# Olympic Recurve Limb Curve?



## Zbone (Aug 4, 2012)

This may a stupid question, but being a traditionalist and crafting a few bows (bowyery) through the years and looking at these Olympic bows from afar, (via photos) most limbs look to have about the same recurve to them, which in the traditional world this is not the case. Are there certain regulation on the amount of curl these limbs may have?

Thanx


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## HikerDave (Jan 1, 2011)

Zbone said:


> This may a stupid question, but being a traditionalist and crafting a few bows (bowyery) through the years and looking at these Olympic bows from afar, (via photos) most limbs look to have about the same recurve to them, which in the traditional world this is not the case. Are there certain regulation on the amount of curl these limbs may have?
> 
> Thanx


There is no such regulation, but the IBO string length guideline of string length 3 inches less than the bow length might constrain the shape of the bow. Hoyt Formula bows take a string length 2 1/2 inch less than the bow length, and my borders use a string just 1 1/2 inches less than the bow length. I predict that more recurve will become fashionable soon.


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## limbwalker (Sep 26, 2003)

No, there is really no set rule that I'm aware of. However, Earl Hoyt Jr. pretty well found the perfect shape of a competition recurve limb many decades ago, and there has been little or no reason to change it since. There are a few manufacturers out there who have a little more agressive curve, but just like most things in physics, there is no free lunch. You usually end up sacrificing one thing for another. 

Traditional bows are not built for the same requirements as Olympic recurves, and so they can experiment with more or less deflex, more or less curve in the limbs, multiple curves (stewart comes to mind) etc. without any real penalties. In fact, the novelty factor helps a particular traditional bow stand out in the market if it has some unique feature to set it apart.

One thing about asking world class athletes to shoot arrows at 90 meters for score - it generally seperates the wheat from the chaff pretty quickly. 

John


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## Zbone (Aug 4, 2012)

Thanx guys....

HikerDave - Interesting the brace height that long...

"sacrificing one thing for another" yeah for sure, archery is definitively a give and take activity.

Thanx again folks...


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## Zbone (Aug 4, 2012)

Oops forgot to ask John - Speaking of 90 meters, am having a big round bale of hay delivered to my house for a target next week, and don't know whether to place it at 90 meter or 70 for long range practice? I barely have enough area to get it out to 90 but it can be done, although 70 fits more comfortably.

Any thoughts?..... Thanx


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## SD40 (Dec 25, 2005)

Z,

Put it at 90 and your done, you can always walk up for the 70!.


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## Zbone (Aug 4, 2012)

Kinda what I was thinking...8^) Thanx


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## limbwalker (Sep 26, 2003)

90 meter shooting always helps your 70 meter shooting. That being said however, ask yourself how many arrows you'll shoot in competition at 90 meters this coming year. Chances are it's going to be 72 or less. I wouldn't put my shooting line anywhere other than exactly where I wanted it for just 72 arrows.

John


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## Stash (Jun 1, 2002)

Limb and recurve design is a lot more complicated than it looks, but the generally the similarity between almost all competition Olympic bows is due to two things.

First, the basic "proven" design as suggested above, meaning the recurve unfolds to store the most energy *at a specific draw length*, and second, the availability of these bows with the same limb design but in different overall lengths to suit the archer's draw length.

Most trad type bows are a single design per model and the same model might end up being used by an archer with a 24" draw length as well as by an archer with a 30" draw length. The best bows are designed to not stack at the longer draw lengths, so some sacrifice in efficiency has to be made for the shorter DL folks in order to not have to have to produce the the same model bow in different bow lengths.

Also, trad bows tend to be shorter, so they require more recurve in the limbs.


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## HikerDave (Jan 1, 2011)

Zbone said:


> Thanx guys....
> 
> HikerDave - Interesting the brace height that long...
> 
> ...


My brace height with the long string is 7 inches. Most of the extra length is wound around the large recurve so the brace height isn't as low as if that string was put on a set of Hoyt Formula limbs.


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## John_K (Oct 30, 2011)

Simply, the sharper the recurve, the more unstable the limb, given more or less the same materials in the limb. So there is a trade off.

However, if you use different and more stable materials, the rules change.

Earl Hoyt's bow geometry was perfect given the materials available at the time. IMHO with advances in material technology, other options become available.

Just my 2p


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## limbwalker (Sep 26, 2003)

> Earl Hoyt's bow geometry was perfect given the materials available at the time. IMHO with advances in material technology, other options become available.
> 
> Just my 2p


Such as?


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## Zbone (Aug 4, 2012)

Tend to agree with John K...

Such as: carbon backing rather than fiberglass, foam core rather than wood, new glues, etc. Laminate materials have came a long way since back in the day.


