Ski Builders Forum

Hello everyone,

I am a engineering student making some composite skis as part of my 3rd year project. (a project I have in mind since i started skiing)

The skis I will be making will be backcountry skis with a target weight between 1400 and 1600g.

I have done a lot of research but didn't find anything on stiffness and other topics. Since it is one of the major characteristic of ski design I need your help.

How do I choose/calculate my longitudinal stiffness? What about the torsional stiffness?

thanks for your help

Nico

Have a look at this: https://www.junksupply.com/guide-to-the-simulator/

This will give you an idea on the longitudinal stiffness.

Everything can be calculated quite easily using laminate theory and quasi static bendingof beams. Choosing is the harder part and in the end comes down to experience and testing.
You could do some bending tests on different commercial skis in different areas, and then from there create your own hypothesis on how to tune things for what you wanna improve. That would probably be the most scientific approach for an engineering project.

You will probably find that the flex profiles can be quite "surprising" for a lack of better words...

If you want i would absolutely share my flex profile i worked out for my skis.

That is all for the longitudinal flex. Torsion is even more voodoo in most cases...

Hi Everyone

I made some test with alpine race ski on hard snow and had some thought about waxing the sides. Is there anyone who tested and gain some real advantage by doing that? Any literature about ? I refer on waxing the sides in ABS or similar matarial . Thanks

What Sleeping awake has written is by far the most concise way of putting this. Plus you can get surprisingly accurate results of the flex down the length of the ski.

and @sleepingawake. If you'd be willing to share, I'd absolutely love to see another's work

For torsion I am now using the paper below, seems to match quite ok for my snowboards.

https://www.fpl.fs.usda.gov/documnts/fplrp/fplrp156.pdf

I have written a script that calculates the core thickness profile based on a pressure distribution and longitudinal deflection pattern as input. Now adding torsion to that. But I am struggling with convergence of the numerical optimization. Should have paid more attention in Math classes.
Any mathematicians on this forum?