# Do you need stiff arrows?



## archer_nm (Mar 29, 2004)

*Stiff arrows*

Jorge, I go to the correct length and weight then add 5lbs to get my arrow to work.


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## Jorge Oliveira (Aug 13, 2004)

*archer_nm*

If I understood correctly, you add 5# to the specified *finger's* setup, right?

That's about what I need to tune the arrow.


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## archer_nm (Mar 29, 2004)

*Stiff arrows*

That's correct, How's the mother country doing? My Grandfather was born in Brazil and raised in the Azores before settling in the US.


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## arrowshooters (Jun 5, 2006)

I add 8# to cover all the bases.


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## Jorge Oliveira (Aug 13, 2004)

archer_nm said:


> How's the mother country doing? My Grandfather was born in Brazil and raised in the Azores before settling in the US.


Overall fine, but if we could gather the politicians in a place and use it as a shooting range, it would be much better!


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## Unk Bond (Aug 1, 2004)

*Reply*



Jorge Oliveira said:


> I have to use stiffer arrows than any table/program suggests, ot they will not bareshaft tune.
> 
> Anyone else?
> 
> [2001 ProTec LX, 65% modules, 29" draw, 46# as measured by my spring scale]


---------
Hello Jorge
1st off where have you been.  

My Barney bow likes Beamon 500 period ,80 grain points .He turns a limb up at 2312- 2512-2316- Xcutters .

Later


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## Jorge Oliveira (Aug 13, 2004)

Unk Bond said:


> ---------
> Hello Jorge
> 1st off where have you been.
> 
> Later


Hello, Unk

I've always been around, taking care of reviews, but a somewhat away from the forums - too much new bow, new release syndrome  

But now that there's a forum for shooters that knows how to let go the string :smile: , I'm back!


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## jerrytee (Feb 5, 2005)

Jorge I found that when I switch to a two finger loose I had to retune because the arrows acted soft. I had to drop the poundage a little. If I remember correctly you use a two finger loose as well.


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## Jorge Oliveira (Aug 13, 2004)

*jerrytee*

You're right, two under.

That may be the reason.


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## Manhunter50 (Oct 23, 2006)

*Absolutely!*

I've always (well, since we finger shooters became an endangered species, anyway) shot stiffer arrows than indicated in the shaft selection charts, which used to make allowances for us. I could get "recommended" arrows to fly well with practice points in most cases, but try to bare shaft tune or mount a broadhead and things changed significantly. I shoot 29.2" 340 arrows with 100 gr. points/broadheads out of my 68# Ross 337s, but 400s will not tune properly.


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## Bowfishen Sully (Jun 2, 2005)

I was always under the impression that the reason that most fingers shooter found that arrows on the heaver ( stiffer ) spine shot better was because of the lower let offs of our bows and the fact that MORE poundage was applied to the shaft earlier during the shot cycle ? 

Are some of you guys saying that because of the" FINGER RELEASE " more spine is needed ? Can someone explain the physics of this , not saying it wrong just don't understand it ?


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## Jorge Oliveira (Aug 13, 2004)

Bowfishen Sully said:


> Are some of you guys saying that because of the" FINGER RELEASE " more spine is needed ? Can someone explain the physics of this , not saying it wrong just don't understand it ?


When one releases with fingers, the fingers are in the path of the string. This moves the string to the left (for a RH shooter) and bends tha arrow.
This is the reason for what is named archer's paradox - the arrow has to aim a bit to the left to fly stright ahead.

take a look at the movies of this site (most unusual recurve, BTW):

http://www.ide-teknik.com/espeed.htm


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## Bowfishen Sully (Jun 2, 2005)

Yes I understand the archers paradox and it happens with a release also ( finger paradox tends to be side to side and release paradox tends to be up and down ) Are you saying there is more bend in the arrow with a finger release then with a mechanical release ? 

I have seen hours of slow motion footage (mostly the old hoyt AIM videos , I was a certifed Easton ArrowSmith from Easton Archery U when I had my shop ) but the topic of finger release VS mechanical release making a diffrence in spine was never brought up.


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## Manhunter50 (Oct 23, 2006)

*Yup...*

I saw some video several years ago that I believe was shot by Bob Ragsdale, formerly of PSE. It examined the difference between mechanical and finger releases in string deflection, and the deflection with fingers was considerably more than with the mechanical release. Conventional wisdom, for what it's worth, has held that a stiffer arrow would recover more quickly from the greater deflection induced by a finger release than would a more lightly-spined arrow. I've held to that belief, with pretty good results, for more than 20 years. I also found that, among arrows of the same spine, a heavier arrow will shoot more consistently than a lighter arrow. Although I'm not an engineer, it seems to make sense that it would take more energy to deflect a heavy arrow than a light arrow.


