# What gives a recurve "forgiveness"...



## OldSchoolNEO (May 11, 2009)

This is a branch off from the Titanium riser thread...

What make or gives a recurve set-up the ability to "frogive" a less than perfect shot.

Vittorio has given a good starting point here...


Vittorio said:


> Forgiveness has nothing to do with alloy or stiffness, but simply to weight distributions and torsional and vertical stability of the limbs.
> Aluminum risers designed in Italy are all made to be usable as barebow risers, first, that means that weight distribution is optimized to allow forgiveness without any added weight (so called natural balance of the riser).
> American and Asian designed risers can only reach forgiveness by the addition of stabilizers, as they are not naturally balanced. And still I question myself why .
> Carbon risers are usually light to very light in weight, so in this case forgiveness can be reached by adding stabilizers, only.
> Forgiveness is anyhow a term to be related to the final full setup, more than to any single part of it, but parts of course contribute to the total...


Weight distribution...
The use of High Speed Video no doubt would be the best tool to test weight distribution while the arrow is leaving the bow, but what if we do not have access to this technology.
What are we really looking for with weight distribution?
I would think that we would want the bow to remain in a "natural" vertical and horizontal plane for some time after the arrow has left the set-up.
In my opinion, this would give the plunger and rest "time" to do their respective jobs.
Is this a correct assumption?
If so, how do we test the best natural balance without HSV?

As for limb stability...
Would having limbs that "mounted to the riser give more stability.
In other word, having a different system than ILF, a "bolt-on" type situation.
The limbs would be secured to the riser in two or three fixed points, essentially removing up-down, left-right at the limb/riser interface.
Would this give more forgiveness or at least remove a "link" in the "un-forgiveness" chain?

Thanks for any thoughts...


----------



## Sanford (Jan 26, 2009)

OldSchoolNEO said:


> If so, how do we test the best natural balance without HSV?


How does it shoot without weights or stabilization? Its natural balance is in its center of gravity. If the upper limb kicks backward after release, more than likely the center of gravity is probably high to center in relation to the grip. The more its natural center of gravity is below and forward of the grip, the more stable the bow will be without additional weighting or stabilization.


----------



## Greysides (Jun 10, 2009)

This is an example of an Italian barebow riser, the Spigarelli 650 Club, designed to be stable without added stabilisers. 

Its low centre of gravity is evident. This is before the integral weight which can be put into the lower riser has been added.
Riser: 1.875 kg
Weight: 210g


----------



## s26286603 (Jul 13, 2008)

ahh thanks for putting this thread up. I have been wanting to ask the question and from experience the stiffness off the riser is a questionable thing to blame. When i did my comparative tests with the hoyt avalon and the KAP winstar 2, the vibartion responses were almost identical and the accuracy tests made no sense till i looked at the limb pocket. The dovetail on the kap was huge when compared to the hoyt and it moved alot. so at the end of the limb the lack of good tolerance on the kap can definitely be seen. i believe that that the weight and correct limb pocket mounting will give better forgiveness. When i look at a bow, i look at the limbpockets cause thats were the business of the bow happens


----------



## OldSchoolNEO (May 11, 2009)

s26286603 said:


> ahh thanks for putting this thread up. ...


You're welcome.




s26286603 said:


> ... The dovetail on the kap was huge when compared to the hoyt and it moved alot. so at the end of the limb the lack of good tolerance on the kap can definitely be seen. i believe that that the weight and correct limb pocket mounting will give better forgiveness. When i look at a bow, i look at the limbpockets cause thats were the business of the bow happens


It would seem to me that a "perfect" mounting system may not have a drastic impact on forgiveness but that a "poor" mounting system would certainly have a negetive impact.
That's what this thread is for, to hash out ideas and share experience, I hope more participate:thumbs_up


----------



## rasyad (Nov 22, 2005)

I was startled at how smooth my new Border HEX 5W MKII limbs were and was motivated to figure out what it was I was experiencing. We had a similar thread on Tradtalk so I edited my post for inclusion here.

Below is a comparison of the Force Draw Curves (FDC) between Border's super recurve limbs and Black Swan's prototype hybrid longbow limbs that will illustrate one aspect of "smoothness". Both limbs were mounted on my Fiberbow. Note, on the Border limbs I have the limb bolts all the way in and have the Brace Height set at 7". Both these settings cause the recurve limb tips to move forward as much as possible. More preload at a lower brace height stores more energy which shows by how steep the FDC rises in the beginning but more importantly, it makes the flatter part of the FDC more pronounced. This is an extreme setting for the Border limbs but better illustrates the effect limb geometry has on what we feel when drawing a bow.

The numbers tell the story. Between 9" and 10" the Border limbs (series 2, red) gain 5.4# where as in the flatter section between 24"-25" the gain is only 1.6#. In contrast the Hybrid limbs gain 3.3# at 10" and have the same gain at 25". My goal was to get the flattest part of the DFC of the Border limbs to happen at my DL of 26.5" (to the button). Mine are medium limbs. Longer draw folks obviously need longer limbs and or longer risers to achieve the same sweet spot at their longer DL.

The difference between recurve and longbow limbs comes down to limb geometry. Recurve limb tips point forward at rest and at brace. When the bow is drawn the limb tips unfold, pass through vertical, and point back toward the archer at full draw. The flatter section of the recurve FDC happens as the limb tips unfold and pass through vertical. Border's "super recurve" shape happens to do this more dramatically than any other limbs on the market. Of course, the shape of the limbs is only part of the story. Border also figured out how to get the tips to unfold in the last third of the draw and remain torsionally stable while doing so. 

I compared Borders limbs with Hybrid Longbow limbs because the reflex / deflex geometry of Hybrid limbs has a very small bit of "recurve" compared to the the Border limbs that have a very large amount of recurve. As you can see, the FDC for the Hybrid limbs (series i, blue) has a subtle flattening between 14" and 20" that matches exactly the subtle recurve of the Hybrid limbs. Conventional recurve limbs will fall between these extreme examples. 

"Stacking" of course is when a bow is over-drawn and the FDC rises steeply. 

Rasyad


----------



## ScarletArrows (May 25, 2007)

after messing with a stabilizer tune I usually test for forgiveness by shooting too damn much...it sounds wierd I know ...but I go till the point that my body says stop and I KEEP SHOOTING...it allows me to see what the worst case senario of my form would be, and can be in high stress situations (I.E. Tournaments). If I can keep them inside the 8 ring (for the most part) at 18m when I am wore slat out then odds are the bow is being really forgiving. (Or I am just getting hella lucky)


----------



## ScarletArrows (May 25, 2007)

rasyad said:


> I was startled at how smooth my new Border HEX 5W MKII limbs were and was motivated to figure out what it was I was experiencing. We had a similar thread on Tradtalk so I edited my post for inclusion here.
> 
> Below is a comparison of the Force Draw Curves (FDC) between Border's super recurve limbs and Black Swan's prototype hybrid longbow limbs that will illustrate one aspect of "smoothness". Both limbs were mounted on my Fiberbow. Note, on the Border limbs I have the limb bolts all the way in and have the Brace Height set at 7". Both these settings cause the recurve limb tips to move forward as much as possible. More preload at a lower brace height stores more energy which shows by how steep the FDC rises in the beginning but more importantly, it makes the flatter part of the FDC more pronounced. This is an extreme setting for the Border limbs but better illustrates the effect limb geometry has on what we feel when drawing a bow.
> 
> ...


ok ok I am sold on these limbs...this was the straw.


