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# One view of PM's tracks.

Try this one: (L to R is top to bottom)

12.00 4.30 60.00 20.00 88.00 30.00

Check the graphs of the turn radii. If this does not suggest Apex to Apex sking, nothing will! For this sort of turn,the three neutrals are at the apices and the transition.

If this sort of track happens on snow with some give, AND the skier is looking for parallel shins/equal edges, then the weight distribution shall favour the inside leg.

This is a banked turn, pure and simple.

Now try:

12.00 12.00 60.00 20.00 88.00 30.00

Assuming that the snow has some give, the graph shows a turn where the inside ski has a larger turn radius at apex than the outside ski. This is not amazing, we see it all the time in the "money shot" when a skier goes round a gate at high edge angles, inside knee flexed way more than outside ski.

Here is a possible view of this turn:

Starting at transition (ie. neutral) up until the skier get to the point where the tracks have the same radius, the skier is inclining. Inclintation puts more weight on the inside leg.

The point where the radius of the tracks are equal is where the skier begins to use angulation -- the weight transfers to the outside ski. This can be considered when "initiation" occurs.

The point after the apex at which the tracks again are the same radius is completion -- the weight it released from the outside ski as it is unflexed. Consider that "completion".

To my mind, this is a perfectly reasonable view of the turn, and it matches well to the three phases of the CSIA view of a turn:

1) Completion to neutral
2) Neutral to initiation
3) Initiation to completion

The "three neutrals" map perfectly to separating each phase:

1: Completion - release old turn
2: Neutral - start inclination to inside of turn.
3: Initiation - outside ski bears most of turning effort.

All turns can be mapped to these three phases. The banked turn at the start of this post would map initiation and completion to the same moment: the apex. However, that is not what we are after, as a banked turn is pretty immobile.....
BigE - I like where you seem to be trying to go with these interpretations, but I’m having a hard time with your unambiguous interpretations of these scenarios. For example, you don’t seem to consider the speed of the skier at all when you say that case #1 must be a banked turn, “pure and simple”.

Think about laying down the tracks for case #1 at a very slow speed (5 mph RR tracks going down the bunny slope). The skier can’t possibly get all 60 degrees of edge angle from banking at the apex because if he did, at such low G forces, he would fall right over. At low speeds skiers must get most of their edge angles from angulation, not banking – OK, he would need a body made of rubber to get such large edge angles by angulation alone, but that’s not the point – scenario #1 doesn’t *have-to-be* banking.

It’s the same deal with your weight distribution interpretations. For example, in your case #1 at very low speeds and low G forces, the skier doesn’t have to favor the inside leg as you state – it depends on exactly where the skier places his CM relative to the 8.6 inch wide base of support he has at the apex. If he moves his CM 2 inches to the outside of the 5 mph turn, more of his weight will be on the outside ski. If he moves his CM 2 inches to the inside of the 5 mph turn, more of his weight will be on the inside ski. In both cases there should still be enough weight on the more lightly weighted ski to force the underfoot area to contact the snow and still carve.

I really like that you are trying to match up the points in PM’s graphs with standard ski instruction and coaching terminology, but I don’t think his analysis can be pushed this far yet. At least that’s the way I look at it.

YOT
You are right, the 5 mph bunny slope and the 60 degree edge can be skied, but it won't be banked. What I am assuming is that speed is related to edge angle, so the higher the edge, the faster you go.

Quote:
 Originally Posted by YOT I really like that you are trying to match up the points in PM’s graphs with standard ski instruction and coaching terminology, but I don’t think his analysis can be pushed this far yet. At least that’s the way I look at it. YOT
For sure it's just looing at track shape. Speed and acceleration are definately key elements to knowing where the body and weight goes. It's funny though, when I look at the track shapes, and edge angles I think of how I'd ski to leave that track.

You have to admit that in every turn turn phases do exist. The CSCF calls them Unloading, edging and loading. CSIA says completion to neutral, neutral to fall-line and fall-line to completion.

I just realized that I misquoted the turn phases in the original post. Somehow, the turn phases are more to my liking when it's neutral to initiation rather than neutral to fall-line.... still "my bad".
Quote:
 Originally Posted by YoungOldTimer …I really like that you are trying to match up the points in PM’s graphs with standard ski instruction and coaching terminology, but I don’t think his analysis can be pushed this far yet. At least that’s the way I look at it. …
Yup. Exactly.
In some previous posts: http://forums.epicski.com/showpost.p...8&postcount=27 ,
http://forums.epicski.com/showpost.p...7&postcount=33 ,
http://forums.epicski.com/showpost.p...&postcount=200 , etc

I mentioned that the present analysis says absolutely nothing about time, velocities, accelerations, forces, pressures, or any variables related to those.

While it might not be obvious, some of the things that BigE mentioned in his first post depend on the above physical quantities. For example, the angle up from the base of support to the CM at the apices is mathematically determined by the arctan of the ratio of cross-hill acceleration to the acceleration of gravity. As YOT pointed out, at low speeds, the cross-hill acceleration will be negligible, so there can be no banking, whereas at high speeds and/or tight course, the cross-hill acceleration will be large and large banking angles are demanded.

Tom / PM
It's just fun to interpret these things against what we know. For the sounds of it, a new spreadsheet is not too far off!
Quote:
 Originally Posted by BigE ... From the sounds of it, a new spreadsheet is not too far off!
I can't imagine what could possibly have given you that idea.

Tom / PM
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