Primitive Archer
Main Discussion Area => Bows => Topic started by: Selfbowman on January 31, 2019, 09:31:58 am
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Question: if bow is overbuilt. Why would the bow take set. I can understand if underbuilt. Seams to me the bow with very little or no set can not be overbuilt. Just asking. Arvin
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That is a good question. I have never intentionally overbuilt a bow, but logic would suggest that if the entire bow is overbuilt, it shouldn't take much set.
"Seams to me the bow with very little or no set can not be overbuilt" Why is that? I would think the other way around, if overbuilt, the bow shouldn't take set.
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Moisture content,..or over stressed when tillering,,,could cause set
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It might only be overbuilt by the perceived qualities the wood is assumed to have but not what it really has.
I left a featherweight "pithy" Elm stave roughed out for years because of my assumption of its quality based on that. I finally finished it out and it had hidden qualities nobody would have ever guessed at.
Conversely I've had Elm that could have passed for HHB and it wasn't particularly good.
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Even if the bow is overbuilt you can have spots that are over stressed and take set. It may not show just looking at it but if you have made tracing of the bow before and after you can pick out the spots where the set is. I tiny bit of set close to the fade can turn into quite a bit by the end of the limb.
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So true. A bow tends to only be overbuilt relative to being well tillered as well.
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Thanks guys . Keep going this sheds some light on the term overbuilt. Arvin
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Definitions matter. My idea of an overbuilt bow is one that can bend some amount beyond what is needed without damage. Then when it is always used at the normal draw length, it will never fail--because it can do more.
That condition results from the tillering and is independent of all other factors.
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Definitions matter. My idea of an overbuilt bow is one that can bend some amount beyond what is needed without damage. Then when it is always used at the normal draw length, it will never fail--because it can do more.
That condition results from the tillering and is independent of all other factors.
How can it be independent of other factors?
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Obviously, the bowyer considers all the other factors. The result is accomplished only by the doing of the tillering. We do that with every bow we make. They turn out well if they are tillered well. A perfect stave will not be a good bow unless tillered well. And a second rate stave can be a first rate bow it tillered well.
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if I make a bow and its too overbuilt,, it may not take set, but it will shoot slow,, I usually think the limbs have too much mass for the weight and draw,, or I didnt tiller the limbs right for the mass they have,,
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Obviously, the bowyer considers all the other factors. The result is accomplished only by the doing of the tillering. We do that with every bow we make. They turn out well if they are tillered well. A perfect stave will not be a good bow unless tillered well. And a second rate stave can be a first rate bow it tillered well.
I don't see the correlation to the bow being overbuilt or not.
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I guess it depends on your definition of overbuilt. I think of Badger's mass theory when I think of overbuilt bows. There's more wood than is necessary to prevent the bow from taking set. If the bow takes set in a certain area, that area is underbuilt.
So by that definition a badly tillered bow or a bow with set in any part of the bow couldn't be considered overbuilt.
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Is this going to turn into a "power lam" definition argument. lol
Overbuilt: More than enough material to do the job. The mass theory was originally about the minimum required to do the job.
No need to go off on a bad tiller or set tangent unless you are using uniform set as evidence that the bow is not overbuilt after all.
Overbuilding does tend to add in a certain amount of protection to overdrawing although doing so routinely ultimately means you are just asking the bow to be an optimally designed bow relative to the materials. It's no longer overbuilt then.
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Very interesting guys. Like most all things . Depends on where you are standing for a meaning or name. Kinda like Osage, hedge apple, horse apple, Bois D'arc . Except these all refer to the same wood. Arvin
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Over built to me means 2-4" longer than the usual recipe for a given draw length. Other than that I don't change anything when I build an over built bow.
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For me it's adding a bit of width.
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Good question and I love the way it makes you think about how to get the most out of a stave.
A good historical example of bowyers trying to push the boundaries could be Bow X1-3 from the 'Mary Rose'.
That Elm bow has had the width of the outer limbs reduced dramatically, probably in an effort to reduce as much weight as possible in the areas where set is less likely to happen!
It's an extreme example of whip tillering and shows those guys were trying to get the best performance from the bow as possible.
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Is this going to turn into a "power lam" definition argument. lol
... Overbuilding does tend to add in a certain amount of protection to overdrawing although doing so routinely ultimately means you are just asking the bow to be an optimally designed bow relative to the materials. It's no longer overbuilt then.
Exactly.
