Wednesday, 25 November 2015

More Than You Want To Know About Skis


 During the past summer I received some pamphlets from Elan about their new shape of skis. The top surface on the back half of the ski is concave and on the front half is convex.  From an engineering point of view I am not sure what these shapes can do better than a standard rectangle cross section.  Elan was one of the first skis with the parabolic shaped sides that changed the way we ski and made turning skis much easier.  So when they bring out a new idea it is worth taking a look at.  My wave skis from Elan, that I like a lot, baffles me because I can’t see what the wavy surface does. 
When laminate skis first came out many years ago all the engineering test data was given in the ads.  For a mechanical engineer this was wonderful stuff.  Pictures of the ski cross section showed all the laminated layers.  Diagrams showed the bending characteristic and some show the dynamic behavior.  You could compare skis just by looking at the data.  Unfortunately this added information confused more than helped and this practice of telling you what you were buying died out. 
Ski manufacturers now have many options in terms of material and ski shape. The odds are good that you can find skis that you will like.  The trend over the last few year is less camber.
 What is the effect of low camber or rocker? It effectively shortens the ski contact edge on the snow.  This causes a sort of barrel stave shape in the snow.  If you work it right there is enough stiffness under the foot so that you can still have enough edge for grip on ice. My guess is that a low soft camber gives you less fore and aft stability and a slower ski. My impression is that low cambered ski is like a shortie ski with higher flotation characteristics. It can also be super fast turning.  I saw a kid last year just standing line, counter rotating his skis.  Normally this is almost impossible on cambered skis.
Skis with camber when laying on a flat surface will have some space under the bindings.    When you step into a ski with camber it will flatten out and look like it has no camber. What happens depends on the ski stiffness along the length front and back from the boot and bindings.  When loaded my Elans,  appear to be stiffer in the front and parabolic in shape, while the back seem to be softer and circular in shape .  The snow in turn is loaded heavily under the foot tapering off gradually towards the tip and tail. You can see the short flat sections in front of toe and heel pieces and the softer ends.
First you should know that changing the thickness of the ski a little bit can make the ski either very stiff or very soft.  The math equation included the thickness T cubed (T³). This applies to the also the high strength material on the top and the bottom of the ski.  By changing the thicknesses and material along the length, a ski can be made to flex and twist to any requirement.
Normally I ski on 165 to 170 cm skis but last year I used some 150 cm skis donated to the Disabled Club. I was surprised how well they worked even in deep snow.  
My thoughts are when buying a ski try several different makes.  When you find one you like then try a size shorter and a size longer to get the best characteristic for you.

No comments:

Post a comment