Primitive Archer
Main Discussion Area => Bows => Topic started by: Jakesnyder on November 25, 2020, 09:20:31 pm
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I'm pretty sure I know the answer to this but in a reflex deflex design such as the one in the picture should the deflex be heat bent in or just let it take set? Also does anyone else think that this bow would have been very efficient design for the time period?
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Add the deflex unless it is natural. When I build a bendy handle bow I like to feel the handle bend only as I hit full draw so the handle area remains stiffer until late in the draw.
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Do you think this is a efficient design?
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Not really but it works fine. With Hickory in that width you can just let set take care of the shape.
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I'm pretty sure I know the answer to this but in a reflex deflex design such as the one in the picture should the deflex be heat bent in or just let it take set?
Badger says set always hurts performance and is to be avoided as much as possible. I would go with that advice.
Mark
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Don't tourture the belly cells any more than necessary. If you let it take set, it's that much closer to chrysaling.
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Always avoid set if possible. Arvin
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A bow that short will have to bend with in itself, and take on a certain shape. Even though a gull wing bow has deflex from about the middle of the limbs out to the tips it will still show reflex in the over all design which should make it a better design than a D shaped bow with deflex. You can let it take the set it is going to take, or as JR Riggs does heat treat the deflex in.
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Avoiding set is a good thing but when replicating a bow the rules change.
If you copy that bow and most others , you will have set. Often quite a lot too.
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I'm curious then how did they do it?
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Look in Jim Hamm's book , and JR Riggs on utube . They show you how it is done. A good Gull wing bow will have no set as we know it. Reflex first, and deflex in the outer limbs yes. Hamm shows shape of an Ash self bow with that design. Riggs uses Red Oak a lot. Their is design ,and heat treating involved.
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No i know how to make a gull wing shape. I was curious as to why there is a high chance I would have alot of set in replicating the bow pictured or another bow similar to it?
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Short bows are prone to set from the beginning. Research as much as you can before you build it.
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No i know how to make a gull wing shape. I was curious as to why there is a high chance I would have alot of set in replicating the bow pictured or another bow similar to it?
Because it's short and pretty narrow. In any event in order to bend wood to a curve, cells need to be compressed. It doesn't matter if that's done by drawing the bow or heating it to that shape.
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if I was curious, i would build several,,and shoot for distance or through a chronograph,,
maybe the deflex allowed for a longer draw,, just guessing,, im sure for close range hunting or war, it worked great or they would not have done it,, maybe the deflex allowed for longer time being braced,,
test one where the deflex is bent in, and test one allowing it to take set and see what it does,,that was a good question,,if you were going to make one with sinew back,, then pre bending the shape would probably work,,,
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I would think shaping with heat. I never like to have a bend in the handle bend to much. It’s usually the last place I get working. Seems like if it was shaped with set it would already be bending to much.
Just my 2cent worth. But I was always thinking that the deflexed handle was t make a shorter bow with a longer draw. The reflex to give so early string tension. That’s just my guess though.
Bjrogg
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I would think shaping with heat. I never like to have a bend in the handle bend to much. It’s usually the last place I get working. Seems like if it was shaped with set it would already be bending to much.
Just my 2cent worth. But I was always thinking that the deflexed handle was t make a shorter bow with a longer draw. The reflex to give so early string tension. That’s just my guess though.
Bjrogg
You're looking at it backwards. It's a double curve/gullwing.
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I guess I’m still looking at it wrong. All I see is a deflexed handle and relaxed mid limbs.
Wouldn’t a gull wing have a reflexed handle then deflexed inners and reflexed outers? I’m not seeing that in the picture I’m looking at.
Bjrogg
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Gotcha Pat. Arvin
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Maybe I’m thinking that the belly is the back?
Bjrogg
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You are.
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Sorry about that. Seems like a design that you might try to salvage a bow that took to much set already.
Bjrogg
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Add the deflex unless it is natural. When I build a bendy handle bow I like to feel the handle bend only as I hit full draw so the handle area remains stiffer until late in the draw.