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## Bowfishen Sully (Jun 2, 2005)

Manhunter50

You are correct in that finger release will cause more string deflection however string deflection has little to with the LOADING forces of your bow ( not saying it does nothing just that the effect is minimum ) 

Below is a very good artical on the subject 


What Factors Affect Arrow Spine?
. 
There are three main ingredients we'll need to stir-in when trying to brew up the perfect arrow spine:

(1) the stiffness of the actual shaft material 
(2) the length of the shaft 
(3) the tip weight that will be used 

But it's not quite as simple as 1-2-3. How stiff an arrow is when it's sitting still on the workbench, and when it's busy accelerating from 0-180 mph as it's fired from the bow, are totally different issues. When the arrow is at rest, we refer to it's stiffness characteristics as static spine. But when that same arrow is in motion, it's stiffness is a matter of dynamic spine - which adds more ingredients into our consideration pot. So pay attention. This one will be on the quiz. 


STATIC SPINE OF THE SHAFT MATERIAL
.
Let's start with static spine. If you support an arrow shaft at two points a given distance apart, then hang a weight in the middle of the arrow - the weight will cause the arrow shaft to sag. The shaft's resistance to being bent this way is known as it's static spine. The actual static spine of the arrow shaft is determined by the elasticity of the materials in the shaft and the geometry of the shaft. In multi-layered arrows (carbon/aluminum, etc.) the bonding materials also contribute to the static spine. The inside diameter, the cross-section shape, and the thickness of the material all contribute to the static spine of the shaft material. However, arrows don't perform under static conditions - like a floor joist or a curtain-rod. Arrows perform under dynamic conditions, with motion. A hanging weight doesn't really represent how forces are applied to arrows when they're actually shot, so static spine is really used as only a benchmark for predicting dynamic spine.

DYNAMIC SPINE OF THE SHAFT
. 
Unless your arrow shaft breaks or is altered, it's static spine remains the same. But your arrow's dynamic spine can change dramatically. The real mean-n-potatoes of arrow performance relies on the arrow's dynamic spine. The dynamic spine is how the arrow actually bends when shot - and there are many factors which affect the dynamic spine. The static spine of the shaft is only part of the equation. When you shoot an arrow, the explosive force of the bow compresses the shaft and the shaft momentarily bends under the strain. Unlike the unwavering characteristics of an arrow's static spine, the dynamic spine of two identical arrows, shot from two different bows of varying output, could be drastically different. How's that possible? If your arrow has a perfect amount of dynamic spine when shot from your modern 70# hard-cam bow - it's stiffness is just right - not too limber - not too stiff. BUT, if you take that same arrow and shoot it out of your son's 40# youth bow, it will be dramatically too stiff. The arrow will have too much dynamic spine. Likewise, if you shot your son's arrows in your 70# bow, it's likely the arrows would be dramatically too limber - not enough dynamic spine. Determining a proper dynamic spine is a bit more complex and requires examination of several contributing factors. So hang in there. We're almost through. 

SHAFT LENGTH AFFECTS ARROW SPINE
. 
An arrow shaft bends, not because it is being pulled down in the middle, but because it is being pushed inward from the ends. It is being compressed when it's shot. And the longer the shaft, the more easily a compressive force can bend it. Imagine a brand new pencil. If you put each end of the pencil between your palms and began compressing the pencil by squeezing your palms together, this would be similar to the forces that cause an arrow to bend when shot. So, with your standard length pencil, could you push your hands together hard enough to make the pencil bend? Probably not. A short pencil is surprisingly stiff and resists bending this way. But if that same pencil were 2 ft long, you could bend it easily by compressing it. Under a compressive load, the longer pencil had less spine than the short one, even though the shaft material (the wooden pencil) remained the same - with the same static spine per given length. Again, same concept applies for arrows. Longer arrows have less spine (more limber), shorter arrows have more (more stiff).
.

TIP WEIGHT AFFECTS ARROW SPINE
. 
Every arrow should have a tip. The tip is the business end of the arrow. It could be a simple steel practice point, a razor sharp hunting broadhead, a small-game judo tip, or a number of other tips designed for a variety of purposes. Each of these arrow tips is also designed to a specific grain weight. The most popular weights are 75gr, 85gr, 90gr, 100gr, and 125gr. However, some specialty tips can be much lighter or heavier. 

OK. Now remember how a bow compresses the arrow shaft? It's not hard to figure out what's pushing in one direction - the forward movement of the bow's string. That's an easy one. But what force pushes back the other direction? You can't get that kind of compression if you don't have two opposing forces - one pushing on each end of the shaft, right?
Right! So what pushes on the other end? Oddly enough, it's the arrow's TIP. Of course, the tip doesn't actively do anything. It's just a weight - hanging out at the end of the shaft. But surely you must remember learning about Newton's Laws of Motion in school, eh? Remember the one that says "An object at rest tends to stay at rest unless acted upon by a force"? AH-HA! Well think of it this way. The arrow's tip is the "object at rest", and the forward movement of the string is the "force". The stationary mass of the arrow resists the forward motion of the string, and since the heavy tip of the arrow is where most of the arrow's mass is concentrated, that's the area of the arrow that resists the most. So the resistance of the heavy stationary tip and the forward motion of the string create opposing forces and.....Viola!....compression.

