JAMT brings up a very overlooked concept about speed control from "collision". I was first introduced to this in Juris Vagners PSIA book from 1995: "The Ski Instructors Guide to the Physics and Biomechanics of skiing". This is a free download on some PSIA division websites, look around.
What is the collision effect? the collision effect is as JAMT described. you run into something, it pushes back. That external reactionary force can slow you all the way to a stop if it pushes back enough. When you run into a wall, the wall pushes back exactly 180 degrees the direction you are going and slows you to a stop, very quickly. If you were to run into a wall at an angle, it would not slow you quite as much because the reactionary force would not be 180 degrees to the direction you are moving, so it would slow you down some, but it would also deflect you to the side a certain amount.
In skiing think of a hockey slide vs a hockey stop. In a hockey stop we maximize the edge angle so that we can slow down faster and stop sooner. This actually minimizes the skidding. a hockey slide we allow the edges to be a little flatter, they skid more..and we slow down less.
So.. as you can see...in a hockey stop vs hockey slide... the skis pointed 90 degrees to the direction we are traveling, provides a perfect pushback reactionary force that is 180 degrees from the direction we are traveling. And less skidding=more slowing. Its the collision itself that mostly causes us to slow down..not the skidding. There can be some transfer of heat, etc.. in skidding, but generally this is extremely minimal compared to the collision effect. The collision effect provides an external force to decelerate us. Literally, brakes.
Now what about ski turns? Well its similar in a ski turn except the skis are not positioned 90 degrees from the direction we're traveling. We have much less steering angle then that. So the reactionary force does not go back exactly 180 degrees from the direction of travel, and the speed bleed is less...but still there is some collision speed bleed that can occur. Again..higher edges will maximize this effect, flatter skis will cause more skidding and will minimize this effect.
It starts to get murkier there because about now everyone is thinking "but wait, when I carve I go fast, when I skid I go slow. What gives?"
The thing is, the way a ski is designed with a side cut, when you have a little bit of steering angle on a carving ski, it is able to deflect the energy to the side very efficiently and minimize speed bleed from the reactionary collision. The external force vector reacting from the snow is closer to 90 degrees, rather than pointing 180 degrees to the direction we're sliding. Thus the reactionary forces while carving deflect us on an efficient curved path. There is a little bit of speed bleed with that too, but not a lot. As you start ramping up the steering angle, the speed bleed starts to happen because the reactionary force will be pointing more rearwards from the direction of travel. So it becomes more of a decelerating force. That's one reason why when you get on the shovels a lot, you will slow down. More collision pointing more backwards, more deceleration, more speed bleed. When you get on the tails as much as you can, the collisions are minimized and so is speed bleed...in other words...work the tails to go faster...
When you get even more steering angle that the ski stops carving and starts to skid...that is when we really slow down, but this is the important point: the speed bleed there is not from the skidding itself, its rather from the larger steering angle which is creating reactionary forces that point more backwards to the direction we are sliding and thus have a greater slowing effect. And in fact, the higher edge angles you can maintain with the high steering angle is how you will maximize speed bleed. Make the ski flatter and it skids more and has less collision effect and less speed bleed. More skidding will become more like a hockey slide instead of a hockey stop.
So...high-c, how does edge engagement help control our speed? Well...as i just described, flat skis don't control your speed. Edged skis do. Edged skis with enough steering angle to get the collision effect slowing you instead of carving you. High-C edge engagement will absolutely add speed control through collisionary speed bleed.
Edited by borntoski683 - 10/21/15 at 1:57pm