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## Greysides (Jun 10, 2009)

limbwalker said:


> No, there is really no set rule that I'm aware of. However, Earl Hoyt Jr. pretty well found the perfect shape of a competition recurve limb many decades ago, and there has been little or no reason to change it since.


Greenhorn made some unusual limbs a while ago.











The fact they no longer make these would support the point above.


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## limbwalker (Sep 26, 2003)

Bill Stewart made the "Greenhorn" limbs before Greenhorn did.

Most promising traditional limb design I've seen in the last 20+ years was O.L. Adcock's ACS (Adcock Cross Section) longbow limb. It added speed AND stability to the traditional flat longbow limb. I had high hopes he'd have it in an ILF-compatible fitting by 2004 but it never came to fruition.

John


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## grantmac (May 31, 2007)

You can get ACS recurve and longbow limbs in ILF flavor right now John, Dryad is making them.

-Grant


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## Zbone (Aug 4, 2012)

Yeah the whole ACS (Adcock Cross Section) thing turned into a real fiasco.

Are there straight limb tournaments for these ILF risers? ....I'm a longbow man myself...8^)


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## limbwalker (Sep 26, 2003)

Zbone, I won't comment on the personal nature of things, but the design is far from a fiasco. Nobody in the traditional world has come up with anything as innovative since. Prior to the ACS limb, I'd say the last real sea-change in traditional archery was the success of the 21st Century R/D longbows that pretty well turned the concept of a longbow on it's head in the late 80's and early 1990's.

In fita recurve, nothing really all that significant has come out since the 1st Syntactic foam core Carbon Plus GM limbs.

John


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## Zbone (Aug 4, 2012)

Thanx John


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## John_K (Oct 30, 2011)

Stiffer, lighter and more torsionally rigid (than glass) carbon laminates for one, and possibly other synthetic core options.

The way I understand it, the more recurved a limb, the more energy it can store, but the less stable it becomes. If you offset that with alternative materials, you change the rules of the trade off.

Of course, you can also stick with a more "conventional" shape and make gains from stiffer and lighter material options.

I'm sure if Mr Hoyt were around and busy designing bows today he'd be exploring more options. I read an interview with him not long after I first started the sport. A great innovator who gave archery so much.


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## Zbone (Aug 4, 2012)

Yeah, agree Mr. Hoyt was a true innovator and ranks right up there with Fred Bear (first to laminate composite materials and market commercially) and both true ambassadors of modern archery and if still around believe Mr. Hoyt would have been experimenting with today's technologies.

Tinkering around with bow materials and designs takes time and money and those pieces parts are just too expensive just to end up in the campfire for amateur bowyers like myself with a full time jobs and no moneys…8^)


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## limbwalker (Sep 26, 2003)

John K, Earl Hoyt Jr. had all those things available to him. No question he would be tinkering, but sometimes we too easily forget that one size/shape/style doesn't fit every archer. I've seen heated debates here about riser geometry, limb construction, etc. as if every single archer is going to benefit from any one design. Nonsense. Each archer should have an opportunity to select the geometry and design that suits them the best. 

What I need at 32.5" and 47-48# draw weight is completely different than what someone shooting 32# at 27" will most benefit from.

John


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## rick11743 (Sep 20, 2010)

It looks like the only contemporary limb manufacturer that is offering more a aggressive recurve shape is Border


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## grantmac (May 31, 2007)

Uukha are also slightly more aggressive, and there are a couple more "trad" manufacturers starting to try to get into the target scene.

-Grant


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## Zbone (Aug 4, 2012)

Yeah, some of the trad bowyers offer limbs for hunting bows with more aggressive curves in the ILF concept, (Morrison comes to mind, and I think he made aluminum risers once upon a time) and even Samick hunting bow limbs of ILF, so I was wondering what kind of performance these limbs would have out of top preforming Olympic Recurve risers?


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## Borderbows (Apr 4, 2009)

harry drake made flight bows with the cross section idea... but our little hawk has taken the ol flight records. the reason the acs is fast is that its a 50 carbon limb to my knowledge and that the limbs are massively preloaded. ie 6+ " infront of the riser.

if your not stressing every fiber up then your not using them all. and the curved cross section only stresses up the peaks. where as a flat limb can have the whole cross section loaded. for example. if a rain gutter buckles with stress its either crumpled at the rim or the middle of the trough. 
thats why we dont use it as in our view the patent isnt worth it. sinces harry drake published the idea in an article in the mid 60s


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## gpb (Feb 14, 2009)

limbwalker said:


> Zbone, I won't comment on the personal nature of things, but the design is far from a fiasco. Nobody in the traditional world has come up with anything as innovative since. Prior to the ACS limb, I'd say the last real sea-change in traditional archery was the success of the 21st Century R/D longbows that pretty well turned the concept of a longbow on it's head in the late 80's and early 1990's.
> 
> In fita recurve, nothing really all that significant has come out since the 1st Syntactic foam core Carbon Plus GM limbs.
> 
> John


I beg to differ, the Hex series limbs especially the Hex6 Borders came out with this year. It has taken a lot of expermenting and an open mindset to figure out the proper setup as they operate under a different set of rules but once I found that they shoot like nothing else on the planet. John I sent you two PM's Greg


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## DWAA Archer (Oct 14, 2011)

I thought that the reason limb shape had not changed much was the cost of retooling the production lines to make limbs with a more extreme recurve.