So, the greater the tip weight, the greater the compression (and flexing) of the the arrow shaft when shot. The lighter the tip, the lesser the compression (and flexing) of the arrow shaft when shot. See where we're going? You guessed it. A heavy tip DECREASES an arrow's dynamic spine (makes it act more limber). A lighter tip INCREASES an arrow's dynamic spine (makes it act more stiff). 

This concept is a bit more abstract, so consider a dramatic example to illustrate the concept. Imagine if you screwed a bowling ball on the end of an arrow and tried to shoot it. Upon firing the bow, the arrow shaft would bend dramatically as it grudgingly inched forward, trying to get the heavy stationary mass of the bowling ball into motion. The arrow would be highly compressed between the forward movement of the string and slowly accelerating mass of the bowling ball. 

MACHO "BIG-MAN" TIP WEIGHTS

we'll discuss the topic of tip weight selection and explore it's effects on arrow mass, front-of-center balance, loss of shot trajectory, and kinetic energy in greater detail. But for now, it's worth noting that many archers choose a ridiculously heavy tip weight for their hunting arrows. There's often no logic behind the selection, other than the macho idea that bigger is better, and the often distorted and misunderstood notion that heavier tips "hit harder". So don't get too puffed-up bragging about how you "always do better when shootin' them big XXX grain super-ultra-magnum broadheads". With today's hot new compound bows often pumping out 50, 60, even 70+ ft-lbs of kinetic energy, much of the "old school" thinking about hefty arrow tip weight is no longer applicable. 


.
BOW OUTPUT AFFECTS DYNAMIC ARROW SPINE
.
If all this talk of spine is becoming a real pain in the neck, don't worry. We have just a couple more details to cover, then we'll sum up the discussion on arrow spine. 

The physical features of the arrow (the shaft's static spine, the shaft length, and the arrow's tip weight) all play a part in giving the arrow it's spine characteristics. But as we mentioned earlier, the arrows final dynamic spine (how much it will actually flex when shot) will also depend greatly on the output of the bow. Your draw weight, draw length, cam-type, let-off percentage, and bow efficiency all contribute to the actual output of the bow. And bows with more powerful outputs will require stiffer arrows to achieve the proper dynamic spine when shot. Bows will less powerful output will require more limber shafts.


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## Limey (May 6, 2005)

The spine charts are usually set up for release shooters so most finger shooters need to shoot slightly stiffer to get the arrows to tune.

I must be a freak because I normally can shoot release spined arrows with fingers. 

For example both my Bowtechs are set at 60# and I shoot one with fingers and the other with a release although I shoot the same 500 spine Fatboys out of both bowss. The only difference is the nock rotation.:darkbeer:


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## Bowfishen Sully (Jun 2, 2005)

> The spine charts are usually set up for release shooters so most finger shooters need to shoot slightly stiffer to get the arrows to tune


 Limey 

The question is WHY do you think that finger shooters need to shoot heaver spined arrows ? What causes this


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## ia bhtr (May 22, 2002)

*my .02 cents would be..*

that " most " finger shooters have less than perfect releases causing more paradox/oscillation , a stiffer/heavier arrow absorbs this misguided energy much better than a weaker/lighter arrow does , the finger flingers with an excellent release can get by on spine closer to that of mechanical release shooters because of this , Dan


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## Karoojager (Dec 20, 2005)

ia bhtr said:


> that " most " finger shooters have less than perfect releases causing more paradox/oscillation , a stiffer/heavier arrow absorbs this misguided energy much better than a weaker/lighter arrow does , the finger flingers with an excellent release can get by on spine closer to that of mechanical release shooters because of this , Dan


I agree, my release is good and I use one spine stiffer arrows than the chart says for mechanical release.


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## Bowfishen Sully (Jun 2, 2005)

Well you guys may be right but I'm not convinced that string deflection does anything but change the direction of the paradox from up and down with a mechanical release to side to side with a finger release ( hence the need for side pressure rest ) 

I believe that the typical aspects of the "normal "finger shooters bow has MUCH more determining factor then then string deflection. Much the same reason recurve bows need stiffer spined arrows even though the bow is not nearly as efficient as a compound BUT because the MAX force is applyed while the arrow is at rest ! IMHO the amount of force and when it is appled during the shot cycle is the whole story not string deflection. 

But I've been wrong before 

If any of you have ever graphed your bows draw cycle will understand the physics of the shot and the way YOUR bow applys the force during your shot .


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## ia bhtr (May 22, 2002)

Hi Sully , you are right , I have never graphed my draw cycle ( guess maybe just to lazy to do it :embara: ) and while I do agree , at least in part , with much of your line of reasoning ..... 

