
> Doesn't matter what the rest does AFTER it goes down and strikes the shelf.


Because most fall away rests are attached to a string or cable. It can't go down until the bow string returns to a certain point. It's the same thing that lifts the rest back up.

KPC


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## gjlama94 (Oct 11, 2013)

GEREP said:


> Because most fall away rests are attached to a string or cable. It can't go down until the bow string returns to a certain point. It's the same thing that lifts the rest back up.
> 
> KPC


Precisely.

Which gives it plenty of time to provide an opposing force to provide for arrow flex.


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## DDSHOOTER (Aug 22, 2005)

Sanford said:


> Here's a good article by Larry Wise on that situation with drop-aways on compounds. The paragraph on "arrow rest considerations" is the meat: http://arrowtrademagazine.com/articles/sept_12/Sept2012-DynamicArrowSpine.pdf
> 
> "The arrow touches the arrow rest for some amount of time during its forward
> flight. This means the rest affects arrow bending and recovery, *making the rest a
> rather important part of the dynamic spine equation*."


Or minimize the affects of the string and bow?
Dan


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## Sanford (Jan 26, 2009)

DDSHOOTER said:


> Or minimize the affects of the string and bow?
> Dan


Agree, it's all in relative degrees. 

A good point made from that research paper of Paradox was: 

"The results of the two causes of the bending of the arrow can intensify each other or reduce each
other. It's not difficult to see that they reduce each other...."

A guy shooting knuckle off a longbow has a different requirement than a center-shot compound, for sure.


----------



## DDSHOOTER (Aug 22, 2005)

Two picture's of my compound with dropaway. It is time to drop out at 4" before the fetching, approximately at the rear node. Shoot perfect holes in the paper, if I do my part and consistent thru the chronograph.














Dan


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## GEREP (May 6, 2003)

gjlama94 said:


> Precisely.
> 
> Which gives it plenty of time to provide an opposing force to provide for arrow flex.


That was my whole point. If the rest itself is flexible enough to contort when it hits the shelf, basically under it's own weight, surely it would flex if there any amount of down force on in from the arrow. It clearly doesn't flex at all.

KPC


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## gjlama94 (Oct 11, 2013)

GEREP said:


> That was my whole point. If the rest itself is flexible enough to contort when it hits the shelf, basically under it's own weight, surely it would flex if there any amount of down force on in from the arrow. It clearly doesn't flex at all.
> 
> KPC


Then I misunderstood what you were saying. I had the impression you were arguing a drop down rest doesn't provide an opposing force to the arrow which helps the arrow flex.


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## centershot (Sep 13, 2002)

It all boils down to timing - when the bow comes to brace at the shot, the arrow point has to be headed on the proper vector to hit the target. If it is off then you will get lefts and rights as the spine and arrow's paradox and point is not in time with the arrow releasing from the string. Once that arrow leave the string all acceleration is over and it is in tension instead of compression and is now just dragging along being pulled through the air by the point.


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## Sanford (Jan 26, 2009)

Center, a good diagram from Tony's book shows the BH changes and the effect (not the timing issue though):


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## centershot (Sep 13, 2002)

It always amazes me that it works at all, let alone with the precision and consistency that it happens with. Add to the degree that we can tune the bow/arrow combination is truly a physical wonder. Mathmatical nightmare that looks so simple and goes mostly unnoticed.


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## ranchoarcher (Sep 26, 2013)

Looking at that drop away video, the rest appears to be flexing a little bit as the arrow is passing by in the first part unless my eyes are playing tricks on me. Then too, there are quite a few other forces and levels of resistance in play, some unknown, that affect how the rest might move in one position under one load versus how it may react being slammed into the riser by a spring pulling it down.

Centershot, you got that right. If we had to understand what was going on to the level of detail being discussed and debated, there wouldn't be any archers.


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## DDSHOOTER (Aug 22, 2005)

Sanford said:


> Center, a good diagram from Tony's book shows the BH changes and the effect (not the timing issue though):


Sanford, if you pluck really, really hard you maybe able to straighten that sucker out. Other, than that the rest looks to be way out to far. Surely, ten times a shaft dia outside center shot. 

It this case I would stick with the manufacturer recommendation on BH. 2" might be a little low. lol
Dan


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## JINKSTER (Mar 19, 2011)

Here ya go....way overspined arrows...fletchings work wonders...but what was amazing was after the vid?...I discovered the more I canted my bow?....the straighter the bareshafts became.....I'm thinking because the lateral string movement was no longer dedicated to just a vertical plane...weird huh?


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## Hank (Jul 5, 2003)

You can point an arrow directly at the target with a non center shot bow, Jim Ploen explains this in an article originally published in the Instinctive Archer Magazine. To prove his point he shot arrows of various spine at a bullseye at 20 yards out of a 21st century longbow without the shelf cut in yet. The flight was not perfect on all the arrows but they did all hit the bullseye. The secret is in the grip and it works better with a longbow.

When Hill built his bows, he would rasp the side in until the arrows flew straight to the mark and they were far from center shot.

So much we do not understand about getting the arrow to it's mark and all the stupid stuff we come up with to try to


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## rattus58 (Jul 9, 2007)

Hank said:


> You can point an arrow directly at the target with a non center shot bow, Jim Ploen explains this in an article originally published in the Instinctive Archer Magazine. To prove his point he shot arrows of various spine at a bullseye at 20 yards out of a 21st century longbow without the shelf cut in yet. The flight was not perfect on all the arrows but they did all hit the bullseye. The secret is in the grip and it works better with a longbow.
> 
> When Hill built his bows, he would rasp the side in until the arrows flew straight to the mark and they were far from center shot.
> 
> So much we do not understand about getting the arrow to it's mark and all the stupid stuff we come up with to try to


Jim Ploem performed ceremonies over his bows and them arrows... something about scared straight..... :laugh:


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## DDSHOOTER (Aug 22, 2005)

rattus58 said:


> Jim Ploem performed ceremonies over his bows and them arrows... something about scared straight..... :laugh:


And Hill's 70lb long bow shot 265 fps.
Dan


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## Sanford (Jan 26, 2009)

Jinks, I don't think you changed the physics part unless you changed in form or how you torque the sting. You did change the geometry. What was a leftward travel out of plane now is in a different plane - same leftward gravitation, less left.


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## DDSHOOTER (Aug 22, 2005)

Sanford said:


> Jinks, I don't think you changed the physics part unless you changed in form or how you torque the sting. You did change the geometry. What was a leftward travel out of plane now is in a different plane - same leftward gravitation, less left.


It would be interesting if he stepped back 10-15 yards and repeated the test.
Dan


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## Hiram (Jul 31, 2013)

GEREP said:


> You're absolutely correct Easy. The other parts of the equation are shaft stiffness, shaft length, tip weight, and bow force or acceleration.
> 
> The amount of centershot has an impact on how the arrow ends up flying, but NOT how much it flexes.
> 
> KPC


Contradiction.


----------



## Hiram (Jul 31, 2013)

JINKSTER said:


> Here ya go....way overspined arrows...fletchings work wonders...but what was amazing was after the vid?...I discovered the more I canted my bow?....the straighter the bareshafts became.....I'm thinking because the lateral string movement was no longer dedicated to just a vertical plane...weird huh?



Because the more you rotated the bow to the right, the stiff reaction became vertical by nature of the Bow rotation.


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## rattus58 (Jul 9, 2007)

DDSHOOTER said:


> And Hill's 70lb long bow shot 265 fps.
> Dan


Yeah... I heard that... he was being chased by lions or something... moved pretty quick for an old guy...... :grin:


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## GEREP (May 6, 2003)

GEREP said:


> You're absolutely correct Easy. The other parts of the equation are shaft stiffness, shaft length, tip weight, and bow force or acceleration.
> 
> The amount of centershot has an impact on how the arrow ends up flying, but NOT how much it flexes.
> 
> KPC





Hiram said:


> Contradiction.


