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Pressure release and turn model on ice

post #1 of 22
Thread Starter 
Hi all,

It's been a dry season in California so I've been practicing carving on ice.

The turn dynamic I've been using is:

1st quarter: early "inversion" edge engagement on uphill ski using hip countering and slight leg extension into diagonal movement across the ski. No up weighting, minimal pivot.

2nd quarter: build pressure on new outside edge, attempt smooth 80/20 pressure redistribution onto new inside ski.

3rd quarter: attempt to hold carve (remember this is ice) via 80/20. I can't seem to get anything close to 60/40 distribution. Elongation of turn radius into "comma" shape.

4th quarter: shift weight back forward, prepare for inversion engagement.

The problem :
Edges are engaging OK through 2nd quarter with almost no skidding. But even with radius elongation and some inner ski weight redistribution, they start slipping in the 3rd quarter.

I'm riding on new head magnum supershapes. Possible culprits are:

1. Technique. Maybe I need more angulation? More inclination feels a bit dangerous given the lack of traction on ice.

2. Edges. I haven't sent the edges in for bevel tune yet and based on eyeballing they look more like a 0/1-deg bevel than a 0.7/3 I would feel more comfortable with.

3. Turn model. I've built this approach based on reading the epicski forums and finding a style I feel comfortable with (5'8", 150lbs, 13.5m radius cambered skis). I'm not sure it represents the right modern approach.

Besides finding a good coach (they're hard to come by in South lake tahoe), do you guys have any ideas for how I might figure out how to hold the edge through phase 3 and 4?

Thanks!

Fwiw I found the following background threads pretty helpful reading along the way:
http://www.epicski.com/t/20767/carving-on-ice-technique-or-gear-or-what

http://www.epicski.com/t/70099/pressure-control-on-ice
post #2 of 22
Instead of thinking about pressure distribution, edging, angulation, and inclination... Think about balance on the outside ski, rolling the ankles without twisting the skis, extending into the turn without pushing on the skis, releasing the pressure in the turn through absorbing/flexing, and the direction/path that momentum wants to take you from turn to turn when you release. Pay careful attention to how the skis feel under your feet. If you're standing still on glare ice with your skis on edge - what causes them to break loose? Twisting the skis, abrupt movements that push the skis, and losing balance with the weighted (downhill/outside) ski. This is no different than when sliding down the hill.

If I recall, the below GS clip was filmed on extremely firm snow. It should give you a pretty good model for what I'm describing above - even though it is a GS turn and not an SL turn. If you prefer an SL turn, I have one of those posted below the GS, but it isn't on ice, though the same mechanics are employed.





Cheers.
post #3 of 22
Quote:
Originally Posted by schraderade View Post

Hi all,

It's been a dry season in California so I've been practicing carving on ice.

The turn dynamic I've been using is:

1st quarter: early "inversion" edge engagement on uphill ski using hip countering and slight leg extension into diagonal movement across the ski. No up weighting, minimal pivot.

2nd quarter: build pressure on new outside edge, attempt smooth 80/20 pressure redistribution onto new inside ski.

3rd quarter: attempt to hold carve (remember this is ice) via 80/20. I can't seem to get anything close to 60/40 distribution. Elongation of turn radius into "comma" shape.

4th quarter: shift weight back forward, prepare for inversion engagement.

The problem :
Edges are engaging OK through 2nd quarter with almost no skidding. But even with radius elongation and some inner ski weight redistribution, they start slipping in the 3rd quarter.
 

 

Would you describe the red part again with new words?  

--what do you mean by "inversion?"  

--can you explain how you are using "hip countering?'"  

--could you describe what you do to "build pressure?"

post #4 of 22

Turning on ice is the same as any other hard snow.  The only difference is that you need more accurate balance and better feel for your edges.  It does no good to describe what you are trying to do, and if you are trying to do different movements than on more edgible snow, you are on the wrong track.  If you are thinking about that much, you cannot do it.  Ice is all about soft feet, balance and feel.

 

BK

post #5 of 22
Quote:
Originally Posted by Bode Klammer View Post

Turning on ice is the same as any other hard snow.  The only difference is that you need more accurate balance and better feel for your edges.  It does no good to describe what you are trying to do, and if you are trying to do different movements than on more edgible snow, you are on the wrong track.  If you are thinking about that much, you cannot do it.  Ice is all about soft feet, balance and feel.

