New Posts  All Forums:Forum Nav:

Carving radius

post #1 of 17
Thread Starter 
Please help me in my discussion with a coworker.
How a carving radius of a straight ski compares with a parablic ski ? In other words if one was to mark a straight ski with a carving radius the way they do it now what it may be ? 50 m ? 100m ?

Just want to have a ballpark figure.

Thank you.
post #2 of 17
Quote:
Originally Posted by Yury
Please help me in my discussion with a coworker.
How a carving radius of a stright ski compares with a parablic ski ? In other words if one was to mark a straight ski with the carving radius the way the do now with parabolic skis what it may be ? 50 m ? 100m ?

Just want to have the ballpark figure.

Thank you.
all depends. a really longitudinally-flexible, torsionally stiff ski, ridden by a good skier at a good velocity will make the same turn as a 'shaped' ski, ridden by the same skier. it'll just require more edging.....
post #3 of 17
Thread Starter 
thanks Vlad.

say given the same edging (provided it's enough not to skid) how much would radius differ ? I am trying to break it down into components.
post #4 of 17
I used to have a pair of 210cm Head Racing Super Gs. Stickered race stock, marked at 70M. My guess is the average 200cm recreational ski was somewhere around 40-50M. One issue with old skis, was the radius of the tip was quite a bit differennt from the tail. My guess is that my race skis were mwasured tip to waist. From waste to tail was probably over 100M (who knows???).
post #5 of 17
Thread Starter 
ok, thanks, that gives me an idea.

in essense i am trying to ballpark the added value of a parabolic ski given the task of a carving turn.
post #6 of 17
Quote:
Originally Posted by vlad
all depends. a really longitudinally-flexible, torsionally stiff ski, ridden by a good skier at a good velocity will make the same turn as a 'shaped' ski, ridden by the same skier. it'll just require more edging.....
But to go along with that, you'd have to have a snow surface that's fairly soft so that you could reverse the camber enough. Then, you'd need a surface that's also firm enough not to mush out from under the ski with all that force. A catch 22, eh?
post #7 of 17
Thread Starter 
what does it mean 'to reverse the camber' in this context ?
post #8 of 17
Quote:
Originally Posted by Yury
ok, thanks, that gives me an idea.

in essense i am trying to ballpark the added value of a parabolic ski.
you need to remember that a modern ski with a 20M radius is measured when laying on a flat surface, so it can't actually carve a turn that big. And I don't know the math (we need to ask PhysicsMan), but I would suspect that if you take a ski with a big sidecut (small radius) and put it on edge and reversed the camber the same amount as an old ski, the realized turn radius reduction may not be 1:1 between the two. To try to explain this better, if you took a ski with a 20M radius and reversed the camber by bending the deck of the ski to a radius of 20M (the same way you put a ski tail on the floor, hold the tip and push on the middle of the ski to reverse the camber), and you took a ski with a 70M radius and reversed the camber the same amount and put both skis at a 45 degree angle to the surface, if for example, the 20M radius ski now had an effective arc of 7M (just about 1/3 the original), would the 70M radius ski have an effective radius of 23.3M or would it be more?

If the size of the arc is reduced at a greater rate for a ski with a smaller radius, then that increases the benefit of the increased sidecut more than just the difference of the radii of the two skis.
post #9 of 17
Quote:
Originally Posted by Yury
what does it mean 'to reverse the camber' in this context ?
In the first image of this sequence, Ted has reversed the camber of his outside ski. Basically, he bent it.

http://www.ronlemaster.com/images/20...l-1a-flat.html

Camber is the amount of bend built into a ski, that when the ski is laid on a flat surface, makes the middle of the ski stay off the surface, and pressures the tip and tail when on a flat surface.
post #10 of 17
JohnH: You sir, are quicker on the button than I am.:



Quote:
Originally Posted by Yury
what does it mean 'to reverse the camber' in this context ?
Camber is built into the ski. Set a ski on a flat surface. The only points of contact should be at the tip and tail. (Make sure the brake is tied up.) There should be a gap between the flat surface and the center of the ski.

When skiing you can reverse the camber by "loading up" the ski in a turn. The tip and tail are bent "upward" and are "above' the center.
post #11 of 17
Thread Starter 
got it.

before these explanations, camber to me meant the angle at which tire meets the road
post #12 of 17
Quote:
Originally Posted by JohnH
But to go along with that, you'd have to have a snow surface that's fairly soft so that you could reverse the camber enough. Then, you'd need a surface that's also firm enough not to mush out from under the ski with all that force. A catch 22, eh?
the surface never much mattered to me for reversing cambre....just the applicable forces against the waists.
i think I get what you mean, though.
frozen cord is always amazing for nice, adhesive carving
post #13 of 17
Quote:
Originally Posted by Yury
got it.

before these explanations, camber to me meant the angle at which tire meets the road

still does, esp. on skiis.
now set your ski caster
post #14 of 17
Going back to the original question, and coming at it another way:

The radius figure that's often cited in describing a ski isn't the "carving radius" (or even the "turning radius," though that's often what it's called), it's the radius of the the sidecut itself. Approximately, anyway, as the sidecut is probably not exactly an arc of a circle.

The typical sidecut radius of a "straight" ski was 50-60 meters. Semi-typical width dimensions would be something like 85-65-74. Some race skis ran a bit narrower or, if you go back to the '60s, a bit wider.
post #15 of 17
Thread Starter 
and how does the effective radius (on some sort of average slope with average effort and decent skier) of weigthed ski would compare ?
post #16 of 17
My old straight 190 RC4 SLS had about a 49 to 50 m radius. My Old 208 Kästle SGs have a 70 m radius. If you put a ski on edge and press the center down so that the entire edge is in contact with a flat surface, you must decamber the ski to match the radius of the curve scribed by the ski on that flat surface. The more you tip it the more you have to decamber the ski, and the shorter the carved radius becomes. Multiply the sidecut radius by the cosine of the tipping angle or something like that (yes I'm too lazy to figure it out right now) to get the radius actually carved.
post #17 of 17
I messed around with data for a while. Here are a few skis I looked at:

Atomic 1995 Arc 18 Slaloms Sidecut radius 45m, at edge angle 45degrees R= 32m
K2 1993 KVC Slaloms Sidecut radius 57m, at edge angle 45degrees R= 40m
Volkl P-10 1995 Slaloms Sidecut radius 42m, at edge angle 45degrees R=30m
Atomic 2000 WC Slaloms Sidecut radius 14m, at edge angle 45degrees R=10m
Atomic 2000 WC GS Sidecut radius 23m, at edge angle 45degrees R=16m

I have lost of data. John H is correct with his general numbers.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Ski Instruction & Coaching