Brace height sound variation

Cereleste

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I wouldn't recommend shooting any *x* string material off a recurve these days. Several manufacturers, including Hoyt (in a roundabout way), Border and Uukha advise against as their properties are not good for limbs. They were designed for compounds that are permanently strung, and whose limbs are short, thick, and wide, with a different construction, so take sudden stops much better. Yes, the material is a tiny bit faster, but much harder on the limbs and has been attributed to failures.
For a basic rod experiment. Take all your rods off and shoot with just you sight. It's an illuminating experience, not just from the noise point of view.
Not planning to change string material permanently, just shoot maybe a dozen or two arrows with it to see how the sound changes between small, medium, and high brace heights.
I've tried (and recorded) pretty much all possible combinations of weights and/or stabilisers and/or dampers. Taping a laser pointer to the sight works nicely to see what's going on. Tried scoring once with the stabilisers switched out for just a barebow weight, the loss in accuracy was only about 20 points on a Portsmouth, despite the high frequency movement of the sight. With more practice I expect the difference would be smaller.
 

KidCurry

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Tried scoring once with the stabilisers switched out for just a barebow weight, the loss in accuracy was only about 20 points on a Portsmouth, despite the high frequency movement of the sight. With more practice I expect the difference would be smaller.
What score are you looking at if you don't mind me asking? I usually shoot about 550-560 Portsmouth BB but can push a 570 in practice shooting six arrows. It's hard to get good BB score data as there is not too much around. At the moment with my bow about as well set up as I can using 8125. BCY 652 is next on my list to test.
 
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Cereleste

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What score are you looking at if you don't mind me asking? I usually shoot about 550-560 Portsmouth BB but can push a 570 in practice shooting six arrows. It's hard to get good BB score data as there is not too much around. At the moment with my bow about as well set up as I can using 8125. BCY 652 is next on my list to test.
Don't mind at all - there's so little data around that I've been unable to find most of what I look for and had to do it myself. The test was part of an (uncompleted unfortunately, and therefore unpublished) effort to determine how many points the clicker, stabilisation, sight, and chin anchor were each worth for me on the continuum between recurve and barebow.
Scores are on a 60cm target face in November, with about 4 barebow sessions prior but 9 years of intermittent recurve experience, so definietly not on the same level. Same equipment (ACEs so quite a large crawl and very loud) though I might have changed the nocking point for barebow.
- barebow setup 232, 236, 209/300
- recurve setup with stabilisers swapped for a 450g weight 277 and 278 /300
- recurve setup with stabilisers but no clicker 273/300
- recurve 286, 289/300
I'd planned to also all other possible combinations but got busy.
Then a few months later, using xx75 more than twice as heavy for barebow point on at 18m, but bareshaft ACEs (technically with miniature 1cm spinwings sticking out 1mm for WA compliance) for recurve:
- barebow setup, aiming arrow at the middle 226/300
- barebow setup, aiming arrow bottom of yellow 243/300
- recurve scores at the same time were 270-281 on a 40cm face and 280-290 on a 60cm face
Recurve scores are all in competition, barebow and mixed bowstyle scores were in practice
 

Stretch

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452x stuff...No, I wouldn’t recommend a Vectran blend string on a recurve either. But as this shot with no vibration or noise I wouldn’t hesitate. Something about the setup really liked the no stretch string. I certainly wouldn’t expect the same 99/100 setups.

When you put a Vectran based string on a recurve it usually sounds like a gun going off with vibration to match - caused by the undamped reaction. But if your’re not getting any noise/ vibration there is no damage being done.

Victor Ruban won the Olympics with a blend. He also killed a lot of limbs doing so but his bow was very noisy. Most manufacturers have a failure rate. Yes Vectran blends might help you find that rate faster. They may - as mentioned- invalidate warranty.

Stiff stabiliser stuff - I agree that most of the talk about stiff stabilisers is nonsense. Most people can’t hold stable enough for it to matter. But... the more weight you have on a less stiff rod the noisier it will be post shot. At least that is my experience.

I shoot Shrewd Revels. They’re not that stiff. They feel nice. But most importantly I like how they look :love:

Stretch
 

Cereleste

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452x stuff...No, I wouldn’t recommend a Vectran blend string on a recurve either. But as this shot with no vibration or noise I wouldn’t hesitate. Something about the setup really liked the no stretch string. I certainly wouldn’t expect the same 99/100 setups.

When you put a Vectran based string on a recurve it usually sounds like a gun going off with vibration to match - caused by the undamped reaction. But if your’re not getting any noise/ vibration there is no damage being done.

Victor Ruban won the Olympics with a blend. He also killed a lot of limbs doing so but his bow was very noisy. Most manufacturers have a failure rate. Yes Vectran blends might help you find that rate faster. They may - as mentioned- invalidate warranty.

Stiff stabiliser stuff - I agree that most of the talk about stiff stabilisers is nonsense. Most people can’t hold stable enough for it to matter. But... the more weight you have on a less stiff rod the noisier it will be post shot. At least that is my experience.

