In his book, Ultimate Skiing, Ron LeMaster says that once the forces of skiing are understood, everything else makes sense. I would qualify this statement and say that until the forces of skiing are understood, nothing makes sense and any assumptions are nothing less than wild guesses.
In his book, Le Master says 2 things that I believe are fundamental to skiing:
1. Most of the expert skiers’ weight is balanced over the outside ski and,
2. The edge angle of the ski with the applied force must be 90 degrees or smaller.
In point 2, it is my position that the angle must be less than 90 degrees. Although he doesn’t appear to say so, I am assuming that LeMaster is referring to the edge angle of the outside ski of a turn.
On page 20 of his book, FIGURE 2.3, a and b show two different alignments of opposing forces, R and S. In Figure a the angle of the transverse aspect of the base of the ski with the snow reaction force S is 90 degrees. In Figure b the angle of the transverse aspect of the base of the ski with the snow reaction force S is greater than 90 degrees. LeMaster doesn’t provide details on what force R represents. As explained my my last post, in order to assess balance in skiing as it pertains to a dynamically balance base of support one needs to know the relationship of Centre of Mass (CoM) and Centre of Pressure (CoP) with the Snow Reaction Force. One also needs to know where the ball of the foot and centre axis of the foot are positioned in relation to the inside edge of the outside ski.
While all of the above are relevant, the key issue, which neither LeMaster’s book or any other literature I have read on ski technique doesn’t touch on, is the nature of the forces associated with a dynamically balanced base of support that would act to cause the transverse aspect of the ski base to assume an angle with the applied force that is less than 90 degrees. Here LeMaster provides all kinds of clues that he is standing on the answer, but not seeing it. For example, on page 44 (Janica Kostelic) he describes how one of Kostelic’s strengths was her ability to maintain contact with the snow through the transition (from one turn to another) with perfect flexion moves so she could get pressure on the edge early in the turn. He goes on to say that Kostelic also knew when and how to use her inside ski to advantage. LeMaster is so close, yet so far.
As I will explain in future posts, Kostelic and all the other great skiers including Mikaela Shiffrin and Ted Ligety, more than simply getting pressure on the new outside ski early in the turn, apply forces to the new outside ski (current inside ski) that sets up and over-centre mechanism that allows them to use external forces acting on them to drive 3-dimensional forces into the new turn. They set this mechanism up in the transition from the current outside ski to the new outside ski, before they apply steering forces to the ski .
References: Ultimate Skiing – Ron LeMaster