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Typical Radii

post #1 of 16
Thread Starter 
I've been reflecting on the ability of my short-radius slalom skis (Fischer WC SCs 13-m) to make long radius turns. They seem to be ok at mid radius turns, but I wouldn't say the make great LR turns on hardpack at speed. Other's have disagreed with me. I realized that after almost two decades of skiing SG skis almost exclusively, I tend to have a different reference base for what to consider a small turn. Being an engineer, I like to be factual and remove as much subjectivitiy as possible.

I was noticing my tracks the other day, and it seemed to me that they were a tiny bit larger radius when viewed from the lift than when viewed from the skis in the process of making them. I also was watching some WC GS racing today. Maybe it's the camera, but the turns seemed pretty tight. It seems that these "GS" turns could easily be handled by my Fischers.

So to those in the know, what radius are the typical (mean, or median or both) WC GS turn radii (not the sidecut radius of the skis, the actual turns on the hill)?
post #2 of 16
The typical radius of turn is the shortest possible while not falling or losing control.

Shorter radius turns in any course will always be faster if cleanly executed.

Sometimes when a silly HS race course would be too turny, we'd throw the slalom skis on and ski much quicker than anyone on GS skis. Seconds quicker. In real racecourses this is neither an option nor likely to be desireable.

If you go to the FIS or USSA sites, you'll find the technical coursesetting info that determines what range of radii the skier can choose. Whether or not these technical criteria are actually maintained to a good degree of fidelity is another story entirely.
post #3 of 16
F.I.S. specs GS skis at a minimum of 21 meter radius and SL and a minimum length or 165cm (men) that typically spec in the 11-13 meter range.

To your question of what do they produce on the hill, techy answer is that is varies according to the amount of edge angle used. I can give some radius for different edge angles with some (unlikley) qualifications that are necessary to exclude variables within any given turn that can alter it's function radius.

So these numbers are theoritical for:
Constant edge angle, constant slope pitch, perfect edge grip, balanced pressure on 'sweet spot' of ski that arcs it evenly along it's contact edge.

Edge Angle --- 10 ---- 20 ---- 30 ---- 40 ---- 50 ---- 60

12 meter SL = 11.8 -- 11.3 -- 10.4 -- 9.2 --- 7.7 --- 6.0

21 Meter GS = 20.7 -- 19.7 -- 18.2 - 16.1 -- 13.5 -- 10.5


Tech note: Tightening of radius is not linier to the amount of edge angle.

Fun factor note: Rolling 'em up just a little further makes them grin a whole lot more
post #4 of 16
Arc, step up to Mozilla Firefox 1.5 http://www.mozilla.com/ You will like the difference.
post #5 of 16
Arc, what Cirque said. You might be able to edit it if you hit "Go Advanced".

That said, I edited your original and deleted the edited one.
post #6 of 16
All of this said, I think that what Ghost is asking is the set of a WC GS course. What are the typical turn radii in the courses?
post #7 of 16
Thread Starter 
That's about right SSH, specifically what is the typical turn radius of the typical turn made by the typical skier skiing a typical line down a typical GS course. Mean, median, mode, double mode, or however you want to define typical is fine.
post #8 of 16
Plus when answering, please make it clear what the number represents. For example a distance between the two gates of ie. 15 meters, needing a turn radius of 7 meters to execute.

I guess what i mean is "what does radius mean?" in my mind the radius would be about 1/2 the distance between the gates.
post #9 of 16
Thread Starter 
A skier might be able to run fairly straight at the gate and make a tight turn with a small radius around that gate and then head straight to the next one. Another skier would prefer to go faster and take a rounder line. There are an infinate number of possible lines. By radius I mean if you traced an arc in the snow where they were turning the tightest, what would the radius of that arc be for the majority of the turns made by WC GS skiers on course.
post #10 of 16
Quote:
Originally Posted by Ghost
A skier might be able to run fairly straight at the gate and make a tight turn with a small radius around that gate and then head straight to the next one. Another skier would prefer to go faster and take a rounder line. There are an infinate number of possible lines. By radius I mean if you traced an arc in the snow where they were turning the tightest, what would the radius of that arc be for the majority of the turns made by WC GS skiers on course.
Hmm, use publically available info on shapes/sidecuts and watch high quality video of several skiers. Note the peak edge angle they achieve while making turns that are visually pretty clean. That will be the instantaneous shortest radius. Figuring out an average radius over the course of a "tight" turn would probably require more than eyeballs Mk I and a video.
post #11 of 16
Quote:
Originally Posted by SkiMangoJazz
I guess what i mean is "what does radius mean?" in my mind the radius would be about 1/2 the distance between the gates.
That is one way to define it, but if you actually skied that line you'd be hella slow in most cases.

In the tech events, the move of the skis across the hill under the body has a significant impact on the resulting radii, so you could in theory ski a longer radius than the simple math would suggest. Video shows racers tend to only do that when they screw up.
post #12 of 16
Well just for simplicity sake, it would give an idea of turn size on the world cup to know about how far apart the gates are on Slalom and Giant Slalom courses.

Anyone know?
post #13 of 16
Quote:
Originally Posted by SkiMangoJazz
Well just for simplicity sake, it would give an idea of turn size on the world cup to know about how far apart the gates are on Slalom and Giant Slalom courses.

Anyone know?
The requirements are right there in the book, but like I said it depends on whether or not actual courses set work with the rulebook. Local races sometimes not, FIS races signs point to yes.

I'll dig up the required links to the info in the morning.
post #14 of 16
Quote:
Originally Posted by skiingman
The requirements are right there in the book, but like I said it depends on whether or not actual courses set work with the rulebook. Local races sometimes not, FIS races signs point to yes.

I'll dig up the required links to the info in the morning.
Great thanks.

It is morning here for me
post #15 of 16
Quote:
Originally Posted by SkiMangoJazz
Great thanks.

It is morning here for me
http://www.ussa.org/PublishingFolder...guidechap8.pdf

Its all in there. I would post the specifics instead of a giant link, but I'm kinda in a rush to get somewhere. :-P

haha.

-supernewb
post #16 of 16
Yeah sorry I've been putting it off because I hate that damn big ugly PDF. Thanks supernewb.
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