I shoot Shrewd Revels. They’re not that stiff. They feel nice. But most importantly I like how they look :love:

Stretch
Definitely the most important aspect of the stabilisers, and the bow as a whole. I got tired of the over-branded rods and the dated sparkly finish on the limbs, so have been trying out a copper patina to match my weights. An odd colour scheme on an odd bow, but not tired of it yet. Plenty of questions at comps; I've alternated between saying it's to keep the slugs off during the outdoor season, or that the superior conductivity means the eddy currents steer the arrow. Though I did discover an unfortunate similarity recently...

Made a Kevlar string this evening. 5 strands of braided 150lb kite string. Centre a bit lumpy, but by luck it's ten grains lighter than my dynaflight97 and nock fit is good. Couldn't resist testing it immediately - first few shots from half draw while wearing a face shield just in case, then at full draw. And I'm baffled - it's nearly silent. No vibration, it's eerie. It's settling in on the bow overnight and I'll see if it's the same in the morning, and will put it through the chronograph too.
 

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KidCurry

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Kevlar was popular back in the 80s. I don't remember limb failure with it but there was probably some. Definitely remember risers cracking in half but risers were cast back then. It was very good but it's major flaw was its failure mode. It used to wear quite quickly then snap at the nocking point with absolutely no warning. If you got the timing right you could take the serving off and find 12 of the 14 strands not connected :)
 
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Timid Toad

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When Kevlar was popular most limbs were using wood and glass, so were slower and better at taking shock. Most people were shooting X7s at 90m so arrows were heavier too. The advent of dyneema was fantastic for the new limb construction materials.
 

Whitehart

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Its interesting that certain wood/glass limbs (normal curve) are still as fast, accurate and reliable, if not faster than a lot of top of the range limbs available today. This using Kevlar or a modern blend string materials like 8125, which for me is more preferable because it is reliable for more than 1000 shots.

The glass wood combination made them heavier, maybe that also contributes to the dampening of vibrations, no problem with modern arrows either...

Nothing wrong with a cast handle if it is made correctly and not cheaply mass produced - great dampening qualities mine is now 29 years old and still going strong.

One other consideration they were also not ILF and designed to work with the riser as a complete package - designed by the bowyer.

I wonder sometimes if we looked backwards we would move forwards quicker or we are being hoodwinked by manufacturers bring out new limbs every year.

Set up is also quicker again with good feed back and less of those what if's that seem to plague archers today and the route of endless fiddling.
 

Stretch

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Kevlar destroyed bows too. I killed a KG1 riser, a set of KG1 limbs and a set of Hoyt glass limbs. Normally the failure was at the limb tip (apart from the riser of course). I shot about 46# with Beman Diva off a 72” bow and for sure it was not slow.

I’m not overly convinced on the modern materials are worse at taking shock. I have a set of Border wood/glass limbs from about 1992 - they need a super soft string to get them to stop anything like a modern limb. (Angel ASB Dyneema which I think is SK65 so quite stretchy). My 1996 Hoyt Syntactic are substantially less fussy.

Generally when a limb fails now it is a construction issue (mainly delamination or limb tip) back in the 80s and 90s you saw more failures due to materials. The string loop just cutting down through the limb was common. But I also witnessed a limb cracking across the laminate itself and core failures. That is an observation based on a reasonably low number so may not be statistically correct. Last set of limbs I killed was 1998 and that was a Stylist so doesn’t count :p they just did that every 8 months or so :cry:

Stretch
 

Cereleste

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When Kevlar was popular most limbs were using wood and glass, so were slower and better at taking shock. Most people were shooting X7s at 90m so arrows were heavier too. The advent of dyneema was fantastic for the new limb construction materials.
What do you mean by better at taking shock? I've heard that the limiting factor for old limbs was the weaker glue technology at the time that made them more prone to delamination. I would expect that delamination to be a result of vibration within the limb eventually causing microcracks between the layers that gradually increase in size with each shot.
While a heavier limb does accelerate less with the same force, the difference in mass isn't huge - based on my limited data from limbs I've owned or others have weighed, at the same poundage foam and carbon each reduce the mass my 30g, or up to a 28% mass reduction going from wood/glass to carbon/foam (though the tip mass matters more and while that reduction could be more or less). A real difference, but not something I would expect to cancel out with the glue technology.
 

Timid Toad

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You don't think 28% is a lot? When people say using a brass nocking point is worth changing for a tied on one? Glue technologies have had to move fast with modern materials and limb designs. But we're getting off topic here, and I don't want to get Whitehart on his soapbox ;)
Suffice to say, no one uses kevlar these days because there are better materials available. Almost as little stretch and far more reliable with better UV resistance. I've got a reel somewhere...in the dark...
 