I still believe the finger vs mechanical loose of the arrow has more to do with this spine thing than the bow itself , my reasoning here ( and sure aint saying I am right , just my beliefs ) is that most of the shooters in my part of the world shoot the same let offs , be it with fingers or a hook and us finger guys , even the ones with a good loose of the string , have to shoot heavier spine than our mechanically aided counterparts to achieve good consistant results from our arrows 

as was stated in an earlier post , there is much more horizontal paradox imparted because of a finger loose as compared to the vertical paradox imparted from a mechanical release , much less deviation for the arrow to recover from 

one place that I do believe the bow itself will come into play here is , not so much the % of letoff between the 2 styles , as the fact that we finger shooters will generally shoot a higher brace height bow than the release shooters will , our arrows are on the string for a shorter period of time than the lower brace height bows , and the longer the arrow is on the string - the better the chance for human error to be imparted to the arrow and as we know , a finger loose has already started down this path of human error , I believe this to be more of the culprit than the actual %ge of let off ...... like I say , sure aint sayin I am right , just that these are my own personal thoughts on the topic ...... this has been a pretty lively discussion that I think we are all gonna gain some knowledge from   , Dan


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## Bowfishen Sully (Jun 2, 2005)

ia bhtr

Please reread these from my earlyer post 


DYNAMIC SPINE OF THE SHAFT
. 
Unless your arrow shaft breaks or is altered, it's static spine remains the same. But your arrow's dynamic spine can change dramatically. The real mean-n-potatoes of arrow performance relies on the arrow's dynamic spine. The dynamic spine is how the arrow actually bends when shot - and there are many factors which affect the dynamic spine. The static spine of the shaft is only part of the equation. When you shoot an arrow, the explosive force of the bow compresses the shaft and the shaft momentarily bends under the strain. Unlike the unwavering characteristics of an arrow's static spine, the dynamic spine of two identical arrows, shot from two different bows of varying output, could be drastically different. How's that possible? If your arrow has a perfect amount of dynamic spine when shot from your modern 70# hard-cam bow - it's stiffness is just right - not too limber - not too stiff. BUT, if you take that same arrow and shoot it out of your son's 40# youth bow, it will be dramatically too stiff. The arrow will have too much dynamic spine. Likewise, if you shot your son's arrows in your 70# bow, it's likely the arrows would be dramatically too limber - not enough dynamic spine. Determining a proper dynamic spine is a bit more complex and requires examination of several contributing factors. So hang in there. We're almost through.

and 

OK. Now remember how a bow compresses the arrow shaft? It's not hard to figure out what's pushing in one direction - the forward movement of the bow's string. That's an easy one. But what force pushes back the other direction? You can't get that kind of compression if you don't have two opposing forces - one pushing on each end of the shaft, right?
Right! So what pushes on the other end? Oddly enough, it's the arrow's TIP. Of course, the tip doesn't actively do anything. It's just a weight - hanging out at the end of the shaft. But surely you must remember learning about Newton's Laws of Motion in school, eh? Remember the one that says "An object at rest tends to stay at rest unless acted upon by a force"? AH-HA! Well think of it this way. The arrow's tip is the "object at rest", and the forward movement of the string is the "force". The stationary mass of the arrow resists the forward motion of the string, and since the heavy tip of the arrow is where most of the arrow's mass is concentrated, that's the area of the arrow that resists the most. So the resistance of the heavy stationary tip and the forward motion of the string create opposing forces and.....Viola!....compression.



> Newton's Laws of Motion "An object at rest tends to stay at rest unless acted upon by a force"


 INERTIA ! 

Inertia is what causes an Arrow to compress ( causing the paradox or Archers arc ) 

The reason Compound bows can shoot lighter weight and lighter spine arrows is the fact that the higher letoffs move the arrow through the shot cycle ( in most cases approx 1/3 through ) before the max force is applyed to the shaft ( that is already on motion ) 

This is a undisputed fact " THE MORE FORCE APPLYED TO AN ARROW EARLY IN THE SHOT CYCLE , THE MORE COMPRESSION THERE IS " 

So as an example lets say we have two identical bows both at 100 lbs max draw weight - Bow A has 50 % let off and Bow B has 80% let off . Now when the string is released on bow A 50 lbs of pressure is relased to a static arrow HOWEVER on bow B only 20 lbs is released on a static arrow ! Apply Newtons law to this and we can see where % of letoff play a huge roll in dynamic spine !


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## Jorge Oliveira (Aug 13, 2004)

*Bowfishen Sully*

You've risen an interesting point re compounds.

It has been my (very limited) experience that a finger's shot compound doesn't bend the arrow as much as classical recurve high speed footage shows.

I've finger shot carbon arrows using a blade rest and the lower vane left a streak in the blade - it shouldn't have (for this particular poundage/spine combo). 

Now, the million dollar question - why then stiffer arrows are needed than the tables/programs show (archer's paradox, etc)?


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## Bowfishen Sully (Jun 2, 2005)

> why then stiffer arrows are needed than the tables/programs show


 Yep Jorge Oliveira that is the question now isn't it ! 

One of the VERY first things that ANYONE from Easton or any of the other arrow companies will tell you is that there arrow selection charts are ONLY GUIDELINES and not the Bible !!!!! We all know how custom Archery is and how many combo's os bows are on the market ! Heck just look at Hoyt bows for an example , How many diffrent Protec's can be made with the limb and cam options available ? and every one will shoot alittle diffrent then the other ! 