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## Borderbows (Apr 4, 2009)

Stash said:


> Limb and recurve design is a lot more complicated than it looks, but the generally the similarity between almost all competition Olympic bows is due to two things.
> 
> First, the basic "proven" design as suggested above, meaning the recurve unfolds to store the most energy *at a specific draw length*, and second, the availability of these bows with the same limb design but in different overall lengths to suit the archer's draw length.
> 
> ...


most of the mass production companies have a shop floor set up with Limb presses to squeeze limbs together during glueing. so one former needs to have the base stability for the base model. this geometry is suited to ud composits. so january and febuary are set aside to make base models. march is for making intermediate limbs. and april top end limbs. so to save on retooling costs. and setup time its easy to use tje same jigs and tooling. from januaru to december. this means that top end limbs have the same profile and widths as bottom end. its called mass production.
if you want a bit more recurve.
there is a video of earl hoyts old presses being used by thier current owner and you will see that the donward pressure lends itself to hoyt profile limb. put some more radical profile limbs end to end in this crossbow prod style and you will see that a downward press wont work. so your limited by your tooling in mass production setups.


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## Zbone (Aug 4, 2012)

Borderbows - Just visited your website, now yeah that's the kind of curve I'm talkn bout...8^)

Couldn't find a price list, so I guess the olde cliche "If you have to ask, you can't afford" applies...8^)


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## grantmac (May 31, 2007)

Zbone said:


> Borderbows - Just visited your website, now yeah that's the kind of curve I'm talkn bout...8^)
> 
> Couldn't find a price list, so I guess the olde cliche "If you have to ask, you can't afford" applies...8^)


Not necessarily, Hex5 with wood core are about on par with the top of the mid-range offerings from anyone else. Shipping is killer though, work finding 2 friends to share it with.

-Grant


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## DWAA Archer (Oct 14, 2011)

Zbone said:


> Borderbows - Just visited your website, now yeah that's the kind of curve I'm talkn bout...8^)
> 
> Couldn't find a price list, so I guess the olde cliche "If you have to ask, you can't afford" applies...8^)


They are what can be described as competitively priced in that their top end kit is a bit cheaper than the top end kit from the big name companies.

compared to top end limbs when shooting the Hex limbs you will notice a day and night difference in how they feel and perform.


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## zal (May 1, 2007)

Current trend seems to be going back to less recurve. Inno ex range has noticeably less curve than previous ranges, and compared side by side with Earl Hoyt's Sky Conquest limb, there isn't that much difference.


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## Borderbows (Apr 4, 2009)

can you show us Zal. its easy to measure. limb bolts at the same positions. brace height at the mid point of the manufacturers range and measure how much string lenght is in contact with the limb. i suppose a winex vs ex range would do... 3-4 mm might show a different core taper but other than that the will be off the same former. but havent seen it myself.


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## Chris RL (Oct 30, 2011)

Sid, hello!
Chris here. This discussion should get interesting!
Have a pair of Sid's Border Hex6 H BB2s, and also a pair of his Hex5 H's, with yet another pair on the way, so I guess you can say I love his products!
"Mongolian" is the most common reaction I get, right after "these must be ultra high efficiency limbs..."


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## limbwalker (Sep 26, 2003)

I'd love to see a manufacturer actually build limbs that perform according to the draw length they are intended to be shot at.

One geometry simply does not work best for all draw lengths. 

Same goes for risers. No reason a 23" riser should have the same geometry as a 27" riser when they will be shot by archers with completely different draw lengths.

John


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## Borderbows (Apr 4, 2009)

limbwalker said:


> I'd love to see a manufacturer actually build limbs that perform according to the draw length they are intended to be shot at.
> 
> One geometry simply does not work best for all draw lengths.
> 
> ...


how would you go about desiging limbs so that they are ideal at the designed draw length?
what criteria does a limb have that makes it meet a certain DL?

and long limbs are 30-33" which is a wider remit than meduims. ad somehow smalls are to be used from 24-29"

edit:
I should have added, that the riser length has little to do actual riser length. For example. Take a one peice bow. how long is the riser in that one. 
Well, there is a backwards way of measureing the real deal on riser lenght. If the working limb (limb tip to fadeout) is say 17" and there are two, then the riser length is 70" - 17"X2 = 36"... where you put the bolts is irrelevant.
So next one is to look at short Meduims and longs and measure the fadeout to limb tip measurement and you will see there are differences in some limbs and not others... same model same brand, just different lengths...


