Primitive Archer
Main Discussion Area => Bows => Topic started by: Tommy D on July 04, 2021, 08:28:44 am
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I wanted to start a thread that compared what people considered to be acceptable set from tillering, so I thought it would be useful if people just posted a bow design, material and what they would consider good, ok or poor in terms of how much set it takes.
For example, my bamboo backed, ash cored, Ipe belly in 66” long R/D profile with 1.25 inch width tapering to .5 inch at the tips now has taken 1.25 inches of set at the tips from its original unbraced side profile. It pulls 63lbs at 27”.
I have no benchmarks to go on - so am curious what others consider “benchmarks”...
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This is largely a matter of opinion and has changed a lot over the years. Used to be that an inch or two of set was totally normal and sometimes preferred. These days you almost can’t find a bow that hasn’t been heat treated to prevent set or even gain reflex. Lower is better as any set is the breakdown of wood. Because it is breakdown of the wood I think the acceptable amount of set doesn’t vary much between designs or wood species. My thought has been that I want shorter bows to take less set and longer bows can take a bit more but saying it “out loud” here I have a hard time justifying any reasoning for that. For personal bows I like to shoot for less than 1” of set but I think it’s time for me personally to lower that as a goal to as close to zero as possible. Set is irrelevant to some as long as your arrow can hit your desired target and with enough energy for hunters.
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I would agree with that mostly. My early bows took more set than mine do now. I'm focused from the start at limiting it to as close to 0" as is possible, with a reasonable width profile. I have some that I came close to achieving that, and others that I didn't. The less set, the better, and I focus on that from floor tiller to finished bow.
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My bench mark (assuming a straight limbed bow).
Put the bow down on a flat floor belly down.
If the tips aren't touching the floor that is very good.
If you can get one finger between floor and grip that's good.
2 fingers ok.
3 fingers poor.
Del
(Assuming British standard finger ;) )
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Depends what you lose in the set. The only wood i have used that will take hunnerds of thousands of shots. Take some set and then put on form add some heat, seal it without any effect on weight and cast is good USA elm. Could build one hunt it yer whole life, get buried with it, they dig you up after ww3 in couple hunnerd years and your kin be hunting one horned glowing deer with it.
Happy 4th to you Patriots out there!
HH~
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All depends on what causes the set. If it is the "breakdown of wood", it cannot be good.
Willie mentioned the peculiar nature of wood.
https://en.wikipedia.org/wiki/Viscoelasticity
https://www.researchgate.net/publication/233069103_A_viscoelastic_model_for_the_compaction_of_fibrous_materials
I have no way of comprehending these articles myself.
Let me ask a stupid question.
Can wood be compacted, either temporarily or permanently, to become stronger?
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My bench mark (assuming a straight limbed bow).
Put the bow down on a flat floor belly down.
If the tips aren't touching the floor that is very good.
If you can get one finger between floor and grip that's good.
2 fingers ok.
3 fingers poor.
Del
(Assuming British standard finger ;) )
I measure straight limbed bows the same way and for recurves flip it over onto the back to measure reflex. :)
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Let me ask a stupid question.
Can wood be compacted, either temporarily or permanently, to become stronger?
The simple answer is yes. Recently I saw an article that described a procedure used to compact wood to a much denser state using chemicals to soften the lignin and then a press to squash the wood down. It was done for research into ways to make wood a better structural material for buildings, I don't know if it would make a better bow or not. The process was complicated enough that it is not a DIY type of thing.
If you care I can dig out the article and the research paper but I don't think it is very applicable to archery.
Mark
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I was thinking about a spliced bow with plenty of set, that means already compacted by the bending. Can it be re-spliced with reflex and make a stronger bow?
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I don't know if it translates to wood but my first solid fiberglass bow got left strung in my truck gun rack for several months and took a terrible amount of set. Most likely due to being black and exposed to sunlight .
Performance was badly effected. It felt very sluggish and velocity was obviously reduced.
Only thing I could think of was to string the bow backwards when I wasn't using it and check it out every few months to see how much it improved. After a few years the set disappeared completely. I thought of leaving it in the sun as well but figured it might warp or not come back evenly. I usually leave that bow unstrung but occasionally string it backwards for a few days to reverse any tendency to gain set when in use. Its very snappy now, but solid fiberglass is never as snappy as a proper wooden bow of good quality wood.