It seems to me it's pretty hard to over spine a adult size compound these days ( not saying it can't be done but you have to go way off the charts to do it ) so I tend to "over spine" ( according to the charts ) and haven't had any problems for years !


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## ia bhtr (May 22, 2002)

OK , after having gone back and reread all the threads , it appears that we are all , kind of , on the same topic , sort of

Everything that has been posted is very true when comparing tradtional to compound , hi to low letoff , how tip weight effects spine , how poundage effects spine , I think most of us understand what effects these different scenarios bring to arrow selection

Back to Jorges original question as to having to go a little stiffer in spine as compared to the arrow charts for a finger loose, on eastons hunting arrow selection chart , you can scroll to recurve , hard / single cam , and soft cam , and to be certain , these are only suggested guidelines

So, to me , I would go to the hard cam chart , (and for each of us will be somewhat different ) and probably start by picking the next heavier spine than called for because over the yrs I have learned that for me , thats where I need to be get an arrow that will fly and group , now lets see why that mite be....

1st off , the only thing that is constant here is the hard cam , draw weight , tip weight and arrow length ....... nothing has been determined as to % of let off , finger or mechanical release , altho I am pretty sure for the compound charts they are all set up for the release shooter ( mite even say that and I have overlooked it ) OK , I am assuming ( and this could be an error on my part ) that the hard cam chart is set up with 65% letoff in mind , regardless it is set up for the same let off as far as the chart is concerned , using these assumptions , everything is now the same except how the arrow is loosed , finger or mechanical 

with the assumption made that we are dealing with a chart set up for mechanical release and that for said mechanical release the chart is accurate , yet to get the arrows to fly and group for a finger shooter we generally go 1 spine heavier ( I think most of us are in agreement here ) the only variable is paradox , horizontal and around the fingers of a finger loose , and straight ahead and vertical for a release loose

These thoughts are why I believe paradox is the culprit here , after taking out all of the variables other than type of loose , as far as having to go heavier for fingers than release with everything else being equal

Make sense to you guys ??????? :gossip:


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## arrowshooters (Jun 5, 2006)

OK. Unless I am reading this wrong, the percentage of let off comes into play because of the amount of force put on the arrow early in the draw cycle. But in which direction? Can a lighter spine be used for 65% because the arrow has more time to equalize after the shot? Or, for 80% because the force is applied more gradually thus reducing paradox to a certain extent? Now this has nothing to do with the fact that I don't think anyone can get their fingers out of the way of the string fast enough to avoid the string. But, does a finger realease actually increase paradox, or does it just contribute to it? It would make sence to me then, that for any given spine the amount of paradox does not change just because of a finger release, but is only gotten off to a faster start because of the deflection off the fingers.


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## Jorge Oliveira (Aug 13, 2004)

*arrowshooters*

Lots of mechanical release shooters tune their bows for absolute center shot or very close to.

Yes, the paradox is a finger's shooter phenomena, and is not significant with mechanical release shooting.

What is not clear is how much difference is there between recurves/longbows and compounds regarding paradox. And why.


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## mitchell (Mar 5, 2005)

I've been bare shafting recurves for a fairly good while, with elevated rest and plunger set ups. My experience with fingers compounds is fairly new, so I am learning as we go.

With a center shot compound, little or no rest contact, a loop, and a release, it seems like virtually all the energy imparted to the shaft will be right down the center of the shaft. That is the laymens explanation I have understood for why a compound can take a fairly wide range of shafts, lengths, head weights and still get good flight. At least it sounds logical. Paradox is not agitated by the movement of the back of the shaft to the side that occurs with a fingers release.

With recurves all the variables are much more critical. Finger pressure, hook depth, how relaxed the hand, how far from centershot the rest is set, shaft length, head weight, spine, ability to exactly duplicate draw length, spring tension.....there are a bunch of ways to affect dymanic spine that can readily be seen in the bare shaft.

With recurves, a heavier front loaded shaft (same dynamic spine, but heavier front end) seems to be more forgiving. Some guys go crazy with FOC for that reason. The downside is what the arrow does down range as it looses energy. But for most trad guys, they are only concerned about short distances anyway.

But as for whether or not a fingers release will allow for a lighter or heavier spine selection, my experience with recurves has been that if a shooter has an excellent release, he can get by with a wider RANGE of spine. What is perfect may be the same for both shooters, but the guy with the perfect release more closely duplicates a release aide and can get by with longer shafts, different head weights, etc.

So I guess I am suggesting that the quality of a guys release must play into it.

I am definitely still learning. Some interesting stuff out here. I really like the fingers forum.


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## ProtecMan (Apr 14, 2003)

First off, thanks guys for some interesting reading! I have some thoughts (none of them do I claim to be correct):smile: .

As far as paradox, isn't this essentially the test of a dynamic spine turned 90 degrees? So a stiffer dynamic spine should reduce paradox?