What contradiction? Please do explain. 

KPC


----------



## GEREP (May 6, 2003)

Sanford said:


> Jinks, I don't think you changed the physics part unless you changed in form or how you torque the sting. You did change the geometry.


Is that not the same thing you are doing when you adjust centershot? 

All other things remaining equal (form, torque, force, arrow length, tip weight, brace height arrow spine), you're not changing the *"physics part"*(flex) but your are changing the *"geometry"*(direction).

Whether or not that's the way it has *come* across, that is what I've been trying to *get* across. At least since the discussion became about something other than the difference between the meanings of *"archers paradox"* and *"arrow flex."* Which by the way, I don't think anyone can dispute, unless of course they are primarily in the business of self-aggrandizement. 

KPC


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## Sanford (Jan 26, 2009)

No, Gerep, not the same thing at all. He's just moving his bow, same as if he moved his sight. Nothing changed to tune.


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## GEREP (May 6, 2003)

sanford said:


> no, gerep, not the same thing at all. He's just moving his bow, same as if he moved his sight. Nothing changed to tune.


Okee Dokee

KPC


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## JINKSTER (Mar 19, 2011)

Hiram said:


> Because the more you rotated the bow to the right, the stiff reaction became vertical by nature of the Bow rotation.


BINGO!!!...GIVE THE MAN A CIGAR!!! :thumbs_up


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## Sanford (Jan 26, 2009)

JINKSTER said:


> BINGO!!!...GIVE THE MAN A CIGAR!!! :thumbs_up


Wow! Tight with them cigars. What happened to mine? Though, I will proudly say that my cigar habit was ended a couple weeks ago and holding so far.


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## GEREP (May 6, 2003)

Sanford said:


> The strike plate is the load bearing surface that along with the inertia of the pile, create the bend from forward force of the string and limbs.


I was actually going to move away from this discussion, however when doing a little research for another discussion, I came across this video.








If the above statement is accurate, and contact with the strike plate is necessary for the flex of the arrow to happen, what do you suppose causes this arrow to flex, when quite obviously the arrow never makes contact with the side plate?

KPC


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## DDSHOOTER (Aug 22, 2005)

Hiram said:


> Because the more you rotated the bow to the right, the stiff reaction became vertical by nature of the Bow rotation.


Not the same as slanting your anchor or your sight picture and do forget in some cases a smoother release/follow-thru.

Dan


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## JINKSTER (Mar 19, 2011)

GEREP said:


> If the above statement is accurate, and contact with the strike plate is necessary for the flex of the arrow to happen, what do you suppose causes this arrow to flex, when quite obviously the arrow never makes contact with the side plate?
> 
> KPC


"ANY"...miss alignment of the point weight from perfect dead center is going to cause a deflection of energy within the shaft itself.


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## Sanford (Jan 26, 2009)

Gerep, there's going to be some inertial reaction from the FOC at the pile and contact at the shelf/hand (see Dan's lizard tongue example). An arrow is a flexible beam. It's just not going to solve the Paradox. IOW, you can't solve what is a complex dynamic action from string deflection off the fingers alone except when there is a true centershot condition and near so in release.

I can take an arrow in my hand and with ease wiggle-bend it, so sure, a huge load of energy is going to induce the same. Comparative to force, the arrow's beam is miniscule in strength. That's why comparatively miniscule changes in inertia (pile), static spine, drag (which we have not even touched on), and force angle have so much effect. 

The flex needed to clear in a Paradox condition and cycle rate (Hz) needed for a straight arrow flight are tangent. Watch your slo-mo videos. When the arrow is clearing the bow, is it bending about the nodes or flexing irrespective of them? When if flight, is it cycling, flexing, everywhere but at the nodes?


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## GEREP (May 6, 2003)

Sanford said:


> Gerep, plain physics. Watch the arrow bend "into" the shelf wall (plunger) on first flex. Test it yourself. Set an arrow on the table with the end overhang. You can swing a 15lb sledge hammer across and against the nock and the arrow will just turn and spin. *It needs an opposing force to bend - which is the bow held by the archer and that contact point being the wall on your bow.* Reckon why those plungers are there to fine tune what is where on the side doesn't matter?  This isn't new stuff, it's explained in many tuning manuals as well.


I've been saying all along Sanford, that the lateral movement of the string coming off the fingers, combined with the weight of the tip, and with the resistance of taking an object at rest and forcing it into motion is what causes the arrow to bend.

You have been saying all along that the bending requires the opposing force of the wall of your bow in order for that to happen.. 

Mathematical equations aside, the video I just posted illustrates that the bending of the arrow is going to happen whether or not there is contact with the riser.

That is why I used the example of a finger shot arrow, through a shoot thru riser, off a fall away rest is still going to flex. While I have yet to find a video of that specific scenario, the video that I did just post illustrates the phenomena quite well.

KPC


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## Sanford (Jan 26, 2009)

No, Gerep, I was responding to you saying that the strike position had nothing to do with the amount of bend. We know that ain't true. The flex you describe is just a piece of the puzzle to creating the "bend" an arrow needs to clear the bow in a Paradox condition. The red-line statement in the quote still holds true by basic physics laws as to creating that bend.


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## centershot (Sep 13, 2002)

Question about nodes - the nodes move together along the shaft as the paradox becomes less and less during each cycle of the arrow as it recovers, if a straight line is drawn between the nodes and extended (at any point of the arrow's flight) - do they always point at the target? Seems that it should.


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## Sanford (Jan 26, 2009)

centershot said:


> Question about nodes - the nodes move together along the shaft as the paradox becomes less and less during each cycle of the arrow as it recovers, if a straight line is drawn between the nodes and extended (at any point of the arrow's flight) - do they always point at the target? Seems that it should.


That's the goal of tune to keep them there. As the dynamics are changing in speed and drag effect on each end of the arrow over distance, it might not stay perfect but can be compensated for in our tune.

But, yes, the nodes stay on same fixed, center plane. The tip and tail flex within the same planes as the flex one side of center plane to other. The flex at launch, though, is out of this synchronization, which is how we "snake" around and come into initial alignment of nodes in the first phase of bending.


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## JINKSTER (Mar 19, 2011)

I don't node. LOL!


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## Sanford (Jan 26, 2009)

Yep, if you are going to tune by adjusting your nodes, don't do it in public.


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## DDSHOOTER (Aug 22, 2005)

Sanford said:


> Gerep, there's going to be some inertial reaction from the FOC at the pile and contact at the shelf/hand (see Dan's lizard tongue example). An arrow is a flexible beam. It's just not going to solve the Paradox. IOW, you can't solve what is a complex dynamic action from string deflection off the fingers alone except when there is a true centershot condition and near so in release.
> 
> I can take an arrow in my hand and with ease wiggle-bend it, so sure, a huge load of energy is going to induce the same. Comparative to force, the arrow's beam is miniscule in strength. That's why comparatively miniscule changes in inertia (pile), static spine, drag (which we have not even touched on), and force angle have so much effect.
> 
> The flex needed to clear in a Paradox condition and cycle rate (Hz) needed for a straight arrow flight are tangent. Watch your slo-mo videos. When the arrow is clearing the bow, is it bending about the nodes or flexing irrespective of them? When if flight, is it cycling, flexing, everywhere but at the nodes?


True, therefore, the only opposing force happens between the string release angle the front node position. Rear node only become a interface problem. If you read the PDF file Easy posted they touched on this as a problem "arrow oscillation by the Pro shooter" they could not simulate it in the wind tunnel.

