You just need to do your active mind a favor and properly sinew a suitable designed bow or six, then make some deductions. Have you measured the elasticity of sinew vs. flax? Do you know which reacts/recovers quicker?
Is there anyone out there who know which reacts or recovers quicker? Anyone who can compare six decently made sinew-backed to six decently made flax-backed? I have the impression that we're having arguments pro this or pro that, but very few hard facts to compare it to.
I haven't measured the elasticity of sinex vs flax, luckily other people have done so (Dick Baugh measured it for sinew, data on flax can be found easily). This article is informative.
http://www.primitiveways.com/secrets_of_sinew.htmlSo if you want to know: the modulus of elasticity (the resistance against tension, in this case) of sinew is about 3.3 GPa, that of flax is 58 GPa. Meaning, it takes close to eighteen times more force to stretch flax a certain amount than sinew, although the specific gravity of flax is just a bit higher (1.45 compared to 1.3). The sinew can stretch in an elastic manner (though it takes about 10% of temporary set, or creep) up to 5%, flax can do so up to 1.8%. I don't know about the degree of creep there.
So if you back a bow with sinew, you need to put a lot on it to gain some poundage. At the expense of adding a lot of mass too. However, you will be able to bend the bow further than if it were unbacked. The limit is then given by the belly properties of the wood (and the thickness of the stave you're backing). The most compression-resistant woods are junipers (especially eastern red cedar), osage, yew (the usual suspects for sinewing), but also lignum vitae, pear, buckthorn, madagascar rosewood, and a few other species.
If you back a bow with flax, you don't want to add a third of the thickness like with sinew, cos the belly would be crushed. Suppose that you'd normally make a self bow 14 mm or 9/16" thick, then you could take a wooden core half as thick, and back it with a thin layer (1 mm) of flax and still have decent poundage, thanks to the high MOE of flax. The belly is protected against set by virtue of its low thickness (in effect, the neutral plane will be close to the flax glue line, nearly all the wood working in compression.
You could make short bows (50" with 28" draw) in this way. These bows will be much lighter than similar poundage sinew bows, because you need to add only a thin layer (<10%) of the heavy flax-glue combo (compared to a third of the nearly as heavy sinew-glue matrix).
The hazel bow I made (but which broke due to an accidental dry fire): suppose I had sinewed it (nobody in his right mind would do that), it would still have had a low draw weight (<30# according to Dick's info), but it would have become a lot heavier, and would therefore be a rather slow bow. With a comparatively thin layer of low-quality plant fiber backing, I got nearly double the poundage (~40#) and a pretty fast shooting bow.
So it isn't about which backing is the best. It's about knowing how to use each of them, depending on what your purpose is and what wood (species and thickness) you are gluing it on. That will give you the best backing for each specific bow. On PA, I rarely read about plant fiber backings, and the default value seems either hickory/bamboo or sinew.
As for sinew: when stretched to 5%, as in this bow for example (
http://paleoplanet69529.yuku.com/topic/60635) it requires as much force to bend to its elastic limit as a similar thickness piece of a heavy wood species like Ipe. That is when the ultimate properties of sinew surface, rather than when you stretch it only 1.5%. In sinew-wood-horn composites, the added weight of the dense sinew-glue matrix is traded against the ultimate performance sinew can give, but also requiring more than most woods can take in compression, hence the horn belly.