BK

And moving with the skis. Look at Heluva's videos.
post #6 of 22
Doesn't mean a good tune isn't darn important too, if surface is truly challenging. Eliminating unnecessary variables / handicaps is step one, I would think.
post #7 of 22
icon14.gif
Quote:
Originally Posted by qcanoe View Post

Doesn't mean a good tune isn't darn important too, if surface is truly challenging. Eliminating unnecessary variables / handicaps is step one, I would think.

Absolutely, q!

Don't wonder about the tune, it is in our control to make sure it is NOT a variable.

I'd wager that HeluvaSkier shows up at the mountain with tuned skis.
post #8 of 22
Quote:
Originally Posted by cgeib View Post

I'd wager that HeluvaSkier shows up at the mountain with tuned skis.

You bet. Every ski is always razor sharp with no burrs and has been freshly waxed and brushed. Leave nothing to chance.
post #9 of 22
Quote:
Originally Posted by HeluvaSkier View Post


You bet. Every ski is always razor sharp with no burrs and has been freshly waxed and brushed. Leave nothing to chance.

 

 

  Das right!!! NO detuning either!!!!!

 

  zenny

post #10 of 22

Consider the down force holding your edge in the ice or cutting the groove.   Because pushing down pushes you up (F=ma), you only have so much down-force in the bank.  If you use it all in the first half of the turn there is nothing left to hold the second half of the turn where more is required.   Don't use any more pressure than you need early in the turn so you will have it when you need it at the end of the turn..   Creative accounting can get you more down-force temporarily (a loan, or expenditure of savings), but master this first.

post #11 of 22
On hard ice you want most of the load on the outside ski. So you definitely don't want 60/40, more like 90/10. Bear in mind that the ski will groan and protest and maybe feel like it isn't carving when in fact it is. Things get a little bit squirrely when you push it to the limit on ice.

Agree with other posters that sharp well tuned skis are essential. It makes all the difference in the world.

Bear also in mind that while it is a frontside ski, the Magnum is a bit wider under foot and a bit softer than a race ski. That makes it more useable in a wider range of conditions but its ultimate ice performance will not match a race ski.
post #12 of 22
Thread Starter 

Sorry for the delayed response guys:  I spent a couple days working through turns on ice and thinking/trying out most of the suggestions here.

I think I got to a breakthrough and wanted to share what I learned.  YMMV.

 

  • Like many skiers/racers, I have been taught over the years to think about building, managing, and releasing "pressure" through the turn.  Depending on terrain, speed, pitch, and turn style, I've thought about managing pressure through mainly the skier's frame of reference:  via edge angle ("rolling the ankle in"), fore/aft pressure ("stay forward, drive knees, flex ankle", etc), inclination, etc. 
  • What I realized when working on ice over the last few days is, when confronted with the unforgiving nature of ice, it can be more helpful to think about pressure in the terrain frame of reference than the skier's frame of reference.  And in the terrain's frame of reference, the carving forces are simplified a lot.  Here, there are only three types of pressure:
    • Forward pressure - this is pressure parallel to the snow that moves the ski forward in the direction of travel.
    • Edging pressure - this is pressure perpendicular to the snow that creates grip.
    • Sliding pressure - this is pressure parallel to the snow that is primarily responsible for skidding out on a turn.
  • See the attached diagram.
  • What I was seeing on ice is exactly what many skiers experience:  as you accelerate through the turn, the sliding pressure builds faster than edging pressure, causing the skis to slip.  
  • So my first observation is:  it can be unhelpful to talk about "building pressure slowly through the turn" because it really depends on what pressure the skier is building:  edging or sliding.  Building edging pressure is fantastic.  Building sliding pressure could be disastrous.
  • So what why do skiers skid out on the 3rd phase of a carve on ice?  Because this phase of a turn has the maximum sliding pressure:  
    • (1) the skier has been accelerating and so centrifugal force from the turn (which is sliding pressure...see diagram) has increased;
    • (2) the skis are beginning to travel across the fall line, so gravity starts providing sliding rather than forward pressure on the ski;
    • (3) the skis are beginning to cross the skier's center of mass, so the skier's body is creating sliding pressure  on the skis.
  • What can be done about this to help carve better on ice?
    • Reduce effect of centrifugal force - (a) ski slower....lower speed means less centrifugal force;  (b) adopt a "comma" rather than "c" shaped turn...this properly adjusts for the effect of increasing centrifugal force as the skier gains speed through the turn.
    • Increase quality of edge contact - This is an important area because it's greatly impacted by technique.  Better contact can come from:
      • (technique) Ensuring angle of edge contact with snow is correct (see http://www.epicski.com/t/111705/what-is-best-edge-angle-for-max-grip)
      • (technique) Ensure ski is on edge throughout the turn (initiate carving early on the high part of the turn, hold the carve, etc)
      • (technique) Ensuring smooth ski contact with the snow (even fore/aft pressure, no sudden change in angles or fore/aft pressure, etc)
      • (equipment) Ensure ski edges are sharp and smooth, use more aggressive edge bevel angles
    • Increase edging force - This was where I made the most progress.  @Ghost was absolutely spot on here, and gave the best advice (for me at least).  If you look at @HeluvaSkier's videos and then at the stop-motion photo attached to this post, it's clear that the skiers apply downweighting to coincide with this 3rd phase of the turn.  This adds to gripping pressure to allow it to balance out the building  sliding pressure in the turn at this phase.
  • My own progress on ice
    • I feel pretty comfortable with managing turn shape/speed and edge contact on ice.  Said differently, I felt OK at managing the sliding pressure in the turn.  What made a huge difference on ice for me was managing the edging pressure through downweighting.....since in this 3rd phase of the turn on ice the skier is already committed to speed and shape, and downweighting is one of the few options he/she has for increasing edge grip.

