Wow--lots of good thoughts here!
Once again, I've got throw out a caution about thinking about "real skiing" in absolute terms of precision and theory. Real skiing, especially at a high level, involves athletic abandon! Watching World Cup racers, you could "disprove" every theory about "correct" skiing that has ever been held. But that does NOT discredit the theory! In almost any pursuit, from art to athletic activity to literature, the highest levels involve breaking the "rules"--but ONLY after those rules have been thoroughly absorbed and incorporated into the skill pool and understanding. Greatness in skiing results from DISCIPLINED CREATIVITY. Without the discipline, creativity leads to chaos!
So this concept of "neutral" involving three separate components that ideally coincide is valid, but it must be taken with a grain of salt! The idea loses its practical usefulness if we view it through a microscope. I agree with you, Ydnar, that the skis are rarely at the same edge angle, in practice. Nor are they ever truly, geometrically "parallel" either, but that does not negate "parallel" as a useful concept. Nor do they ever move truly simultaneously, if we divide time fine enough, but the distinction between "simultaneous" and "sequential" movements still has use in practice.
Rick's "O-frame," which is a great image of the active inside ski and leg that Ydnar described, does indeed suggest that both skis may not tip at equal angles, and they may not be flat on the snow at the same moment. Likewise, in true wedge turns, both skis remain at opposing edge angles and neither ski EVER becomes flat on the snow. But there is still a "neutral" moment in the transition.
Like many ideas in skiing, the "three neutrals that coincide" idea, while valid, is oversimplified. For anyone interested, let's look at some of the finer technical points (consider this fair warning to those who are NOT interested...). Those three neutrals relate to the three basic skills and fundamental movements of rotary, edging, and pressure control. (For newcomers, these skills stem from the reality that there are three, and only three, things you can do with your ski, using your boot: turn it, tip it, and push and pull on it--and that all ski technique distills down to increasing our skill at these three things.)
As with the front wheels of a car, when we turn left, our skis point to the left (we turn them with our feet with or without the help of their built-in carving ability), and when we turn right, they point right. In between, they pass through "neutral" when they point straight ahead. And if they turn independently of each other, each around its own pivot point, again like the wheels of a car, when they turn right, the right ski leads--its tip actually moves ahead of the left tip. Again, as they turn from right to left, the lead changes, passing through "neutral" when the tips are even. I'll call this "rotary neutral."
Also, when we make a left turn, the skis tip toward their left edges (the inside ski may, in a parallel turn, or may NOT, in a wedge turn, actually ENGAGE its left edge, but it rolls in that direction either way; otherwise it is a different kind of turn). When we turn right, they tip right. In between, they pass through "neutral." Let's call this one "edging neutral."
Finally, when we turn left, again as in a car, the forces of the turn pull us to our right, tending to cause more pressure on the right (outside) ski than the inside ski. And vice-versa. Between turns, there is a moment of equal pressure--the "pressure neutral."
These three "neutrals" all occur at that moment between left and right turns, so they must coincide if everything is to flow smoothly, right? Sounds simple, so why are we even discussing it? Because it is really NOT that simple, of course! (Few things are....)
There are TWO reasons why one ski will lead the other, BESIDES the obvious one of intentionally pushing one forward or back. One is the independent steering action, described above. The other is the natural outcome of having one leg more bent at the knee and hip than the other. (When standing, lift one knee--that foot moves ahead of the other one, right?) So in a traverse, or when inclined into a turn, the uphill or inside leg is "shorter" than the other, ADDING to the lead from steering--or perhaps NEGATING the even tips in the "neutral" moment between turns! Ahah! So the tips really do NOT have to be perfectly even in "neutral"! There may well be a little "lag" between the other neutrals and the change of lead.
Edging may be even more complex. Remember that there are several kinds of "flat"--there is "level"--perpendicular to the pull of gravity, and there is "flat on the snow"--parallel to the slope angle. The "line of action," which indicates the degree of lean of the skier balancing against the various forces of the turn, is often more significant in skiing than true "vertical." So tipping and flattening the skis relative to the inclination of the body is another meaningful concept. What do YOU mean by "flat"? It would be simple if we were standing still on a level surface, but that hardly describes skiing!
Furthermore, skis do not have to be entirely flat on the snow for their edges to release. They simply have to flatten beyond the "critical edge angle" that causes them to hold. This is why, for example, it makes perfect sense to talk of edge release in a wedge turn!
Finally, "presure" too becomes more complex when we add motion and a tilting slope to the mix. In a car on a level surface, pressure shifts to our left the instant we begin a right turn, and equal pressure does indeed happen at that moment of transition between left and right. But in a traverse across a hill, even when going straight, pressure tends to shift to the downhill side (think of a car crossing a slope). Since that transition between ski turns usually occurs when traveling across the slope, once again the actual moment of equal pressure may lag behind the turn transition. The actual timing will depend on speed, turn radius, and steepness of the hill--in ADDITION to any active movements the skier makes to "shift weight."
So again, "three neutrals" is a helpful concept, but as Kneale points out, it should not be taken too far, or too literally!
One final thought, regarding the "pulling the feet back vs. pushing the body forward" debate: remember that these are both RELATIVE concepts--what matters is the relationship between the feet and the body. Remember that, even if you "pull them back," your feet, and the rest of your body, probably continue to move forward, or down the hill! As long as both are free to move, we can easily adjust the relationahip of our feet and our upper body, by muscularly moving them against each other (equal and opposite reactions, remember--they BOTH move, making this "either-or" argument perhaps meaningless). What we cannot do without involving some EXTERNAL force is actually accelerate our center of mass "fore and aft."
So if you're sliding down the hill, and you decide you're too far back, you can easily adjust your balance by pulling your feet back, relative to your upper body. Your feet move back, your upper body moves forward, and YOUR CENTER OF MASS REMAINS UNDISTURBED. You CANNOT simply accelerate your center of mass FORWARD to "catch up with your feet"--without pushing off from the slope with your poles or something. I believe that this is the core of the issue of this debate. When you "pull your feet back," like I said, your upper body also moves forward (relative to the feet), but since it is much heavier, the upper body moves much less, and it FEELS like the movement is entirely in the feet. Ydnar alluded to this above. Hence the validity of the advice, "pull your feet back for balance." It's right, practically!
For another image, imagine you are balancing on top of a mogul, leaning back on your tails. You can pull your feet back under you to center yourself, but someone ELSE would have to push your body forward to move it over your feet. It's simply not a "choice." This is why racers push off HARD with their poles to start a race--they can't just "move their bodies forward" by internal muscular force alone!
OK, back to "flow" and skiing!
Bob Barnes[ October 04, 2002, 10:36 AM: Message edited by: Bob Barnes/Colorado ]