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Although this could be in the Ski Gear thread (I just copied it there), it effects our technique greatly. I've been thinking quite a bit about stated Turn Radii as it's on most skis now. I have both 16m and 13m skis. As I've found this is NOT the turning radius of the skis. Think about it. that's 40-50 feet, (and if that's the radius, then the diameter of the circle is 80-100 feet!) Slalom skis have a turn radius of much less than that.

What this metric is, as the link below explains, is the radius of a circle that the sidecut would be a part of with the ski layed flat. The turn radius of a ski is a completely different thing, created by 3 elements; the sidecut, the amount the ski is pressured and thus decambered, and the edge angle. This makes perfect sense as you can tighten up a ski's turning radius by pressing down hard on it and bending it into a tighter arc. There is no "natural" turn radius of a ski, only a range.

So all this hooey about turning radius is flawed, as it is only one component of the turn size that a ski makes. My Atomic SX:11's are stiffer, and don't tighten up their turns as much as my Fischer RX8's thus making the difference between them much more than the numbers reflect.

See this great piece on the physics of it. http://www.math.utah.edu/~eyre/rsbfaq/physics.html
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 Originally Posted by SkiMangoJazz Although this could be in the Ski Gear thread, it effects our technique greatly.
I agree with you that the turn radius of a ski is just a comparison number but I think that deep sidecut skis affect the tactics of turning (timing, intensity and duration) and not so much the techniques (movement patterns that produce a turn). Maybe this is what you meant.
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 Originally Posted by SkiMangoJazz See this great piece on the physics of it. http://www.math.utah.edu/~eyre/rsbfaq/physics.html
Well worth the read. I can still remember all the lights going off in my head back in 198? when that ski salesmen (and shop owner I think) cut out an hour glass out of a piece of paper and showed me how I needed to bend the ski into a curve in order to get the edge on the shop floor. I had been skiing for years, and didn't really know exactly what I was doing. A good shop owner, he was questioning me about how I skied etc. so as not to sell me the wrong skis. He was incredulous that I was buying SG Racing Skis that seemed way too long for me, but couldn't tell him how I made them turn, other than "I just sort of lean right to go right". I assured him that I had demoed other skis and this ski in different lengths and this was what I wanted (by the time I made up my mind, the shop I demoed them at was sold out ).

The sidecut radius is the starting point that can be made smaller by tipping the ski. Making tighter turns that the mathematical model predicts from the tipping angle and sidecut is an art that requires a bit more skill (you basically jam the tip and bend it more, like buckling a slender column such as a yardstick). Carving a longer turn than the sidecut radius is a feat which requires the ability to perform miracles. That's why A SG ski has a 50 m radius and a soft shovel.

Edit: Oh, and even a ski with an infinite radius will be curved on soft snow because the weight presses down on the centre, but the snow pressures the whole ski up.
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Maybe even more important than the tip's resistance to forward movement flexing the ski, is the idea that the pressure perpendicularly down on the ski increases as the edge angle is increased, bending the ski more till the middle engaes, creating a tighter radius than the sidecut gives.

As far as longer radius turns than the sidecut, I guess I perform mirracles, as I can ski from straight to tighter turns than the sidecut, and any radius in between. Later, RicB.
Ric,
Try it on hardpack, I bet you will be scarving, not carving.
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 Originally Posted by Ghost Ric, Try it on hardpack, I bet you will be scarving, not carving.
Or maybe that one can manage pressure on the ski so that only part of the edge is really engaged or maybe it is that a turn with a longer radius than sidecut is being scarved. Whatever the case it never felt like a miracle to me. Later, RicB.
Quote:
 Maybe even more important than the tip's resistance to forward movement flexing the ski, is the idea that the pressure perpendicularly down on the ski increases as the edge angle is increased, bending the ski more till the middle engaes, creating a tighter radius than the sidecut gives.

very good point RicB. It is the resistance of the tip and tail of the decambered ski trying to go to it's uncambered shape that caused the ski to carve while the edge is engagued. The flex of the ski is a factor (softer flex = less resistance).
Click on the link at the bottom of post #8 for more technical stuff.
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 Originally Posted by BillA Click on the link at the bottom of post #14 for more technical stuff.
Hey thanks for that. I think you meant post 8 however (that poster has 14 posts
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