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Well I have the habit of making my bows quite wide from handle to mid limb and slimming my tips to the extreme sometimes... So I probably overbuild and underbuild my bows at the same time ::)
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Overbuilt to me means like Pearl and Jim Davis said. Most all of my early bows I consider overbuilt. I was looking for a successful bow and not pushing the limits. Some were tillered well and some not so much. The not so much ones took a bit of set but probably not nearly as much if they had been 2"or 4" shorter. They survived. As my tillering skills advanced I still overbuilt bows but got all the limb moving. My profiles held much better. My bows were capable of being draw a bit further than my intended draw. I still believe I overbuild my bows a bit. I have started pushing the limits a bit more though. I'm still in a comfortable spot yet though. I think sometimes when we have a few extra inches of bow length to work with we maybe don't try to get everything working as well as we could possibly get it. I like what Badger once said. Something like, when you think the tiller is good and you need
More draw length. It's time to perfect the tiller. Don't just think of removing weight.
Bjrogg
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If I was a young bowyer just starting off and I was trying to unlock all of the secrets of building the perfect bow I think I would invest my energy into studying set and trying to identify one type of set from another. I am pretty sure that several types of set exist although I can't prove it or for that matter even positively identify it when I see it. Over compensating to the point of getting diminishing returns is how I would define over built.
Here are some things to think about when a bow starts taking set. Has the back of the bow gotten compressed and we are simply uncompressing it or are we crushing belly cells. I suspect a lot of reflex we loose is often because the back of the bow is simply becoming uncompressed. The only way I have found to tell the difference is to actually start monitoring the efficiency of the bow in the very early stages ( say around 22" draw on a 28" draw bow) Any bow will loose weight if it takes set regardless of the reason but it will only loose efficiency if we are crushing belly cells. This requires taking force draw curves and shooting through a chrono until you become familiar with expected performances at various draw lengths.
I started over building my bows 6 or 7 years ago and got much better results than when I was underbuilding them. I think about 2 years ago I may have started taking it just a tad too far and this year I am backing off a little but not much. I am hesitant to throw numbers out there because we all have different releases when we test so one guy might be thinking his bows are slower where in reality he may just be using more of a hunter or target shooters type release. But speaking only for myself I can say I have had a pretty dramatic increase when I started using more wood per the mass formula. I used to figure about 172 fps using a 10 grain arrow and 28" draw. When I went to more of a no set tillering technique 175 to 176 became more typical with 180 to 182 not being unusual. I didn't notice much of an increase in my boo backed bows but the gap between self bows and boo backed became much smaller.
When I say overbuilt I am usually referring to starting wider at the fades. That little 4" area coming off the handle can be a god send. If a bow is starting to take a little set and we still have 6" to go if we had kept that 4" area a little on the stiff side we can now go back in there and get what we need. If we don't need it all the merrier, less working limb equates to more efficiency.
Losses in efficiency are mostly do to hysteresis which drastically increases rapidly when the belly starts crushing. Uncompressing the back does not seem to have this same effect. If a bow is truly overbuilt you will notice low efficiency numbers early on even before set becomes an issue if you are testing. Once you are finished with a bow I don't really know how you can tell the difference except maybe some extra handshock.
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My idea of an overbuilt bow is the way Paul Comstock described it in the Bent stick, full width for most of the limb with the tip taper in the last few inches. This is a good design for a weaker wood or if you want a less stressed, more durable bow.
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I suspect a lot of reflex we loose is often because the back of the bow is simply becoming uncompressed.
I've noticed that a backed bow with glued in reflex holds the reflex much much better than one with heated it reflex. As PatM said a while back it's because the backing is actually shorter rather than being compressed.
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I had the Sinew come off a bow,..even though the bow had been drawn quite far,,,it showed no set,.I think the Sinew kept the wood back from becoming uncompressed
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Thanks for the insight Steve. One of those re-read a bunch of times write ups to let it soak in.
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I've noticed that a backed bow with glued in reflex holds the reflex much much better than one with heated it reflex. As PatM said a while back it's because the backing is actually shorter rather than being compressed.
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I'm trying to understand this. Wouldn't a glued in back be compressed too?
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I think the term compressed isn't the best for describing a back. The cells probably shrink but that's not the same as being squeezed in compression. So they are shorter but for a different reason and by a different mechanism.
When done as a glue-up the compression on the back has to be insignificant relative to the actual shortening of the backing strip due to moving the glue line.
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I'm trying to understand this. Wouldn't a glued in back be compressed too?
If you glue in the reflex as soon as you take it off the caul the back goes into tension. The belly wood is trying to straighten it. Does that help?
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It has been widely said that a bow is 90% broken at full draw. My observation is that an overbuilt bow is some amount less than 90% broken at full draw. (Don't recall whether the % was 90 or 95, but the concept remains.)
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I'm trying to understand this. Wouldn't a glued in back be compressed too?
If you glue in the reflex as soon as you take it off the caul the back goes into tension. The belly wood is trying to straighten it. Does that help?
