Primitive Archer
Main Discussion Area => Horn Bows => Topic started by: Ryan Jacob on April 20, 2018, 09:47:08 am
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At what draw length, would, say, a 60ish pound 50 inch horn bow fail? And which would fail first, the sinew or the horn? Not planning on working on one now though I easily could start as I can readily get water buffalo horn and sinew, just out of curiosity
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Depends on who makes it and the quality of work performed. ;)
Too many variables for there to be a simple answer to that question.
All things being right, I believe horn will fail before the sinew. I believe, & don't quote me on this, but sinew is supposed to stretch 8% before failure, and horn will compress 6% before failure.
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I wonder if the glue would fail first...
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Or would it just stack to a point where the string is pulling in line with the limbs and the bow is effectively folded in half?
Bearing in mind the V high draw weights that these bows can achieve. I'd imagine a 60# bow would have a vast amount of flexibility...
So if bow is 50" and say string is 46" ...
The bow folded in half would be about say 22" from grip to tips and the string would be 23"when folded in half... so that gives 45" absolute maximum physical draw length. Would anything fail other than the archer? Maybe not!
Del
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If your glue is good and properly applied, then in theory the core will fail first. A wooden core cannot take more than around 2% strain
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Practically speaking, I'd imagine Del is right, that the archer will be the limitation. Perhaps the glue or wood, if the construction or materials were not up to par. I think that since the core is supported by the horn and sinew, it can take the deformation of the bend without taking too much strain. Adam mentions a 1/2" thick limb bending to a 3" radius and only taking set, which gives .83% tensile/compressive strain for the surface of the sinew and horn. Perhaps if the bow was pulled beyond the aforementioned absolute maximum physical draw length, the tops of the tips would just be sliced off by the string.
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Just browsing through some older topics:
It depends on humidity. Very dry sinew will tolerate less deformation, and may break at a strain of much less than 5% (which is typically the max strain in a turkish hornbow at 32”).