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## massman (Jun 21, 2004)

So if I understand Sid's production explination, each limb is manufactured in it's own mold/press. Why are the set of limbs not made in a single mold/press that is double width, and then cut this blank into each seperate limb?

If not then it has to be VERY difficult if not impossible to manufacture multiple molds that are "exactly" the same. Or is their variance some acceptable standard?

My best, Tom.


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## Borderbows (Apr 4, 2009)

yamaha i think it was had double width presses. BUT if you buy from the usual Industry standard material suppliers then you will have the options of 2", 1.75" or 1.5" strips of materials.

so this kinda sets a precident as to where the molds evolve from.

most of this has spawned from the days that target bows are one peice... Id guess. have you never questioned why limbs are all under 1.75"... thats the blank stock most come from...


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## massman (Jun 21, 2004)

So Sid, I have a few other questions...don't laugh. From a side profile, why is the butt end (where is attaches to the riser) the shape it is? Why not have this app. 3/8" wide? Is it beefed up to minimize/eliminate flexing?
what do you think would be the effect of milling a 1/4" - 3/8" slot through the limb from app 3" from the tip dowm toa about 6" from the dovetail? Lastly how much do you think limb speed is depleted due to a lack of aerodynamics of the limb. You're pushing a flat surface through the air. Are we not?

My Best,

Tom


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## limbwalker (Sep 26, 2003)

> how would you go about desiging limbs so that they are ideal at the designed draw length?


Well, for starters I'd have more than one set of forms (presses) for three lengths of limbs. Each length should have it's own form designed to optimize performance in the draw length range it's used for. 

Just like risers... Short draw archers don't need as much deflex in their risers. And yet we have manufacturers that put the same amount of deflex in a 23, 25 and 27" riser..... Seriously?

23" risers should be neutral, 25" risers should be mildly deflexed, and 27" risers should be the most deflexed to accomodate the expected draw lengths. 

It's not rocket science. Right now, we've got archers shooting riser/limb combinations at 1" less than where they stack, at the point where they begin to stack, and 1" past where they begin to stack. That makes no sense.

John


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## Harperman (Sep 3, 2006)

limbwalker said:


> Well, for starters I'd have more than one set of forms (presses) for three lengths of limbs. Each length should have it's own form designed to optimize performance in the draw length range it's used for.
> 
> Just like risers... Short draw archers don't need as much deflex in their risers. And yet we have manufacturers that put the same amount of deflex in a 23, 25 and 27" riser..... Seriously?
> 
> ...


John, my personal guess on the riser deflex amount of each riser length is so that Manf. can get a "ballpark" figure for limb weight??....Just a guess....Not the same subject, but I've never understood why most ILF risers have the balance so out of whack...Take a naked riser, with limbs mounted and strung....Hold it out, and with a relaxed bow hand, and most risers will tip back hard with the top limb toward the shooters head/face.....This means that some folks will have to mess with Tiller more than they should have to, and add more weight to the front of the riser to get the balance they need.....I'm sure that this has been discussed at length on here before, but I dont remember....Not hijacking the thread, just wanted to mention that because it's another thing that in my mind goes along with why Manf. have stuck with the equipment being pretty much the same designs (with minor tweeks here and there) for so many years...But, hey, if it aint broke, dont break it, right???.................Jim


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## DWAA Archer (Oct 14, 2011)

Harperman said:


> John, my personal guess on the riser deflex amount of each riser length is so that Manf. can get a "ballpark" figure for limb weight??....Just a guess....Not the same subject, but I've never understood why most ILF risers have the balance so out of whack...Take a naked riser, with limbs mounted and strung....Hold it out, and with a relaxed bow hand, and most risers will tip back hard with the top limb toward the shooters head/face.....This means that some folks will have to mess with Tiller more than they should have to, and add more weight to the front of the riser to get the balance they need.....I'm sure that this has been discussed at length on here before, but I dont remember....Not hijacking the thread, just wanted to mention that because it's another thing that in my mind goes along with why Manf. have stuck with the equipment being pretty much the same designs (with minor tweeks here and there) for so many years...But, hey, if it aint broke, dont break it, right???.................Jim


Maybe its because your hand is not in the centre of the bow?


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## John_K (Oct 30, 2011)

limbwalker said:


> John K, Earl Hoyt Jr. had all those things available to him. No question he would be tinkering, but sometimes we too easily forget that one size/shape/style doesn't fit every archer. I've seen heated debates here about riser geometry, limb construction, etc. as if every single archer is going to benefit from any one design. Nonsense. Each archer should have an opportunity to select the geometry and design that suits them the best.