----------



## rasyad (Nov 22, 2005)

Woops, bit more....

...A flatter FDC at anchor means that form errors of creeping or overdrawing have less impact on arrow flight. 

Rasyad


----------



## Borderbows (Apr 4, 2009)

There are some basics in riser geom that make it stable in our books
If the grip is closer to the target than the limb pads, then the riser will sit with good stability as when you pull it back the forces are helping to settle the rotation in your direction. If the grip is on the archer side of the limb pads, then the riser will be more prone to rotating when drawn.
This rotation/torque will also show then parradox is at work.
If the riser is inline then the bow will be inbetween.
Kinda the reason aeroplane wings tip upwards, oposed to downwards as the lifting forces converge above the plane opposed to below it.
so, the next trick comes when: the more you make the riser stable by putting the grip further forward from the line of the limb pockets, the shorter your draw length becomes and you loose speed. as the brace height is a function of limb string interaction (in many respects, as sound is one of the main tuning remits for brace height for many people), opposed to grip position.
SO you then have to flick the limbs forward (preload) to gain some speed again.

This problem then brings you into Vertical Nocking point instability. as the more you wind your limbs in or increase your BH, the more radii you end up with at the fade out area and the more the bow shape changes from a triangle to a rectangle. and 4 sided shape is less stable than 3.
if you see where im going.
(try pulling and pushing the string up and down inline with the string on a bow with a high Brace height or the limbs wound in and see how much string movement you get, VS one with a low BH and limbs at minimum.)

The object of this game is to make a bow that shoots, everyone quotes its better to have a slow hit than a fast miss, BUT its better to reach the target then not at all.
So there is a compromise between stability and speed.

Other than that id say a distributed mass, would be more stable than a central one. Hence the reason for stabilisers. so heavy limb pockets are better than light ones.

A)Good Vertical nocking point stability, 
B)Good torsional stability
1)grip a little infront of the line of the limb pockets (not inline or reflexed),
2)and a good amount of speed to get the arrow out of harms way. Wind, rain etc.

A and B could be said to be good string stability. Vertically and horizontally.

And even more important, consistant techneque

Thats our thinkings. there are a million ideas out there, and most work, so thats not to say we are right


----------



## OldSchoolNEO (May 11, 2009)

Thanks Sid, those are some good points, I appreciate you taking the time.
Good test for nock stability, never thought of it in those terms.


----------



## Sanford (Jan 26, 2009)

rasyad said:


> I compared Borders limbs with Hybrid Longbow limbs because the reflex / deflex geometry of Hybrid limbs has a very small bit of "recurve" compared to the the Border limbs that have a very large amount of recurve. As you can see, the FDC for the Hybrid limbs (series i, blue) has a subtle flattening between 14" and 20" that matches exactly the subtle recurve of the Hybrid limbs. Conventional recurve limbs will fall between these extreme examples.
> 
> "Stacking" of course is when a bow is over-drawn and the FDC rises steeply.
> 
> Rasyad


Can you explain something about the graph. I have seen before but did not fully understand your comparison. Assuming all braced force (energy) is retained in the bow, I can understand from your graph that starting from the BH, force (draw weight) should be equal to -0- (zero) for both 7" and 9" BHs.

On the x-axis, both lines start at the same DF of -0-, that I understand, but both x-intercepts begin at the same BH of 7". Shouldn't the longbow start at 9", which would shift its path over?


----------



## rasyad (Nov 22, 2005)

Hey Stanford,

You are correct, I made an error starting the data columns on the same row. Here is the corrected chart. The shapes of the curves did not change but it is a better representation of the difference in the total energy of each limb set-up (area under the curves).

Good catch, thanks.

Rasyad


----------



## Sanford (Jan 26, 2009)

rasyad said:


> Hey Stanford,
> 
> You are correct, I made an error starting the data columns on the same row. Here is the corrected chart. The shapes of the curves did not change but it is a better representation of the difference in the total energy of each limb set-up (area under the curves).
> 
> ...


Hey, if Murphy can happen, he/it will. Always does for me . Yes, the corrected lines show significant power difference in the middle-to-end range, only barely converging at the end of the 30" draw. Secondly, it shows the extra 10#-over-2" oomph one obtains by having the lower BH. Thanks!


----------



## Vittorio (Jul 17, 2003)

Discussion is shifting from forgiveness of a bow (design) to forgiveness of the set up (tuning). Of course, any existing riser-limbs combination can be tuned to its best forgiveness by all usual tuning elements (almost everything, including diameter of the string and shape of the grip).

One remark about the limbs comparison on fiberbow. Fiberbow has pockets around 1/2 inch on the back of the pivot point, making it a very deflex riser. This geometry makes:
a) the minimum brace to increase of around 1/2 inch 
b) the measured poundage to decrease of around one pound in comparison to the other 
As of this, limbs precharge and brace are changing a lot the final resul on the stacking area of the draw curve. 
For sure, on Fiberbow limbs at 28" are working like at 27 1/2 on other risers and even at less on some specific model that has different inner pocket planes. 
Making a 7" brace (medium limbs?) on FB means that you are keeping them almost unbent and all measure and comparisons on stored energy has nothing to do with reality, as working bracing should be in the range of > than 9" for medium limbs and close to 10" for long limbs, on that riser. 
Limbs curves comparison should ever be made by equalling starting parameters :
- Using a riser with standard geometry
- Using limbs of the same lenght and same poundage measured at AMO draw after adjusting only sligtly the bolts and having the brace in the range suggested by manufacturer. 
It means that all drawing curves should in any case cross at the AMO draw.


----------



## Borderbows (Apr 4, 2009)

Sanford:
Thats why we have tried to make the Hex5 limbs work lower than normal.
We have aimed at 3/4-1" lower brace height than your average recurve.

Also as a rough rule, longer working limbs store more energy. (though normally less efficent in the return due to the extra mass of the longer limb. (rough rules)

Rasyad: your right about dropping your BH when you increase your prelaod.
And your observations of how the Hex5 limb works is spot on. You have a better grasp of recurve limb design than some pros!

We are currently thinking 2 things for bow stability.
decrease the unsuported string length at brace height. Also grab the string as early as possible in the power stroke to help reduce this length. Control the left right string movement in the string grooves early on in the power stroke. This should help reduce the size of the ossilations due to parradox.

the next one is lower brace heights should allow the bow longer to settle out, so the NP downward travel will have more chance to flatten out, and any side wards ossilations should have a chance to do the same.
But this is very small and very subjective as we cannot seem to get much info on it. 

All thinkings at the mo!


----------



## Borderbows (Apr 4, 2009)

Vittorio said:


> Discussion is shifting from forgiveness of a bow (design) to forgiveness of the set up (tuning). Of course, any existing riser-limbs combination can be tuned to its best forgiveness by all usual tuning elements (almost everything, including diameter of the string and shape of the grip).
> 
> One remark about the limbs comparison on fiberbow. Fiberbow has pockets around 1/2 inch on the back of the pivot point, making it a very deflex riser. This geometry makes:
> a) the minimum brace to increase of around 1/2 inch
> ...