 

For what it's worth, I'm not a real believer in the philosophy that says "ice skiing is just like regular skiing....if you get your regular technique right you can ski ice", or "if you're thinking about it, you aren't going to figure it out".  

Ice is no different from other terrain.  Sure, it relies on common, strong fundamentals, but it also benefits hugely from a more focused technical understanding and approach.  Again, ymmv.

 

thanks guys for all your advice!

 

 

 

post #13 of 22

Schraderade,

I bet people tell you to stop overthinking this all the time.  Ignore them.  I get it.  You want to carve on ice.  

I want to redirect your thinking a bit.  It's not what you do in the middle and at the end of your turn that keeps your skis gripping ice.  What you do to start the turn matters most.  

Gear counts too so let's get the gear stuff figured out first.

 

1.  What skis are you on? 

2.  What's the waist width of your skis?

3.  What's their turn radius?

4.  When did you last sharpen them?

5.  What are the base and side bevels?

 

6.  What size turns are you attempting to carve with these skis on ice?  Long, medium, or short?  Can you be specific?

7.  Are you working on carving on greens, blues, or blacks?  

8.  Can you carve on blue runs with softer snow, leaving consistent pencil thin tracks all the way down, using these skis?  

9.  (most important) ..... What do you do to start your turns?

post #14 of 22
Thread Starter 

Hey LiquidFeet, 

 

i think i got it working pretty well this week so i'm all set.   the missing element was the timing of the downforce on the lower part of the turn where the sliding pressure was greatest.  

i was letting downward pressure build too slowly and too early on the ski and so -- using @Ghost's vocab -- squandering my downforce budget too early.

frankly, this was the result of bad technical doctrine i learned as a kid skiing in in europe....build edging pressure slowly on ice to avoid sudden changes in force.

once i adjusted the timing of the downforce, there was enough pressure to hold the carve even at high speeds.

 

for ice i'm usually on head supershape magnums, 72mm underfoot, 13.5m radius, factory tune at what looks like 0.5/1 (i need to send them in to reset at 0.7/3).

i prefer turns ranging from cross-through gs to more pivoty slalom, depending on terrain.

have been skiing for 30+ years, raced as a kid.  generally i start turns quite early, around the rise line (e.g. upside down traverse, as in http://www.epicski.com/t/109956/how-to-hold-edge-thru-gates-on-icy-course).

 

i also thought the issue was in turn initiation and edge set, but i'm pretty sure my edges are well set early into the turn starting from the rise line as that has been drilled into my thick skull for decades now, and the specific problem i had was matching downforce in the 3rd phase of the turn.  And shitty bevels.

 

i wanted to share the model above because i found it helpful for sorting out the different areas where a given skier, for a given style, might have trouble on ice since it captures the key forces a bit more simply than the conventional (e.g. ron lemaster) way for ice carving.

post #15 of 22

Oops, wrong thread. Post deleted.


Edited by jc-ski - 1/7/14 at 9:51pm
post #16 of 22
Quote:
Originally Posted by schraderade View Post
 

Hey LiquidFeet, 

 

i think i got it working pretty well this week so i'm all set.   the missing element was the timing of the downforce on the lower part of the turn where the sliding pressure was greatest.  

i was letting downward pressure build too slowly and too early on the ski and so -- using @Ghost's vocab -- squandering my downforce budget too early.

frankly, this was the result of bad technical doctrine i learned as a kid skiing in in europe....build edging pressure slowly on ice to avoid sudden changes in force.

once i adjusted the timing of the downforce, there was enough pressure to hold the carve even at high speeds.