Well, we won't agree on one thing, John - materials science is advancing all the time thanks to factors outside archery (other sporting applications, military research, construction, etc.). Mr Hoyt just wouldn't have had access to the same materials bowyers do today.

But yes, we do agree that no one geometry necessarily fits all. I could certainly ask a custom bow maker to build a bow to my biomechanical specifications (to coin a phrase ) but even if I could, it would cost me an enormous amount of money. Alternatively, I can pick a riser that I like the feel of, pick a bow length with a string angle that suits me, and spend my money on a set of limbs that performs well at my draw.

Then it's just a matter of putting the hours in, as I know all too well as I try to come back from injury 



> What I need at 32.5" and 47-48# draw weight is completely different than what someone shooting 32# at 27" will most benefit from.


Agreed. This is why it's important to select a limb that works well for each individual, budget allowing of course.

Also, I've been having a think about this bow geometry issue. An excellent example everyone here will know of is the Winex limb - it followed a more enhanced recurve shape than the norm and contained laminates to improve the torsional rigidity. We all know how successful it's been in all its guises. Interestingly, the limb profile is almost identical to that of the old (pre-Sids) Border Black Douglas limb profile, and also of a Nishizawa limb from the 80s (I have photos somewhere...).


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## Borderbows (Apr 4, 2009)

id say its also a technological breakthrough. if you can make a limb with modern materials that can shoot a 1300+ score that wouldnt even hold a string if it used the hoyt carbon plus construction. wouldnt be able to shoot in a straight line.... now that for me puts massive stress on the importance of harry drakes rain gutter effect on limbs. its as important to archery as electronics is to aircraft stability. its importance has been copied world wide. and im not talking about putting a weave in at 90deg to the limb. im talking about the XP10 idea of running it at 45deg.


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## John_K (Oct 30, 2011)

limbwalker said:


> Well, for starters I'd have more than one set of forms (presses) for three lengths of limbs. Each length should have it's own form designed to optimize performance in the draw length range it's used for.


Isn't that how all limbs are made? I've only seen behind the scenes at one archery manufacturer, but I was under the impression there were forms for each limb length.


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## Borderbows (Apr 4, 2009)

johnK it is possible to do several things on the one former. that make different limb, but its complicted to explain. You can add or subtract 2-3mm from each end of the limb, Moving the area that the limbs profile comes from. 
so for example from the exact same former, you can move the limb butt up a little and move the tip up a little to get more recurve, or vice versa. if your formers have the room.

BUT you can also make all your limbs off the same former. For example if you look down a limb butt you can see that its straight, this means you can keep the tip where it is, and just slide the same limb butt down the former shortening the limb up a bit.
you can also make your fadeout longer or shorter to change the working limb length to optimise the DFC for a set draw. BUT this isnt easy to see, but doesnt mean is not happening in limbs out there.

I think most Bowyers employ some or all these techneques to make the best of the resources and designs. so no one has any one advantage.
But one thing is for sure. Since the gates on design are 100% open, ie there is no perfect design as materials are different today than they were in 30 years ago, i can see no real benefit in a 100% attention being paid to optimising the exact draw length... the ILF adjustment makes for a bigger Geometry change than this level of detail.

For example. There is a ratio of core size to composit to give best results. Have you noticed that 25lbs limbs have little in the way of stability compaired to 50lbs limbs. the 25lbs limbs are noodly. spinldy and weedy in terms of torsional stability and vertical stability. that is bacause these ratios are optimised for the top performers. the bows are designed for the teams that shoot them.
Be onspec for one of the team members and the bow will suit you.

we have 6 different laminate specs to control these vairables as best we can. keep within these ratios. one laminate doesnt give best results for every bow.
this means you can retain Torsional stability and retain alot of the vertical stability for each of the bow weights. keeping it relative to the bow in hand.
I think there is more to limb design than just a former, for that i think limbwalker might be right, but hes still only looking at the mass production outfits. who are pushed by turnover and profit for the shareholders opposed to the smaller nutty proffesor outfits that eat sleep and walk the gear that they make!


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## Borderbows (Apr 4, 2009)

Harperman: a Target riser needs the grip low so that the bow can have a full size sight window. this window needs to be this size so that the bulk of archers cans ee the sight with a good amount of sight extension. etc.
Least changes the better. anchor and sight extension.
The DAS 17" is the same, its got the grip low so that the bow has a bigger more usefull window. this compromises the shooting traits in our view, (only our view) and this compromise needs a heavy weight down low.
this heavy weight is always there on a target bow because of the stabiliser setup.

Target risers are always weighted down low so are not really ideal for barebow.
Alot of barebow risers actually have target geometry but the inclusion of a weight pocket. this in our view isnt a barebow riser, just a target riser with weight facility.

and there is a chicken or egg thing going on here.
lets make an ILF bow.
lets make a new ILF limb. = Same limb pad angles = same base limb geometry.
now we have 3 ILF limbs lets make a new riser = conforming to the limb geometry = same riser design.
its the limb pads angles and deflex that dictates the limb profile in many ways.
so while your all buying ILF geometry components there is less room for design changes.