Sounds like the Fiberbow should be stable but slower.
IN essence the 1lbs less draw is due to 1/2" less draw length, the extra 1/2" brace hight is due to the grip being further out front and we meansure the BH to the grip and not to the pocket, which means you have the bow,Excluding the grip, half an inch closer to you. This would as i explained above, make the bow less susseptable to parradox induced torque.
But you would loose a smidge of speed. Again, a slow hit is better than a fast miss, if your not struggling for the distance. 

Good example Vittorio.


----------



## FITA Freak (May 4, 2009)

I would be interested in seeing these draw specs on the same limb-riser combo...
then compared to which set up gave better results. my current set up gives much better scores when i shoot my best. my previous rig showed A BETTER AVERAGE!!!!!!


----------



## Borderbows (Apr 4, 2009)

FITA Freak said:


> I would be interested in seeing these draw specs on the same limb-riser combo...
> then compared to which set up gave better results. my current set up gives much better scores when i shoot my best. my previous rig showed A BETTER AVERAGE!!!!!!


Whats the difference between your two setups??? (if you dont mind me asking)


----------



## OutPerformed (Jan 20, 2009)

How about the string? It is often said that thicker string is more stable. Is it the stiffness or the mass that makes it more "stable". If you choose Majesty you get lighter and stiffer string and 8125 would be heavier and weaker. Most of the archers choose fairly thick 8125 so heavy is good? 

I have a feeling that heavier string hits more easily arm guard after release. So is it after all more stable? Heavier is harder to move sideways, but the sideway movement is also harder to stop due to higher inertia. So the real question is whether it is irrelevant because the difference is so marginal?

Stiff,light string and heavy arrow sounds good to me. Comments?


----------



## straat (Jan 22, 2009)

I was told by an experienced archer more strands in a string reduce the amount of vibration in it, resulting in a straighter movement of the string.

I have to say I haven't noticed any difference in scores using more or less strands (12-20). I use BCY 8215.


----------



## OldSchoolNEO (May 11, 2009)

straat said:


> I was told by an experienced archer more strands in a string reduce the amount of vibration in it, resulting in a straighter movement of the string...


I'm sure there is some theoretical truth to this but I doubt that anything less than the most elite world class archer could tell a difference or see one via HSV.


----------



## Shinigami3 (Oct 7, 2009)

Theoretical? Maybe.

But no more than this stuff posted about paradox throwing the limb tips off (that you conveniently can't see in video?)-


----------



## ryan b. (Sep 1, 2005)

why dont you bury the limb bolts for the longbow limbs and set them at the same brace and see what you come up with.


putting the bolts all the way in on the recurve limbs is the same as having a more reflexed limb--this allows you to use a lower brace ht and still get nice performance and a lot of pre-load at brace.



when you back the bolts out you are increasing deflex--taking away from preload at brace height.


yes, raising the brace height increases the pre-load but you lose the benefits of string angle/smoothness. if the limbs are reflexed enough (bolts all the way in) then you should be able to get decent pre-load with a lower brace ht on the longbow limbs.



i think you found the sweet spot on the recurve limbs. nice work!



the longbow limbs are already at a disadvantage because of their side profile geometry (theres not as much limb to "unfold"--string angle isnt as good) so raising the brace ht makes things even worse.



i think a fair comparison would be to max out the reflex (burry the bolts) and have the brace hts set the same.
you basically want both of the limbs performing at their best so you can compare shooting qualities better. i dont think you have the longbow limbs performing at their best. if you really want to run with this idea then you can probably drop the longbow brace even lower (no the recurve wont perform well at 6" but the longbow might--especially with enough pre-load from tightening the limb bolts/increasing reflex).


right now it is:


highly reflexed radical recurve, hi pre-load, low brace ht
vs.
moderately reflexed longbow, low pre load, hi brace ht.


its a no brainer that the recurve limbs are going to beat the longbow limbs.




what your draw force map doesnt show is the physical wt of the limbs. im guessing the mass wt of the longbow limbs is much lighter. so while storing less energy they may be more efficient. i dont know? try the test above and see what you come up with.

you could also reverse the set up and see what you come up with.
thanks for sharing all the great info!:darkbeer:


----------



## Borderbows (Apr 4, 2009)

Shinigami3 said:


> Theoretical? Maybe.
> 
> But no more than this stuff posted about paradox throwing the limb tips off (that you conveniently can't see in video?)-


Well can you explain the reputation that the FX has for being twitchy.
Yet our TX40 Gold limb wasnt, and dont say speed.... because the TX40 limb was faster!
And that was in the hands of a 1200 shooter.

If all things are kept the same, riser, string, stabilisers... our limbs were stable.

so how come the left right spread is not as much a concern. on a limb with nothing tangable on HSV.

Try working out the Vairiation that a 0.010 of an inch variation in launch angle would be at 70 meters.
and do you think HSV can see that vairation from 30+ inches away.

So if torsional resistance is high enough you end up with threads like this one.
arrow choice and spine question

http://www.archery-interchange.net/forum/border-archery/24153-bow-stability-torsional-resistance-3.html

and Jaegers Post 54 on this thread http://www.archery-interchange.net/forum/border-archery/22007-new-me-black-douglas-ultra-6.html

If you understand that parradox and arrow spine are linked. all though a loose, the parradox is liked to the size of the loose, hence a spine difefrence is needed to accomodate a different loose vairable, Now you need to read Gteks comment (George technikov) who is qouted to say that Torsional stability makes little difference, BUT the size of the loose is controlled on a compound with a release aid. So the parradox spine and left right deflections are all linked. This means that the Hex5 observations By multiple witnesses Inc Various people at Lancaster Archery Supplies witnessed for them selves on a very Underspined arrow out of a Hex5 limbed bow. on HSV. Yet this tolelrance to spine can also be attributed to forgiveness of a release.

To me thats pritty conclusive evidence that torsional stiffness is forgiving yet you cant see it on High speed Vid. BUT you can if you know what your looking for.
I think when Gtek waited for baited breath to see the explanation of torsional stability he should have looked at the FX.


----------



## Shinigami3 (Oct 7, 2009)

If what you say is true (and if I understand it correctly- I have to confess, it's real hard to follow your reasoning!) then you are giving up a lot of arrow clearance with your limbs.

But, I have never heard of anyone needing to shoot a couple sizes less stiff with Borders or WW's so how is the paradox being changed?

Either you're reducing paradox and killing clearance OR your speculation is incorrect. Can't have it both ways.

(Looking over the threads you mention I see a lot of speculation and no real evidence to back it up.)

By the way, I shot all my PB's with FX limbs back in the day. If they were "twitchy" as you put it, then i must have been "lucky". LOL


----------



## Borderbows (Apr 4, 2009)

Shinigami3, you must have a good loose. Very good trait to have!

not sure about the Clearance reduction as the string still needs to clear your fingers.
The difference is the speed at which the limb recovers its straight line,

A plucked loose will not strighten up as quick.
But will recover Less quickly on a less torsionally resistant limb.