Probably many wooden bows can't be strung backwards at all. The Mongolian and Turk horn bows certainly can't since when unstrung they form a C shape. The Scythians and perhaps the Mongols as well always carried two bows when on campaign. They left one unstrung and the other strung ready for use. They switched these out every day.
Some Egyptian bows had a lot of deflex by design, limbs were at more an obtuse angle than a curve. I suspect they wanted a minimum of stress on the limbs and if the bow got weak they could just shorten the string a bit as a stop gap measure.
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I was thinking about a spliced bow with plenty of set, that means already compacted by the bending. Can it be re-spliced with reflex and make a stronger bow?
The back would break before the amount of set needed to gain any strength in compression.
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All depends on what causes the set. If it is the "breakdown of wood", it cannot be good.
Willie mentioned the peculiar nature of wood.
https://en.wikipedia.org/wiki/Viscoelasticity
https://www.researchgate.net/publication/233069103_A_viscoelastic_model_for_the_compaction_of_fibrous_materials
I have no way of comprehending these articles myself.
Let me ask a stupid question.
Can wood be compacted, either temporarily or permanently, to become stronger?
About set that recovers after resting (Viscoelasticity).
If anyone has a tillering method that makes use observing this behavior to avoid permanent set, please share. I use a method on my tillering tree that seems to work, but it is hard to quantify.
BTW, some woods (especially conifirs) do this more than others
Bill Sweetland compressed bolts of Port Orford cedar 3:1 to make Surewood shafts with very high spines @ 5/16
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I was thinking about a spliced bow with plenty of set, that means already compacted by the bending. Can it be re-spliced with reflex and make a stronger bow?
The back would break before the amount of set needed to gain any strength in compression.
We are not stressing the bow enough to break the back. Are you saying that we need to stress the back more than its tension strength to "compact" it?
The back has already taken set and possibly "compacted" enough not to recover fully. Can this compacted limb be stronger than before, against our intuition? I am asking this silly question just because I have no idea how the "compaction" works in wood.
I am thinking about the effect of burnishing. Some say it does nothing, but some say it makes the limbs somewhat stronger by crushing the cells to be more "compacted", both in the back and belly. [paraphrased]. What if we burnished the limbs that have taken set?
Let me rephrase the question: Does this "compaction" in the viscoelestic material have anything to so with the set in wooden bow limbs?
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If we think back to science class we learned that compressing a substance causes the molecules to speed up. Anything rubbing together fast causes heat.
I would guess the compressing wood (like the arrows) if you found the right compression rate at the right temperature for the right time would work. You're compression would cause heat(maybe helped by more heat, maybe not) which would fuse the molecules together making them stronger.
Burnishing on the other hand is fusing the outside fibers together. It's the same theory, just not as deep or as far reaching.
Set however is caused by compression at weak spots in the wood. It's like running over a 2x4 with a tractor. Even if small portions wind up fused together, they're split off from the "good" wood.
All redneck theory of course!
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scp, You can’t pull that bow back forever. Your hypothetical bow already has spongy limbs from set. Not only would that design cause early stacking, you’d continue to stretch the back causing even more strain. Eventually it’ll break before any performance gains from a compressed belly. Or if it never breaks it’ll be a dog. It doesn’t make sense to use the motion of a bending bow limb to compress wood for performance advantage. Do it before the bow is bent and do it to a belly lam. Also, there still has to be some elasticity in compression to not overstretch and break the back.
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I am simply trying to understand in ordinary language terms, what it means for viscoelastic material like wood to get the set, possibly in view of the "compaction" hypothesis. And whether such set is always detrimental and irreversible. Are we all agreeing that the set in bow limbs is bad? If so, do we really know how to prevent it? Wouldn't shooting the bow cause the set eventually? Is there any way we can actually prevent the set in wooden bows? How about all other viscoelastic materials? Do they all get the set?
"Cracking occurs when the strain is applied quickly and outside of the elastic limit."
https://en.wikipedia.org/wiki/Viscoelasticity
Is the set in bow limbs basically a kind of cracking? Can it be cured somehow?
What would be the best way to keep the stress in bow limbs within the elastaic limit of the material? No set tillering?
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It is my understanding a piece of wood can exhibit some viscoelastic properties, and to different degrees
What would be the best way to keep the stress in bow limbs within the elastaic limit of the material? No set tillering?
