Seems like everyone is pinning this down pretty well Rick...
Remember (all) that a 'fulcrum' is the point (or collection of points) at which things pivot or rotate - an axis.
'Contact Point' was a term used earlier but it isn't necessarily accurate. When two 'material things' are involved in the fulcrum mechanism it's their Mass
the CM of each such Mass is located that's important. (When in firm contact with the ground it's the Mass of the whole earth we're working with.)
This is why the proposed ideas of a Javelin Turn or a Royal Christie work so well - better in fact than keeping our lifted ski close to the central axis of our body.
Even when we have no other leg to wield as counter-Mass there's no reason why our own internal mass can't be used for us. Remember that each hip socket is off-center
from our body's centerline which also helps.
Kazooski's office antics on his chair show this nicely. (I'm sure it was a popular show too!) The Lazy-Suzan ball bearings that permit reduced-friction swiveling are more like sliding on snow than any exploration of the idea while standing on sheets of paper.
Statements about Equal & Opposite Reactions above are exactly why this does
work. Using our muscles, we move one body-part's Mass in relation to another body-part's greater
(and possibly more axially distant) Mass.
The further from the Fulcrum (in this case the average of many internal "locations-of-partial-pivot") our base-Mass is, the more leverage we have on our moving-Mass. This means that we are more effective twisting that single leg when we have a Mass held out to the side further away from it (like the other leg & ski).
We gain even more advantage when we move that lifted leg & ski forward
as we ski into the direction toward the lifted-leg-side, and added advantage when we move our lifted-leg backward when Turning away from it.
Finally, we have more
leverage for this in a Flexed
position than in a very straight (upright) stance because more of our body Mass is located further from the center-axis of the pivot point. In this case further fore and aft - but still further away.
In answer to shortcomings of this mechanism in slow, long-radius turns - yep, this is so - to a degree. But remember also that in a large radius turn the Whole Skier
is actually Rotating
around their turn somewhat with their skis.
In such a Turn we can systematically alternate
between foot-steering (via this mechanism) and accepting some ski-induced rotation (let's call this 'Upper-Body Guidance') throughout the turn and might unconsciously 'reset' our rotational range a number of times.
Is this BB's ILS? Nope, not in the pure form he describes which specifically
uses leverage from the snow surface. His ILS provides much more leverage than what is described above and more continuously
as well (until you feet or skis whack together that is
One final thought is that the ski itself provides considerable turning force once on edge. If we make use of the mechanism described above and integrate it with the ski's own inputs, that's when we see the greatest advantage. and yes, this idea works best in shorter radius turns.
The purpose of the idea described above (and of ILS) is NOT to do all the Turning for the skier! Each mechanism is a skill/tool to refine and augment control of our skis. Is it Active Rotation? Yep, the best kind - the kind that makes skiing easier and more fun.
(Gee - I hope this is kinda where Rick wanted us to go.)