The other way to look at it, would be, lets have wibbly wobbly limbs. slight side load, and the limbs wobble left right like jelly. Where is the string going to be on a deep pluck vs a tight nice loose.

So if the final launch angle is wobbly as there is nothing to resist this vairable what happens to the arrows desitination.

also. if the arrow is silly weak. The parradox will make the string want to overtake the nock? this will snap the arrow. see this youtube effort.
Parradox Vid

but if you can provide a base for the string to resist the parradox, opposed to wobbling, then you end up helping to resist the overtaking stage of the weak arrow.

But the past centre arrow setup is still present and so is the deflection due to your fingers. so why would you end up with clearance issues.
You dont get clearance issues on a shelf shot bow, shelf and no button, so why would you get it on a metal riser bow with big clearance? couldnt you just adjust your button position???

we dont have clearance issues with large 5" hunting feathers shot off the shelf... the centreshot is well setup, the arrow spine groups well on a bare shaft test. Clearance isnt a issue, yet Lots of archers with GOOD experience some 30 years+ are noticing the Spine tollerance of stable limbs.
Please consider, our CXC laminate is MEGA stable, 100% stiffer than our XP10 laminates.

Shinigami3: Have you shot our limbs?


----------



## Shinigami3 (Oct 7, 2009)

I guess I fundamentally don't get your point about a side load on the limbs- the string can't exert leverage on the limbs in the manner you're asking us to imagine.


----------



## Borderbows (Apr 4, 2009)

Shinigami3 said:


> I guess I fundamentally don't get your point about a side load on the limbs- the string can't exert leverage on the limbs in the manner you're asking us to imagine.


Thats the exact words ive read in a fax in responce to a french magazine article from Mr Park (of which i have copy of) when they had the Winact and Focus. NOW they have torsional stability. Mr park said there is about 5lbs of side load when the release happens... 
What is there to resist this side load. what stops it continuing... as it must meet an equal force to stop the bow from unstringing it self, and i couldnt think of any more an unstable bow that one that unstrings itself.
And might i ask, if Hoyt done see the need for it, why are they laying claim to it now.

That doesnt add up.
ALL makers are claiming torsional resistance. so whats the point in it in your books?

Also alot of trad makers who use UD glass make there limbs out of 2" limb blanks, opposed to others 1.75". That extra width at the fade out helps control tip flex without having the mass in the tips to keep what they had.

Its simple bow design!

Longbows can get away with slim limbs due to the limb pulling the string. the recurve part of the limb on a recurve pushes the string. and to stop that push from doing a jackknife effect it must NOT twist due to that 5lbs side load mr park illuded to!


----------



## Shinigami3 (Oct 7, 2009)

Five pounds of side load from what ? Certainly not the string, there's no leverage at the tips. This makes no physical sense. And. Five pound force on a liimb at full draw would show up clear as day on HSV.


----------



## Borderbows (Apr 4, 2009)

5lb side load when released, as the string deflects round the fingers. (and the fingers defect from the string) I assume when Mr Park quoted that, it would probably be from a higher lbs bow. as a 10lbs bow will not show that kinda force needed to part from a release hand.


----------



## rasyad (Nov 22, 2005)

Sinigami3,

Here is a link to W&W testing of Alaska Bowhunting's new Adcock longbow prototype. It is a great birds eye view of the limb tips moving sideways in a gentle arc after the significant deflection of the string coming off the machine.

http://www.youtube.com/watch?v=_WGjrDVq-jM&NR=1

I can't find it at the moment but I have seen motion capture data W&W did of the lateral displacement of various recurve limb tips during and after the shot. 

Torsional Stability is absolutely a variable in limb design. How significant a variable, I have no idea. I don't design bows for a living and only have limited experience shooting the darn things. Is more better, my guess is yes and the top manufacturers are certainly studying it. 

Rasyad


----------



## ryan b. (Sep 1, 2005)

rasyad, anyone,

any thoughts on my post?


----------



## ryan b. (Sep 1, 2005)

i read sids reply at tradtalk.com and i think it makes a little more sense to me now. 

..still wonder if you cant get more out of those longbow limbs.

comparing different limbs at same brace ht with limb bolts in or out will favor one limb depending on how you have it set up.

the best setup for the longbow limbs may be a lot different than the best set up for the recurve limbs but its still the best set up for each that you should compare imo.

thanks again for the info.

have you tried any of morrisons ilf longbow limbs? morrisonarchery.com. stock bows--ILF


----------



## John K (Dec 13, 2004)

It's surprising how much pressure people can exert on limb tips while shooting, even just by drawing the bow.

I used to help out at a shop. One day a customer brought her bow back, complaining that the string had twice come off while she was at full draw. We checked the bow and string over and could find nothing wrong. We then asked her to shoot in the range, and it transpired that she was twisting the string at full draw. Her coach was there, and he confirmed that this was a flaw of hers that kept creeping in. 

Once we pointed out the source of her problem, she went from being quite stroppy to very sheepish. Still, at least we solved her problem


----------



## rasyad (Nov 22, 2005)

Hey Ryan,

I was not trying to compare the limbs to see which was better, rather to see how they are different. As you correctly pointed out the Hybrid longbow was not set up the same way as the recurve. My point here was to exaggerate the difference in the limb geometry so as to explain one aspect of how the recurve in recurve limbs works to make a bow more forgiving. 

I am learning here like everyone else and apologize for any confusion I may have caused. 

Rasyad


----------



## Greysides (Jun 10, 2009)

Well I learnt a bit anyhow. Thanks Rasyad.


----------



## Sanford (Jan 26, 2009)

rasyad said:


> Sinigami3,
> 
> Here is a link to W&W testing of Alaska Bowhunting's new Adcock longbow prototype. It is a great birds eye view of the limb tips moving sideways in a gentle arc after the significant deflection of the string coming off the machine.
> 
> ...


It would seem that lateral movement of limb tips would be related to grip. If my grip is non-torquing and free, I should be able to pull the string as far sideways as my draw hand and arm will allow without putting any lateral stress at the tips. The bow will merely rotate on its axis. 

Now, the question is how much lateral movement of the tips can there be after release if the axis of the bow grip is free to move in relation to string angle, i.e., loose grip? In the video, I suspect the bow handle is anchored in a test bench, or so it appears to be so. If so, all string angle and side force for that test will naturally swing the tips, since the bow cannot rotate on its axis. Just a thought.


----------



## Shinigami3 (Oct 7, 2009)

Sanford said:


> It would seem that lateral movement of limb tips would be related to grip. If my grip is non-torquing and free, I should be able to pull the string as far sideways as my draw hand and arm will allow without putting any lateral stress at the tips. The bow will merely rotate on its axis.
> 
> Now, the question is how much lateral movement of the tips can there be after release if the axis of the bow grip is free to move in relation to string angle, i.e., loose grip? In the video, I suspect the bow handle is anchored in a test bench, or so it appears to be so. If so, all string angle and side force for that test will naturally swing the tips, since the bow cannot rotate on its axis. Just a thought.


I had the exact same thought- a rigid grip in a mechanical shooter will do things to the bow that people can't.