Now you could argue that if I attached a solid rod to the bow string then installed the arrow shaft over that rod and shoot it thru the same bow the resulting POI would be differant? Read the paper then let me know.
Dan


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## GEREP (May 6, 2003)

Sanford said:


> No, Gerep, I was responding to you saying that the strike position had nothing to do with the amount of bend. We know that ain't true. The flex you describe is just a piece of the puzzle to creating the "bend" an arrow needs to clear the bow in a Paradox condition. The red-line statement in the quote still holds true by basic physics laws as to creating that bend.







So are you saying, that in this video, if he were to move his arrow over 10mm so at brace it touches his riser, he would therefore have a completely different tune because the actual flex of the arrow would be different? Or would he have a different arrow impact point because the arrow started out 10mm farther to the right?

KPC


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## DDSHOOTER (Aug 22, 2005)

JINKSTER said:


> I don't node. LOL!


It's because your to stiff. Got you. LOl.
Dan


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## DDSHOOTER (Aug 22, 2005)

GEREP said:


> So are you saying, that in this video, if he were to move his arrow over 10mm so at brace it touches his riser, he would therefore have a completely different tune because the actual flex of the arrow would be different? Or would he have a different arrow impact point because the arrow started out 10mm farther to the right?
> 
> Yes, you got my point.
> 
> ...


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## GEREP (May 6, 2003)

DDSHOOTER said:


> Start and stop the video and you will see that the arrow does not flex until 5-6 of 14 sec.
> 
> Dan


I'm going to disagree with you on that one Dan. That arrow flexed immediately when the string went laterally off the fingers. (about at the 3.5 to 4 second mark, when you first see the tip start to move forward.) It had to, otherwise the angle of the arrow would have changed by the amount that the string moved laterally. The flex you are seeing at the 5-6 mark is already the recovery from the first flex. 

KPC


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## Sanford (Jan 26, 2009)

GEREP said:


> So are you saying, that in this video, if he were to move his arrow over 10mm so at brace it touches his riser, he would therefore have a completely different tune because the actual flex of the arrow would be different? Or would he have a different arrow impact point because the arrow started out 10mm farther to the right?
> 
> KPC


Gerep, it's all in the amount of change of angle to the fixed position of force from the rear as to how much flex is changed by a move in angle. On a loaded shaft, with a longitudinal force, any change in the angle of the flexible shaft to the front and rear forces is going to have an effect on its flex. The opposing forces to the exerted force are at a minimum, moment of inertia of the point (front), static spine of the shaft between the two forces, and angle of the shaft between the two forces acting against its anchor in strike. There's no other explanation you can have. Again, basic high-school physics. You are trying to solve the Paradox from one dynamic, which is ludicrous.


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## GEREP (May 6, 2003)

Dan:

Same guy, different position.






KPC


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## xxxJakkxxx (Apr 17, 2014)

GEREP said:


> Dan:
> 
> Same guy, different position.
> 
> ...


 In this video, the arrow doesn't seem to be using the riser for anything. It doesn't flex that direction and just moves perpendicular to it but free of it. It doesn't appear to be causing any extra flex or change in the arrow's behavior. That's going on just what I see.


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## DDSHOOTER (Aug 22, 2005)

The arrow cannot recover until it is free free. until it is free from the string it is still under the bow strings and front point weight forces, which are apposing each other at launch. The arrow vibrated the whole lenght . http://www.archerytalk.com/vb/showthread.php?t=2251404&page=4&p=1070185872#post1070185872
Dan


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## Fury90flier (Jun 27, 2012)

xxxJakkxxx said:


> In this video, the arrow doesn't seem to be using the riser for anything. It doesn't flex that direction and just moves perpendicular to it but free of it. It doesn't appear to be causing any extra flex or change in the arrow's behavior. That's going on just what I see.


it flexes directly into the riser...arrow moves forward about 1", then flexes "around" the bow- you need to watch again.


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## Sanford (Jan 26, 2009)

DDSHOOTER said:


> The arrow cannot recover until it is free free. until it is free from the string it is still under the bow strings and front point weight forces, which are apposing each other at launch. The arrow vibrated the whole lenght . http://www.archerytalk.com/vb/showthread.php?t=2251404&page=4&p=1070185872#post1070185872
> Dan


This is true! But, this brings another fly to the ointment!

If we know from a draw-force curve that the force is diminishing from the point of release to brace, then, max bend should have only one position, in the beginning at first moment of inertia. Does it inertial bend any more after that point? I say slightly more for a good reason, but interesting question for others to ponder.


----------



## GEREP (May 6, 2003)

DDSHOOTER said:


> The arrow cannot recover until it is free.


What I meant by "recovery," is the rebound of the initial arrow flex.

KPC


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## GEREP (May 6, 2003)

Fury90flier said:


> it flexes directly into the riser...arrow moves forward about 1", then flexes "around" the bow- you need to watch again.


Not this one. Arrow shaft never makes contact with riser.






KPC


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## Sanford (Jan 26, 2009)

GEREP said:


> Not this one. Arrow shaft never makes contact with riser.
> 
> 
> 
> ...


Gerep, the arrow is attached to the rear of the string. The rear of the string oscillates back and forth across median plane before it comes to brace. What else is going to happen when you wag the arrow back and forth from tail? You see it also walk over his hand?

That's not to say there ain't some intertial bending, but as to answering your Paradox, come on, let's look at stuff for what it really is.

I would hope you ain't suggesting folks can tune a bow with no shelf without a stabilizing shelf wall!


----------



## GEREP (May 6, 2003)

Sanford said:


> Gerep, the arrow is attached to the rear of the string. *The rear of the string oscillates back and forth across median plane before it comes to brace. What else is going to happen when you wag the arrow back and forth from tail?*


Finally, after 4 days and hundreds of posts, we've come full circle.

Seems to me I pretty much said that in the 5th post of this entire conversation.



GEREP said:


> OK, so what causes an arrow to flex?
> 
> We've seen it suggested that the linear (in line) force of the string pushing the arrow actually causes the shaft to bend. This isn't really the case. If the forces were perfectly "linear" from the start, the arrow wouldn't flex at all. It is because the force is *NOT* linear, that the flexing happens. When the string rolls off the fingers, it first moves *laterally* before moving forward. It is this *lateral* (not linear) movement that causes the arrow to bend, or flex.


I knew if I was patient, things would finally come around.



Sanford said:


> I would hope you ain't suggesting folks can tune a bow with no shelf without a stabilizing shelf wall!


Please.

I never said, or implied anything of the sort.

KPC


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## xxxJakkxxx (Apr 17, 2014)

Fury90flier said:


> it flexes directly into the riser...arrow moves forward about 1", then flexes "around" the bow- you need to watch again.


 I just rewatched. At 2-3 seconds the tail kicks left. At 3-4, the center kicks left. At 4-5, the center kicks right after it is past the riser. I see no point in it where if you drew a line from nock to point that the line would cross the riser. I'm not saying the riser didn't play a part but from that video, the riser doesn't 'appear' to do anything to the arrow. At the 3-4 second when the center kicks left and the riser is in the center of the bend, it's about an inch out from the riser in the center and the point and nock are in line with where the arrow started, not bending past the riser.


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## JINKSTER (Mar 19, 2011)

so at the end of the day and 9 pages later we discovered.....

what? :dontknow:


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## Sanford (Jan 26, 2009)

Jinks, we learned that if you are going to hold a class out of Wikipedia, at least study and know the seminal work that contributed to it. If not, plenty of students will know your lacking of understanding. Most will walk away and avoid, but get a pig headed one like me and no amount of diversion tactics get a pass. See, this ain't the kiddie pool where the pirates like to play.