Exactly. Evergreen advice. 👍🏽
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Sorry about that. Seems like a design that you might try to salvage a bow that took to much set already.
Bjrogg
The design was nearly universal over a very large area for quite a while. People still puzzle over exactly why but it would likely become clear if we lived in that era and area.
Even with sinew the same shape was often used.
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Thanks Pat. I know I probably should but I have never studied artifacts.
It does seem like a very odd design. I’m wondering how it does shoot? It seems like they got it bass ackwards. Especially for sinew backed. Very interesting
Bjrogg
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Isn't it just a bend through the handle reflex deflex design?
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Isn't it just a bend through the handle reflex deflex design?
I guess not. I thought so to, but it’s reflexed in the handle and deflexed through the mid limbs. Exactly the opposite of what I was thinking.
Bjrogg
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Now you guys are confusing me. In the illustration in OP the back of the bow is to the right?
Mark
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No, it's the left.
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No, it's the left.
Apparently I had it backwards as well.
Mark
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I have an Ash bow that looks very much like that. The stave gull winged naturally. I put 2-1/2” of reflex in the tips. About half of which pulled out. The limbs took a lot of set and now it looks like the OP pic.
Why it took so much set ( I think ). This was a dead tree so I thought it might be workable sooner. Dead is not dry. Not sure how long from cutting to bow but no more than a couple weeks. Didn’t heat treat the belly.
This bow pulls 55 lb at 27” and shoots the same arrow 10 fps slower than my 40 lb bow with straight ends.
You could say I’m not a fan of this design
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Here is a natural bending Hickory stave still green that sort of takes on a gull wing design. I followed the grain width wise , and I will shape it better on a form. Throw it in a hot box, heat treat the belly, and tiller it as a Gull wing design. May fire harden it to try, and get better results.
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I can not get the pic to come up.
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Don't tourture the belly cells any more than necessary. If you let it take set, it's that much closer to chrysaling.
The real question is whether a heat induced permanent bend is same as a set caused by over-pulling. Usually heat treating wood makes it weaker in some way. However heat treating the belly of a stave appears to make it stronger in compressive strength. Still it might be making the stave weaker as a whole by reducing its tensile strength. That's probably why kiln dried wood is said to be weaker than air dried and well seasoned wood, mainly because kiln drying reduces the tensile strength without increasing the compressive strength much.
It appears that causing set by over-stressing a stave makes it worse; while heat induced set makes it better as a bow material by changing its side profile to be better or by changing the ratio of its relative strengths in tension and compression. The question is, as suggested, whether causing set by over-stressing is much worse than causing it by applying heat. A set is a set whether it was induced by over-stressing or intentional heat treatment, boiling, steaming or otherwise. It basically make the stave weaker where it was affected.
But heat treating of only the belly is an exception. It increase the compressive strength of the belly, at least relative to the tensile strength of the back, thereby making the stave a better bow material. In other words, over-stressing makes the belly weaker while heat treating the belly makes it relatively stronger.
As for the change of side profile, over-stressing always makes it worse, while heat bending might improve it depending on the design. This is the way my "primitive" mind works without the benefit of math and physics.
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I think you're agreeing with me. I think that cells crumble with set, but they get 'melted' into a new form in heat tempering.
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I get a feeling,, I dont know, and would have to make some bows to tell,,but its a great question,, I just wonder if it would translate into a loss of performance either way,,,but very interesting,,
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I think you're agreeing with me. I think that cells crumble with set, but they get 'melted' into a new form in heat tempering.
Yes, proper heat treating appears to be hardening the belly wood into something with more compressive strength. But it is also possible that heat treating also weakens the tensile strength of the back somewhat and makes the belly comparatively stronger, thereby evening out the relative share of work for back and belly, making the bow safer to bend. Just a speculation at this point. We need a wood scientist here. I don't mind being found out to be silly so long we learn something. Thanks in advance.
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I think Marc St. Louis's tests are some pretty strong evidence that heat tempering improves the overall performance of the bow. I think heat tempering clearly alters the belly wood a lot more than the back wood, so I think the belly is made stronger more than the back is made weaker.