----------



## whiz-Oz (Jul 19, 2007)

I'd actually have a fair bet that of all the people who have quoted the word "stability" in their posts, none of you can define it. 
Considering that people use it to describe limbs, risers, designs, entire bows, in relation to others, it seems to be used with abandon. 

I'm yet to find someone with a satisfactory explanation which demonstrates that they know what they're talking about.


----------



## Joe T (Apr 5, 2003)

I think the confusion re limb twist is between a static and dynamic view. If you just move the string sideways with a free bow pivot point then the bow just rotates under the applied torque - no limb twist. If you move the string sideways with with a clamped riser then the limb (and riser) twist under the applied torque. Real world (dynamic behaviour) where accelerations/inertia come into it lies between these two extremes, the limb twists and the bow rotates.


----------



## Borderbows (Apr 4, 2009)

Whiz: I have debated with you on other forums, and you still seem set in your ideas, which is fair play, But somehow everyone else doesnt know what they are talking about yet you do... this is a forum afterall and some people post to stimulate debate... At least you have tried to address some of my points bit by bit. I know your great friends with Marcus, who is a Hoyt dealler in OZ. so can i ask you the same that i asked Shinigami3... Have you Shot our Limbs?

Shinigami3: I have asked you a question... you have not answered. Gtek has also adpoted this techneque when i challenged him to an independednt Bow Test Our Cheapest vs his best, on his terms and i got no reply there too.
If your here to belittle others ideas without answering other questions then fair do's, I asked you if you had shot our Limbs? and can i add what do you shoot now? Cyberspace is a great place to be bold and your profile is blank so please excuse me for not knowing who im talking to?

Sanford: Please trust me its not a bow hand torque issue. Just work on mega thin limbs would be twitchy idea, and there for what the difference is there between thin and wide limbs... Its about reducing limb mass and improving stored energy, yet keeping a resistance to side loads. Thats it, its that simple.


----------



## Borderbows (Apr 4, 2009)

Joe T said:


> I think the confusion re limb twist is between a static and dynamic view. If you just move the string sideways with a free bow pivot point then the bow just rotates under the applied torque - no limb twist. If you move the string sideways with with a clamped riser then the limb (and riser) twist under the applied torque. Real world (dynamic behaviour) where accelerations/inertia come into it lies between these two extremes, the limb twists and the bow rotates.


that is exactly what we think too... the added bonus sits with some simple use of distributed mass to help control the riser torque during this dynamic process. Stabilisers help hold this together. We have always said Barebow will not get as much benefit as a stabilised bow would.


----------



## Joe T (Apr 5, 2003)

Borderbows said:


> Sanford: Please trust me its not a bow hand torque issue.


"bow hand torque" is another area where limb torsional stiffness makes a difference (I think) in principle to forgiveness. Say your string is incorrectly aligned with your riser. When you draw the bow you torque it so at full draw you have some built in limb twist which can be either in the same or the opposite sense to the arrow buckling generated limb twist. Big difference to the torque input to the arrow with this string misalignment. Can believe Mike Gerard's comment somewhere on this forum about this problem making a bow un-tuneable. Very complex topic but intuitively I feel that a more torsionally stiff limb has to help with string misalignment or archer generated limb twist leading to a more "forgiving" system.


----------



## s26286603 (Jul 13, 2008)

wow some people can be stubborn, but thats what discussions are for, Mr Borderbows, everything you say makes sense... Like for intance the 5lb laterral force, for the people that dont believe him here is a break down. All of you will agree that the string is displaced about 2cm about ( it has to move something otherwise it it would cut right through the fingers!) Now if you had to take Mr Newtons 3rd law " every action has an equal and opposite reaction...." to move the arrow the string at speeds of 300-400 fps sideways ( dont attempt to argue this as it is an approximation of my own opinion after seeing the duration of the arc climb after the string is released in slow mo shots) that there is going to be one hell of an acceleration and an opposing force, I have personally done vibration analysis of three bows and the sideways acceleration at the pockets reaches values of 150g's upon the limb returning to its strung posistion. If the g's are so hi there, imagine what they are at the tip of the limb. Ok back to the point. In order to displace the string at that speed and acceleration, some force will be needed ie. F=MxA 
lets say mass= 150 grains = 0.00972 kg acceleration = 150g's x 9.81m/s^2 = 1471m/s^2 ( choice of 150g's is an estimation and should be worked out from the high speed camera, ie known displacement and time, therefore the acceleration can be found) therefore the force present = 0.00972kg x 1471m/s^2 = 14.30298 N = 1.458 kg = 3.21 lbs!!!!!:mg: If you have a look at the layup of the carbon fibres that are present in a hoyt g3 there are fibres in there to take up torsion. Ok with that down argue some more please.... And Mr Borderbows, we would love to see a set of limbs in South Africa ....


----------



## Sanford (Jan 26, 2009)

Joe T said:


> "bow hand torque" is another area where limb torsional stiffness makes a difference (I think) in principle to forgiveness. Say your string is incorrectly aligned with your riser. When you draw the bow you torque it so at full draw you have some built in limb twist which can be either in the same or the opposite sense to the arrow buckling generated limb twist. Big difference to the torque input to the arrow with this string misalignment. Can believe Mike Gerard's comment somewhere on this forum about this problem making a bow un-tuneable. Very complex topic but intuitively I feel that a more torsionally stiff limb has to help with string misalignment or archer generated limb twist leading to a more "forgiving" system.


I'm new to studying these issues and certainly have done no testing, but here's where I see issues in play. There should be two issues resulting from string arc and paradox to deal with: 1)side load; and 2) torsion.

Side load is a bending force. Torsion is twisting. Try to bend a flat recurve limb perpendicular to its flat side, and naturally, it can't bend. Grap it by the nock end and twist; the limb twists fairly easily. The wideness of the string nock in relation to the wide/thin limb leverage torsional twisting. For a narrow longbow limb with symmetrical sides, the limbs can bend in any direction, but lack leverage at the nocks for much torsional effect. 

This has always been my understanding as to why flat limbs are more stable in better keeping of their desired forward/backward travel only. They are less prone to side loads, which imparts the load to the bow's axis and ultimately the bow hand. The natural arc of the string is absorbed in torsion.

Given the goal is to keep lateral load/movement of a limb to a minimum, it seems that a good degree of torsional movement (twisting) of the limbs can work as a benefit - the energy has to be displaced somewhere. Preferably, the arrow, so I can see where one might research keeping the limbs stiff for lateral bending (wide, flat, and thin for less mass but begs for twisting), while at the same time, finding ways to make the same limb more resistant to torsion (twisting).


----------



## Borderbows (Apr 4, 2009)

We refer the difference between Longbows and recurves like the Pushing of the string forward by the recurve section and pulling the string of a longbow. And just like a caravan, you can pull it for ever, and it will follow, but you cant push a caravan without it jack Knifing.

You need to maintain this resistance yet improve the recurve action. And thats where *True* recurve bow design innovation lies on our opinion. And im not talking about Klopstegs static "ears" and heavy mass outers. 

for your information.
We have 2 sets of limbs in South Africa. as set of old ML2 limbs and some Hex5 MKII went to johannesburg which left last week.