I mostly agree Pat, I think when you do a glue up as you said earlier the wood is just shorter, But when a piece of wood is forced into reflex either by heat or through the drying process I think the back cells are compressing some. If it grows that way natural I would suspect they are just shorter as in a glue up.
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That may come down to whether the natural "laminations" slip a bit when lignin plasticises with heat.
It seems like dried in reflex is more like the shrinkage of sinew where the elastic nature of the material causes it to shorten with drying.
Certainly if you bend a stave the proper way a few inches the stave bounces right back so it's hard to imagine a compressed back holding like set after only being bent to such a small degree also.
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Comstock in The Bent Stick seemed to feel over built bows performed better than those that were not.
Jawge
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Comstock in The Bent Stick seemed to feel over built bows performed better than those that were not.
Jawge
Pat, that is not what I said, I said if a compressed back pulls back out to some degree is doesn't act like set where the belly is getting crushed. The belly crushing creates more hysteresis and when a back pulls out you just loose some reflex.
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I wasn't comparing it to the effects of belly set. I was arguing that it likely can't be any sort of compressive "set" in the back at all but rather temporary shortening that gets stretched back out to a degree.
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I think that is the same thing that I was saying. When the temporary shortening comes out it looks like set
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I would agree with that. A straight grown tree usually attains reflex when split and dried but it may be better to keep in mind that the shape it was in before splitting and drying is more representative of its true shape.
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I was watching video of horn bow, the guy cut horizontal slots in the core wood,, from this discussion,, I am assuming it was to prevent the wood from being compressed on the back, so the sinew could pull it into reflex without as much resistance,,????
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I was watching video of horn bow, the guy cut horizontal slots in the core wood,, from this discussion,, I am assuming it was to prevent the wood from being compressed on the back, so the sinew could pull it into reflex without as much resistance,,????
Which video?
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I think it was the same one Marc posted
XIAOSHAO BOW | ZWE its on utube,, nearly has 3 million views
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I think that was more to establish the curve there. You will note that he bends the bow in that spot and glues on a piece that acts like a form. Then after the belly is glued on to set that curve he removes the form chunk and the notched areas completely before sinewing.
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ok cool,,I love that video
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That may come down to whether the natural "laminations" slip a bit when lignin plasticises with heat.
It seems like dried in reflex is more like the shrinkage of sinew where the elastic nature of the material causes it to shorten with drying.
Certainly if you bend a stave the proper way a few inches the stave bounces right back so it's hard to imagine a compressed back holding like set after only being bent to such a small degree also.
couldn't the cause of dried in reflex be that the recently living and wetter sapwood hasn't undergone as much shrinkage as the older wood towards the heart?
Steve,
I think there is more to be understood about the different kinds of set. On thing I have noticed is that conifer wood seems to recover differently than hardwood. probably something to do with microfibril angles. Just guessing, but there is probably even a variety of ways a specific hardwood can differ from one tree to the next, or even from one part of the tree to another. Primitive accounts often show bowyers putting much value on just what part of a tree to get the stave from. I like to harvest my own staves for this reason, but still have a lot to learn about just what makes for a better bow.
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That may come down to whether the natural "laminations" slip a bit when lignin plasticises with heat.
It seems like dried in reflex is more like the shrinkage of sinew where the elastic nature of the material causes it to shorten with drying.
Certainly if you bend a stave the proper way a few inches the stave bounces right back so it's hard to imagine a compressed back holding like set after only being bent to such a small degree also.
couldn't the cause of dried in reflex be that the recently living and wetter sapwood hasn't undergone as much shrinkage as the older wood towards the heart?
Steve,
I think there is more to be understood about the different kinds of set. On thing I have noticed is that conifer wood seems to recover differently than hardwood. probably something to do with microfibril angles. Just guessing, but there is probably even a variety of ways a specific hardwood can differ from one tree to the next, or even from one part of the tree to another. Primitive accounts often show bowyers putting much value on just what part of a tree to get the stave from. I like to harvest my own staves for this reason, but still have a lot to learn about just what makes for a better bow.
I doubt the inner wood has shrunk much if it's still wet. Likely a function of more total surface area able to shrink in both length and width that wins that battle. Even with the bark on.
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Yes this is good info once more. Thanks. I am not sure I am ready to give my two cents just yet . I don't understand all the terms being used but maybe the theory. Arvin
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I definitely lean toward overbuilt, hopefully overall, and not just in one spot. I see it as the less overbuilt, the closer I am to the bow breaking, and how close to that line do you want to dance. I make bows to hunt with and give away, so I mostly want durability. But who doesn't want performance?...maybe Ill get a little closer to that line.