I agree with the amount of energy being imparted down the shaft in a mechanical release vs. fingers release. With a mechanical release, all the energy is imparted down the center of the shaft. Thanks Mitchell.:thumbs_up Whereas, a finger release, some of the energy is imparted into your fingers as it rolls around the fingers. But this goes against the need for a stiffer spine for finger shooters. 

Last but not least, I agree with you Sully about Newton's Law, but wouldn't the Law that states "for every action, there is a equal, but opposite reaction" be more suitable? As the energy is imparted down the shaft and collides with the weight of the tip, the energy must go in the opposite direction, thus compression. 

Not trying to stir the pot, because this is an exellent thread. Just trying to raise some more questions.

Thanks for the info!


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## luckyhit (Dec 8, 2006)

Here's my shot at the layman's explanation.

The arrow flexes as it comes of the bow simply because it is in compression and the point where the force is applied is not perfectly in line with the center of mass of the arrow.

With with a finger release, the arrow, at the nock end, is pushed off to the side as the string comes around the fingers. This moves the center of mass to one side. For a right handed shooter it moves to the left. When the string is around the fingers, it returns to its straght-down-the-middle path. To do this it drives the nock back to the right, flexes the arrow sideways, and leaves the center of mass a bit behind (to the left).

The nock is flicked back to the right, the arrow bows and the "belly" of the bend is out towards the riser. That's why you most usually need a contact point on the side of a good finger rest. 

With a mechanical release, the force is delivered very near to the centerline of the arrow and flexing to the side is very small and has minimal impact on the path of the arrow as it comes off the bow.

This is why you need more spine in an arrow shot off the same bow with fingers as compared to a release. You are introducing a bigger difference in the line of the string returning to rest and the center of mass of the arrow.


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## Bowfishen Sully (Jun 2, 2005)

> Yes, the paradox is a finger's shooter phenomena, and is not significant with mechanical release shooting.


 Sorry Jorge Oliveira but that statment is not true The compression of the arrow is as significant with mechanical release as it is with finger shooting ! The ONLY diffrence is that the arrow Bends / flexs up and down with a mechanical release and side to side with a finger release. As I stated earlier this side to side flexing causes the need for the side pressure contact rest , where rest used for mechanical releases have the arrow sitting on top of them . 

*Once again the flexing of the arrow is from compression caused by Inertia from the forces applyed to a static arrow *! 

The physics of the Archers Arc , paradox , compression ( which ever term you choose to use ) does NOT stop happening because the force is released by fingers or mechanical releases ( only changes the direction it travels down the shaft ) 

IMHO string deflextion is not signifigant enough to even mention in the dynamic spine equation. The reason I say this is as I mentioned earlier I took the Easton University , Arrow Smith certification course several years ago ( and yes I passed ) and the subject was never brought up SO I am assuming that it is a NONFACTOR and believe me when I say that this course covers EVERY aspect of the arrow !


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## Bowfishen Sully (Jun 2, 2005)

> Last but not least, I agree with you Sully about Newton's Law, but wouldn't the Law that states "for every action, there is a equal, but opposite reaction" be more suitable? As the energy is imparted down the shaft and collides with the weight of the tip, the energy must go in the opposite direction, thus compression.


ProtecMan the answer to your questionis here in what I posted earlier ! 


OK. Now remember how a bow compresses the arrow shaft? It's not hard to figure out what's pushing in one direction - the forward movement of the bow's string. That's an easy one. But what force pushes back the other direction? You can't get that kind of compression if you don't have two opposing forces - one pushing on each end of the shaft, right?
Right! So what pushes on the other end? Oddly enough, it's the arrow's TIP. Of course, the tip doesn't actively do anything. It's just a weight - hanging out at the end of the shaft. But surely you must remember learning about Newton's Laws of Motion in school, eh? Remember the one that says "An object at rest tends to stay at rest unless acted upon by a force"? AH-HA! Well think of it this way. The arrow's tip is the "object at rest", and the forward movement of the string is the "force". The stationary mass of the arrow resists the forward motion of the string, and since the heavy tip of the arrow is where most of the arrow's mass is concentrated, that's the area of the arrow that resists the most. So the resistance of the heavy stationary tip and the forward motion of the string create opposing forces and.....Viola!....compression.

*So, the greater the tip weight, the greater the compression (and flexing) of the the arrow shaft when shot. The lighter the tip, the lesser the compression (and flexing) of the arrow shaft when shot. See where we're going? You guessed it. A heavy tip DECREASES an arrow's dynamic spine (makes it act more limber). A lighter tip INCREASES an arrow's dynamic spine (makes it act more stiff). *

This concept is a bit more abstract, so consider a dramatic example to illustrate the concept. Imagine if you screwed a bowling ball on the end of an arrow and tried to shoot it. Upon firing the bow, the arrow shaft would bend dramatically as it grudgingly inched forward, trying to get the heavy stationary mass of the bowling ball into motion. The arrow would be highly compressed between the forward movement of the string and slowly accelerating mass of the bowling ball. 