 

for ice i'm usually on head supershape magnums, 72mm underfoot, 13.5m radius, factory tune at what looks like 0.5/1 (i need to send them in to reset at 0.7/3).

i prefer turns ranging from cross-through gs to more pivoty slalom, depending on terrain.

have been skiing for 30+ years, raced as a kid.  generally i start turns quite early, around the rise line (e.g. upside down traverse, as in http://www.epicski.com/t/109956/how-to-hold-edge-thru-gates-on-icy-course).

 

i also thought the issue was in turn initiation and edge set, but i'm pretty sure my edges are well set early into the turn starting from the rise line as that has been drilled into my thick skull for decades now, and the specific problem i had was matching downforce in the 3rd phase of the turn.  And shitty bevels.

 

i wanted to share the model above because i found it helpful for sorting out the different areas where a given skier, for a given style, might have trouble on ice since it captures the key forces a bit more simply than the conventional (e.g. ron lemaster) way for ice carving.

 

Sounds all good, Schraderade.  Happy turns!

post #17 of 22
Quote:
Originally Posted by schraderade View Post

 

i was letting downward pressure build too slowly and too early on the ski and so -- using @Ghost's vocab -- squandering my downforce budget too early.

frankly, this was the result of bad technical doctrine i learned as a kid skiing in in europe....build edging pressure slowly on ice to avoid sudden changes in force.

once i adjusted the timing of the downforce, there was enough pressure to hold the carve even at high speeds.

 

I find myself experiencing the same lost edge on the 3rd quarter of the turn and would like to understand this solution better.  Would like a good mental picture before I give the solution a try next trip.

 

@schraderade @Ghost : Could I get a more newbie (plain english) oriented translation of this quoted bit? @schraderade your "adjusted the timing of the downforce" was earlier, later?  Also, harder or softer?   My current guess is: later and harder, specifically more pressure on new outside ski.

 

Thanks!

post #18 of 22
Thread Starter 
Quote:
Originally Posted by plai View Post

@schraderade your "adjusted the timing of the downforce" was earlier, later?  Also, harder or softer?   My current guess is: later and harder, specifically more pressure on new outside ski.

 

Thanks!

Hi @plai let me give it a shot.

 

1. First take a look at this site and determine what kind of turns you are making on ice:

http://www.yourskicoach.com/glossary/SkiGlossary/Cross_Over_Under_Through.html 

 

2. Ice doesn't like sudden movements or shifts in momentum so if you are doing crossunder turns you will probably need to smooth out your turn style before addressing the 3rd quarter issue.  Cross-through turns are generally smoothest in terms of momentum transfer so they work well with ice.  Cross-over turns can also work well but you have to be a bit more careful to engage the edge early in the turn after "upweighting" your body to get into the turn.

 

3. Assuming you have #2 sorted out and have a reasonable carved turn, let's answer your question.  Take a look at the following image which (credit: Ron Lemaster / Ultimate Skiing):

 

 

The skier creates downforce between frame 1 and frame 2 by driving his body downwards (as well as forwards) into the turn.  You can see the compression clearly between the red lines.

The downforce drives the edges perpendicular into the ground, and so it creates positive gripping pressure.

 

The point about timing is:  you only have a certain "budget" of downforce at the beginning of the turn, i.e. you can only compress your body so much.

So, it's best to apply the downforce when you really need it, which is at the point where you need the most grip, i.e. the 3rd quarter of the turn.

If you look at the racer in the picture, that's what he's doing....he's closest to the ground when he's in the 3rd quarter of the turn.

If you drive your body down too early, you will have wasted your downforce early and you're not gonna be able to create more downforce without doing some weird stuff with your turn. 

 

Note that downforce is only one component of force in a turn, so if you over-focus on downforce you may screw up other parts of your turn model.  But in terms of trying to address 3rd quarter traction on ice, it can be useful to understand how downforce timing relates to edge grip.

 

Hope that helps!

post #19 of 22
Quote:
Originally Posted by schraderade View Post
 

 

The skier creates downforce between frame 1 and frame 2 by driving his body downwards (as well as forwards) into the turn.  "Creates downforce"????  What an odd way of putting it.  The skier is compressing his body as he angulates out over the outside ski; he does this to keep that outside ski gripping as the forces accumulate (on their own); he is also timing the whole folding-of-his-body so he passes the gate as closely as possible and stays on the fastest line he can hold.   He is not "creating" any extra forces that aren't building from his turn shape itself, the speed he's carrying, and his body's weight.

