|Originally posted by oboe:
But that begs the question. "Tortional rigidity" is seldom an absolute. %100 tortional rigidity probably would be horrid for most skiers, even if hunky dory for some. The balance of tortional rigidity is the key. With today's control over materials and dimensions, is it not possible to obviate any need for detuning? PhysicsMan, although I do respect your intellect, I bet a person involved intimately in the design and production of modern skis may have an answer different from yours. My bet is that design, construction and manufacture can eliminate the need for detuning.
1) I don't see how my response begs the question. You put forth a proposal for one specific design variant, increased torsional softness, and I responded with three examples of serious problems it would face and would have to be overcome if that approach were to be investigated.
2) In fact, I think that the need for detuning actually *has* decreased over the past few years. As I think I mentioned, I rarely detune my (modern) skis, and I think the trend is towards no detuning at all. The difference in our opinions is that you suggested this could be accomplished with decreased *torsional* stiffness, whereas I'm quite sure that the reduced need for detuning has been due to the well-known trend towards decreased *longitudinal* stiffness while keeping torsional stiffness much higher than it was in decades past. With longitudinally softer (but non-detuned) tip and tails, if they do momentarily grab, the problem is not transmitted as forcefully to the mid ski area, and so the skier (and hence the motion of the skier's CM) is isolated from the perturbation.
3) I totally agree with you that 100% torsional rigidity may not be for everyone. I would go even further and add that even a very competant skier often encounters situations where increased torsional flexibility is useful to them. For example, when such a skier intentionally decides to add significant skidding into his turns, a torsionally softer ski makes feathering in some skidding much easier. In fact, I think that this is exactly what Head is trying to do with their piezo fiber design. I think they are trying to broaden the performance envelope of their skis by having them start a bit on the soft side torsionally (*) in non-icy, low speed conditions, but having the fibers tighten them up torsionally in hard snow and fast (presumably carving) skiing. Using these fibers, they could do this quite simply by only having the higher frequency components of the electrical signal fed back to the fibers, thereby achieving a frequency dependent torsional rigidity, and hence a speed- and surface-texture dependent torsional rigidity.
Just my $0.02,
Tom / PM
PS - * - "on soft side torsionally": By this, I mean compared to other modern high performance skis, not compared to skis of old.[ June 19, 2003, 07:36 PM: Message edited by: PhysicsMan ]