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## limbwalker (Sep 26, 2003)

harperman, there are balanced risers out there. BEST Zenit comes to mind, as does Belcher's SKY Conquest Advantage, and I believe the PSE X-appeal too.

John


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## Borderbows (Apr 4, 2009)

limbwalker said:


> harperman, there are balanced risers out there. BEST Zenit comes to mind, as does Belcher's SKY Conquest Advantage, and I believe the PSE X-appeal too.
> 
> John


what are the deflex measurements like on these?


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## TomG (Dec 4, 2002)

Regarding the optimum draw length of a limb, I always though of it as the "smooth" part of the draw curve. In real numbers, it is the part of the draw curve where there is the least #/in increase - the force curve derivative minimum. I have seen Sid graphs in the past that showed that.


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## limbwalker (Sep 26, 2003)

I believe a limb should be drawn to the point at which it begins to stack. No more, no less. To me, that's where you're getting optimum performance from the limb, WITH THE ARROW YOU'VE SELECTED. If you shoot a limb beyond where it starts to stack, you will need a stiffer arrow, which will also be a heavier arrow, and you've reached the point of diminishing returns. If you are shooting a limb well before the point at which it starts to stack, you aren't getting the full potential out of that limb.

That's my opinion, in very simple terms. Folks like Sid, Jim Belcher and others have much more experience than I have at building them, but I have much more experience than they have at shooting and tuning Olympic bows for competition, so there are always two ways to view the equasion. Sometimes what looks good on paper just doesn't perform on the field of play, and vise-versa.

Another element to this is what does the archer want to feel when they draw the bow? This cannot be understated. Each elite archer has programmed themselves to feel a certain force at different stages of the draw. If you give them a limb or riser/limb combination that alters this significantly, chances are they won't shoot as well with that rig even if the numbers are better.

For me personally, and also for a few top level archers I've spoken with, a slight feeling of pulling into a "wall" at the clicker is helpful to know where you are in your setup. All my personal best scores have been achieved with a bow that was set up to start stacking at exactly my draw length of 32.5". I can feel this. It helps me know where I'm at in the draw and helps me set up under my clicker. Then I just focus on expanding that last fraction of an inch and really "getting into the limb" so to speak.

If you haven't mapped out the draw force curve for your own bow to see where your draw length is in the curve, I'd suggest you do it. Then, I'd suggest you ask yourself if that's the feeling you want at the clicker. Experiment with different limbs and find one that stacks a little before your draw length, and one that stacks beyond it, and see what your body prefers. 

To me, this is part of the "final fitting" of a bow to an individual archer.

John


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## Borderbows (Apr 4, 2009)

stack preference is down to experience. the human body is very sensitive to change for sure.
it used to be slack head angles on downhill mountain bikes were classed as choppered in unstable. now suspension has caught up slack just got slacker but tje old school boys are still scared of the new bikes. the reason they are now acceptable is the increase in speed and severity of slopes that is now "downhilling" suits these mega slack frames. tje geometry allows it to happen
stepping away from conventional design setup is a brave step. and compounds accept new technology and look at thier progress.


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## edgerat (Dec 14, 2011)

the newer ultra slack DH bikes are also meant to be slid around corners and not steered....


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## Borderbows (Apr 4, 2009)

i dont think the early 90 designs could cut the mustard now though


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## limbwalker (Sep 26, 2003)

Yea, maybe why most tennis racquets weigh in at under 11 oz. nowdays, but I still hit with a 25 year-old, 12.5 oz. Prince 

In golf, archery, tennis and other similar sports, there are technique players and "feel" players. I've always been the latter in all three sports. Technique players are less sensitive to changes in equipment and more consistent from day to day. Feel players are more sensitive to equipment and are streaky hot and cold. Their highs are higher and lows are lower than technique players. 

You get used to it though... 

John


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## DK Lieu (Apr 6, 2011)

John_K said:


> Simply, the sharper the recurve, the more unstable the limb, given more or less the same materials in the limb. So there is a trade off.
> 
> However, if you use different and more stable materials, the rules change.
> 
> ...


