Tactics and best ski and turn selection for Frozen Granular

[Delicious]

I think you also have to be able to forgive yourself for mistakes in difficult skiing conditions like this. I fill my head with thoughts(lies?) about how much better this is going to make my skiing the next time I'm in favorable conditions.

 

[Jamt]

Request for clarification: does "up-down acceleration" as you use it refer to the body going up/getting taller and going down/geting shorter? Or are you referring to the skier speeding up and slowing down on the hill?

Sorry for the late reply, busy weekend.

Not necessarily. The movement direction of the body does not imply the direction of acceleration. Technically you can be accelerating down while moving up.
Further it does not imply a tall or compact body or anything like that. You can do almost fully inclined turns with good up down acceleration and you can do very deep flexed and angulated turns also with good up down acceleration. Carved or not etc.
If we take a turn in some phases starting in the middle of transition this is they way I see it for a "constant up and down acceleration turn":
1 In the middle of transition you are at the highest position from the surface, tall or flexed depending on the turn. Not moving up or down. You are light, perhaps hardly touching the snow. This means the perpendicular force from the snow is less than your weight and thus you are accelerating down.
The down acceleration starts to move you down.
2 Eventually the forces must increase, but you can delay this e.g. by angulation etc.
3 The forces increase until the vertical (from the snow) force is equal to your body weight. Now you are not accelerating up or down, but in a good turn this moment is very short. The turning forces are beginning to be substantial.
The vertical force is then larger than your body weight and keeps increasing. You are still moving down but the speed towards the ground decreases more and more. You may have a feeling that the edge grip is rock solid.
4 The forces continue to increase until they are at their maximum. In a very dynamic turn the vertical force can be around twice your body weight (2g). Around this time you will also have the lowest position and maximum edge angle.
5 Now it is time to exit the turn, because the forces are rapidly pushing you up. You can manage the exit e.g. by pressure management (flexing etc).
6 The forces will decrease until the vertical component is less than your weight. Now you are accelerating down, but still moving up.
We continue this until we are back where we started, in the middle of the transition.

Here is a picture that exemplifies the above in a typical SL turn where I have put the numbers from above at approximately when the occur.

Not all turns have a smooth and continuous up and down acceleration, e.g. if you skid with an offset into the turn more or less inclined and then angulate heavily and pull the skis back for a carved entry. (off topic in this thread)

No. Acceleration up or down.
Gravity accelerates down always. (Well, towards the earth’s center) So falling inside, shortening inside leg or inclining, is down.

When you’re in a turn, there’s a component of the centripetal force from making that turn that is vertical. Up.
If you just skid out this is nothing, but in a fast carved turn it’s quite strong, close to or greater than body weight.

If you watch some racers free ski, they often start the turn with huge initial inclination. (The Ted Ligety free ski video is a good one.)
They are relying on the edge to initially hold, thus the sharp skis. Once it does, they then get a large centripetal force and thus a strong up component of that force which propels them out of the turn when released.

It’s a bit of a conundrum though. You can’t get the force without the commitment. And you can’t commit unless you trust the force will be there.

Hopefully @Jamt will clarify

I hope I clarified with the above.

 

[dbostedo]

Sorry for the late reply, busy weekend.

Not necessarily. The movement direction of the body does not imply the direction of acceleration. Technically you can be accelerating down while moving up.
Further it does not imply a tall or compact body or anything like that. You can do almost fully inclined turns with good up down acceleration and you can do very deep flexed and angulated turns also with good up down acceleration. Carved or not etc.
If we take a turn in some phases starting in the middle of transition this is they way I see it for a "constant up and down acceleration turn":
1 In the middle of transition you are at the highest position from the surface, tall or flexed depending on the turn. Not moving up or down. You are light, perhaps hardly touching the snow. This means the perpendicular force from the snow is less than your weight and thus you are accelerating down.
The down acceleration starts to move you down.
2 Eventually the forces must increase, but you can delay this e.g. by angulation etc.
3 The forces increase until the vertical (from the snow) force is equal to your body weight. Now you are not accelerating up or down, but in a good turn this moment is very short. The turning forces are beginning to be substantial.
The vertical force is then larger than your body weight and keeps increasing. You are still moving down but the speed towards the ground decreases more and more. You may have a feeling that the edge grip is rock solid.
4 The forces continue to increase until they are at their maximum. In a very dynamic turn the vertical force can be around twice your body weight (2g). Around this time you will also have the lowest position and maximum edge angle.
5 Now it is time to exit the turn, because the forces are rapidly pushing you up. You can manage the exit e.g. by pressure management (flexing etc).
6 The forces will decrease until the vertical component is less than your weight. Now you are accelerating down, but still moving up.
We continue this until we are back where we started, in the middle of the transition.

Here is a picture that exemplifies the above in a typical SL turn where I have put the numbers from above at approximately when the occur.

View attachment 159403

Not all turns have a smooth and continuous up and down acceleration, e.g. if you skid with an offset into the turn more or less inclined and then angulate heavily and pull the skis back for a carved entry. (off topic in this thread)

I hope I clarified with the above.

When you say "accelerating down", do you mean decelerating? (I.e. is "down" a direction, or does it just indicate negative acceleration?)

 

[François Pugh]

It can be difficult to think of acceleration, velocity, and displacement separately without confusing them. Perhaps a simplified example will help.
Imagine skiing in a straight line down the hill on a perfectly flat smooth run. Keep you body at the same distance from the hill. You mass is constant. Gravitational acceleration is constant. The force pushing your skis into the snow is constant. Now if you start moving up and down with a constant rhythm, (changing your distance from the snow) you will notice that not only does your distance from the snow change, your velocity changes; sometimes you are going up and sometimes you are going down (as does the speed at with you go down or go up). You will also notice that the force you need to push against the snow changes. When you stop going down and when you start going up you push harder. Thinking of force is easier, than thinking of acceleration since you can feel it without doing math (if you want to do math, F=ma).