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Actually for wood like Hickory that is relatively too strong in tensile strength, it might not be a bad thing for the back to be weakened in tensile strength a little by heat treatment. If the belly's compressive strength becomes stronger as well in the process, Hickory might become a better bow material like Osage Orange through heat treating. I was mainly looking at the hardening of the belly wood, just weeks ago. But it might be better to look at the change of relative ratio of back's tensile strength and belly's compressive strength. While kiln drying might just weaken the tensile strength of the whole board or stave, heat treatment of the belly works both ways to make it the better bow-wood.
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The relative strength of the back and belly is important, but remember that this is in context of the limb mass. It's important to maintain as much strength as possible per mass unit.
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Speaking about a conventional R/D design (not the inverted like in the original picture)
In TBB1, Tim Baker says:
The cause of set, deflex, or string follow is irrelevant to a bow's performance
I'd like to see if there's any difference in the F-d curves between two all-things equal bows, where one has been allowed set and the other was given deflex with heat bending during tillering.
My theory is there in fact would be a slight advantage to intentional heat deflex vs set. And it would be more pronounced in a case where the stave was cut and spliced to have deflex. But in either case heat treating the belly would diminish the difference.
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I understand the wood gets closer to its failure point as it takes set.
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I believe the best way to make that design for the best performance would be clamp it to a form green, let it dry to the shape, then heat treat the belly.
If I heat treat a hickory or HHB bow that is fully tillered or close to 50#@28", it will gain so much weight I can no longer string it. I've heard guys say they get a 5# gain, I don't know if it's different wood type, but I always get a lot more gain.
I'm fairly new to bow building, but not building with wood, and coaxing wood is usually not bad, forcing it always is!
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Speaking about a conventional R/D design (not the inverted like in the original picture)
In TBB1, Tim Baker says:
The cause of set, deflex, or string follow is irrelevant to a bow's performance
I'd like to see if there's any difference in the F-d curves between two all-things equal bows, where one has been allowed set and the other was given deflex with heat bending during tillering.
My theory is there in fact would be a slight advantage to intentional heat deflex vs set. And it would be more pronounced in a case where the stave was cut and spliced to have deflex. But in either case heat treating the belly would diminish the difference.
I don’t totally agree with Tim. Set is not good in any wood bow but if it happens in the fades to mid limb it’s not as bad for performance. Put the set in the outer limbs it’s a dog. Arvin
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Set in the inner limbs is worse as it moves the tips proportionately further. Easy to prove.
Set and heat treated deflex are very different animals.
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Prove it for me.
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I believe the best way to make that design for the best performance would be clamp it to a form green, let it dry to the shape, then heat treat the belly.
If I heat treat a hickory or HHB bow that is fully tillered or close to 50#@28", it will gain so much weight I can no longer string it. I've heard guys say they get a 5# gain, I don't know if it's different wood type, but I always get a lot more gain.
I'm fairly new to bow building, but not building with wood, and coaxing wood is usually not bad, forcing it always is!
I agree don. I’ve had the same effect on my heat treatment of white woods. Especially hickory. I’ve gone too far and too dark on occasion and found that the browning crept into and up to the back of the bow wood. I’ve had failures more from these staves then just sticking to light brown on the belly leaving a pristine back. Testing the limits of heat on white woods has led me to my own method but principle the same.
Cheers
Dave
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Speaking about a conventional R/D design (not the inverted like in the original picture)
In TBB1, Tim Baker says:
The cause of set, deflex, or string follow is irrelevant to a bow's performance
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I think that maybe this line gets read wrong.
If you read it like this:
--The cause of set is irrelevant to a bow's performance
--The cause of deflex is irrelevant to a bow's performance
--The cause of string follow is irrelevant to a bow's performance
Which the word "or" seems to apply it makes a little more sense.
I'm not sure he meant that set induced reflex would be the same.
Total speculation on my part though
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I think you're right Don... that's a good way to put it.