or Connect
New Posts  All Forums:Forum Nav:

Base Structure Physics

post #1 of 10
Thread Starter 
Its common knowledge that an aggressive base structure is great for spring skiing as it helps to reduce the suction between the ski and wet snow by channeling more water. What's interesting is that this same structure can make a ski very difficult to ski in light dry snow. Does anyone know the actual physics at work that cause the aggressively structured base to be nearly unskiable when its light and dry?
post #2 of 10
Friction? More surface area for the dry snow to stick too thus creating more drag/resistance?
post #3 of 10
Skis with spring structures on cold snow act too directionally stable and steer very poorly. A ski with an aggressive structure on cold snow will act worse than a ski with a winter structure on warm snow.
post #4 of 10
Thread Starter 
Originally Posted by DropCliffsNotBombs View Post
Skis with spring structures on cold snow act too directionally stable and steer very poorly.
Yes, this is it exactly. They just don't want to turn. Its a very interesting feeling.
post #5 of 10
Can someone enlighten me on those structures?
What does a spring structure actually look like? And a winter structure?

Is it only about direction of the structure (longitudewise, diagonal...) or depth also?
post #6 of 10
Thread Starter 
A spring grind is definitely deeper.
post #7 of 10
I'm typing from my iPhone and can't get into a dissertation (perhaps good) but the suction comes from a fluid flow phenomena called low Reynolds Number 'creeping' flow. It occurs when you get flow in a very thin channel. In this case frictional effects dominate inertial effects. You can experience the same phenomena with two plates in soapy sink water -- put them together and then slide them to generate intense suction.

Structure alleviates this effect on a ski base by increasing the Reynolds number (bigger channel, rougher channel, less orderly).

I am guessing that the directional issues mentioned above are due to a different effect, likely how the snow crystals scale relative to the structure grooves. Cold, fine-grained snow is obviously smaller in scale than granular wet spring snow, and more likely to 'rail' in the structure.
post #8 of 10
Today on cold, moderately dense/finer grained powder, my skis with a moderately aggressive structure were no problem turning but were a little bit slower than a friend with the same wax on a tighter structure. Not for sure if it was only the structure though, versus a wider ski for him since we weigh about the same.
post #9 of 10
post #10 of 10
Nice writeup Doc.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Tuning, Maintenance and Repairs