Primitive Archer
Main Discussion Area => Bows => Topic started by: stuckinthemud on November 16, 2015, 08:12:18 am
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Hi All,
up to now I have only used stems/trunks for my bows, but am I limiting my stash of timber by not using clean, straight branches? I have always thought there must be stresses in branches not that are not imposed on trunks, but are there, or am I being daft to avoid using such wood?
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Yes, daft :)
But then we all are ::)
Gotta use what you can find unless you have a load of perfect timber at your disposal.
Some of the stuff I use would make your hair curl.
Del
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yes use what you find. itll have character. its o.k., doesnt have to be board flat, perfectly straight, and without knots lumps and bumps. as long as tiller is good and tips,handle lines up, whatever else it does is just its spirit shining through. lol Tony
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Branch wood rules. With most tree species, branch wood has higher density than trunk wood. It also tends to have higher compression strength. The stresses a living branch experiences are good for wood quality. Important to take the position of the stave in the living branch into account, though, to prevent unneccessary sideways warping. Center of back crown aligning with the most skyward side of the branch is good strategy.
Tuukka
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When I harvest branch wood, I try to remove some of the bark on the side that was facing the sky so that I have a definite marker of which side should be the back (for softwoods, the opposite is true, use the side that was facing the ground). The only issue I seem to have with branch wood is that I have to climb 25ft up a tree with a bow saw to get it! :D
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so if a branch is thick enough to split and get bows out of the skywards and ground-facing sides , I should only use the one and not the other side of the branch?
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Not necessarily, I have heard that in hardwoods, the top side develops tension wood, which is stronger, and the bottom develops compression wood, in hardwoods the compression wood is supposed to take more set or be less elastic or something like that. in softwoods, the compression wood is supposed to be superior to the tension wood. If I cut a branch that was splitable into several bows, I wouldn't waste the compression/tension wood, I would still try to make a bow out of it and in all honesty I would probably still succeed as I dont think there is a massive difference between tension and compression wood. But those are just my thoughts, others may vary.
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from some of the branches and leaning tree I have looked at, I think that there are significant differences between the types of reaction wood, but the tricky part if finding enough of that wood to make a bow from. I would be happy to dedicate a single branch to a single bow, and not be concerned too much about the other side, if I thought I could get one good bow from the branch or log
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Problem with some of this is that the upper side of a branch often has shoots growing from it and the underside is likely to be cleaner...
It's the difference between theory and practice.
Q:- What's the best wood for a bow?
A:- The bit you can get.
Del
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Hi.
Some of my best bows came out from branches (I'm remembering two black locust and one hackberry now). I always knew what side was upwards. But at the end I chose the side that I thought that was going to give a better bow (or as in the hackberry one I put the upper side on bottom limb and the other for top limb (spliced)).
I agree with Del...I try my best with what I have and use theory only as a reference point :)
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I like what Del says. Softwood(juniper, incense cedar), my favorite bows are made from the top of a upward curved branch
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Hardwoods don't develop compression wood on the underside of branches. They deal with gravity by developing tension wood on the topside. Compression wood only occurs in softwoods. These are opposites in characteristics, as well, but both have desirable qualities as bow material, as long as compression wood's low tension strength is dealt with.
In branches and trunks with reaction wood (either tension or compression wood) the wood on the other side, opposite wood, is also different from normal wood. With conifers, higher in tension strength and appreciably denser than trunk wood. Few studies on the opposite wood of hardwoods, though.
With leaning hardwood branches and saplings (probably a good 50 % of the bow material I harvest), I use both sides if possible, but still mark the upper side and split the wood so the upper and lower halves make the staves. Have built quite enough sapling bows with serious sideways twisting by ignoring this practical notion.
Tuukka
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Q:- What's the best wood for a bow?
A:- The bit you can get.
Del
Good advice. Keep it simple and don't over think it.
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With leaning hardwood branches and saplings (probably a good 50 % of the bow material I harvest), I use both sides if possible, but still mark the upper side and split the wood so the upper and lower halves make the staves.