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## GEREP (May 6, 2003)

JINKSTER said:


> so at the end of the day and 9 pages later we discovered.....
> 
> what? :dontknow:


We learned what archer's paradox *means* and what it *doesn't* mean. And we also learned what actually *causes* the arrow to flex.

Which, by the way is exactly what my goal was by starting the discussion.

We knew all that by the end of the first page of posts. All the rest has been posturing, chest beating, and attempted one-upmanship...just like the post prior to this one.


KPC


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## Mo0se (Sep 24, 2002)

[URL="[/URL]


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## BLACK WOLF (Aug 26, 2005)

Lol!!!


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## gjlama94 (Oct 11, 2013)

For anyone that makes it this far, I'll reiterate what I posted on the 1st page of this thread: the arrow flexes because of the inertia of the tip resisting the acceleration provided by the force of the string on release. 

The arrow would bend/flex regardless of finger roll. If an ordinary arrow were theoretically suspended in space and a theoretical force applied directly inline with the arrow, it would still bend. The difference is, there would be no predictability to the direction of the bend. Could bend up or left or up-and-right or whatever.

Finger roll is useful because it provides for a predictable bend to the arrow from the string. This allows for things like the plunger or strike plate to be useful in tuning. Without the known direction of the flex, none of it would be useful because the arrow could potentially bend in any direction- including away from the strikeplate or plunger rendering them useless.


----------



## Fury90flier (Jun 27, 2012)

gjlama94 said:


> For anyone that makes it this far, I'll reiterate what I posted on the 1st page of this thread: the arrow flexes because of the inertia of the tip resisting the acceleration provided by the force of the string on release.
> 
> The arrow would bend/flex regardless of finger roll. If an ordinary arrow were theoretically suspended in space and a theoretical force applied directly inline with the arrow, it would still bend. *The difference is, there would be no predictability to the direction of the bend. Could bend up or left or up-and-right or whatever*.
> 
> Finger roll is useful because it provides for a predictable bend to the arrow from the string. This allows for things like the plunger or strike plate to be useful in tuning. Without the known direction of the flex, none of it would be useful because the arrow could potentially bend in any direction- including away from the strikeplate or plunger rendering them useless.


it would barrel out.


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## gjlama94 (Oct 11, 2013)

Fury90flier said:


> it would barrel out.


I'm not familiar with the term...


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## Sanford (Jan 26, 2009)

gialmama, you are correct as to the dynamic of directional stability. 

Also, in keeping with the topic of what *is*, and what *is not* a condition of Archer's Paradox, which centershot conditions like in the first pages of the Easton Tuning Guide are not subject to, are *not* Archer's Paradox. For the solutions to the needed dynamic flexing of the arrow, the solution to Archer's Paradox, there's more than one flexing dynamic and bending dynamic involved.

We know that tune and Archer's Paradox are tangentially related, but they are not one in the same in discussion. IOW, the flex needed to solve the Paradox cannot all come from the string deflection alone, but you still tune a bow via that same flex only when it's not a bow subject to the Paradox condition, like modern centershot bows. 

Here's the research that was cited no less than 3 times in that Wikipedia article which explains both forces, or actually, more, but page 1 is the meat:

http://www.bio.vu.nl/thb/users/kooi/kosp97.pdf


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## GEREP (May 6, 2003)

Just so we have this straight...(for the non-experts of course :wink

You need arrow to riser contact in order for the arrow to flex with a finger release, as shown below.








And without a finger release, the arrow still flexes, as shown below.






KPC


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## Sanford (Jan 26, 2009)

Gerep, this will be good if we can stay on track.

You bring up a good point.

Answer: 

You need a force that can not only flex, but can also change direction of the shaft from where it's aligned for a bow where the arrow NOT laying along, aligned with, the visual line of path to the target - Paradox. Flex alone is just flex - no directional relationship. That's what Gilmama was saying.

In the second bow, you just have flex. The arrow IS laying along the visual line of path to the target with only a slight holding to keep it that way in front - NOT Paradox condition.


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## GEREP (May 6, 2003)

Sanford said:


> Gerep, this will be good if we can stay on track.


Indeed.

The "track" of this discussion was.

A. What "archers paradox" *IS*, and what "archers paradox *IS NOT.*

B. What causes a finger shot arrow to flex.

Both of those were covered in full on page one of this thread. All the rest was pretty much off track.

KPC


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## Sanford (Jan 26, 2009)

GEREP said:


> Indeed.
> 
> The "track" of this discussion was.
> 
> ...


Gerep, if we could do away with all the centershot diversions stuff, which is NOT related, we could have about 2 pages of Paradox discussion.

The problem you have had is trying to pin that deflection alone at solving the Paradox. The only way it could is if the string and nock parted at full outboard swing of the string. Otherwise, there's no force that can move the tail of arrow over to the front plane. All the flex in the world created in string deflection will just go with the arrow the way the shaft is aligned - (barrel out).

See, with Paradox, the riser is in the way of center plane of string force - that's the point. The shaft meets directly with it in its pathway but at an angle. You need another force, an opposing force to the directional travel, to make the bend to make the turn around the obstruction and to solve the paradox. 

You can't turn that extra amount without creating the bend to do it. Simple.


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## GEREP (May 6, 2003)

The only paradox left unreconciled Sanford, is the one where I've apparently given you the impression that I'm even remotely concerned about what you think my problem is.



KPC


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## BarneySlayer (Feb 28, 2009)

GEREP said:


> And without a finger release, the arrow still flexes, as shown below.
> 
> 
> 
> ...


It looks like it flexes almost entirely in the vertical direction, which would make sense, given the expected force vectors that would be involved. Is this the case?


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## BarneySlayer (Feb 28, 2009)

Sanford said:


> See, with Paradox, the riser is in the way of center plane of string force - that's the point. The shaft meets directly with it in its pathway but at an angle. You need another force, an opposing force to the directional travel, to make the bend to make the turn around the obstruction and to solve the paradox.


I think that something we perhaps need to clarify.

The solution of the Paradox is not to go completely around the riser. The end result of solving the paradox is not to have the arrow travel in a direction in line with the bow. Rather, it must travel in the direction that the arrow is pointed before release. With most finger shooting, this is slightly off center, to WAY off center.

In this case, the fingers not only induce flexure of the arrow, but an oscillation of the string. The flexure of the arrow travels from back to front (I took a video at 1000 fps, if you inch it frame by frame, you can see the flexure travel down the arrow in a few thousandths of a second, like a wave). When that wave hits the riser, the arrow subsequently bounces off, away from the riser, laterally. From that point, the arrow _never_ comes back. As the arrow then flexes in the other direction, with the string following the nock, back into the riser, we see it bend _around_ the riser. This is fortunate, because it allows the nock to follow the string as it oscillates towards the riser, without bringing the middle of the shaft into contact. The arrow then flexes back, and the nock comes past center, and clears the riser...

But, if you look at the center of mass, the arrow never actually goes _around_ the riser as a whole. It may look like it, but the bending _around_ the riser really just provides a kind of lateral suspension, to keep the string from slamming the arrow into the riser from the back end during the portion of the cycle where it moves inward.

It seems elegant to think of the flexure of the arrow allowing it to shoot _around_ the riser, but the truth is, it is a controlled deflection, that simply avoids collision based on a suitably-timed oscillation.

It is, truly, a beautiful mess


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## BarneySlayer (Feb 28, 2009)

DDSHOOTER said:


> GEREP said:
> 
> 
> > Start and stop the video and you will see that the arrow does not flex until 5-6 of 14 sec.
> ...


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## Aronnax (Nov 7, 2013)

Sanford said:


> ...You need another force, an opposing force to the directional travel...