This is pretty much correct. Longbows are very accurate because the lack of recurve makes them very stable, very forgiving. However longbows are not good at storing energy because they stack quickly, resulting in high holding forces at full draw. Introduction of recurve reduces stacking and makes the limbs better at storing energy, i.e. more energy with the same holding force. However recurve also introduces instability. This becomes obvious when examining the mechanics of deflection and return of the limbs. This instability, in turn, can be minimized by increasing the torsional stiffness of the limbs. New materials, such as unidirectional carbon, offer unique opportunities to tune the deflection-force curve and also improve the torsional stiffness of the limbs by laying the proper amount of carbon in the proper direction. A conventional 0deg/90deg lay which was first used (because it was easy to do) when these materials became available, for example, gives good bending strength and stiffness, but does little to improve torsional stiffness. Torsional stiffness is improved by laying the carbon at an angle that is parallel and perpendicular to the principal stresses produced by the twisting. Carbon is also lighter and stronger than older materials, making the limbs more efficient. All this is conventional engineering wisdom. The art is in trying to get all the different materials to stick to each other, i.e. the adhesion technology.


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## limbwalker (Sep 26, 2003)

The late, great Howard Hill used to say that he shot longbows because he wasn't good enough to make the shots he needed to make with a recurve. And he made some incredible shots. 

I had high hopes that Adcock's ACS limb design on an ILF riser would give us the best of both worlds. But O.L. became a victim of his own success, and moved on. So we'll never know.

John


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## grantmac (May 31, 2007)

limbwalker said:


> I had high hopes that Adcock's ACS limb design on an ILF riser would give us the best of both worlds. But O.L. became a victim of his own success, and moved on. So we'll never know.
> 
> John


John:
http://www.dryadbows.com/ILF/ilfsystem.htm

ACS is alive and kicking.


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## Borderbows (Apr 4, 2009)

DK Lieu said:


> This is pretty much correct. Longbows are very accurate because the lack of recurve makes them very stable, very forgiving. However longbows are not good at storing energy because they stack quickly, resulting in high holding forces at full draw. Introduction of recurve reduces stacking and makes the limbs better at storing energy, i.e. more energy with the same holding force. However recurve also introduces instability. This becomes obvious when examining the mechanics of deflection and return of the limbs. This instability, in turn, can be minimized by increasing the torsional stiffness of the limbs. New materials, such as unidirectional carbon, offer unique opportunities to tune the deflection-force curve and also improve the torsional stiffness of the limbs by laying the proper amount of carbon in the proper direction. A conventional 0deg/90deg lay which was first used (because it was easy to do) when these materials became available, for example, gives good bending strength and stiffness, but does little to improve torsional stiffness. Torsional stiffness is improved by laying the carbon at an angle that is parallel and perpendicular to the principal stresses produced by the twisting. Carbon is also lighter and stronger than older materials, making the limbs more efficient. All this is conventional engineering wisdom. The art is in trying to get all the different materials to stick to each other, i.e. the adhesion technology.


glad you see what we see. 
longbow limbs can store good energy. and they can be smooth. they just need long working limbs. the problem with that is the longer limb is it carries mass. this more simple limb design has made good progress at catching up with recurves. but only because its Alot easier to make carbon longbow limbs that carbon recurve limbs. but they still cant keep up with the equivelant spec recurve limb. the limb mass vs energy. vs limbs centre of mass hinders its acceleration


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## Borderbows (Apr 4, 2009)

gpb said:


> I beg to differ, the Hex series limbs especially the Hex6 Borders came out with this year. It has taken a lot of expermenting and an open mindset to figure out the proper setup as they operate under a different set of rules but once I found that they shoot like nothing else on the planet. John I sent you two PM's Greg


Greg did you get a reply to your pm's.
id like to know where the other set of limbs are too.


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## limbwalker (Sep 26, 2003)

> id like to know where the other set of limbs are too.


Oh give me a break. Really?


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## Borderbows (Apr 4, 2009)

limbwalker said:


> Oh give me a break. Really?


ok. deal!


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## limbwalker (Sep 26, 2003)

Sid, you and Greg both have a PM


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## John_K (Oct 30, 2011)

DK Lieu said:


> This is pretty much correct. Longbows are very accurate because the lack of recurve makes them very stable, very forgiving. However longbows are not good at storing energy because they stack quickly, resulting in high holding forces at full draw. Introduction of recurve reduces stacking and makes the limbs better at storing energy, i.e. more energy with the same holding force. However recurve also introduces instability. This becomes obvious when examining the mechanics of deflection and return of the limbs. This instability, in turn, can be minimized by increasing the torsional stiffness of the limbs. New materials, such as unidirectional carbon, offer unique opportunities to tune the deflection-force curve and also improve the torsional stiffness of the limbs by laying the proper amount of carbon in the proper direction. A conventional 0deg/90deg lay which was first used (because it was easy to do) when these materials became available, for example, gives good bending strength and stiffness, but does little to improve torsional stiffness. Torsional stiffness is improved by laying the carbon at an angle that is parallel and perpendicular to the principal stresses produced by the twisting. Carbon is also lighter and stronger than older materials, making the limbs more efficient. All this is conventional engineering wisdom. The art is in trying to get all the different materials to stick to each other, i.e. the adhesion technology.


