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Ski's turn radius and skidding

post #1 of 10
Thread Starter 
I've read in a previous post that if a turn is less in diameter than the skis turning radius that there is a skidded component to the turn. Is this correct? If so, in short radius turns, unless on slalom skis, do most of us do some skidding as opposed to pure carving? I'm just trying to figure out when it's appropriate to be skidding vs. carving given my skis with a 20 meter turn radius.
post #2 of 10
Not an answer to your question, but I am curious, is it truly possible to carve a turn without skidding? I just have a hard time with the physics of the concept.
Thanks,
Chas
post #3 of 10
chasboy,

It is very easy to carve a turn. Just look at how many people can do RR tracks today. However, the shorter the turn radius the harder it gets because you need speed and momentum to bend the ski and keep it on edge while ensuring that the edges do not slip out of the carve.

Prosper,

Slalom skis or not, most skiers do some skidding (as opposed to pure carving) in the majority of their turns. It is hard to describe what is a good skarved turn, but in general you want to make sure that the tails have minimum displacement in a direction perpendicular to the edges. Any such displacement should be the result of "physics" rather than you pushing them out. In other words, the tails should "slip" out of the carve because you don't have the force required to keep them going along the direction of the carve (direction the tips are taking). They should not slip out of the carve because you are displacing your feet in that direction. This is even more important at the top of the turn (unless you are on steep terrain or bumps and really want a lot of rotary component in your turn).

Nobody should be able to answer your question about "when is appropriate to skid vs carve". It all depends on your intent. And your intent should be dictated by the terrain and the situation. In other words, your intention may be to carve the turn, but if you are on a 45 degree narrow slope, then you need to reconsider.
post #4 of 10
Prosper I would like to expand on Tom B's idea of intent and the whole definition of skidding.

The short answer is yes, skidding is totally appropriate. The long answer is, the type of skidding is determined by the intent of the skier. If the skiers intent is to control speed through skidding then the skidding will be defensive and in the form of breaking where the tails are intentionally displaced by pushing or brushing them out to the side.

If you're intent is to control the line and direction that you are skiing and control speed by line selection rather than breaking, the skidding is incidental to carving a short turn. Instead of pushing the tails into a skid the left tip is guided to go left and the right tip is guided to go right. The skier moves the whole body forward and into the direction of the turn and the edges of the whole ski bite in.

If the skiers intent is a shorter turn than the radius of the skis and the speed will allow, the skier doesn't edge as agressively and guides the inside ski tip more, then the ski tails tend to drift a bit in relation to the tips. The skis feel like they are carving but not a perfect carve. Technically perfect carves are possible in larger turn radii but require more precision than the average bear is capable of.
post #5 of 10
More or less skidding happens in every turn. Pure carve is ultimately a hopeful description of an outcome. It takes a lot of real estate to execute anything approximating a pure carve. Consequently, the narrower the corridor, the skiddier the turn.

Pure skidded turns are also an outcome that are at times necessary in skiing and therefore as critical to skilled performance as the ability to leave two distinct parallel lines in the snow with seamless transition between strokes.

Let me evoke the spirit of Weems Westfeldt and say that skiing, like life, is a matter of polarities. To devote yourself to one pole over the other causes imbalance. One is strongest when both poles in any dichotomy are developed equally.

[ January 10, 2004, 09:12 AM: Message edited by: nolo ]
post #6 of 10
Quote:
Originally posted by Prosper:
I've read in a previous post that if a turn is less in diameter than the skis turning radius that there is a skidded component to the turn. Is this correct? ...
I know what you mean, but (a) you've got radius and diameter mixed up and (b), you didn't include effect of a non-zero edge angle in your statement. The way I would say it is this:

If the radius of the turn you are actually making is smaller (ie, tighter) than the sidecut radius times the cosine of the current edging angle, then you must have some skidded component in your turn.

OTOH, if the radius of the turn you are making is larger than the sidecut_radius * cos(edge_angle), you could be either carving or skidding.

HTH,

Tom / PM

[ January 10, 2004, 11:57 PM: Message edited by: PhysicsMan ]
post #7 of 10
Quote:
Originally posted by PhysicsMan:
</font><blockquote>quote:</font><hr />Originally posted by Prosper:
I've read in a previous post that if a turn is less in diameter than the skis turning radius that there is a skidded component to the turn. Is this correct? ...
I know what you mean, but (a) you've got radius and diameter mixed up and (b), you didn't include effect of a non-zero edge angle in your statement. The way I would say it is this:

If the radius of the turn you are actually making is smaller (ie, tighter) than the sidecut radius times the cosine of the current edging angle, then you must have some skidded component in your turn.

OTOH, if the radius of the turn you are making is larger than the sidecut_radius * cos(edge_angle), you could be either carving or skidding.

HTH,

Tom / PM
</font>[/quote]
post #8 of 10
Quote:
Originally posted by J.P:
</font><blockquote>quote:</font><hr />Originally posted by PhysicsMan:
</font><blockquote>quote:</font><hr />Originally posted by Prosper:
I've read in a previous post that if a turn is less in diameter than the skis turning radius that there is a skidded component to the turn. Is this correct? ...
I know what you mean, but (a) you've got radius and diameter mixed up and (b), you didn't include effect of a non-zero edge angle in your statement. The way I would say it is this:

If the radius of the turn you are actually making is smaller (ie, tighter) than the sidecut radius times the cosine of the current edging angle, then you must have some skidded component in your turn.

OTOH, if the radius of the turn you are making is larger than the sidecut_radius * cos(edge_angle), you could be either carving or skidding.

HTH,

Tom / PM</font>[/quote]
</font>[/quote]Maybe you will find out the article:
“Physics of Skiing: The Ideal-Carving Equation and its Applications” interesting in http://xxx.lanl.gov/abs/physics/0310086
post #9 of 10
JP - Thank you very much. I hadn't seen it. I liked it and saved a copy. It looks to be a bit more rigorous and complete than the corresponding section of in "Physics of Skiing" by Lind. How did you happen upon it? Are you a physicist?

Tom / PM
post #10 of 10
Quote:
Originally posted by PhysicsMan:
JP - Thank you very much. I hadn't seen it. I liked it and saved a copy. It looks to be a bit more rigorous and complete than the corresponding section of in "Physics of Skiing" by Lind. How did you happen upon it? Are you a physicist?

Tom / PM
I am not a physicist.
I had a private lesson with two men who were physicist and
they e-mailed me that section.
I am glad you like it.
J.P
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