When I first started out, I thought my lack of set was due to my skill in tillering, but soon realized it was that I was overbuilding the bows a good bit.
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With boards, overbuilt seems to be best for me. Don't get me wrong, I have dozens of "failed" bows in either the board or stave variety. During my "phase 1" of learning, I chrysalled a number of hickory staves, because of too stiff inner limbs. With boards, I am not sure what exactly is the broad underlying cause of failure. But crossing that line rsp3 mentions is risky and overbuilt to me means not crossing that fine line. I am not that good of a bowyer. Yet.
Willie: I think that a board comes from some unknown part of the country, is kiln dried or stored in a manner I'll never know, and you are on to something about Natives being specific about choice of tree material.
Overbuilt. To me that means not chasing performance needlessly unless you are willing to risk the bow. I built a 50" hickory shorty, originally drawing 20.5 inches. Great bow. Little set, under an inch. Wanted to go from 44# draw weight, go stronger. So I shortened it to 48.25 inches, and it worked great, sitting pretty in my hands as I did not take the shot on a big Coues Whitetail, lol hashtag "Not dynamic in releasing".
As the season went on, I got stronger, and kept puling the draw length out to 22, 23". Well, the bow lifted a tiny splinter.
Should have left the bow at a ratio about 2.5:draw length. Overbuilt. ( Leaving that extra length, a few inches and a bit of width)
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I bent a pine arrow today until it broke. I realised that the splinter that was under tension barely took any set. The compression side took a huge amount of set. The wood cells on the compression side collapsed, as badger wrote earlier.
I think the reason, why perry reflexed bows take less set, is quite obvious. When unstrung, the shorter back of the bow puts the belly under tention. When bending the bow a bit, there is a certanin point, where the belly is neither under tention nor under compression. When bending further, the belly starts to compress.
In comparison, a bow made of a naturally reflexed stave with the same amount of reflex behaves different. When unstrung, the belly is neither under tention nor under compression. Whith the slightest bend, the belly starts to compress. When fully drawn, there is more compression.
When drawn to 28 inches, the belly of the perry reflexed bow is under less compression. Less compression means less set. As a result, the perry reflexed bow can be built narrower and lighter without being underbuilt.
lonbow
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I tend to think that most of mine are overbuilt to some degree, although I would struggle to define the term. 2 inches wide when 1.5 would have worked. 66 inches long when 64 would have been fine. If I manage to keep set to a minimum in the process, which is no given, then I'll take it, overbuilt or not.
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There is a point of diminishing return,,,.where the bow no longer performs well,,.even showing no set,,.
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Brad are you speaking of a longer draw but gaining less weight per inch on the end of a force draw ?
Arvin
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Sorry I wasn't very clear,,.if you make the bow wider and longer to to reduce set,,,,at some point the bow will be to wide or too long or both,,,show no set,,..but will be too,,Overbuit to perform well,,,having slow cast,,,and handshock
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A bow can be overbuilt in actuality by tillering it to endure more stress than normal use requires. However, it can also be falsely overbuilt if the material is forced to compress beyond the elastic limit of the wood in the limb. A bow like this would be deeper and narrower than expected for the species, condition, and quality of the material. This would result in a heavy limb for its draw weight. Also compression fractures would be likely in the belly or the bow would weaken dramatically or lose tiller when being shot in. All woods have a limit to how thick they can be and remain springy to a certain bending radius. So tiller gently and overbuild by adding width, not depth to the limb all else being equal.
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Sorry I wasn't very clear,,.if you make the bow wider and longer to to reduce set,,,,at some point the bow will be to wide or too long or both,,,show no set,,..but will be too,,Overbuit to perform well,,,having slow cast,,,and handshock
So the weight of the mass it's self and the energy the bow needs to propel this extra weight forward at some point over comes the atvantage of no set?
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Usually when I think of over built I just think of a bow that is under strained and the front profile doesn't match the tillered side profile. Usually it is the outer limbs that are overbuilt.
A few years ago I built some osage bows on the short side around 60" long and recurved, I went very wide in the working areas with them assuming they would come in heavy in mass but the opposite happened. They came in light in mass just very thin. I think it is best to err on the side of too wide on the inner limbs. The outer limbs seems to penalize us more for too much mass.
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Steve I agree that extra width on the inner limb can go with the overbuilt side without hurting performance. More mass on the inner limbs is not as critical as the outter limbs. At least that's what I have found with the pyramid design. Arvin
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Arvin, how wide do you normally go with your osage pyramids?
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Pretty much as wide as the stave permits. Most of my flight bows are 2-1/8 -2-3/8 making the mid limb about 1-1/4 on 28" of limb.
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Glad I asked. I didn't realize you went that wide.