MACHO "BIG-MAN" TIP WEIGHTS

we'll discuss the topic of tip weight selection and explore it's effects on arrow mass, front-of-center balance, loss of shot trajectory, and kinetic energy in greater detail. But for now, it's worth noting that many archers choose a ridiculously heavy tip weight for their hunting arrows. There's often no logic behind the selection, other than the macho idea that bigger is better, and the often distorted and misunderstood notion that heavier tips "hit harder". So don't get too puffed-up bragging about how you "always do better when shootin' them big XXX grain super-ultra-magnum broadheads". With today's hot new compound bows often pumping out 50, 60, even 70+ ft-lbs of kinetic energy, much of the "old school" thinking about hefty arrow tip weight is no longer applicable. 


.
BOW OUTPUT AFFECTS DYNAMIC ARROW SPINE
.
If all this talk of spine is becoming a real pain in the neck, don't worry. We have just a couple more details to cover, then we'll sum up the discussion on arrow spine. 

The physical features of the arrow (the shaft's static spine, the shaft length, and the arrow's tip weight) all play a part in giving the arrow it's spine characteristics. But as we mentioned earlier, the arrows final dynamic spine (how much it will actually flex when shot) will also depend greatly on the output of the bow. Your draw weight, draw length, cam-type, let-off percentage, and bow efficiency all contribute to the actual output of the bow. And bows with more powerful outputs will require stiffer arrows to achieve the proper dynamic spine when shot. Bows will less powerful output will require more limber shafts.


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## Jorge Oliveira (Aug 13, 2004)

Sorry Bowfishen Sully, but nowhere I've staed there's no compression in the arrow - I stated the paradox (the need to adjust center shot slightly to the left for a RH shooter) only applies to finger shooting due to the side forces applied to the nock side of the arrow by the fingers.which are not significant for mechanical release.


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## Lfutral (Feb 25, 2005)

Thank you guys for a brilliant technical discussion. All I know is everyone has made some good points. I have enjoyed following your views. Keep our minds working. If they say it can't be done; keep trying. Pushing the envelope is what keeps us moving forward. My beliefs have been changing as I gain more knowlege and I plan to study this great sport of ARCHERY! Thanks for the Brain Candy.


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## Jorge Oliveira (Aug 13, 2004)

*Deeper math*

For the ones interested in digging deeper on the matter of archery forces:

http://homepage.ntlworld.com/joetapley/


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## ProtecMan (Apr 14, 2003)

I agree with Leldon, this has been an excellent "brain candy" thread! 

Sully,
Not trying to argue with you, rather I do agree with what your saying. I was just trying to bring up some other thoughts for discussion. Someday we will sit down and ponder this subject over some :darkbeer: !

Thanks guys for another great thread in our own forum!

Mark


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## arrowshooters (Jun 5, 2006)

Still though, does it not seem logical that a bow with a higher letoff percentage could get away with a weaker spine because the forward momentum starts out slower? Or would it be the exact opposite because of the lack of a more "crisp" release and the effects of the string coming off of the fingers?


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## luckyhit (Dec 8, 2006)

Maybe I shouldn't feed the debate.... but I can't help it.

I don't think the higher letoff will get you to a lighter spine. Because (I know that all here don't agree) I still believe that the deflection of the nock to the side is the main reason for aggravation of the dynamic spine with fingers release compared to a mechanical release.

If this deflection didn't affect anything, why do you need that side pressure on a finger shooters rest? Why would the direction of the direction of the bending of the arrow change from up/down to sideways?

I think you are changing the dynamics by pushing the nock to the side with your fingers. At higher letoff, you push it more. That's the whole issue that you shooters are talking about when they observe that its harder to get a clean release with high LO. That sideways deflection is whats "not clean" about it.

With high LO chances are that the nock will be further to the side when the draw force curve really kicks the arrow in the butt. I think that will require a stiffer dynamic spine.


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## ia bhtr (May 22, 2002)

Jorge Oliveira said:


> I have to use stiffer arrows than any table/program suggests, ot they will not bareshaft tune.
> 
> Anyone else?
> 
> ...



Jorge , no doubt about it , ya got a pretty lively thread started here :clap2: , long as we can all keep our cool and learn from one another , archers helping archers ya know


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## Lfutral (Feb 25, 2005)

I have got a situation with my new Hoyt Proelite with 65% c2 cams. I have my same arrows that I shot in 2006. I had to lengthen them last year to break them down and use 66 lbs. LAst year's bow was 75% let off. The new cam wants a arrow 1 inch shorter at only 62 lbs. Same draw length just different cams. This is making the light come on for me. LEtoff or cam design has to be the culprit. The new bow will shoot 283 with 62 lbs and the same arrow. LAst year's 75% letoff model 280 at 66 lbs and the same 335 grain arrow. I am sure my info is correct because I spent countless hours with length of arrow last year. I also believe having the arrow hang past the rest helps start the arrow out better. There are variables that sometimes we overlook. What have I overlooked?


