Hard pressure on tips while on steeper terrain (Carved short turns?)

[Sanity]

How much more would you like? (That's not a water injected surface.)



JFB, Lorenz, Gellie, numerous others - all these guys are perfectly capable of getting the hip on the snow in a wide variety of snow conditions. And they all speak (in various ways) of the need to keep the BoS between the CoM and the force coming from the ski. And the need to keep the outside foot coming through. JFB refers to pushing the outside foot forward and pulling the inside foot back. Lorenz and Gellie refer to pulling the outside foot through with the hip flexors. Prefer the L/G approach (for the modest performance I get) as it:
1. Loads the ski tails without the risk of getting back (cue thought: pull toes to nose)
2. The pull through becomes flex to release all in one.

In a high edge angle turn with lots of centrifugal force, the body has angular momentum around the COM which means your body rotates back, always, as you release the turn. Then through transition you have to move diagonally forward to compensate every time. When you release the turn there's a lot less pressure and less friction. Often there is no friction since the skier is floating during this phase. For any given amount of friction you'll find the balance point during the turn, which sets the COM speed relative to the skis, and then as you release, the skis will shoot out as there's less pressure and thus less friction and your body has angular momentum around the COM rotating the body back.

 

[geepers]

Yes.

And?

 

[Sanity]

How much more would you like? (That's not a water injected surface.)



JFB, Lorenz, Gellie, numerous others - all these guys are perfectly capable of getting the hip on the snow in a wide variety of snow conditions. And they all speak (in various ways) of the need to keep the BoS between the CoM and the force coming from the ski. And the need to keep the outside foot coming through. JFB refers to pushing the outside foot forward and pulling the inside foot back. Lorenz and Gellie refer to pulling the outside foot through with the hip flexors. Prefer the L/G approach (for the modest performance I get) as it:
1. Loads the ski tails without the risk of getting back (cue thought: pull toes to nose)
2. The pull through becomes flex to release all in one.

I was just watching a Paul Lorenz video about the transition, and he said that because he's not a racer, he's not confined to a corridor and he can ski longer across the hill. This may be the disconnect as to why many top level racers talk about being aft at the end of the turn whereas, you haven't felt that a number of non-racers have communicated this to you. When you don't have to make that next turn, you can extend the transition period and ski flat across the hill for a longer period of time, and yes, if there's drag it could center you without as much effort that racers give. You can have a gradual transition to lessen the effects I talked about in the last post.

 

[geepers]

In a high edge angle turn with lots of centrifugal force, the body has angular momentum around the COM which means your body rotates back, always, as you release the turn. Then through transition you have to move diagonally forward to compensate every time. When you release the turn there's a lot less pressure and less friction. Often there is no friction since the skier is floating during this phase. For any given amount of friction you'll find the balance point during the turn, which sets the COM speed relative to the skis, and then as you release, the skis will shoot out as there's less pressure and thus less friction and your body has angular momentum around the COM rotating the body back.

Except when the skier doesn't get that far 'cause they were too forward (not centered) and the tails wash out.

Depending on the snow the drag at the feet has to be dealt with - less so on ice and more so as the snow get heavier. Really noticeable in freeze/thaw situations either as the day warms or from one day to another.

Regardless of snow, wrt the valley, the feet have to come from somewhere above the CoM (at the top of the turn) to roughly level with the CoM (at the fall line) to ahead of the CoM (at the bottom of the turn). Lorenz shows this in the 'Road To Carving' full vid sitting on the snow showing the positions his legs are in wrt to the CoM and the valley through the turn. Don't think that's in the youtube preview.

That all has to happen before transition.

I was just watching a Paul Lorenz video about the transition, and he said that because he's not a racer, he's not confined to a corridor and he can ski longer across the hill. This may be the disconnect as to why many top level racers talk about being aft at the end of the turn whereas, you haven't felt that a number of non-racers have communicated this to you. When you don't have to make that next turn, you can extend the transition period and ski flat across the hill for a longer period of time, and yes, if there's drag it could center you without as much effort that racers give. You can have a gradual transition to lessen the effects I talked about in the last post.

Took that vid to be about different types of transitions. He mostly stays low in transition to have a fast, efficient transition to create an exciting run - his words around 2:00. Only uses an extended, leisurely transition if that's the path he wishes to take.

Feel it's more to do with the snow hardness - less effort needed on firm surfaces - and speed - torso has much more air resistance then feet at, say, 60mph. Plenty of experience with the former. Which is why I prefer the toes to nose cue - getting behind on ice: no thanks. For the latter the amount of time I spend at anything like that speed can be measured in seconds per day. And none of it is in high angle turns.