Not trying to get involved in this one, but I just wanted to point out that the opposing force your a looking for is the mass, or inertia of the arrow, and arrow head/point. The heavier the front end of the arrow, the greater that resisting force, the more shaft deflection.

It'd be interesting to set up a bow with a drop away rest (but keep the same offset as is normal on a trad bow, not center-shot) so at the moment the string is loosed there is nothing contacting any part of the arrow shaft and see a down angle slow-mo, but the video of the guy shooting off the hand does show it pretty well.

BM


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## GEREP (May 6, 2003)

Just for clarification Barney, it appears as though you attributed that quote to me about the flex not happening until second 5 or 6. That was not me that said that.

What I said was:

*"That arrow flexed immediately when the string went laterally off the fingers."*

KPC


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## BarneySlayer (Feb 28, 2009)

GEREP said:


> Just for clarification Barney, it appears as though you attributed that quote to me about the flex not happening until second 5 or 6. That was not me that said that.
> 
> What I said was:
> 
> ...


sorry, i had clerical errors!


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## GEREP (May 6, 2003)

BarneySlayer said:


> sorry, i had clerical errors!


No problem Barney, happens to the best of us.

:wink:

KPC


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## Sanford (Jan 26, 2009)

BarneySlayer said:


> But, if you look at the center of mass, the arrow never actually goes _around_ the riser as a whole. It may look like it, but the bending _around_ the riser really just provides a kind of lateral suspension, to keep the string from slamming the arrow into the riser from the back end during the portion of the cycle where it moves inward.
> 
> It seems elegant to think of the flexure of the arrow allowing it to shoot _around_ the riser, but the truth is, it is a controlled deflection, that simply avoids collision based on a suitably-timed oscillation.
> 
> It is, truly, a beautiful mess


Sure, correct Barney. Will say I was guilty of thinking like you mention years ago. But, yes, the median plane of the bow is not the path, it's the median plane of where the arrow tip is pointed. The tail just needs to get around to follow it.


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## Sanford (Jan 26, 2009)

Aronnax said:


> Not trying to get involved in this one, but I just wanted to point out that the opposing force your a looking for is the mass, or inertia of the arrow, and arrow head/point. The heavier the front end of the arrow, the greater that resisting force, the more shaft deflection.BM


Agree, just been adding that it's a two part bend. The arrow flex from moments of inertia based on the arrow is only part of it. The nock leaves the string near center plane of bow/string. 

Cycling of the arrow from the string alone will not bring the tail around to match on plane with the head, though, without a directional shove and bend. At or near centershot is a different matter, though. 

The shaft bends into the riser first, and the location of that spot on the riser (strike depth or width of bow) is part of the dynamics bending the arrow from longitudinal force.

Here's the second bend described again:

“The *second cause* of the bending of the arrow is related to the *width of
the rigid middle part of the bow*, called the grip or handle. When we
Consider a classical bow in fully drawn position, the arrow will form a
small angle with the median plane of the bow. After release this *angle increases
swiftly* because the distance between nock and grip decreases swiftly.

Then again by inertia the arrow will bend. The bending resulting from
The two mentioned causes is* increased by the large longi-tudinal force* exerted by the string on the nock.

This force *has a buckling effect* on the arrow.”

_1 Journal of Engineering Mathematics 31 (4):285-306 (1997)_


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## GEREP (May 6, 2003)

Serious question Sanford, but first let's establish a few "givens."

Lets assume we have a riser that is cut 3/16 past center.

Attached to that riser is a strike plate that is 1/16" thick

Let's just assume for the sake of this example, based on the length and spine of the arrow, weight of tip, brace height, draw weight, finger release, etc., this particular arrow flexes exactly 1" at the farthest point, when shot. 

If we do nothing but change the thickness of the strike plate from 1/16" to 1/8", and everything else remains the *exactly* the same, will the arrow flex more than one inch, less than one inch, or remain at one inch? 

Forget about where the arrow goes, all we are concerned about for this question is the amount of flex.

KPC


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## Sanford (Jan 26, 2009)

Gerep, very interesting question and has a good answer. You are doing two things, which as the good scientist pointed out in your posted research, one has diminishing effect on the other.

We know from tuning, that spine is measured in .001", where, it takes very little change in point weight, shaft length, strike plate move , etc...to create a whole .100" change, which is a whole spine change. This is due to the differential of massive force compared to what is a relatively small mass in arrow beam and point weight. Here, we know from tuning our bows that moving the strike plate out makes the shaft act stiffer. Less bend is induced into the shaft. Simple explanation is that the point of the shaft, the inertial pile, is moved farther away from the string deflection.

Now, the second half, if we are still talking a bow under Paradox condition. We just diminished things in another respect. We've got an arrow that acts stiffer, but, WE INCREASED the amount of the Paradox to overcome. Second Paradox? No. We increased the angle, which as the good scientist told us, is under compressive force against the strike in longitudinal force. Now, will we stay in tune? Probably not. Will we still solve Paradox and get the tail around, sure. It will all be limited though by the static spine of the arrow.

See, there's two forces to deal with, really, way more forces, than just string deflection. If we could narrow it all down to one flexing to solve all parameters of change in dynamics, it would not be the complex dynamic it is.


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## rattus58 (Jul 9, 2007)

GEREP said:


> Serious question Sanford, but first let's establish a few "givens."
> 
> Lets assume we have a riser that is cut 3/16 past center.
> 
> ...


I'm thinking that the arrows goes because flex doesn't change... in other words, if it flexed more, you wouldn't have to worry about spine would you? But you do have to worry about spine and if you move the striker out... it shoots left in my bow... so I'm assuming that flex remains constant....


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## Sanford (Jan 26, 2009)

rattus58 said:


> I'm thinking that the arrows goes because flex doesn't change... in other words, if it flexed more, you wouldn't have to worry about spine would you? But you do have to worry about spine and if you move the striker out... it shoots left in my bow... so I'm assuming that flex remains constant....


Ah, the old chicken/egg debate  Just kidding. If the flex didn't change, though, one spine would satisfy tune no matter the strike position up to the tail striking the riser, no?


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## GEREP (May 6, 2003)

Sanford said:


> Gerep, very interesting question and has a good answer. You are doing two things, which as the good scientist pointed out in your posted research, one has diminishing effect on the other.
> 
> We know from tuning, that spine is measured in .001", where, it takes very little change in point weight, shaft length, strike plate move , etc...to create a whole .100" change, which is a whole spine change. This is due to the differential of massive force compared to what is a relatively small mass in arrow beam and point weight. Here, we know from tuning our bows that moving the strike plate out makes the shaft act stiffer. Less bend is induced into the shaft. Simple explanation is that the point of the shaft, the inertial pile, is moved farther away from
> the string deflection.
> ...


So, all things remaining 100% equal, *except* that the strake plate is now 1/8" thick instead of 1/16" will the flex of the arrow be: 

A. More than one inch.

B. Less than one inch.

C. One inch.

Just the letter, A, B, or C please.

KPC


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## Sanford (Jan 26, 2009)

GEREP said:


> So, all things remaining 100% equal, *except* that the strake plate is now 1/8" thick instead of 1/16" will the flex of the arrow be:
> 
> A. More than one inch.
> 
> ...


Which flexing and in what stage of the arrow's "complete" cycle? Could be "D", all three! Gerep, I don't think you even realize what you are asking, which again shows that are reducing a complex dynamic into a single action of "one flex", which the final flex needed but not the originating bending in complete dynamics. The problem with discussing the physics of this with you is that you are bringing a discussion of cap guns to a gunfight 

The explanation I gave above wouldn't even scratch the surface of the number of different forces and the constantly changing forces we are dealing with during the whole process of loosing an arrow and its bending. Remember, tail drag hasn't even been brought up yet.