"No set" tillering as proposed by Badger can tell you early on when your chosen draw weight for the stave is too high. Lowering your weight goal lets you tiller for lower stresses before the damage/set/compaction becomes too apparent. Steve (Badger) also has remarked, staves that take some permanent set without exhibiting viscoelastic properties make better flightbows.
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I think it would vary depending on what the bow is intended to do,,
I hunt with a bow that has taken quite a bit of set over the last 25 years,, but it will shoot a hunting arrow at acceptable fps to take game,,
I would not be happy with that much set on a new bow,, so I have a wide range of what is acceptable for a bow,, of course I always stirve for least amount of set,, but if it shoots hard and accurate,, with some set, Im ok with that too,,
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Steve (Badger) also has remarked, staves that take some permanent set without exhibiting viscoelastic properties make better flightbows.
How do you arrange for that?
Mark
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From what I have read, wood exhibits varying degrees of recovery depending on microfibral angle (MFA) of the fiber in the cell wall.
How do you arrange for that?
By selecting a stave of mature wood rather than juvenile wood or compression wood. IIRC, wood from lower down in the bole has straighter MFA also.
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Mature wood as in bigger older trees?
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I think the evidence showed that juvenile wood was better. That's likely why people report great results from practically sapling sized trees.
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I think the evidence showed that juvenile wood was better. That's likely why people report great results from practically sapling sized trees.
Better for what Pat? I must have missed something. Something that I have come across in my relatively little experience working with saplings is that I can ask more of a sapling than I can of a large tree of the same species. I know that it isn’t a scientific statement, and scientifically I don’t know why, but I will explain what I mean. Last handful of bows I’ve made has been from elm and hackberry saplings. The diameter of the saplings demanded a limb width of 1 1/8”-1 1/4” at the widest point. Length has been 60” - 66” and draw weights were in the low 40’s to the mid 50’s. All bent through handle eastern woodland inspired bows. I haven’t had an appreciable amount of set in any except one hackberry gave me 2” and I’m certain it was my fault. I have tried to go narrow and short with staves from larger trees before and can’t achieve what I can with saplings. That may be my inexperience, or a fault in my tillering. I can say with certainty that the rule of wide and long for less set with whitewoods can be bent when using saplings, at least in some species, and I don’t know for sure why? Is the wood itself more pliable and or resilient? Or is it the inherent crown that helps? Or have I been lucky?
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To address the question of the post. Acceptable amount of set is a personal matter. If it’s ok with you it is acceptable. I like to be under 1 1/2” on string follow. More than that and early string tension feels soft. I have not hunted with the bows that I make, but I make every one with the idea in mind that I may, and though I haven’t chronograph proof or anything like that, I know that a light limbed 50 lb bow with a tight early string shoots harder than the same with a soft early string .
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I think the evidence showed that juvenile wood was better. That's likely why people report great results from practically sapling sized trees.
I would think the high crown in sapling staves has a lot to do with the better compression abilities of saplings….. Morgan, have you ever tried trapping a bow made from a large diameter tree and then using the same widths as you use on your saplings stave bows?
I have basically no experience in this matter, just what I believe from reading…. That said I did make one bow a while ago that was hickory 59” long bend thru the handle and only maybe 1 1/4” wide… although it was only drawn to 26” at 35# but it only took 1/2” of set.
Set over 1” starts to annoy me…
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I think the evidence showed that juvenile wood was better. That's likely why people report great results from practically sapling sized trees.
For flight bows?
Mature wood as in bigger older trees?
Yes. One thing I have found in bigger older trees however is a declining earlywood/latewood ratio as the tree becomes more aged, or otherwise less robust. I think it has a lot to do with the size/health of the crown relative to the trunk it serves. wood density can be a good indicator of this ratio in ring porous species.
Wood grown in windy conditions or otherwise subject to more severe bending, develop cells with a higher MFA. It does seem to make a tougher bow from my limited experience with a few species I have local, but the ability to bounce back from severe strains, in my opinion, comes with a higher hysteresis, which hurts efficiency when shooting very light arrows.
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Fox, I have not ever really trapped a bow. I have came close a couple times, but can’t ever bring myself to do it. I know it works and others are successful with it but there’s some reason I just haven’t committed to it.
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Black Locust for me always seems to work out best with a trapped back, and your tillering skills must be spot on to make one with a nice reflex profile when finished. If you end up with no belly frets, or broken backs, and the bow holds it's profile after number of shots over a period of years you can give your self a little pat on the back, and that all has to start with a good stave.