Primitive Archer
Main Discussion Area => Bows => Topic started by: upstatenybowyer on November 14, 2016, 08:51:02 pm
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Just wondering under what circumstances a bow stands to benefit from D section limbs. Thoughts?
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Continuous war.
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And so it begins...
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Uh oh. I hope I didn't open Pandora's box with this one. :o It's just that I noticed Marc (whose work I greatly admire) often employs shallow D section limbs.
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I think Pat is being overly dramatic ;).
D section limb are best used with wood elastic in compression and are very useful in taking strain off the back. This is good for a higher stress design since the elastic belly wood works harder giving the back a "break" in the workload :D.
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Overly sarcastic. ;)
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The English war bow came about because with the longer, narrower bow you could get more bows from a tree. The rounded limbs mean you can turn them out faster.
Marc, sounds good but most woods are stronger in tension than compression. So specifically what woods are you talking about?
Jawge
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I build primarly Osage but D comes in to play usually when my stave is on the thin side. They seam to take a bit more set but has good cast from the limb being long and narrow. Most are not completely D in design. The belly is still flat some what in the mid limb section. Yes they do seam easier to tiller. Arvin
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I heard that osage in longbow "D" configuration (more rectangle then D) produces handshock, is it true?
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George
Wood is stronger in tension but all that means is that it resists stretching more than it resists compressing. That has nothing to do with the wood's elasticity. A wood can be elastic and strong in tension and a bow made from that wood will not likely fail in tension and/or it will make a great backing material. A wood that is elastic in compression will resist cellular compression failures (chrysals)
You've been making bows for quite awhile now so you should know which wood species are elastic but just in case here are some. Yew, Osage, ERC, HHB, those are some of the better NA species
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I have YET to make a wooden bow with a flat belly, and have no plans to. My bows range from deep D cross section in English longbows, through the spectrum, to a squashed, yet fully radiused belly on woods that aren't nearly as elastic in compression. That said, three of those four Marc mentioned are #1, 2, & 3 of my favorite three bow woods. Coincidence probably ;)
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I know Dean Torges in his book Hunting with the osage bow is a big fan of the radius belly & goes into some detail about it , when I get my tillering skills better I would like to try one , I read that there saposed to easer to tiller.
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This has been very informative to say the least. Lots to sublimate. Thanks to everyone for your input. :)
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Yes, Marc, I do know which woods are considered to be elastic.
I've read TBB 1 :)
I meant to ask which woods do you prefer for your particular design- rounded belly, high stressed..
Jawge
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Yes George I've also read TBB 1 but experience has been a better teacher :)
When talking backed bows then I prefer Yew and Osage in that order with ERC not far behind then HHB. I would change that order and put HHB before ERC for selfbows and add top grade Elm to the list next to HHB. Heat-treating adds another dimension to this altogether since that increases the compression strength of wood thereby increasing the stress to the back, doesn't increase the elasticity of the wood though.
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Does it DEcrease the elasticity? and/or alter it's propensity to fret one way or the other?
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Does it DEcrease the elasticity? and/or alter it's propensity to fret one way or the other?
Not if done properly
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Yes, Marc, experience is a good teacher but bowyers have to start somewhere. I like those woods you mentioned too. Thanks, Marc. Jawge
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Marc
Not if done properly
Marc, DWS 's question has always been on the back of my mind also. Could you explain a little more about what happens when it is not done properly? Maybe help us learn more from your experiments?
Obviously, too much heat is detrimental for any number of reasons, but that aside, have you noticed any trade-offs when you heat treat? Specifically, I am curious about what you have noticed about the way a bow takes set or acts different otherwise?
I work a lot with birch, have seen others write about mixed results when heat treating. Soon I should try seeing what heat treating will do to some other hardwoods that grow local, woods that hopefully will respond well, as they are not usually considered "bow woods".
thanks
willie
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Too much heat will affect the elasticity of the wood negatively, black is a no no. Because of its very thin rings HHB is a touchy one for heat-treating. It responds extremely well to tempering but the back becomes the weak point in the bow and I have had some explode on me, not fun. As I have said before, because heat-treating will increase the compression strength of the wood then the back is subjected to more stress hence the need for tension strong wood. Some tension strong wood species like Elm do better with a high crown even when heat-treated, too much crown is not so good though. There has to be a proper balance between tension and compression regardless of whether the wood is elastic or not. The more elastic the wood is the more forgiving it is though plus you can adjust the sectional shape of the limbs to compensate for a weakness in tension due to a high crown or a flaw such as very thin rings. Knowing everything about bows is impossible but the more experience you have the better decisions you can make with the wood you have to work with
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Thank you, Marc