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## ia bhtr (May 22, 2002)

Leldon , dont think you have over looked anything , what you are finding sounds correct .... there definately is , or can be , a difference when you are comparing 2 different bows with 2 different cams 

( I know , they are both pro elites but they are still different bows )

in your case the new proelite is serving up a quick kick in the pants to the arrow where last years was more of a gentler shove ....... as far as that being the culprit , in this case , yes 

in Jorges original question , if I understood it correctly , would be why a stiffer arrow was needed for finger shooting , ..... release vs fingers , with "the same bow" ...... as with most things in archery there are or can be several factors causing similar results ....... cam style / let off can and does cause what you are seeing ........ when using only 1 bow and having the spine differential between fingers and release , then the answer is paradox

I think here a person can see that there actually are multiple possible reasons for this whole spine issue thing we have going .. and all of the different views that have been posted can and do come into play

with all that said ... How do you think you are going to like the new bow vs last yrs model ????????? I just gotta believe that is going to be a great cam once a person gets used to it , nice thing is , with lower peak poundage - should be easier on the body , and I would believe with the lower let off that it probably draws smoother than the 75% , mite take a little more effort , but smoother 

Congrats on the new Hoyt !!


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## Lfutral (Feb 25, 2005)

Maybe it seems like I changed topics but the point I was trying to make is I pay no attention to the charts. I switch back and forth from a release and fingers and use the same arrow. I set my parameter and work to it. I do not believe you need a stiffer arrow if your release is good. I decide what speed I want and work out the details for a setup. I see no difference in the need for added spine for finger shooting. I only have to change my center shot on my rest when I go from fingers to release and my nocking point. The charts seem to be stiff anyway.


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## ia bhtr (May 22, 2002)

yep , same for me ( when the TP isnt in high gear , which it usually is  ) but I do think for most finger shooters with not quite as good of release as shooters of your caliber ,it probably will take a little stiffer spine for fingers

which makes me wonder something , I agree with you about the charts being a little stiff anyway , does that mean that maybe we are a little overspined when we are using a release in this type of scenario ??????? , just a ponderment , what do you think about this idea , wrong , right ??????


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## mnjeff (Jun 19, 2004)

*arrow spine*

here is what i have been taught. the reason fingers shooters need a stiffer arrow is how the string rolls off the fingers. it creates pressures not in a straight line. with a release it comes out straight or nearly straight. the let off thing is that a higher lettoff bow needs a stiffer arrow because of the acceleration from let off to peak weight those bows usually have had a very short valley and were at peak weight for longer period of time than low let off bows. this is of course cams are the same style.


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## Lfutral (Feb 25, 2005)

I think this may be related to aluminum arrows more so. The carbon seem to have a bigger range. I only shoot carbon CXL 250 now and they seem to have a wider range. You got me wondering now. Were are all the engineers?


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## Jorge Oliveira (Aug 13, 2004)

Lfutral said:


> Were are all the engineers?


I´ve exchanged some emails with Joe Tapley, the author of the math page I posted above.

He stated the behaviour of compound bow/arrow combo wasn´t really studied compared to classic bow (recurve, longbow) combo.

So, the engineers are just looking for a bow and trying to figure out... 

I for one am looking for some high speeed footage of a finger´s released compound with the same level of detail as there is for recurves or mechanical released compounds


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## arrowshooters (Jun 5, 2006)

I could not play the videos posted previously but I found these. Awsome.

http://www.wernerbeiter.com/en/products/videos/video.php


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## Karoojager (Dec 20, 2005)

It is very interesting to show the own arrows fly in slow motion. In August I had a meeting with Werner Beiter to make some slow motions from my shooting in a TV show. It was very awesome to shoot for 1 milion spectators and they saw my shooting in all sequences.
At this time I use my Mathews Conquest II set up at 74 lbs and a draw lenght of 29" with a Carbon Express 3D select 400. The arrow came out pretty good. This was a chance for a live time to see my shooting in slow motion.


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## Jorge Oliveira (Aug 13, 2004)

Hello, caracal

Any chance these videos could be in the WEB?

Thanks,


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## bobht (Jan 23, 2005)

*finger shooting paradox*

Go to Bob Ragsdale's sit and look up finger shooting . It shows the fletching clearing way to the left of the arrow rest due to paradox.


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## jerrytee (Feb 5, 2005)

Jorge Oliveira said:


> I´ve exchanged some emails with Joe Tapley, the author of the math page I posted above.
> 
> He stated the behaviour of compound bow/arrow combo wasn´t really studied compared to classic bow (recurve, longbow) combo.
> 
> ...


Easton seem to have it sorted out.The only difference is that on a recurve the limb center is just that. the limb goes straight forwards. On a compound as the cams may not be in the middle of the limb and the string running on those cams may also not be the middle of the limb it is necessary to find the dynamic limb center to set up the off set from center to set the button at.


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## Jorge Oliveira (Aug 13, 2004)

bobht said:


> Go to Bob Ragsdale's sit and look up finger shooting . It shows the fletching clearing way to the left of the arrow rest due to paradox.


bobht

Could you post a link to the site?

The one I know is quite old and hasn't any photos or whatever.


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