I'm not sure about that. If the ski is under torsional load the majority of it has to be along the 90 degree. Remember my good friend that the 0/90 are not independent from one another, they are anistropic, they are composite and they do not look the same way at the forces put on them as if they were independent. I absolutely do not agree that the torsional load is only in shear. I know that from floating 80.000 lb rigs over muskeg. I'm going to run this idea past one of my aerospace composite guys and see if I am on the right track or you are simply correct and I should just get on board with the triax.twizzstyle wrote:I would love if you could explain how 90 deg fibers can add any torsional stiffness, because I just don't buy it. There is zero load path for the shear stresses to follow. As you just said, the load is carried along the fibers, and all torsional stress is in shear, no?
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This is settled by a pretty simple test... layup a simple core with only longitudinal fibers (0 deg), then another with the same longitudinal fibers, but the addition of lateral fibers (90 deg). Twist and see which takes more force. Everything I've always known about composites would tell me it'll be nearly the same (ignoring the additional epoxy, which carries some load of course)
By my way of thinking however the two major issues of skis revolve around torque and flex. I may be right that isolating the two to as great a degree as possible gives better performance. Or I may be wrong and the status quo is right.
I do not know of any ski made with my structure. So the only way I will really find out is by building some and reporting to you the results. Or get someone to do about $25 grand worth of FEA for pretty much free.
Cheers,
Bloefeld