Our view is that with the paradigm of recurve torsional stability being based on UD glass and Wood core has changed, then with this advent of the new levels of torsional stability then the paradigm can change! IN our view it changed in 1998 as we saw with the XP10 laminate, its benefits and where it can go. This is not about a tweak in a core taper. This is Fundimental.


----------



## s26286603 (Jul 13, 2008)

Mr BorderBows, check your pm. And I have read those articles. Now i believe you even more!!


----------



## Vittorio (Jul 17, 2003)

Joe T said:


> "bow hand torque" is another area where limb torsional stiffness makes a difference (I think) in principle to forgiveness. Say your string is incorrectly aligned with your riser. When you draw the bow you torque it so at full draw you have some built in limb twist which can be either in the same or the opposite sense to the arrow buckling generated limb twist. Big difference to the torque input to the arrow with this string misalignment. Can believe Mike Gerard's comment somewhere on this forum about this problem making a bow un-tuneable. Very complex topic but intuitively I feel that a more torsionally stiff limb has to help with string misalignment or archer generated limb twist leading to a more "forgiving" system.


There are several interrelations in between all elements of this problem, as Joet T is mentioning. Trying to make a simple list:
1) There are 2 contacts between the archer and the bow: Grip and String.
2) There are 2 possible generators of static twisting in limbs: strightness and twisting
3) There are 2 possible generators of satic twisting in risers: strightness and twisting
Everybody will agree that a bow satically aligned on all its planes should be ok. But, same bow is still aligned at full draw? And, are limbs tips travelling on the same line all the time after release? This is the first thing to be checked after aligning a bow. And there are easy tools to do this.
Of course, in many combinations of 2 and 3 different situations, the limbs will NOT travel on the same line. Sometime, more the limbs are statically aligned for the best visulal compromise, less they will travel on the same line after release. And this is the first element of your multi solution equation
Then, going from static (ie= tests mede without any human introduced torsional factor), you have to analize torsions introduced by 1) factors during drawing and release. 
Long time ago I have stated somewere on the sagi forum that "all secrets lay in the grip". Yes, because the shape of the grip and how you position your hand on it will introduce a variable torque to the drawing line that will have different effects on release, 
Then, fingers, their spacing and their position on the string will introduce a variable torque during drawing and at the release too. 
Finally, all these elements will also combine with static and built in natural tiller as well as vertical changes of the pressure point on grip and of the fingers on the string that are influenced by the vertical stability of the bow tuning, making the problem a 3 dimensions one 
What cames first for forgiveness in this complicated situation?
For sure, first is to have limbs and risers not twisted at all and perfectly straight without intervening on aligenment
Second is to have limbs travelling as close as possible to the same line while closing
Third is to have a strong vertical static stability 
Fourth is to have a consistent hand placing on the grip that shows no torque at all while drawing 
Fifth is to have a consistent positioning of fingers on the string
Sixt is to have a consistent drawing line 
Seventh is to have limbs torsionally stable at static level
Eight is to have limbs recoverring to the same line as soon as possible after release..
Nineth is to have stabilizers not effecting the bow during the travel of the string after release
Tenth is to have a good button tuning and vertical stiffness of the rest
11th is to have arrows bending well under a bad release but recovering fast to the line. 
Oh... I'm now talking about bow tuning... :angel:

Yes, there are situations were the bow is simply untuneable. If too many of the starting factors are wrong, then the final solution (tuning compromise) can't give a reasonable consistence and some of the basic elements have to be fixed. Limbs and risers, first, of course.
But if limbs and risers are satically ok, then a simple way to find if your set up is forgiving is to change intentionally the position of the hand on the grip and shoot bare shafts and fletched arrows several times for each position. I have found for some archers and some specific bows that the bare shaft may show up to 2 size weeker/stiffer results simply bychanging the position of the hand on the grip. It means that these archers are using a critical set up were surely limbs quality is playing a very critical role. 
If this is the case, you can change their grip shape in order to compensate human introduced torsion on the grip, and grip becomes the solution key to the problem, up to a certain level. After that , change limbs.


----------



## s26286603 (Jul 13, 2008)

Ok so we have estabilshed that limbs have to be torsionally and statically stable.... Now the question is does a shorter limb setup help. I have the case were i can use 40# samick athlete limbs on a 27" riser to give me a 70" bow, but i can also use a 25" riser configuration with 70" limbs to get a 70" bow (limbs are G3 but i question the straightness but regardless) Would shooting a shorter limbs be more benificial, well i think it would. What do you guys think?


----------



## Joe T (Apr 5, 2003)

Sanford said:


> Try to bend a flat recurve limb perpendicular to its flat side, and naturally, it can't bend.


Presume you meant parallel else all the limb manufacturers just went out of business :smile:

This is true. However if you first bend the limb as normal i.e. stress it and then apply a side load then the limb can twist. The effect is not dissimilar to the archers' paradox where an axial load generates a lateral bend. i.e. it's not intuitive


----------



## Borderbows (Apr 4, 2009)

s26286603:
There is a complex mix at work here.

if you make the riser longer for the same given bow length you end up with more bend near the fadeout at brace hight. This increased bend will increase the vertical Instability. For example test a 66" bow 25" riser vs a 70" on a 25" riser'd bow for vertical stability.
The next idea with vertical stability in terms of increased vertical instability would be to increase that radii at the fadeout. you can do this in 2 ways. Increase the preload, ie wind the bolts in, or increase the brace height. and you will end up with more curve at the fadeout.
This will turn the bow into more of a square shape opposed to a triangle.
Again this is where the myth that fast bows are unstable. as to gain speed you normally increase preload.

The more the bow can resist this vertical movement it indicates it will also help haul the string (vertically) into line from a dragging top or bottom finger and stabilse the nocking point path quicker.

Now, if you are not struggling with vertical release problems, then would the increased speed help your accuracy??
To help contain this radii at the fade out the limb pad angles are the way they are.

This is the complex game all bow makers play with and why speed is the holy grail to sell bows today, but twitchy wont sell bows tomorrow. get the mix right and you gain more friend that you loose.
For example, there are archers who need speed. Short draws and low poundages. vs archers who dont struggle with cast so they want stability.


----------



## Borderbows (Apr 4, 2009)

Joe T said:


> Presume you meant parallel else all the limb manufacturers just went out of business :smile:
> 
> This is true. However if you first bend the limb as normal i.e. stress it and then apply a side load then the limb can twist. The effect is not dissimilar to the archers' paradox where an axial load generates a lateral bend. i.e. it's not intuitive


Joe T:

Do you think that slim longbow limbs will bend sideways due to length and width, while recurve limbs twist due to the torque of the recurve profile?

For example target longbows are generally wider in limb shape. For example. so far we could conclude that longbows are more accurate than recurves, but they are not in the target shoots in with the recurves?

I could add that stability could also be smoothness though the clicker, which a longbow is not!


----------



## Joe T (Apr 5, 2003)

Borderbows said:


> Joe T:
> 
> Do you think that slim longbow limbs will bend sideways due to length and width, while recurve limbs twist due to the torque of the recurve profile?


Don't know the answer to this. I would guess that the longer/narrower limb would twist more but the recurve pushes stress down the limb so .... Worst case is probably a highly recurved longbow.


