Primitive Archer
Main Discussion Area => Bows => Topic started by: upstatenybowyer on March 11, 2017, 09:19:30 am
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Hi folks. I was just looking at bubby's bows he's got in the works and it got me wondering. When is it wise to employ longer gradual recurves that work some and when is it better to go with short, sharp static bends at the very end of the limbs? I've got some ideas but I'd like to hear from some of you more experienced PAs. Thanks :)
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I think long recurve lend themselves better in lever type bows.statics need more meat to prevent tourquing .
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when is it better to go with short, sharp static bends
different designs for sure, are you asking about the merits of one design over the other?
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I like to make what my eyes enjoy at the time, that's just one benefit to making your own rigs. Sometimes its just some nice reflex and sometimes its static tips. As far as design, stave length plays the biggest role. If you want to pull a 62" bow 28", you'd be best suited to make a short static section or short working reflexed section to save working length. If you have a 65" bow you can do either with great results. Whatever makes your eyes happy. I have no chrony, but have shot and built a few bows. Only a few out of hundreds and hundreds really stood out in the speed category. In the end most 50# bows are 50# bows give or take 5-8 fps. That's why I lean towards pleasing my eyes.
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I agree with Pearlie. I have a hard time keeping the long hooks stable.
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I like to make what my eyes enjoy at the time, that's just one benefit to making your own rigs. Sometimes its just some nice reflex and sometimes its static tips. As far as design, stave length plays the biggest role. If you want to pull a 62" bow 28", you'd be best suited to make a short static section or short working reflexed section to save working length. If you have a 65" bow you can do either with great results. Whatever makes your eyes happy. I have no chrony, but have shot and built a few bows. Only a few out of hundreds and hundreds really stood out in the speed category. In the end most 50# bows are 50# bows give or take 5-8 fps. That's why I lean towards pleasing my eyes.
Pretty much what Pearl said :BB
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Those curves you got on the ones you posted today bubby are very much eye pleasers :OK
bjrogg
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Thanks bj
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Thanks to all for your responses.
bushboy, that certainly makes sense for sure.
Willie, I guess I was kinda getting at that. I like PD's explanation that a 50# bow is a 50# bow give or take a few fps.
PD, I had a feeling that length of working limbs had a lot to do with it. But I'm glad to hear you say that ultimately it's what's pleasing to your eyes at the time. That's pretty much how I've been making design choices at this point. That and what the particular piece of wood looks like it wants to do.
Badger, with you and PD in agreement, I'm inclined to agree with just about anything (within reason of course)!
bubby, I agree with bj. Those curves are eye candy for sure. ;)
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A gradual bend is a lot easier to accomplish successfully.
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A gradual bend is a lot easier to accomplish successfully.
Agreed. Every successful sharp bend I've ever done has been with steam and I go at least 60 minutes per 1/2" of thickness. Probably overkill but it's worked so far.
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I'm curious if there's a different drae force curve between the two between the string starting to lift off and finally on just the nock. One that has no real transition just jumps from on the hook to the nock . Essentially a sharp kink recurve. vs one that is more curved so there is a gradual lift off.im sure it's been tested a bunch. If just like to see side by side graphs. I might just have to do so myself. I feel like they would feel different on the draw too.
Kyle
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The Bob Kooi papers address this. Sharper angles store more energy but lower angles are more efficient. Clear? ;)
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The Bob Kooi papers address this. Sharper angles store more energy but lower angles are more efficient. Clear? ;)
Man those papers are way over my head ???
dy
ds
= cos θ , dx
ds
= sin θ , 0 ≤ s ≤ L . (2)
The moment M(s) is caused by the tension force K(b) in the string, we find
M(s) = K(b)h(s) = K(b)
¡
b cos α − x(s) cos α − y(s) sin α
¢
, 0 ≤ s ≤ sw ,
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Makes sense to me. The the higher efficiency of the lower energy design, they probably fling and arrow at comparable speeds. Probably just feel a bit different during the draw cycle.
Kyle
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A gradual bend is a lot easier to accomplish successfully.
Agreed. Every successful sharp bend I've ever done has been with steam and I go at least 60 minutes per 1/2" of thickness. Probably overkill but it's worked so far.