I am very relieved to see you agree, Prof Lieu 

I have an Arts background, so all I've picked up about bow performance and design has been by my own research over my years as an archer. I'm glad to know that some of it stuck between my ears!


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## Borderbows (Apr 4, 2009)

Cheers for the PM Limbwalker.


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## Festivus (Oct 9, 2009)

I've always wanted to know how does a little more recurve or reflex make a recurve limb unstable or how does a static tipped limb make a bow more unstable? I know there is obviously a diminishing rate of return, and that extreme recurve can cause instability. 

Also, in a recurve limb is it better to have a thinner, wider limb or a thicker, narrow limb? Which is faster or more stable?


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## limbwalker (Sep 26, 2003)

A "D" shape is more stable than an "S" shape, to put it in simple terms. A person only really needs as much "recurve" as they can use to prevent stack at their draw. 

John


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## Borderbows (Apr 4, 2009)

limbwalker said:


> A person only really needs as much "recurve" as they can use to prevent stack at their draw.
> 
> John


yes.
and here is for the fun bit.
Longbow limbs are long to prevent stack as you say.
Recurve limbs have shorter working limbs to prevent stack as you say.
our limbs are getting shorter. because we have an excess of smoothness.
now. im not talking about bow length here.
im talking about the length of the riser.

for example, if you have 2 limbs with a working length (tip to fadeout) of 17" thats a working limb length of 34". so on a 70" bow that makes the riser 36" long. and the bolts are placed at 25"
on the second bow, the working limb lengths might be 18" meaning that the riser is 32" long, making a 70" bow, but still on the same 25" bolt layout.
a longbow would need 4 more inches of limb length to get even close to equal.

smoothness is a function of limb length vs mechanical advantage. when you step away from earl hoyts designs, it all starts to change.

so if extreme recurve is a bad thing then some recurve must also be bad. since smoothness can be constructed in a longbow limb as long as its long enough.
the trick is to solving the instability.


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## limbwalker (Sep 26, 2003)

> so if extreme recurve is a bad thing then some recurve must also be bad


This is true, which is probably why Howard Hill said what he said. But he wasn't too worried about speed either...

Speed is only about 5% of this game anyway. It's a highly overrated, but much talked about topic in our sport.

John


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## Borderbows (Apr 4, 2009)

limbwalker said:


> This is true, which is probably why Howard Hill said what he said. But he wasn't too worried about speed either...
> 
> Speed is only about 5% of this game anyway. It's a highly overrated, but much talked about topic in our sport.
> 
> John


there must be a debate to say that the higher the % of floppy compnent the harder it is to control. For example the tip movement on a 3 foot pole must be more than a 1 foot pole.
I think this is the benefit that recurves have over longbows and why recurves have taken no1 spot on the target archery poduims.
as so many people rightly point out, ever aspect of archery is a mixed and confusing topic as its all intertwined!


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## limbwalker (Sep 26, 2003)

Sometimes I sit back and laugh at how wrapped around the axle some folks get about these "tools" we use to compete. Because that's all they are. Just tools. I mean, isn't this supposed to be a competition between archers?

Maybe we need a "stock bow" event once/year like Nascar has, where every archer shoots the same model riser and limbs and arrows so we can really see who's who.

John


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## Vittorio (Jul 17, 2003)

Someone in Italy is deveolping almost linear ILF limbs (semi-long bow like), with a very slim front profile.
They have been tested also in competition during last indoor season by one medium/high level archer (just close to National team level) and shot quite well, very forgiving, with score up to 580. Problem, as expected, is the lack of efficiency when you want to shoot long distancies, but this design is now used by some bare bow archers already. Believe me, the combination of long bow like limbs on ILF risers is very original (can't say nice ...). May be this is the solution for indoor rounds ...


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## Borderbows (Apr 4, 2009)

there are 3 other companies that make ilf longbow limbs not including ourselves. ilf longbow limbs are not new


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## Vittorio (Jul 17, 2003)

Borderbows said:


> there are 3 other companies that make ilf longbow limbs not including ourselves. ilf longbow limbs are not new


Nothing to do with already existing ILF long bow limbs... they have a different shape and and S curve in the limb... I 'll try to get pictures to show how they look like ..


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## limbwalker (Sep 26, 2003)

If I were going to test an ILF longbow limb, the first one's I'd try would be the ACS limb, now produced by Dryad Archery in Weatherford, TX. 

I shot the very first ACS longbow, and in fact, watch O.L. build the forms for it. It's one of the few truly innovative limb designs I've seen in the past 15 years.

John


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## lksseven (Mar 21, 2010)

John,

_"Maybe we need a "stock bow" event once/year like Nascar has, where every archer shoots the same model riser and limbs and arrows so we can really see who's who."_

God forbid! I want a technological edge!


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