----------



## Sanford (Jan 26, 2009)

Joe T said:


> Presume you meant parallel else all the limb manufacturers just went out of business :smile:


Ah, yes, there would be one great inefficiency to not bend there. The "no bend" should be at the edge and not flat of the limb.


----------



## Borderbows (Apr 4, 2009)

Joe T said:


> Don't know the answer to this. I would guess that the longer/narrower limb would twist more but the recurve pushes stress down the limb so .... Worst case is probably a highly recurved longbow.


Id say thin and wide will flex more rotationally verses a more square sectioned limb, BUT.... i think the difference is the unsupported string length on a longbow will not help reduce the amplitude of the string ossilations while the recurve would support the string sooner and help control some of the swing in the string...


----------



## nyamazan (Jan 31, 2008)

I've nothing to add to this thread except to say it's probablly the most interesting insight into the workings of a recurve limb I've ever read, even though I have to read most of the technical aspects at least twice!


----------



## Sanford (Jan 26, 2009)

Joe T said:


> This is true. However if you first bend the limb as normal i.e. stress it and then apply a side load then the limb can twist. The effect is not dissimilar to the archers' paradox where an axial load generates a lateral bend. i.e. it's not intuitive


That's basically what I was trying to state, although much more backwardly. That lateral load cannot bend the limbs laterally but CAN impart twist into the limb. Is this all that bad, though? 

We know from Borderbow's explanation that with rigid limbs, limbs that resist twist, the lateral load goes though the bow hand, riser, and is finally met with the opposing resistance of distributed mass and long-rod stabilization, i.e., the stiffer limbs don't work as well barebow. 

The alternatives appear to be: 1) allow "some" twist but control lateral limb movement (a twist does not necessarily have to deviate centerline); or 2) stiffen to prevent twist and move that lateral force on down the line to stabilization. Still no expertise here, just thinking through things and learning.


----------



## Borderbows (Apr 4, 2009)

Sanford:
Due to the recurve you cannot have a twist that does not avoid a detrimental effect on the centreline! That springy recurve tip will want to take the path of least resistance and to jack knife is its ultimate goal.

Its the bow maker with materials and design that should prevent this jack knife effect.
The Input to cause this jack knife is installed the moment you release from fingers. We cant run away from those dam pesky fingers!!! :teeth:


----------



## Sanford (Jan 26, 2009)

Borderbows said:


> Sanford:
> Due to the recurve you cannot have a twist that does not avoid a detrimental effect on the centreline! That springy recurve tip will want to take the path of least resistance and to jack knife is its ultimate goal.
> 
> Its the bow maker with materials and design that should prevent this jack knife effect.
> The Input to cause this jack knife is installed the moment you release from fingers. We cant run away from those dam pesky fingers!!! :teeth:


Is there a graphical representation of this out there? A slow movie of the recurve? I've tested mine. My long 900CXs, pulled to full force. I can literally pull sideways enough to pull the sting off the limb, but the limb tips do not budge. Not one iota. The string does swings on the loop hinges. There should be no greater force than my full draw, but I am trying to visualize the dynamic process not seen in this static test.


----------



## rasyad (Nov 22, 2005)

Sanford said:


> ....I suspect the bow handle is anchored in a test bench, or so it appears to be so. If so, all string angle and side force for that test will naturally swing the tips, since the bow cannot rotate on its axis. Just a thought.


Hey Stanford, 

Check this out: http://www.youtube.com/watch?v=O8RXg66h9Kk

I know we (as a group) have conversationally agreed that torsional stability is a good thing. Nonetheless, I went back and looked at other videos in W&Ws testing series to see if the bow was fixtured so as to prevent any twisting. To me it looks like the bow is resting unrestrained on an arm that allows perfect alignment with the drawing element.

If you look closely at the first overhead video again you will see that the string continues to move away from center after clearing the release "fingers". The limb tips only start moving laterally (in a long arc) at the apex of the string's lateral deflection. I am speculating here but I think this shows that the stored energy of the bow is being deflected by the nock end of the compressed and bent arrow. The sequence of events as I see it:

The stored energy of the limbs is released and guided laterally around the fingers.
The arrow starts to bend and continues to push the string sideways.
At maximum arrow bend (max deflection of the nock and string) a lateral force is delivered to the limb tips that starts the limb tips on a single arcing path that only ends after the arrow has left the string.
Just after delivering it's little "punch" to the limb tips the arrow bends the other way and completes its "s" shaped path before leaving the string. 
Looking at lots of slow motion video it looks like the first bend of the arrow is the biggest bend and the only arrow oscillation that significantly effects the limb tips path. Between the first bend and second bend, the arrow passes through straight. When the arrow is straight the point of the arrow matches the speed and rate of acceleration of the nock and the rest of the arrow. 

If we were little (very little) scientists strapped onto the nock of an arrow we would experience being shot from the bow as a sequence of violent surges of acceleration coming from several directions. Obviously the first thing we would want would be to untied and let off the nasty ride. Second choice we would be to ride on an arrow shot from a compound. At least it would be smoother, more like a rocket sled on tracks laid over gently rolling terrain. Unfortunately, we are being shot from a recurve so the first and traditionally most important thing is to ride an optimally spined arrow. Too stiff or too weak and we start banging into things. 

I have read reports that Border Hex 5 limbs seem to tolerate a wider range of arrow spine. I have had the same experience and have been puzzled by this. Sid has explained that his Super Recurve Limb Geometry significantly shortens the free length of bow string during the shot. From the Draw Force Curves we know that the limb tips unfold in the last third of the draw. However, does it also hold that the limb tips somehow roll forward first? I would love to see slow motion video of the Border limbs shooting so we could see how and when the string becomes supported by the string grove. That the Border limbs support more bowstring is clear. My question is when does this happen during the shot and does this account for the anecdotal reports of greater spine tolerance?

This forum has a wealth of top level archers that have spent years fine tuning for optimum performance. Is it true that a bow capable of tolerating a wider range of arrow spine would be more forgiving to shoot?

Rasyad


----------



## Vittorio (Jul 17, 2003)

rasyad said:


> This forum has a wealth of top level archers that have spent years fine tuning for optimum performance. Is it true that a bow capable of tolerating a wider range of arrow spine would be more forgiving to shoot?
> Rasyad


The answer is of course yes, but it will also be giving more troubles to user to find the optimal tuning for it. 
Modern limbs with improved curve shape bend more at the middle than at the tip, and curves are showing it clearly. It means that the energy retuned increases faster after some inches from release. This also means that the maximum poundage x inch is available to a shorter dynamic arrow and when arrow has already left the rest. This makes differencies between spines less visible by normal tuning ways. But because of this, optimal tuningand best arrow size is more difficult to find. 
Same as compound bows, were an extreme "curve" is built by the rotation of the cams and the problem of finding the perfect arrow becomes more and more difficult, as many sizes tend to perform apparently the same way.


----------



## Joe T (Apr 5, 2003)

Sort of lost the original point re forgiveness so how, or can, limb torsional stiffness affect "forgiveness". Forgiveness as ever is defined in arrow scatter on the target (group size).