You can see the compression clearly between the red lines.  Yes, I can see him angulating. 

The downforce drives the edges perpendicular into the ground, and so it creates positive gripping pressure.  The edge angles look very similar to those in the previous frame. But even if they are higher at #2, that isn't why the skis are gripping.  It's because of his angulation that the skis are gripping, and this angulation does not create any extra "force" or extra pressure.

 

The point about timing is:  you only have a certain "budget" of downforce at the beginning of the turn, i.e. you can only compress your body so much.

So, it's best to apply the downforce when you really need it, which is at the point where you need the most grip, i.e. the 3rd quarter of the turn.  If you stand on a scale and go "down" suddenly, what does the scale register?  Do you suddenly weigh more, or less?  It's called down-unweighting for a reason.  

If you look at the racer in the picture, that's what he's doing....he's closest to the ground when he's in the 3rd quarter of the turn.

If you drive your body down too early, you will have wasted your downforce early and you're not gonna be able to create more downforce without doing some weird stuff with your turn. 

 

Note that downforce is only one component of force in a turn, so if you over-focus on downforce you may screw up other parts of your turn model.  But in terms of trying to address 3rd quarter traction on ice, it can be useful to understand how downforce timing relates to edge grip.

 

Hope that helps!

post #20 of 22
Thread Starter 
If it helps, let's say the skier' body compresses and extends from turn to turn.
You can try this at home if you have an analog scale.
Compress your body by going from standing to squatting, then from squatting the standing.
The scale will register less pressure as you move towards the ground, then more pressure as you extend back up to standing.

The point of highest pressure is usually the point at which you are most compressed and then start pushing the get extended again (but in reality it depends on the acceleration profile rather than your position in space). So you're absolutely right that one cannot "create down force" any more than one can "create centrifugal force". They are both virtual forces. It'd be maybe more accurate to talk about up force that the ground exerts on your skis, but that seems as confusing to me as talking about centripetal rather than centrifugal force during a turn.

Angulation absolutely creates the best gripping angle, but it is not the only gripping force at work when a skier turns. Maybe a thought experiment would be:

Skier A uses absolutely no compression and just inclines into a turn, using some body angulation to stay balanced.

Skier B is like Skier A, but also uses compression and extension to manage edge pressure.

Which skier is likely to be more successful on ice?
To me, it is skier B. So, it cannot just be a question of angulation because skier A would be able to achieve angulation through appropriate hip and body posture.
Skier B has the added ability to add and release pressure on the edge through body compression and extension, which allows her to achieve more grip. That compressive pressure must resolve itself into primarily down force on the edges, because otherwise it would be sliding rather than gripping pressure.
post #21 of 22

Here's how you grip on hard snow and ice; all you ever needed to know to get started:

http://www.epicski.com/t/111705/what-is-best-edge-angle-for-max-grip#post_1451199

post #22 of 22
Quote:
Originally Posted by plai View Post
 
Quote:
Originally Posted by schraderade View Post

 

i was letting downward pressure build too slowly and too early on the ski and so -- using @Ghost's vocab -- squandering my downforce budget too early.

frankly, this was the result of bad technical doctrine i learned as a kid skiing in in europe....build edging pressure slowly on ice to avoid sudden changes in force.

once i adjusted the timing of the downforce, there was enough pressure to hold the carve even at high speeds.

 

I find myself experiencing the same lost edge on the 3rd quarter of the turn and would like to understand this solution better.  Would like a good mental picture before I give the solution a try next trip.

 

@schraderade @Ghost : Could I get a more newbie (plain english) oriented translation of this quoted bit? @schraderade your "adjusted the timing of the downforce" was earlier, later?  Also, harder or softer?   My current guess is: later and harder, specifically more pressure on new outside ski.

 

Thanks!


I will let schraderad explain himself.  For my part I will say let your weight press the ski into the snow as much, but only as much as you need it to press as the turn progresses, so that by the end of the turn you can still have enough force pressing down to hold the edge.  A gradual increase in pressure is essential to get things going, and then more will be required, how much more you have to judge.  You have to balance the down force throughout the turn and every bit you push down or allow your ski to push down, accelerates you up.  You can only accelerate up so much before you are actually moving up with little left to give in the way of a downwards force.

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