(http://i623.photobucket.com/albums/tt320/bubncheryl/Mobile%20Uploads/IMG_20170220_135856190_zpstjzbkbyl.jpg) (http://s623.photobucket.com/user/bubncheryl/media/Mobile%20Uploads/IMG_20170220_135856190_zpstjzbkbyl.jpg.html)
This curve was accomplished with dry heat by a 9 year old, while it is not a sharp static it is a pretty good hook, i think guys try to bend stuff too thick and don't round the corners or sand them, this was bent with no backing strip either
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That's a beaut. I kinda consider osage an exception. Do you think that could be done with other woods?
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I havmt tries it with others, but black locust can also take a pretty good bend too with just dry heat. About what bubby shows there. It just seems a bit more finicky than osage, essentially a more narrow line between hot enough to bend and scorching. Which means a crack and splinter at the burn. With steam and assistance heat from a heat gun you can take BL to a 90* hook on a 4"diameter curve with mild splinters.
Kyle
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That's a beaut. I kinda consider osage an exception. Do you think that could be done with other woods?
It could definitely be accomplished with hackberry, it bends super easy,
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Never tried hackberry, but I'd like to. Heard it's one of the best for bending. :)
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Gotta check into that hackberry.Fuel for the fire heh???
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The Bob Kooi papers address this. Sharper angles store more energy but lower angles are more efficient. Clear? ;)
Is that because sharper requires more thickness due to stability, or just because? Guess I should check out those papers again... yeah, they're pretty hard to digest.
Guess it kind of depends on what gpp you intend to shoot, too.
From what I understood reading, Adam Karpowicz says sharp is better (like in Turkish bows) because, basically, a straight line is shorter than a curve.. :P (Doesn't seem like it'd be a big difference though...)
I like in-between, more pleasing to the eyes. My beauty ideal is something like a Korean or Crimean Tatar bow...
(https://i.imgur.com/BgQ8oGo.jpg)
(https://i.imgur.com/lybhDMo.png)
(https://i.imgur.com/Mq4eCgG.jpg)
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+1 what Pearlie said.
For me it belongs also on the wood species, I got only with osage and yew really sharp hooks.
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Reading up on Bob Koois results is quite filling there.I keep wanting to get to the bottom to see the final bottom line results without reading fully to see how he gets there.Taking his word for it I guess.I only went through in high school through Algebra 2 I think or maybe more.That's been 43 years ago too.
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Reading up on Bob Koois results is quite filling there.I keep wanting to get to the bottom to see the final bottom line results without reading fully to see how he gets there.Taking his word for it I guess.I only went through in high school through Algebra 2 I think or maybe more.That's been 43 years ago too.
Me too Ed. I think I pretty much understand the bottom results and that's good enough for me!
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Is the conclusion yet then that the static needs to weigh more compared to working to make the difference in efficiency like what's been said before in the past?
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I think one thing to consider here when looking back at the old writings is that most of the well established bowyers on this sight have allready exceeded kooi's expectations. R/d style long bows as well as all types of recurves. One thing that most agree on is that the bowyer who gets the most set back in the limbs successfully without breaking down the wood will usually have the fastest bow regardless of design.
My feeling about recurves is that extra wood in the outer limbs is required to keep them stable and not twisting. That may not be true for everyone. But just based on that the extra energy storage attained may be lost in efficiency. We will always have exceptions. Some guys can pull off impossible designs but for most of us they are not practical. As Pearlie mentioned earlier the difference between a solid well made efficient bow and a hot rod is relatively small, a lot of fun to chase but not if your main objective is a good reliable bow.
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I respect simplicity. For me, any possible gain in efficiency (which I'd have to see to believe) in a recurve is totally outweighed by the added difficulty of making one.
The only reason I can see to recurve the tips is to get a better string angle on the nocks of a short bow.
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I hear ya Jim. The plum ALB I just finished up is about the sweetest shooting bow I've ever made. :OK
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Sharp statics have cleared 500 yards in both self and sinewed models. What's the straight or gradual curve record?
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I've made a few of both and I think as far as shooting (3D course/lots of shots) the sharp static can have a little hand shock as it slams home, and the gradual recurve is easier to draw and has less hand shock. As far a performance over many shots, I just can't really tell much difference. JMHO
DBar
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I just had'nt understood everything that was written in Bob Koois' writings there.Did'nt look at the copyright date I quess.....lol.
