Torsional Flex

[A_B]

Does anyone know how torsional flex is measured?

Is this something that manufacturers measure and have specs on?

Can it change over time?

Just trying to find out more about it, but knowledge seems pretty limited on it.

[CsSkis]

With regard to your first question, Adam Cord told me how he measured torsional flex on the Elite, but I have to admit that I have forgotten the details.  (I vaguely recall that it was similar to the way longitudinal flex was measured.)  So, in regard to your second question, in the case of the Elite, yes, they measure the torsional flex and keep track of it.  With respect to the torsional flex changing over time - it might, depending on how the ski is manufactured.  But, the effect would be insignificant relative to any change in longitudinal flex.  (And, we have had plenty of discussion on that topic.)

[A_B]

Wouldn't that be an important # to publish about a ski, as well as the flex #'s?

 

When you get a ski, some have the flex #'s on a card, some don't.

 

I would like to see the range for these measures for each ski PRIOR to buying. I understand that nit every ski will be the exact measures, but it should be in a range, sort of like published horsepower of a car engine.

 

Thoughts?

[DW]

AB, yes, envision a ski clamped at the tail and then at particular spots on the ski a twist load is applied and documented.  On a race car frame, the back is clamped on a flat surface the frame twisted at certain points with a given load and the deflection measured with dial indicators.  This then gives you a torsional spring rate.  IMO, it is a very important component to the performance of the ski, the torsional flex will determine the deflection of the fin from vertical particularly as one crosses the wake or holds angle.

[eleeski]

Flex matters someone once claimed. That is why a flexible fin works well. The longitudinal stiffness needed to make most skis perform will cause the torsional stiffness to be extremely stiff - from the materials and manufacturing choices. So you are stuck with fin flex to make differences you can feel.

Eric