|Originally posted by daslider:
PM - you wrote 'The simple geometric sidecut radius of a flat ski at least allows skiers to have a ball-park idea of one aspect of how the ski will perform. '
but, there must be more to the published figure than that? If 2 identically shaped skis have different flexes, they will turn differently, surely?
The usual numbers (ie, the three widths and the sidecut radius) have to be taken at face value - they simply describe the shape of the ski (looking down from above), nothing else is implied.
As you point out, two identically shaped skis with different flexes will indeed turn differently (on a deformable surface) and the radius of those turns is called (no surprise), "the turn radius", not "the sidecut radius".
Unfortunately, as we talked about earlier, the turn radius is influenced (and influenced dramatically) by just about everything under the sun including the sidecut radius.
Some of these things are properties of the ski (eg, longitudinal and torsional flexibility, swing weight, etc.), but many do not (eg, the skier's edging, rotary and pressure input, the compressibility of the snow, speed, etc.). Because of the importance of these other inputs, no single "turn radius" can be stamped on a ski.
I suspect that you were hoping that one might at least be able to wrap up all of the ski-related turning properties in one number and give it its own name. Unfortunately, even this lesser goal isn't possible. The reason is that the different physical properties of the ski rise and fall in importance depending on how the ski is being used and the snow underfoot. For example, the swing weight (ie, the polar moment of inertia) is all important in pivoted turns, but almost negligible in importance in carved turns. Torsional flex is important on hard snow and of negligible importance in more than a few inches of soft snow. Longitudinal flex is of supreme importance in determining turn radius in powder, but of lesser importance to the radius on a hard surface.
I hope these concrete examples give you some idea of the impossibility of ever coming up with a "turn radius" number for a ski.
Tom / PM