Tuukka,
when using hardwood reaction wood for a self bow, do you prefer using the top tension wood
or the bottom opposite wood?
or do you make composite bows with the tension wood?
thank you
willie
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Don't horizontal branches of conifers have high amounts of compression wood? If so, it'd be great for sinew backed or laminated bows I think
I assume the compression wood is in the area that is being compressed by gravity, not stretched
ugh i gotta start trying to build bows
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What about yew? It's so different to all the other woods and I have access to some nice branches that are screaming to be thinned-out.
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What about yew? It's so different to all the other woods and I have access to some nice branches that are screaming to be thinned-out.
My comments were based on my experience with Yew.
Even the underside of "Landscape Yew" branches, once heat treated produced a decent bow.
Del
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The landscape yews here are all what I would call multi trunk, a lot of branches but they're all vertical. Would they be considered branches or trunks?
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In yew I haven't seen any difference with the top or bottom sides. I find that usually the tension side is the cleanest. I recently made a compression wood yew branch bow, just because the tension side had some rot to dig out
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Little experience with yew, but i have heard others talk about older, large trees, with long lower branches sweeping out from under the shade of the branches above them. Those branches often yield long, twist-free staves from their upper sides. This is true of juniper, for sure.
Wizardgoat just mentioned that tension wood is often cleaner, and the thing about those branches spreading is my theory why. The top of the branch is shaded by the foliage above it and has been growing longer and longer like that, so fewer knots and cleaner wood.
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The landscape yews here are all what I would call multi trunk, a lot of branches but they're all vertical. Would they be considered branches or trunks?
They are considered bow wood :laugh:
Trunks, I'd call 'em... but I wouldn't wear 'em to go swimming.... (dunno if that translates across the pond?)
Del
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I've just about quit replying on threads like this, but there is a lot of anecdotal material presented above that just doesn't agree with extensive testing by the Forest Products Laboratories and others.
First, all wood is 2.5 to 4 times stronger in tension than in compression. You will save lots of otherwise wasted time and energy if that principle is recognized.
Second, all varieties of wood produce compression wood on the earth side of branches. It's just that softwood's difference in growth between sky and earth sides is more pronounced.
Someone posted about making a compression side bow or a tension side bow. There will be differences in the degree of compression or tension conditions as they are considered point by point through the thickness of the bow. If the top of the limb is the back of the bow (as it should be), the back will be using tension wood and the belly will be using "less tensioned" wood if the belly wood is between the original center of the branch and the original top of the branch.
if the earth side of the limb is used for the back of the bow, the belly side will be "less compressed" wood than the back. This is the worst condition because the back is weak in tension and the belly is fairly weak in compression.
In all the pre-1960 writings about wooden bows, any reference to compression wood in trunks or limbs advised to never make a bow from compression wood.
Or we can all set to and reinvent the wheel again, and again, and again....
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Yeah, we hear you, and thanks for the technical info.
But if the only clean wood I can get is the underside of a long straight Yew branch... you can guess what I'm going to use.
If I waited for the perfect Yew stave, I'd have never made a bow.
Del
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Tuukka,
when using hardwood reaction wood for a self bow, do you prefer using the top tension wood
or the bottom opposite wood?
or do you make composite bows with the tension wood?
thank you
willie
Willie,
Typically, the top half of the split trunk will gain in reflex while seasoning (thanks to the tension wood in it), while the bottom half stays straight or even gains follow while seasoning, which isn't all that surprising. This is different from simply drying a stave clamped to a reflex etc, as the tension wood fibers actually actively keep the bow from gaining set at a normal rate. Most of my favorite bows come from the tension side, having lower set and higher cast, but I've made good bows out of the lower halves, as well. Plenty other qualities in the mix, as we all know.
Pictured is an average case from this fall; a pencil-straight, leaning saskatoon trunk was cut, split through the middle according to the upper-lower division, and set aside to season. After two weeks of drying, the top half sports a 32 mm reflex, while the bottom half is still straight. (Plenty of twist there, too, but building D-bows with straight tips, it's a non-issue). This particular trunk had the cleanest and the flattest side on the side, not on the top, but I knew better. Splitting that way would've resulted in massive alignment issues.