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## grapplemonkey (Nov 2, 2005)

Can anyone come up with a test for this?


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## Sanford (Jan 26, 2009)

grapplemonkey said:


> Can anyone come up with a test for this?


Grapple, it was called College


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## grapplemonkey (Nov 2, 2005)

I was being serious?


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## GEREP (May 6, 2003)

Your snide remarks aside, apparently you are trying to avoid answering the question. 

When an arrow is shot, there is going to be many cycles, but one of those cycles is going to have the largest degree of flex. Subsequent cycles will become smaller and smaller until the shaft fully recovers.

For purposes of this question, the maximum amount of flex is 1 inch. 

*All other parameters remaining exactly the same, except for the width of the strike plate,* will the maximum flex of the arrow now be.

A. More than one inch

B. Less than one inch

C. One inch.

If you don't know, just say you don't know.

Thank you,

KPC


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## Sanford (Jan 26, 2009)

grapplemonkey said:


> I was being serious?


Sorry, to tell you the truth, it's over all our heads. The technical math to track it in full dynamic is but hen-scratch. Computer modeling might be better, then, we could see it and understand it better. For the most part, it's better to just shoot and not worry about it except to where we need to know for our own tuning. There, the simple stuff doesn't need to be argued, just discussed.


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## Sanford (Jan 26, 2009)

GEREP said:


> Your snide remarks aside, apparently you are trying to avoid answering the question.
> 
> When an arrow is shot, there is going to be many cycles, but one of those cycles is going to have the largest degree of flex. Subsequent cycles will become smaller and smaller until the shaft fully recovers.
> 
> ...


Well, you get an F, because if you didn't change the flex, you didn't change the tune. Moving an aiming point over is not a tune, that's just moving your arrow over, but again, which does affect your tune.

Curious, how come you can tell me I'm wrong but you won't even address your own expert from your Wikipedia posting. He's wrong too, you know. You keep walking over that one.


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## GEREP (May 6, 2003)

Sanford said:


> Well, you get an F, because if you didn't change the flex, you didn't change the tune. Moving an aiming point over is not a tune, that's just moving your arrow over, but again, which does affect your tune.
> 
> Curious, how come you can tell me I'm wrong but you won't even address your own expert from your Wikipedia posting. He's wrong too, you know. You keep walking over that one.


I didn't say you were wrong. How could I, you haven't answered the question yet.

I'm *still* trying to get an answer from you.

I'll ask it yet again.

When an arrow is shot, there is going to be many cycles, but one of those cycles is going to have the largest degree of flex. Subsequent cycles will become smaller and smaller until the shaft fully recovers.

For purposes of this question, the maximum amount of flex in any cycle is 1 inch. 

All other parameters remaining exactly the same, except for the width of the strike plate, will the maximum flex of the arrow now be?

A. More than one inch

B. Less than one inch

C. One inch.

It's really just A, B, or C.

KPC


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## Sanford (Jan 26, 2009)

GEREP said:


> I didn't say you were wrong. How could I, you haven't answered the question yet.
> 
> I'm *still* trying to get an answer from you.
> 
> ...


Ain't that an old tactic. I answered twice, you gave your answer once, yet you left your important meeting with your client yesterday and still haven't addressed your conflict with your own expert  Gerep, if you really were out for the edification of the community, back when you knew, when you avoided the obvious of your own expert, we be would having that conversation now. Talk about throwing new folks under the bus. Now, the topic is, your silly test that has no pat answer.


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## GEREP (May 6, 2003)

You typed a lot of words, but you never answered the question.

However, your refusal or inability to answer is all the answer we need.

Thank you,

KPC


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## Sanford (Jan 26, 2009)

GEREP said:


> You typed a lot of words, but you never answered the question.
> 
> However, your refusal or inability to answer is all the answer we need.
> 
> ...


No, that's the typical "out" you have been setting up.


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## GEREP (May 6, 2003)

We can take the questions one at a time if you wish?

I'd really like to get the answer.

KPC


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## Sanford (Jan 26, 2009)

Get the answer? You gave it to us when my previous two didn't satisfy you. Carry on with your nonsense or say what's on your mind. Games are for kids.


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## grapplemonkey (Nov 2, 2005)

Man somebody has their panties in a bunch.


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## BarneySlayer (Feb 28, 2009)

I volunteer,

I think I got lost...


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## GEREP (May 6, 2003)

Sanford said:


> Get the answer? You gave it to us when my previous two didn't satisfy you.


I haven't given any answers to the question Sanford. I've set the parameters for the question, given the three possible multiple choice answers, and I've asked the question three separate times. You have yet to answer my question, all you've done is filibuster. The only one playing childish games is you. 

I'll ask the question a 4th time. 


_*
When an arrow is shot, there is going to be many flex cycles, but one of those cycles is going to have the largest degree of flex. Subsequent cycles will become smaller and smaller until the shaft fully recovers.

For purposes of this question, the maximum amount of flex in any of the cycles is 1 inch. 

All other parameters remaining exactly the same, except for the width of the strike plate being increased from 1/16" to 1/8", will the maximum flex of the arrow now be?

A. More than one inch

B. Less than one inch

C. One inch.

*_


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## rattus58 (Jul 9, 2007)

Sanford said:


> Ah, the old chicken/egg debate  Just kidding. If the flex didn't change, though, one spine would satisfy tune no matter the strike position up to the tail striking the riser, no?


 No... the more the offset, I'm thinking that you'd need a weaker spine to keep the arrow on target... in my limited capacities anyways that's how I roll.... :laugh:


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## Sanford (Jan 26, 2009)

rattus58 said:


> No... the more the offset, I'm thinking that you'd need a weaker spine to keep the arrow on target... in my limited capacities anyways that's how I roll.... :laugh:


Right. That's why when we tune we say the arrow "acts" of "behaves" stiffer when we move the strike out.

Some say it's just moving the impact point over by moving the arrow over. Wrong.

By the physics of it, we didn't move the arrow over at all. It's launch point is always the string. We just changed the angle.

So, how did the arrow act stiffer if it didn't change flex? But, you are right, we just get a weaker spine shaft to compensate.


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## GEREP (May 6, 2003)

Still no answer.

Very telling.

KPC


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## Sanford (Jan 26, 2009)

GEREP said:


> Still no answer.
> 
> Very telling.
> 
> KPC


Not only did I previously answer in full based on the below, I just answered it in my post to Rattus.

See, the answer has always been in this little anthill:

“The *second cause* of the bending of the arrow is related to the *width of
the rigid middle part of the bow*, called the grip or handle. When we
Consider a classical bow in fully drawn position, the arrow will form a
small angle with the median plane of the bow. After release this *angle increases
swiftly* because the distance between nock and grip decreases swiftly.

Then again by inertia the arrow will bend. The bending resulting from
The two mentioned causes is* increased by the large longi-tudinal force* exerted by the string on the nock.

This force *has a buckling effect* on the arrow.”

_1 Journal of Engineering Mathematics 31 (4):285-306 (1997)_[/QUOTE]


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## Sanford (Jan 26, 2009)

Rattus, when I say we select a weaker spine to compensate, that's where my chicken/egg comment came from.

IOW, the strike position sets the bending forces we have to work around, or conversely, if we are tuning from the strike, to match an arrow's spine. 

If we were just working from the bending forces of string deflection alone, the strike would be irrelevant, which we know it isn't because it's an independent variable that changes how the arrow acts.

For many folks, it's one thing to not have to know all this in detail to tune a bow and arrow. That's highly acceptable protocol. From the other side of the coin, though, someone butchering the laws of physics to explain one's "own" notions is worth debating for the sake of those who are interested in the details.


