Main Discussion Area > Bows
Stress and performance
bradsmith2010:
thats a very good point Aussie, I have made bows with little set ,, but shot slow,, to much mass,,
sleek:
--- Quote from: Aussie Yeoman on July 03, 2022, 01:26:17 am ---The short answer is "quite a bit, but I'm not sure".
It would take some re-figuring. I might have some time tomorrow.
The thing is though that reducing strain means making it wider and thinner. Going in this direction increases the mass per unit of stiffness. So while you might have less set (no set), the performance will suffer by virtue of more of the stored energy being required to accelerate the limbs.
--- End quote ---
the 63 inch Molly needs to be almost twice it's width.
Aussie Yeoman:
I suppose you are quite right, on average. I tried to pick a timber that would be common in the US (almost none here), and I guess I picked a truly exceptional sample.
I'll run the numbers on some other samples and see if we get something more conventional. Closer to average.
Aussie Yeoman:
Gonna conduct some necromancy on this old thread:
I found an old project where I followed the dimensions calculated and got pretty much exactly what I wanted. This was a pretty long Molly design, made from boo-backed ironbark. I calculated the dimensions and printed them out 1:1 as templates, then did the same with the projected tiller shape. It didn't take much tillering to get it to spec, and when it was done the draw weight/length were just what I wanted, the tiller shape matched the projection, and the dimensions were pretty much bang on. Just small fractions of an inch here and there.
Aussie Yeoman:
Here's another one, in which I make a longbow from Maple, using an average of figures collected by others (Tim Baker's bend test data)
Because I didn't use figures from a sample from this very board, the set was a little higher than I'd have liked, but otherwise it turned out pretty much as designed:
https://ozbow.net/phpBB3/viewtopic.php?f=34&t=17080
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