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Plant fiber backing questions
richgibula:
The names are a bit confusing. I looked it up and yucca, sotol are species in the agave family. The blue agave fibers are like rubber bands in the plants I harvested them from.
Regular yucca and sotol fibers are very similar except that sotol are a little longer unless your yucca is huge. I use whatever I can get my hands on. I wish I had some kind of power rollers to crush the leaves to separate out the fibers faster without damaging them. I would bet that these long fibers would also make good paper, too.
WhistlingBadger:
Interesting stuff, guys. I've been working some dogbane fibers--something relaxing to work on while the family watches TV. Might try backing that chokecherry molly bow I've been dreaming of.
I can't remember who, and I'm at work right now so I can't look it up, but somebody in one of the TBB volumes suggested that plant fiber might actually be superior to sinew, because it does the same thing but is lighter in weight. He was thinking of flax and milkweed, if I remember right. I'm a little skeptical about that. If plant fibers were better than sinew, I think the natives would have been using it. Still, dogbane is strong stuff, so it should at least keep a bow from exploding, and maybe even increase performance. It's a lot easier to get than sinew, too--growing all over the mountains, free for the taking.
joachimM:
--- Quote from: WhistlingBadger on February 06, 2023, 10:14:44 am ---
I can't remember who, and I'm at work right now so I can't look it up, but somebody in one of the TBB volumes suggested that plant fiber might actually be superior to sinew, because it does the same thing but is lighter in weight. He was thinking of flax and milkweed, if I remember right. I'm a little skeptical about that. If plant fibers were better than sinew, I think the natives would have been using it. Still, dogbane is strong stuff, so it should at least keep a bow from exploding, and maybe even increase performance. It's a lot easier to get than sinew, too--growing all over the mountains, free for the taking.
--- End quote ---
Sinew is more rubber band like: it can stretch easily 5% (wood at best 1%) but it's also more easily stretched than wood: its modulus of elasticity is 3 to 5 times lower than that of wood (it takes 3 to 5 times less force to stretch it a give percentage), while having a higher density. But the advantage of sinew is that you can stretch the hell out of it, and it shrinks as it dries, putting the belly under tension. It's advantageous in short bows where the back is strained far beyond 1%. If the back isn't strained >>1%, sinew is just dead weight making your bow sluggish.
Plant fibers on the other hand are much stiffer (modulus of elasticity of flax is 50 to 70 GP, compared to 2.7 GP for sinew and 12 for osage and 15 for hickory, just for reference), and although some plant fibers can stretch (allegedly) more than 3% (like sisal), they don't shrink like sinew as they dry.
It was Tim Baker who lauded flax as the ideal backing (for regular long bows), as it behaves like incredibly strong wood that you can mold as you like, and apply easily wherever you want.
But since flax is so strong in tension, it can easily overpower the belly of a bow.
So summing up, sinew and plant fibers can both shine or be awful as backing material, it all depends on the design of the bow.
bjrogg:
--- Quote from: joachimM on February 06, 2023, 06:13:37 pm ---
--- Quote from: WhistlingBadger on February 06, 2023, 10:14:44 am ---
I can't remember who, and I'm at work right now so I can't look it up, but somebody in one of the TBB volumes suggested that plant fiber might actually be superior to sinew, because it does the same thing but is lighter in weight. He was thinking of flax and milkweed, if I remember right. I'm a little skeptical about that. If plant fibers were better than sinew, I think the natives would have been using it. Still, dogbane is strong stuff, so it should at least keep a bow from exploding, and maybe even increase performance. It's a lot easier to get than sinew, too--growing all over the mountains, free for the taking.
--- End quote ---
Sinew is more rubber band like: it can stretch easily 5% (wood at best 1%) but it's also more easily stretched than wood: its modulus of elasticity is 3 to 5 times lower than that of wood (it takes 3 to 5 times less force to stretch it a give percentage), while having a higher density. But the advantage of sinew is that you can stretch the hell out of it, and it shrinks as it dries, putting the belly under tension. It's advantageous in short bows where the back is strained far beyond 1%. If the back isn't strained >>1%, sinew is just dead weight making your bow sluggish.
Plant fibers on the other hand are much stiffer (modulus of elasticity of flax is 50 to 70 GP, compared to 2.7 GP for sinew and 12 for osage and 15 for hickory, just for reference), and although some plant fibers can stretch (allegedly) more than 3% (like sisal), they don't shrink like sinew as they dry.
It was Tim Baker who lauded flax as the ideal backing (for regular long bows), as it behaves like incredibly strong wood that you can mold as you like, and apply easily wherever you want.
But since flax is so strong in tension, it can easily overpower the belly of a bow.
So summing up, sinew and plant fibers can both shine or be awful as backing material, it all depends on the design of the bow.
--- End quote ---
Very interesting and explained well. I never thought of it like this but I suspect you are on to something here.
One other problem with sinew is keeping it dry in a wet humid environment. It really likes to absorb moisture and then it loses its effectiveness. I guess I shouldn’t make that statement as a matter of experience, more from what others have said but it seems to make sense.
Love how much knowledge and experience is shared on this site
Bjrogg
Aaron1726:
Thank for all the good info guys! I have been inspired enough that I picked up a new spool of sisal and a 2x2 oak board from the store yesterday to play around with.
The dogbane bow is coming along, I will get some picks up on that one too when I get a chance.
Thanks again for sharing yalls knowledge, it really helps those of us wanting to learn this stuff.
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