Whitehart

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Back on topic the Italians 10 years ago started looking at the noise of a bow and whether technology could help with brace height and tiller adjustments and made a device that could measure the frequencies from shot to shot - the ideal tuning tool they thought, yet quieter sound and group sizes did not always correlate and even archer to archer the results were confusing, that was before different equipment such as arrows, nocks, strings were taken into consideration. IMO tuning a recurve bow is about following some rough guidelines and from then on feel and what is in your head, after all a bow is a machine, however it is set up it is still capable of repeating the same task time after time - we are the inconsistent bit. Just a poor release can increase the noise and reduce an arrows fps by up to 2fps a range of 0.5fps is considered too inconsistent for top scores.
 

Cereleste

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Back on topic the Italians 10 years ago started looking at the noise of a bow and whether technology could help with brace height and tiller adjustments and made a device that could measure the frequencies from shot to shot - the ideal tuning tool they thought, yet quieter sound and group sizes did not always correlate and even archer to archer the results were confusing, that was before different equipment such as arrows, nocks, strings were taken into consideration. IMO tuning a recurve bow is about following some rough guidelines and from then on feel and what is in your head, after all a bow is a machine, however it is set up it is still capable of repeating the same task time after time - we are the inconsistent bit. Just a poor release can increase the noise and reduce an arrows fps by up to 2fps a range of 0.5fps is considered too inconsistent for top scores.
Do you mean Stefano Ghedini's master's thesis? He had a vibration sensor on each limb bolt. Though the change in noise (measured as the time the vibration is above 25% of the maximum value) and speed were quite minimal relative to the scatter in the data, to the extent that a wide range of values could be considered the minimum or maximum.
 

Whitehart

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Do you mean Stefano Ghedini's master's thesis? He had a vibration sensor on each limb bolt. Though the change in noise (measured as the time the vibration is above 25% of the maximum value) and speed were quite minimal relative to the scatter in the data, to the extent that a wide range of values could be considered the minimum or maximum.

Sounds familiar but it was over 10 years or so ago :)
 

Cereleste

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You don't think 28% is a lot? When people say using a brass nocking point is worth changing for a tied on one? Glue technologies have had to move fast with modern materials and limb designs. But we're getting off topic here, and I don't want to get Whitehart on his soapbox ;)
Suffice to say, no one uses kevlar these days because there are better materials available. Almost as little stretch and far more reliable with better UV resistance. I've got a reel somewhere...in the dark...
28% mass difference to the limb doesn't give 28% speed difference though. The faster a component is moving, the more its mass matters. The nocking point and centre serving accelerate to the same speed as the arrow. In the same time, the limb tips travel only half as far, and the rest of the limb even less. If the entire limb mass were included in the virtual mass of the bow (which it isn't as the limb mass accounts for only a small fraction of the energy of the moving components), then the 28% mass difference would give only a 4% speed difference. There is a more rigorous analysis in this paper (p12) though it doesn't give example values, and an even better one that incorporates how the limb shape affects speed, but I can't find it currently.
People say a lot of things about increasing arrow speed; not all are justifiable. A brass nocking point (4gr) should only make a 0.8% change in speed for a 250gr arrow, and the effect diminishes as arrow mass increases. The sound is definitely different with the heavy nocking point though, which probably contributes to the perception. Sometimes that 0.8% is all that's needed to have a sight mark.

I've put the kevlar string through the chronograph - for the same brace height as the d97 string, I get 60.6+-1m/s with braided kevlar kite string, and 62.6+-0.4m/s with dynaflight. As the five strands of kevlar give a lumpy cross-section, the nock fit is much more variable hence the speed variation. The more twists/braiding a string has, the more it behaves like a spring so I would expect a real kevlar (or 452x or other non-stretch material) bowstring to give back that speed loss. It's still deathly quiet at several brace heights, so I think there's a reasonable chance that I could catch this elusive "sweet spot" in brace height.
 

Cereleste

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Kevlar destroyed bows too. I killed a KG1 riser, a set of KG1 limbs and a set of Hoyt glass limbs. Normally the failure was at the limb tip (apart from the riser of course). I shot about 46# with Beman Diva off a 72” bow and for sure it was not slow.

I’m not overly convinced on the modern materials are worse at taking shock. I have a set of Border wood/glass limbs from about 1992 - they need a super soft string to get them to stop anything like a modern limb. (Angel ASB Dyneema which I think is SK65 so quite stretchy). My 1996 Hoyt Syntactic are substantially less fussy.

Generally when a limb fails now it is a construction issue (mainly delamination or limb tip) back in the 80s and 90s you saw more failures due to materials. The string loop just cutting down through the limb was common. But I also witnessed a limb cracking across the laminate itself and core failures. That is an observation based on a reasonably low number so may not be statistically correct. Last set of limbs I killed was 1998 and that was a Stylist so doesn’t count :p they just did that every 8 months or so :cry:

Stretch
The data I have on limb mass is from modern limbs only - and has a considerable fault in that the high end limbs all have carbon and the wood/glass ones are from the bargain bin and are likely to give an overestimate to the difference between carbon/foam and wood/glass limbs of the same quality. Do you happen to know how mass (and length and draw weight) of the 1992 Border limbs? It would be nice to compare
 
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