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## DDSHOOTER (Aug 22, 2005)

BarneySlayer said:


> DDSHOOTER said:
> 
> 
> > I will argue this. I don't know about that video, but a video I took shows the back of the arrow flexing _immediately_ with a finger release. I will try to find it, and leave my crappy form out of it, okay? It was a 70# recurve, for pete's sake!
> ...


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## DDSHOOTER (Aug 22, 2005)

Aronnax said:


> Not trying to get involved in this one, but I just wanted to point out that the opposing force your a looking for is the mass, or inertia of the arrow, and arrow head/point. The heavier the front end of the arrow, the greater that resisting force, the more shaft deflection.
> 
> It'd be interesting to set up a bow with a drop away rest (but keep the same offset as is normal on a trad bow, not center-shot) so at the moment the string is loosed there is nothing contacting any part of the arrow shaft and see a down angle slow-mo, but the video of the guy shooting off the hand does show it pretty well.
> 
> BM


I have the bow but not the video at 1000 fps rate. If I move the rest over I have to move the sight with other than that the tune is the tune and the release is the release.
The arrow pretty much following the path in which it has been pointed as long as there is very little interference on the way. Also, the tune is to absorb as much energy from the bow as possible into the arrow and flight of the arrow is maintain, less drag, the energy to the target. In this case study of a barebow we are detuning a perfect system for the shooter.
Dan


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## GEREP (May 6, 2003)

Sanford:

While I'm sure some are impressed by your verbal diarrhea, I'm just looking for a very simple answer.

A, B, or C?

It can really only be one of the three.

KPC


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## rattus58 (Jul 9, 2007)

GEREP said:


> Sanford:
> 
> While I'm sure some are impressed by your verbal diarrhea, I'm just looking for a very simple answer.
> 
> ...


Question.... with your approach to the question, why would anyone answer you?


----------



## rattus58 (Jul 9, 2007)

Sanford said:


> Rattus, when I say we select a weaker spine to compensate, that's where my chicken/egg comment came from.
> 
> IOW, the strike position sets the bending forces we have to work around, or conversely, if we are tuning from the strike, to match an arrow's spine.
> 
> ...


 That would be me.... :laugh:


----------



## Sanford (Jan 26, 2009)

rattus58 said:


> Question.... with your approach to the question, why would anyone answer you?


Multliple times at that. Other than "if you move the strike plate out, the arrow "acts" stiffer, or, if you move the strike plate in, the arrow "acts" weaker", there's just that common tuning knowledge. 

Moving an arrow over to impact in a different place does not cause the arrow to "act" differently, it just changes the path - tail would still be congruent with head at impact, which those of us who bareshaft can readily see is not all that happens when you move the strike.

There must be some hidden "answer" he's looking for, one of those Pirate tests, as someone, somewhere, has evidently fed this question to him to elicit a "wrong" answer from me. Wrong, that is, based on some hidden supposition that we won't get to see till I give the wrong answer.

In my opinion, what do these silly games benefit the community. If a man has something to say or demonstrate, just offer it up for all to discuss and learn from.

In the end, I hope all this doesn't give reason for the Mods to shut the thread down, as there's some good discussion and information in all this. Let's get back to that.


----------



## BarneySlayer (Feb 28, 2009)

DDSHOOTER said:


> BarneySlayer said:
> 
> 
> > Thanks, Barney but I was already told I was wrong in my statement. I will say this again, straight or flexed arrows have nodes. Unless Easton and few others have been wrong all this years I am going to stick with that. So I like to see your video.
> ...


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## GEREP (May 6, 2003)

rattus58 said:


> Question.... with your approach to the question, why would anyone answer you?


My approach was very respectful rattus, the first, second, and third time I asked the same question. Sanford doesn't want to answer the question, and he and I both know why. He wants to dance around me with words like "acts" stiffer, and "acts" weaker but he just can't bring himself to answer the question with:

A. The arrow will flex more.

B. The arrow will flex less.

C. It will flex the same.


As you can see by the following, I was very respectful when I asked the question the first time...a mere 30 or so posts ago.





GEREP said:


> Serious question Sanford, but first let's establish a few "givens."
> 
> Lets assume we have a riser that is cut 3/16 past center.
> 
> ...


I'll stop asking now. Sanford's refusal to answer is all we need to know.

KPC


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## rattus58 (Jul 9, 2007)

GEREP said:


> My approach was very respectful rattus, the first, second, and third time I asked the same question. Sanford doesn't want to answer the question, and he and I both know why. He wants to dance around me with words like "acts" stiffer, and "acts" weaker but he just can't bring himself to answer the question with:
> 
> A. The arrow will flex more.
> 
> ...


So what is the answer?


----------



## Sanford (Jan 26, 2009)

rattus58 said:


> So what is the answer?


It's actually a geometry puzzle as well. Think triangle.

Deflection side is fixed in length, 1", arrow side is fixed in length by the shaft length and determines the remaining side's length by the triangle formed. If you change the position of one corner, the arrow tip end, can you do so without changing the length of one of the sides? 

That is, assuming all other factors are kept equal.


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## rattus58 (Jul 9, 2007)

Sanford said:


> It's actually a geometry puzzle as well. Think triangle.
> 
> Deflection side is fixed in length, 1", arrow side is fixed in length by the shaft length and determines the remaining side's length by the triangle formed. If you change the position of one corner, the arrow tip end, can you do so without changing the length of one of the sides?
> 
> That is, assuming all other factors are kept equal.


Sanford...... I suffer from ADDHD..... that would be, for the uninitiated, Adult Deficit Disorder in High Definition.... you're asking me to think? :laugh:


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## fotoguy (Jul 30, 2007)

This is one of those times I am content with treading water in the kiddie pool!:BangHead:


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## CAPTJJ (Dec 24, 2007)

Come on in, the water is nice.


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## Sanford (Jan 26, 2009)

Get your arm floaties on, first! We've already had one drown on us


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## DDSHOOTER (Aug 22, 2005)

I'm thinking one to many, here. Lol.
Dan


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## GEREP (May 6, 2003)

fotoguy said:


> This is one of those times I am content with treading water in the kiddie pool!:BangHead:


Good point.

This was one of the best exchanges of the whole thread:



grapplemonkey said:


> Can anyone come up with a test for this?





Sanford said:


> Grapple, it was called College


Especially when you stop to realize that Obama was a professor of constitutional law. Makes one wonder if he did a stint teaching physics too?

:wink:

KPC


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## Hiram (Jul 31, 2013)

Semantics.


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## Borderbows (Apr 4, 2009)

i havent read all of this, but i think its important to say that a button also gives an average position during the shot which is not the same as the initial starting point. the deflection of the button will have an average movement based on the softness of the spring....

but there are more things that upset "paradox" and that also includes limb stiffness.

but getting back to the original 2-3 pages.
paradox was based on the lack of window on self bows. (arrow not pointing where it will evenutally go)
this is also dictated by the spine of the arrow.
so it is possible to tune a bow with paradox. and without paradox same as its possible to tune a bow under centre opposed to over centre.

so i think the term paradox still applies to the same topic as a naming convention even if its not visable.
Paradox to me is tuning the arrow to get round the bow. be it microns, millimeters, or inches. its still possible to class the same forces under the same term. and for me that term is paradox.
its the forces of non column loading an arrow (release) and the arrows flexing cycle, into clearing the bow.


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## GEREP (May 6, 2003)

Borderbows said:


> Paradox to me is tuning the arrow to get round the bow. be it microns, millimeters, or inches. its still possible to class the same forces under the same term. and for me that term is paradox.
> its the forces of non column loading an arrow (release) and the arrows flexing cycle, into clearing the bow.


