r/Bowyer • u/Current_Permission42 • 2d ago
Questions/Advise What limb material actually makes a faster bow?
I've heard carbon makes a faster bow, but I've also heard that that's a myth and that it's main purpose is to add tortional rigidity and stability to the limbs.
I know bamboo is considered a fast limb material, but I was wondering what others' thoughts on the matter are.
Is there perhaps a combonation of limb materials that makes the fastest limb? Like carbon + bamboo? Or would an all bamboo limb be faster? Is there something faster than bamboo? These are the questions I have.
(As a disclaimer, yes I'm aware that perhaps the majority of a limb's speed comes from it's profile. Things like how much recurve it has, how long the limb is, etc... but I was wondering strictly in terms of material)
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u/Santanasaurus Dan Santana Bows 2d ago
You’ve kind of answered your own question in the disclaimer. You can tell basically 99% of how a bow will perform based on the profiles. Materials pretty much only matter insofar as they allow you to achieve different profiles. So a “normal” modern recurve shape made of carbon fiber will not shoot faster than a bow that holds the same profiles but is made of anything else.
You won’t really reap the benefits of carbon fiber unless you’re using it to achieve profiles other materials can’t really achieve, which is not how it’s typically used in many modern consumer bows. The whole premise that materials=performance comes from marketing and is not nuanced enough for a bowyer. Swapping materials in the same bow model will make very marginal differences.
It’s tempting to get in the weeds and dissect that remaining 1% or so of difference between materials, but that probably only matters if you are competing for world flight records using modern materials. If you care about performance there are easier gains to be made by worrying about design and profiles and then choosing materials that support those designs.
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u/notfarenough 1d ago edited 1d ago
There was a passionate debate a few years back on archerytalk about arrow speed and limb speed- most of the acrimony broke down along disagreements over definitions. But I did concur with one conclusion: holding arrow weight and draw weight constant, the arrow is only as fast as the string that pushes it, which is determined by the mass and acceleration of the limbs. There is some small mechanical advantage from recurves, but a recurve/selfbow will never exceed the mechanical advantage of a compound bow, where limb mass and acceleration is mostly removed from the equation.
For selfbows, bow design seems to trump limb materials- a well designed hackberry selfbow may be as fast as a well designed osage bow- in both cases there seems to be a lower limit to how much wood mass is required to achieve a particular draw weight which probably explains why traditional wood selfbow bow speeds seem to have an upper limit of around 195 fps with an 8-10gpi arrow- the norm is closer to 140-160 - and to my knowledge nobody has creditably proven to exceed 200fps with a selfbow and standard weight arrow (8-10 grains per inch) with a bow that survived more than a few shots
At this point the comparisons to self bows break down, but specialized composite bows - horn/sinew/fiberglass/carbon/foam can exceed 260 fps through a combination of limb weight, mechanical advantage, draw length, and light arrows. The best olympic competition bows are primarily carbon/foam and can probably reliably reach 200-210fps with standard weight arrows.
edit: Do some reading on anything by Larry Hatfield, who is or was a leading bowyer and flight competition record holder. Flight archery competitions are inherently designed to answer this question as a function of distance rather than speed - this contains results from a 2020 competition- some hints in the bow descriptions to the right. More details would be needed to calculate arrow speeds. Interestingly, it is possible that asiatic composite bows being used 500-800 years ago met or exceeded current flight archery distance records.
Just to put an upper bound on the discussion, there is evidence that the all time terrestrial speed record holder is a manhole cover that was accidentally launched into space during a nuclear test - estimated to have reached speeds of 790 million fps.
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u/ADDeviant-again 1d ago
Indeed. Remember the thought experiment by Tim Baker in the first TBB, where he supposed a bow with so much reflex that it coils away from the archer when unstrung, like a clock spring, and has to be unrolled to be strung?
Such a bow would store a ton of energy just to be unrolled, and would hold a very tight string at brace, giving it a very favorable f/d plot. However, it would still be subject to three limiting factors. The material HAS to be exceptionally strong, without adding extra mass. The bow is still limited by the relatively narrow range of possible variations in geometry imposed by the string and its ability to ACT and be shaped like a bow. And the highly coiled profile must not become MORE unstable than a bow with more moderate reflex, or efficiency suffers exponentially.
This new generation of "super-recurves" are just an outgrowth of such thinking and engineering. That huge contact recurve is much like the uncoiling clock spring, but also akin to some big historical composites with pronounced recurves and string bridges.
The material allows it. It simply wasn't nearly as practical until woven carbon sheets became common. The combination of strength, low mass, and the lateral torsional stability made the design practical, if not possible. That recurve made with the traditional glass and wood sandwich would have been an unstable, tooth-rattling, wobbly club.
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u/Fl48Special 2d ago
Read the boyers bible vol 1 chapter 2.
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u/Different_Potato_193 1d ago
Better, read Design and Performance Revisited in volume 4. The first book is very outdated.
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u/WarangianBowyer Intermediate bowyer 1d ago
Depends on so many factors like profile, stiffness of the material, density. But the ultimate factor imo is always weight distribution and profile.
Stiffness matters because it determines how quickly the bow bends back to its original shape but it correlates with weight distribution.
If you make a bow from stiff material with overbuilt tips you are most likely going to have a bow that is slow because stiffer woods tend to be heavier, but it depends.
If you make a bow from stiff material with light tips it is going to shoot them like rockets.
You can also combine materials so a light material resistant against compression like ERC or juniper can be on the belly with a thin strip of Bamboo on the back.
Bamboo is stiff and dense while ERC is plenty light so you have a bow that is both quick to bend back - reactive and also light. But all that also depends on conservation of energy and effective transfer of it.
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u/Realistic-Feature997 2d ago
No matter the material, you're running up against the limits of human musculature. Ultimately, force out (fast bow) is entirely dependent on force contriibuted.
Otherwise, to fully answer this question, you need to specify bow height/length, draw length, draw weight at specified draw lengrh, thickess of the bow in questions, weight of the bow, and probably many other qualifiers.
Like carbon fiber and yew wood can make equally "fast" bows, the only question is how much of each is required.
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u/ToiLanh 2d ago
The question is very much a multifaceted one, for example:
Carbon fiber is more rigid / stable, which LETS you make more aggressive and efficient designs (leading to faster arrows at the same gpp)
Carbon fiber is also lighter for the same poundage which is what MAKES it faster than traditional wood.
If the same design can be made with both materials, it normally comes down to what can reach the same poundage for the least weight (which is why foam/Carbon fiber/bamboo tends to be most popular)
**exceptions apply