Tuukka
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I've just about quit replying on threads like this, but there is a lot of anecdotal material presented above that just doesn't agree with extensive testing by the Forest Products Laboratories and others.
What I've been relaying here is not based on anecdotes but on wood science of the past 30 years or so. Sources like Timell (1986): Compression Wood in Gymnosperms; Hakkila (1989): Utilization of Residual Forest Biomass; and the latest: Barnett et al 2014: The Biology of Reaction Wood.
First, all wood is 2.5 to 4 times stronger in tension than in compression.
No. Applies only to normal-grown wood. Very low tension strength is a major characteristic of compression wood. Many softwoods are "only" about twice as strong in tension compared to compression. Compression wood's tension strength is as much as 50 % lower than normal-grown wood, so around 1: 1.
Second, all varieties of wood produce compression wood on the earth side of branches. It's just that softwood's difference in growth between sky and earth sides is more pronounced.
Arguably true, strictly-speaking, but quite misleading. Compression wood in hardwoods and tension wood in softwoods is a fringe-level, suggested phenomena, compared to the well-established fundamental difference in how hardwoods and softwoods deal with gravity.
Barnett et al 2014: p. 2: [What is reaction wood?] "It is divided into two types: tension wood in dicotyledons, and compression wood in conifers."
Or take the classic, Hoadley's Understanding Wood, pp. 30 -32: "In softwood species, reaction wood forms principally toward the underside of the leaning stem" [...] "In hardwood trees, reaction wood forms predominantly toward the upper side of the leaning stem."
Anyone who's cut into reaction wood in softwood trunks and reaction wood in hardwood trunks can tell this much, it is quite graphic under the eye as well as under the blade. Philosophical relativities have little real-world weight.
In all the pre-1960 writings about wooden bows, any reference to compression wood in trunks or limbs advised to never make a bow from compression wood.
For the past 1 000 years, from the Pacific all the way to the Atlantic, over the vast Boreal zone of Northern Eurasia, the predominant and highly sought-after bow material was none other than compression wood (pine or larch). Compression wood has superb characteristics, once it's lousy tension strength is dealt with, as I wrote earlier. A backed compression wood bow is the only natural-material or other bow in the world that gains in reflex and cast when relative humidity rises, a pretty huge deal when living in the wet Northern woods, bow in hand.
Tuukka
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Thanks guys, so to sum up, branch wood is composed of compression wood, the level of compression increasing from earth side to sky side; all branch wood is usable but sky facing is best, but do not use left or right facing timber ;D?
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Stickinthemud-
I hope that you do not mind me posting a pic in your thread. This is some compression wood from a spruce trunk. How usable it is I have yet to find out. I have laminated some to a birch back, and it indeed gains in moves with MC changes. A wet rag on the belly of a 48" bow, moves it 3" overnight. I did not start with it as dry as possible, so my bow is straight when damp and has 3" deflex a day later, and I have not started to tiller it yet. Still trying to figure out what moisture content the compression wood needs to be when I make the glue-up.
(http://)
the white is normal for spruce, and the orange is compression wood
end of stave is wetted to enchance color
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Thanks Willie, I had no idea the cross-section could look like that, makes things a lot clearer :)
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I wonder whether anyone here made a backward bow out of compression wood.
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That's a good idea scp. Might have to try that with some branches I have.
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Hello everyone, this subject has interested me for years and it seems it is hard to get the head around it. I just made a yew branch bow amd it does opposite to what Willie just described. When I put the bow in the front room (not even close to the wood burner) it will increase its reflex by at least a couple of inches over night and when i leave it in a cold damper room it straightens out....this bow was made with the sky facing wood as the belly....simply because if I did it the other way around then the bow would have had a large natural deflex, which I didnt want.
the problem is most branches bend downwards giving a natural deflex if the sky facing wood is used as a back....
dave
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dave
If I understand you correctly, our bows are acting in the same directions with the dry/moist cycle, but "shouln't" because I have the compression wood on the belly and you have it on the back?
I will agree that I am having a hard time getting my head around it also
Perhaps I will post my bow a bit later, and I hope you can comment more on yours
willie