*"Paradox,"* as in *"archer's paradox"* isn't a *"force"* at all. At least not in terms of bending an arrow. Archer's Paradox is simply the *contradiction* between where an arrow is pointed and where it ends up impacting.

Technically, the *"paradox"* has nothing to do with the flexing of the arrow. In reality, it is the flexing of the arrow, and all the forces involved, that serves to *reconcile* what actually *is* the *"paradox."*

KPC


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## Borderbows (Apr 4, 2009)

GEREP said:


> *"Paradox,"* as in *"archer's paradox"* isn't a *"force"* at all. At least not in terms of bending an arrow. Archer's Paradox is simply the *contradiction* between where an arrow is pointed and where it ends up impacting.
> 
> Technically, the *"paradox"* has nothing to do with the flexing of the arrow. In reality, it is the flexing of the arrow, and all the forces involved, that serves to *reconcile* what actually *is* the *"paradox."*
> 
> KPC


yeah, thats the symantics you wish to get hung up on.

the reaons the arrow doesnt point in the right direction was due to the lack of centreshot. but is now due to the sideways movement of the string. between the two you have clearance. so the concept of clearance is due to spine, and spine is related to the non column loading on the arrow. which is related directly to the arrow not pointing at the target!

so what ever you fancy getting hung up on, it still all comes round full circle and means the same thing.

Now if you want to debte things round and round in circles that have NO pointless sense to mankind
why is CHurch pronounced with a "CH".
yet Christ is more a "K" sound

"english"... dont you love it!


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## Sanford (Jan 26, 2009)

It is very common in any specialty, affinity, or common group to use the noun for the verb. As mentioned before, we do it all the time in language. "Zerox a copy for me!" 

In archery, it even helps because arrows have more than one thing going on. You have a certain amount of frequency needed and a certain amount of amplitude needed. But, it's all flexing.

If I say I need a certain amount of flex, or Paradox, it helps distinguish that clearing the bow properly is my thought process, though, it's all flex I'm dealing with. In this regard, it also helps others know what I'm talking about.

While it helps to know the term's true roots to begin with, getting too technical about it doesn't really serve anything useful. IOW, it's all good for discussion and helpful in learning of the parameters and process to overcome them, but it's not confusing at all to describe the flex as paradox either.


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## GEREP (May 6, 2003)

Borderbows said:


> yeah, thats the symantics you wish to get hung up on.



Words mean things Sid, and it was the *meaning* of *"archer's paradox"* was the sole purpose of the thread. 




GEREP said:


> With all the tuning discussions lately, there seems to be some confusion about the term *"Archer's Paradox."*
> 
> I thought it might be good to have a discussion about what *"Archers Paradox"* is, why it exists, and what it does, and does not mean.
> 
> ...


The reason I started the discussion was to clear up any confusion, especially for new archers that were having trouble understanding certain concepts in other tuning threads, caused by the use of meaningless terms, such as *"paradoxical forces"* and arrows being *"in paradox."* 

You may think it's semantics Sid, but nobody, especially new archers can ever expect learn anything when the terminology being used isn't at least consistent, and not completely made up.

If you went to your doctor for your annual physical, which of the following would you understand more, and therefore be more likely to follow?

_1. You'd be a lot healthier if you cut down on the*"paradoxical forces"* you are putting on your diet, because it's making your arteries less *paradoxible,* and will eventually cause your heart to stop *paradoxing.*_

2. You better start eating better. If you don't, your arteries are going to become less flexible, you're going to have a heart attack, your heart will stop pumping blood, and you will die.

I don't know about you, but if my doctor told me that first line of crap, I'd be looking for another doctor.



KPC


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## Borderbows (Apr 4, 2009)

Sanford said:


> It is very common in any specialty, affinity, or common group to use the noun for the verb. As mentioned before, we do it all the time in language. "Zerox a copy for me!"
> 
> In archery, it even helps because arrows have more than one thing going on. You have a certain amount of frequency needed and a certain amount of amplitude needed. But, it's all flexing.
> 
> ...


Its the same when someone tells you your talking [email protected] You dont suddenly change topic to recycled grass. But you know what they mean.
The language is a living thing. It changes with time and needs. 
It wasnt even 15 years ago LOL wasnt even a "word" or lmao. But we now dont even need to break it into its individual component to know what it means.

KPC.
your right.
but i like many others will continue to do so. Discribe the release/spine/centreshot/powerstroke interaction as paradox as its industry jargon everyone knows about. Imho lol


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## GEREP (May 6, 2003)

Borderbows said:


> KPC.
> your right.
> but i like many others will continue to do so. Discribe the release/spine/centreshot/powerstroke interaction as paradox as its industry jargon everyone knows about. Imho lol


You can *"paradox"* the meaning of words all you want Sid, but if it was such *"common jargon that everyone knows about,"* people wouldn't have been having so much trouble understanding what others were trying to say.

The reason I started the thread in the first place was because some people did *NOT* understand what was being said, and therefore sent me a private message. 

Contrary to what other's would have you believe, getting an arrow to fly right isn't rocket science. You don't need a PhD in physics, you don't need a Ouija board, and you certainly don't need a dictionary of made up terms.

All you need is an understanding of the terminology that actually does exist, what happens when an arrow is released by fingers, and how to manipulate your setup if it isn't doing what it needs to do.

All the rest is just someone's attempt to show everyone else how much smarter they are than someone else.

Everything that really needed to be known was posted on the first page of this thread. All the rest was posturing, plain and simple.

KPC


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## Sanford (Jan 26, 2009)

T.J. Conrads - _Traditional Bowhunter's Handbook_ glossary of archery terms:

*Archer's Paradox* -- The horizontal flexing of an arrow as it goes around the riser of the bow, after which it straightens out and flies its normal trajectory.

People do not has so much trouble understanding the common jargon to archery where I have come across. In the beginning, what is simple to one man, though, is out of reach and pure rocket science to another. So, again, it helps to know the origin of the word, but that's about it as to naming it. Once understood, the industry jargon is not complicated at all.


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## BLACK WOLF (Aug 26, 2005)

One thing I know for sure is that words/terms can have multiple meanings and definitions..AND...can evolve over time to also mean something different than when the word was first created....take 'Instinctive' for example or the word 'hot' :wink:

Ray :shade:


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## Borderbows (Apr 4, 2009)

Or back and belly or back and front. Or right handed vs left handed bow is the opposite to the hand you hold the bow in. Along with negative and positive tiller. Or should it be balance. Since tiller is the art of getting limbs to track straight too. Balance is only the difference that shows up when you check tiller. Heck the list of funnies goes on and on.
Or even the term you dont fire a bow because there is no explosion yet you can dry fire one.


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## Sanford (Jan 26, 2009)

Borderbows said:


> Or back and belly or back and front. Or right handed vs left handed bow is the opposite to the hand you hold the bow in. Along with negative and positive tiller. Or should it be balance. Since tiller is the art of getting limbs to track straight too. Balance is only the difference that shows up when you check tiller. Heck the list of funnies goes on and on.
> Or even the term you dont fire a bow because there is no explosion yet you can dry fire one.


Or, whether President GWB said "nucular" instead of nuclear, the outcome was well understood by all


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## Arcus (Jul 7, 2005)

Sanford said:


> Or, whether President GWB said "nucular" instead of nuclear, the outcome was well understood by all


http://www.usnews.com/news/blogs/wa...-carters-nuclear-pronunciation-might-be-right


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## Sanford (Jan 26, 2009)

Arcus said:


> http://www.usnews.com/news/blogs/wa...-carters-nuclear-pronunciation-might-be-right


Great! . Man, the time I've seen wasted trying to convince some word-police of that.


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