Your average force is still the same as before, but now you have greater force at times and less force at other times. Add turns. With turns, those times requiring more downforce holding the skis into the snow is at the appex, where the turn force is greatest (See @Jamt 's graph). Time your up and down accordingly. Time your force (making you stop going down (more force), start going up (more force), stop going up (less force), start going down (less force)) so that you have the greater force when you need more force to keep your skis pressed harder into the snow.

Advanced students - integrate this into flex to release turns and up-unweighted turns and play.

 

[Jamt]

When you say "accelerating down", do you mean decelerating? (I.e. is "down" a direction, or does it just indicate negative acceleration?)

Acceleration is always associated with a direction. Since we are talking about up and down here, what I mean with accelerating down is accelerating towards the snow. That can be either increasing the velocity towards the snow, or decreasing the velocity from the snow.

 

[dbostedo]

Acceleration is always associated with a direction. Since we are talking about up and down here, what I mean with accelerating down is accelerating towards the snow. That can be either increasing the velocity towards the snow, or decreasing the velocity from the snow.

Thanks. I get that and the physics aspect/terms... I think what gets confusing for folks is that "accelerating" for most people colloquially always means "increasing speed".

One more question... when you say "accelerating up and down", is that active, with the legs driving it? Or passive, due to building and releasing forces throughout the turn? Or both?

 

[bbbradley]

Frozen granular can mean different things to different people. To me, it means piles of loose granulated sugar on top of some harder surface that you may or may not be able to get down to.

Skiing in this is one of my least favorite conditions, the ski just rolls like it's on marbles, you can't really hammer a turn as the ski seems to be riding on top of the marbles. It requires a softer touch and taking what the surface will give on each turn.

 

[Johnny V.]

To me, it means piles of loose granulated sugar on top of some harder surface that you may or may not be able to get down to.

One of my least favorite too. Usually icy between the sugar mounds (which don't give at all), as it gets skied off. Certainly skiable, but one of those days,especially in flat light, when it's time to call it early and live to ski another day. Preferred ski under those conditions is a FIS spec slalom or some other fairly stiff short turn radius ski.

 

[Jamt]

Thanks. I get that and the physics aspect/terms... I think what gets confusing for folks is that "accelerating" for most people colloquially always means "increasing speed".

One more question... when you say "accelerating up and down", is that active, with the legs driving it? Or passive, due to building and releasing forces throughout the turn? Or both?

You are probably right that "acceleration" gets misunderstood in this context.

Whether it is active or passive it can definitely to both. In a race context the up-down dynamics can be combined with extension e.g. when you are pumping speed, whereas when the course is more turny and steep it becomes more passive.
Even then it is a bit of a topic for misunderstanding and terminology confusion.
For example in an SL turn like above you are resisting some serious forces, and this means that as the forces increase you have to resisting more and more force.
Some may view this as "pushing" even though the legs are normally bending a bit due to the forces, and some view it as simply resisting.
If you would "push" in a turn involving the crappy snow in this thread, chances are that you just push some snow away and when your leg is extended you may loose grip. Better then to have patience and manage the force with some feel.

 

[Racetiger]

I had always thought stivot was short for stem pivot, since it is done at the top of the turn.

Hi Thomas, Please excuse my delayed response to your reply as I have been working on the following response all this time. Thank you for your most earnest reply to my plight for clarity. I feel people are making efforts to describe ski technique and instruction with an overly complicated approach simply to enhance its exclusivity. This is why I prefer being very simple and straightforward, appealing to the common knowledge of the masses:

I think what you may be referring to is the “stem christy pivot skid”, better known as its common portmanteau, stistypivid … right? A quadruple portmanteau is really what it takes to most adequately interpret any movement that functions in all three planes and the one vertical axis of movement. Furthermore and backronymically speaking, sagittal + frontal + transverse + vertical = sagifronversical. Simplifying things further, sistypivid and sagifronversical form a parallel quadrant anagram and thus, the triple portmanteau, quadralellogram. Which, by the way and, curiously enough, is also the name of my new ski instruction program so, probably along with anyone else forcing themselves to read this, we are very glad you asked. You likely have heard of it already. It is the Quadralellogram Movement Teaching System, QMTS, where we teach the sagfronversical sistypivid all day long. Anyone who I can successfully channel through my exclusive sagfronversical sistypivid development matrix may very well make it all the way through to the other side with all or most anatomy intact.

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[ThomasD]

Hi Thomas,...

... Still reading this malarkey fee: $99.95 due immediately.

After that sort of effort how could I not feel obligated to read to the end?

Sorry, I don't happen to have $99.95 Canadian lying around. Would you accept a double Looney and some loose change? I could mail it to you.

 

[dbostedo]

The SkiTalk staff would like to apologise for any faults in @Racetiger 's post. Those responsible have been sacked.

 

[dbostedo]

And after further review of the pricing, we apologise again. Those responsible for sacking the people who have just been sacked, have been sacked.

 

[Chris V.]

We interrupt this program to apologize for the last apology.

 

[James]

This thread has gone all Looney with the apologies.

 

[François Pugh]

This thread has gone all Looney with the apologies.

Sorry about that.

 

[dbostedo]

This thread has gone all Looney with the apologies.