torsional stability just might be the controlling factor. what cross section shape is best for that?
Round is the best in terms of carrying torsional loads and for torsional stability. What bowyer's call a torsional failure mostly looks like lateral buckling to me, which is a different thing.
I did some reading , and round and smooth seems to make sense for most torsion bar applications, as they are expected to flex millions of times, and cracks tend to start at corners. found nothing on tubes versus solids. I suspect more squareish might be better than flatish for rectangular.
Square will be better than flat. The closer you get to a circular section, the better for torsional properties. Solid versus hollow makes no difference, it is the section shape of the outer surface that matters.
Triangular is best from a weight versus stability point of view.
That would be for lateral stability, which I think is the real issue.
I partially emptied the lead bucket to get it down to 50#. Then I hung it on the recurve. Then I started filling it back up. It's tire weights mostly. I got it up to 67# and called it quits.
In that case you could probably still take more material off, but it does get sketchy when you are down to those dimensions. My last bow was 5/16" wide at the nocks and looks impossibly delicate and thin to my eye, but works fine.
Mark