When you shoot an arrow the nock travels (horizontal plane) in an arc. The arc height with a weak arrow is higher then the arc height with a stiff arrow. i.e. with the weaker shaft the nock travels further sideways. One could amost define weak/stiff in terms of the arc height (nock sideways movement). A weak arrow goes (in flight) to the right and vice versa. 

Archer variations result in variations in arc height and consequent left/right arrow hits on the target. The hypothesis is that anything that increases the string pull back to the centre on the arrow nock (stabilisation, increased limb torsional stiffness, getting the string onto the limb surface) will reduce *variations* in arc height and hence lateral arrow hit variations.

The same in principle applies to variation in vertical nock movement.

PS simultaneous key board hits - re Vittorios comment if you installed string guides on the riser to restrain sideways movement on the nock you would be able to shoot a much wider range of arrow spines.


----------



## Borderbows (Apr 4, 2009)

Sanford said:


> Is there a graphical representation of this out there? A slow movie of the recurve? I've tested mine. My long 900CXs, pulled to full force. I can literally pull sideways enough to pull the sting off the limb, but the limb tips do not budge. Not one iota. The string does swings on the loop hinges. There should be no greater force than my full draw, but I am trying to visualize the dynamic process not seen in this static test.


If you mal-align your limbs in the riser, then as you pull the string back you will see that the limb tips will try and rotate round which will result in a twisted and broken limb.
Now, that is because the limb is out of line to the string.

Now upon release you kick the string out of alignment to the limb, (same situation, but in reverse, but it has the same consiquence)
This side load is the little rotter that gives us the problem...


----------



## Borderbows (Apr 4, 2009)

I would aliken arrow spine to a standard distribution curve...
we have two basic ideas that effect the peak of this curve.
Both come back to the same horizontal string path.

vairations in release and variations in spine.

Now, if we can make a bow thats tollerant to spine then the platau on the top of the Dstribution curve gets bigger. So once you nail down your arrow choice, and you find the middle of that bell shaped graph, then you will also benefit from a wider tollerance to release vairiations. this is the basic idea behind torsionally stiff limb.


----------



## Sanford (Jan 26, 2009)

rasyad said:


> This forum has a wealth of top level archers that have spent years fine tuning for optimum performance.
> Rasyad


Yes it does. I know I can sound critical. I'm not. I'm just the critical student.:teeth: Heck, most archers here have more hours on their favorite string than I have in total shooting time. I tend to push where I don't see a point or understand - get's me some affirmation or the answer quicker.

I actually can understand your free length of the string explanation, as that reaffirms some of what I have already understood as to the forgiving nature of recurves over longbows, other than just side load rigidity. I shoot both and have anecdotal references to boot.

On the compound ride v. the recurve ride, I can see that analogy as well, as the load application is a contributing factor to arrow spine forgiveness. Taking off from zero to 200 fps does more in terms of dynamic spine than starting with controlled acceleration and hitting the gas towards the end of line. 

Thanks again.


----------



## rasyad (Nov 22, 2005)

Vittorio,

Fantastic response! I see your point that finding the optimal tuning and spine becomes more elusive with more forgiving designs. I get it and this seems like a good problem to have. For the intermediate archer (me) good tune is good enough. For the top tier archers optimal tuning (however tedious to establish) would yield even higher levels of performance due to the extremely forgiving nature of equipment optimally tuned.

Here is another question dealing with arrows that group close enough that the archer is unable to determine a difference in performance. Is there a general rule that would suggest shooting the weaker or stiffer arrow?

Thanks,

Rasyad


----------



## rasyad (Nov 22, 2005)

Hey Stanford,

No worries, I read nothing critical in your response. Great thread.

Rasyad


----------



## OutPerformed (Jan 20, 2009)

What would be the outcome of a test like this:

Straight torsionally stable limbs aligned twisted vs straight torsionally not so good limb aligned twisted. It would be also nice to know how it compares with correct alignment.

New 90m world record was shot with a set of Vera limbs. Those limbs must be quite stable.
I have been playing with a set and it is surprising how heavy the limbs are actually. They are significantly heavier than other high end limbs yet their speed is similar to them.(very close to Inno) Especially the limb tips are made heavy on purpose. The DFC is very nice(yet not even close to Hex5mk2)which keeps the speed decent. Torsional and vertical rigidy is close to Inno(which is good imo).

So how does the limb mass effect forgiveness(theoretically)? Atleast heavy limbs give nice forward bow jumping.(adds to forgiveness?)

Still waiting for a reply about strings. What kind of string would be most forgiving?


----------



## Borderbows (Apr 4, 2009)

its very often said that the archer will be the deciding factor in the score.
Id say that when two archers are equal in ability, then the bow will help.
Nothing will make up for tune and techneque.
I personally have a "jury out" on string mass other than, add 5-10 grains on to your arrow and save it off the string and give yourself some arrow mass down range for the same arrow speed... due to a more efficent bow?


----------



## OldSchoolNEO (May 11, 2009)

To summerize in overly simple terms.
It's assumed that the archer,the the arrow and a basic tune are optimized.

The orignal question was "What gives a recurve forgiveness?"

It would seem to me that riser design and construction must be sound, after that it plays a small part in the forgiveness equation.
The bulk of the forgiveness comes from the limb's abiltiy to, after release ...
get the nocking point to its correct "at rest" position in the straightest PointA to PointB path.
The same example could be viewed at the limb tips as well i.e getting to the "at rest" position via the straightest path.

My summerization...
*The sooner the limbs respond and recover from the archer's influence, the more forgiving the set-up.*

Is my understanding correct?

Does anyone have anything else to add?
This has been an interesting read, thanks for all the participation.


----------



## gig'em 99 (Feb 1, 2008)

I know most of this thread has been dedicated to recurve forgiveness, but I think we could easily add "arrow" forgiveness too, for overall "set-up" forgiveness. I've been playing around with different arrow's over the years, and am coming to the conclusion that heavier mass in the arrow, leads to a more forgiving set-up. Not to bash any particular arrow manufacturer, but I've found that my ultra light weight carbon arrows are more reactive to minor form variations than say my heavier aluminum/carbon arrows of the same spine. I can get each set up to tune great, but a pluck on the heavier one might cost me 2 points, and a pluck on the lighter arrow might cost me 4.

This leads me to the conclusion that, at least for me, I should be using a heavier arrow that I can get down range fairly quickly, rather than a light arrow that is blazing fast.

So would anyone agree that you should use as much mass in the arrow as allows you to comfortably shoot all of the distances required? Obviously within reason of course...

Has anyone experimented with this concept?


----------



## Old Hoyt (Jul 28, 2005)

I have definitley noticed this indoors, even within different weights of aluminum at approximately the same spine. For example 1916 XX75's on average give me 3 to 5 points better score on a 30 arrow round at 18 meters than 2013 XX75. 

Maybe we need another thread addressing *overall "set-up" forgiveness*???

Grant
:canada:


----------



## OldSchoolNEO (May 11, 2009)

Old Hoyt said:


> ...Maybe we need another thread addressing *overall "set-up" forgiveness*???
> ...


That was kinda the (my) plan, take individual elements of set-up and through them out to be hashed among the resident experts.

My next direction was to talk specifically about the arrow rest but you're [obviously] more than welcome to start your own.

This has been interesting to say the least.


----------

