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Radius and speed vs. pop

post #1 of 13
Thread Starter 
This is a poll but you need to write. :)

Background:
I'm interested in how fast you need to go for each sidecut radius (in general) to get a pop out of the turn while carving arc to arc. With a pop I mean the feeling you have on a trampoline, bouncing up and down. It should be a distinct feeling of a force that you'll either get airborne from or that you'll *need* to absorb not to get thrown.

Is it possible to calculate the likelyhood to have pop for a sidecut at a certain speed? Does it pretty much conform to how many newtons the feet are loaded with during the latter part of the turn?

I much realize that torsional stiffness, overall stiffness and tail width plays a huge role, but I'm still very interested in seing if there's a pattern emerging in the answers.

Question:
Which of your skis (brand, model, length and *sidecut radius*) gives you the pop described above while carving arc to arc?
For each of the skis you listed, what speed is necessary? Preferably GPS measured, but otherwise described in terms of how far you straightline and on how steep or something else it's possible to relate to. If you need to have a gs suit to get that speed please also indicate that.

If you have skis with a sidecut that you think should give you a pop at a certain speed but it really never does, please write what skis those are.
post #2 of 13
All my carving skis give me a pop, but it depends primarily on the speed. I like the sense you get when edging a lot and getting the hip close to the snow. The force that keeps me upright is proportional to the inverse of the turn radius and the square of the speed, so to have the same sense on my 24m radius compared to my 13m, I have to go 35% faster. I get a pop with both skis, but its slower with the longer radius. Since I do primarily flex releasing, its more of a quick edge transfer than becoming airborne after the pop.
Edited by Jamt - 2/10/10 at 12:51am
post #3 of 13
Edit: I have tried to measure speed with GPS but it does not work for quick turns. SL turns take less than a second and the GPS typically have a 1 second update interval.
post #4 of 13
Thread Starter 
Some gps'es use doppler for speed measurements and saves speed data for every instant. GT-31 is such a gps.
post #5 of 13
Yes, I just used the one built into my phone.
post #6 of 13
I use the BGT31. Same as for windsurfing. Will check out the speeds later for you from a track last year in the alps.

The pop is more a technique, surface and equipment thing than a speed thing. The suit has IMO no play in it. On shorter radius skis its easier to feel the pop. On soft floppy skis the pop results in a flop.
post #7 of 13
Thread Starter 
I don't think I could make the SG or DH skis pop on a red or blue slope without a suit.
post #8 of 13
Quote:
Originally Posted by tdk6 View Post


The pop is more a technique, surface and equipment thing than a speed thing.

 
I usually agree with what you say TDK, but not this time. I think that a ski has a certain range of speeds where it gives you the desireable sensation. For example this weekend I skied with some friends that all like to go really fast. Then I chose the 24 m, because with that ski I can still try to get maximum turn out of the ski without going slower. If I would try that with the 13 m race-stock SLs, it is simply not possible to go that fast. In that case I would have to do shallower turns, with less "pop" to keep up.
Likewise, if I ski with my kids that don't go as fast, I can still enjoy turns on the SLs without going particularly fast.
In other words, I think that speed is definitely one of the more important factors, and the only one I can modify at a given occasion.
post #9 of 13
Quote:
Originally Posted by Carl R View Post

I don't think I could make the SG or DH skis pop on a red or blue slope without a suit.

I dont have SG or DH skis so I would not know for a fact but when I practise GS and its cold I usually wear clothing on top and I feel the pop . But you are right about speed being a factor. Not that I personally believe that the small increase in speed from a suit will make the difference. When I ski I usually always were my POC suit and shorts and jacket over but when Im with my family on holliday or ski for purely fun or give ski lessons I wear normal skiing wear. I think I can still make my sl and gs pop with those clothes. As for speeds I need to go back to some thread about gps skiing from last year were I reported the speeds. Let me check.... here:
http://www.epicski.com/forum/thread/82535/gps-speedskiing-tdk6-joining-the-honorable-60mph-club

Quite an intereting OP there. Good I have it all written down because I cannot remember any details. I need to take my GPS with me on our GS races this weekend and check for the speeds. Problem is I dont know where to put it when Im in the suit. Maybe tuck it in under the suite behind at my boot.
post #10 of 13
To get the "pop" you just have to decamber the ski in a turn.  The more you decamber the ski, the more pop you're going to get.  You could get pop out of a GS ski at SL speeds simply by tipping it enough to make SL-sized turns, so long as you had enough weight to decamber it at SL speeds.  Getting big edge angles at slow speeds requires a lot of angulation. Getting pop-producing small turns out of stiff long radius skis requires good edge grip at tip and tail and significant down force and good technique.

To answer your question;
165 Fischer WC SC 13m Radius - can play jump in the air where there is no jump at about 15 + mph, but more fun at higher speeds.  Above about 25 - 30 mph, I can't match their tipping angle, arcing radius and g-force produced to make a really good edge-locked turn and have to start drifting my turns and the pop factor goes down.

190 Volant Machete G twenty something radius - Can get pop at about 20 mph, only because I don't have the weight to decamber it much at slower speeds.  They feel good from 20 mph to about 50 mph.

208 Kästle RX National Team SG radius somewhere around 60-70 m - I would need about 45 mph before I could play with the rebound and have it worth my while.  I must confess when I get on them I don't think of doing that; I just ski faster and faster.  They loose their 'dead" feeling and start feeling like a truly good ski at about 50 mph.  They feel good at any speed over 50 mph I've been able to reach.
post #11 of 13
Thread Starter 
Quote:
Originally Posted by tdk6 View Post

Not that I personally believe that the small increase in speed from a suit will make the difference. 
Small? 
post #12 of 13
Quote: LOL, that was a great OP, 60 mph on WC SLs, that's hardball.
post #13 of 13
Jamt - thanks. Thats pritty fast on SL skis yes. But I have skied with SL skis for 6y straitht now as my main skis. Powder, bumps you name it. I think they are pritty good allround skis considered that they are great at moderate speeds on normal pists if you dont want to frequently go over 100km/h that is .
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