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.... One thing that most agree on is that the bowyer who gets the most set back in the limbs successfully without breaking down the wood will usually have the fastest bow regardless of design.
.... As Pearlie mentioned earlier the difference between a solid well made efficient bow and a hot rod is relatively small, a lot of fun to chase but not if your main objective is a good reliable bow.
Good summary. This is what TBB4 says as well. Hence the agreement mentioned, I guess.
My main ongoing question is whether it is worthwhile to do any reflexing or recurving after the set has already occurred. I would love to start a new thread on this, as soon as I can tinker with my bows. They all have some set already, of course.
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A large recurve that stores a ton of energy without degrading wood and causing set and degradation, yet somehow miraculously maintains efficiency through light weight and high stability is essentially one of the Holy Grails of bow design.
Small, radiused recurves go on nice wide, straight limbed (otherwise) shorter bows. Larger, sweeping recurves belong on deflexed staves and glued up deflexed handles. I like a parabolic curve with working reflex below a sharper, static recurve. in wood, not much else will work.
The R/D bow is partly popular because it melds low strain with high energy storage, but allows stable, stiff tips. Toss in Perry reflexing and flexible wood combinations and you got a winner.
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I guess i don't like to follow rules , I've put short tight statics on pyramid bows, albs, eiffel tower molly pyramids, no need to button hole something just make stuff that works😉
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I guess i don't like to follow rules , I've put short tight statics on pyramid bows, albs, eiffel tower molly pyramids, no need to button hole something just make stuff that works😉
Good call. I think it's cool to learn about what's out there and what people think, but ultimately we all have the freedom to make what we want. What's that they say... rules were made to be broken (S
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Parabolic curve keeps jumping out at me as the wrong term for that shape. I think an involute or Fibonacci curve describes it better.
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Lol pat only you would pull that out
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A large recurve that stores a ton of energy without degrading wood and causing set and degradation, yet somehow miraculously maintains efficiency through light weight and high stability is essentially one of the Holy Grails of bow design.
Small, radiused recurves go on nice wide, straight limbed (otherwise) shorter bows. Larger, sweeping recurves belong on deflexed staves and glued up deflexed handles. I like a parabolic curve with working reflex below a sharper, static recurve. in wood, not much else will work.
The R/D bow is partly popular because it melds low strain with high energy storage, but allows stable, stiff tips. Toss in Perry reflexing and flexible wood combinations and you got a winner.
100% agree.
Pat I take it you mean the start of a Fibonacci curve? A fibonacci curve is actually a spiral...I don't think a spiral recurve would be all that great ;) As I'm sure you know an involute curve is a term for the resultant curve obtained from a given curve by attatching a 'taut string' to the given curve and tracing its free end as it is wound onto the given curve....so an involute curve can be of any curved form. ;)
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That's right mike, either of those two. The same way we describe tiller as arc of a circle without the bow actually being a circle.
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I guess i don't like to follow rules , I've put short tight statics on pyramid bows, albs, eiffel tower molly pyramids, no need to button hole something just make stuff that works😉
Well, those are the kind I am talking about, although as bow length gets longer, I go to less sharp and more reflexed or flipped. A short (almost) pyramid might get a nice tight hook.
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I just meant that, say I have a 66" pyramid that is doing fine. Slapping 70 degree, 7" long recurves on that, putting the tips 4-5" ahead of the straight handle is asking for trouble with set, breakage, etc...
But the same bow with1.5"-2" of deflex, I can make work.
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Well, those are the kind I am talking about, although as bow length gets longer, I go to less sharp and more reflexed or flipped. A short (almost) pyramid might get a nice tight hook.
sounds like a good way to look at it.
BTW would that logic change if the handle was working vs non working?
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Logic, huh? That's giving me more credit than I deserve. :P
Why not. I have done bendy handles with recurves, and I think that is a good application for them. Recurves improve FD curve on short bows. The issue there is that the bows are already pretty narrow, right? And, if it's short already, you still gotta have enough limb bending, one way or the other.
I'd do more of that if I had more osage orange and less of whatever is randomly available.