 

[HardDaysNight]

In a high edge angle turn with lots of centrifugal force, the body has angular momentum around the COM which means your body rotates back, always, as you release the turn. Then through transition you have to move diagonally forward to compensate every time. When you release the turn there's a lot less pressure and less friction. Often there is no friction since the skier is floating during this phase. For any given amount of friction you'll find the balance point during the turn, which sets the COM speed relative to the skis, and then as you release, the skis will shoot out as there's less pressure and thus less friction and your body has angular momentum around the COM rotating the body back.

What a great explanation!

 

[James]

In a high edge angle turn with lots of centrifugal force, the body has angular momentum around the COM which means your body rotates back, always, as you release the turn. Then through transition you have to move diagonally forward to compensate every time. When you release the turn there's a lot less pressure and less friction. Often there is no friction since the skier is floating during this phase. For any given amount of friction you'll find the balance point during the turn, which sets the COM speed relative to the skis, and then as you release, the skis will shoot out as there's less pressure and thus less friction and your body has angular momentum around the COM rotating the body back.

You’re talking angular momentum in the sagittal plane distinct from the carving circle on snow?

 

[Sanity]

You’re talking angular momentum in the sagittal plane distinct from the carving circle on snow?

Right, the mass has angular momentum around the turning circle described by the turning radius, but then the mass also has angular momentum rotating around some central point of the body (COM?), because different parts of the body have different instantaneous speeds.

 

[Zirbl]

And?

Nah.

 

[geepers]

Nah.

Same.

 

[geepers]

Right, the mass has angular momentum around the turning circle described by the turning radius, but then the mass also has angular momentum rotating around some central point of the body (COM?), because different parts of the body have different instantaneous speeds.

Thinking some more on your theory...

So we balance against the ski/snow friction and then we release the friction decreases so the feet shoot forward? That it?

First point - wouldn't the friction decrease be larger in softer/heavier snow than hard snow so the feet would shoot out more? 'Cause seems that staying on top of the skis is more of an issue on hard snow than soft.

Second point - it's ignoring the virtual bump which tends to slow the feet turning out of the fall line. Size of that depends on pitch, speed and how far the turn is finished.

 

[Sanity]

Thinking some more on your theory...

So we balance against the ski/snow friction and then we release the friction decreases so the feet shoot forward? That it?

First point - wouldn't the friction decrease be larger in softer/heavier snow than hard snow so the feet would shoot out more? 'Cause seems that staying on top of the skis is more of an issue on hard snow than soft.

Second point - it's ignoring the virtual bump which tends to slow the feet turning out of the fall line. Size of that depends on pitch, speed and how far the turn is finished.

In a fast, sharp turn with high edge angles the skier has angular momentum around their COM. That angular momentum puts the skier aft. This is more pronounced with quick releases. Stated plainly, the skis are going faster than the torso, and the skier has to work to catch up. Did you watch that video I posted earlier? Not just my theory.

https://videos.usskiandsnowboard.or...14701222001/phil-mcnichols---turn-shape-model

 

[James]

In a fast, sharp turn with high edge angles the skier has angular momentum around their COM. That angular momentum puts the skier aft. This is more pronounced with quick releases. Stated plainly, the skis are going faster than the torso, and the skier has to work to catch up. Did you watch that video I posted earlier? Not just my theory.

https://videos.usskiandsnowboard.or...14701222001/phil-mcnichols---turn-shape-model

I watched the vid. Don’t recall anything about angular momentum.

 

[Tony S]

was just watching a Paul Lorenz video about the transition, and he said that because he's not a racer, he's not confined to a corridor and he can ski longer across the hill. This may be the disconnect as to why many top level racers talk about being aft at the end of the turn whereas, you haven't felt that a number of non-racers have communicated this to you. When you don't have to make that next turn, you can extend the transition period and ski flat across the hill for a longer period of time, and yes, if there's drag it could center you without as much effort that racers give. You can have a gradual transition to lessen the effects I talked about in the last post.

This is great observation. I'm posting here not to disagree with its substance, but to add some context for recreational skiers on many days in many parts of the world, notably including here in the American NE when there is not much snow or trail acreage to go around, but plenty of people there to use it.

The implied idea that racers are the only ones constrained to a narrow corridor is false. More significantly for this discussion, perhaps, it's very notable how these hot skier demos take place on slopes that tend to be quite wide and are invariably virtually empty. This "arena" disparity presents a very real practical challenge for those of us who like to practice arc to arc turns, but are not yet retired and/or are otherwise constrained as to when we can go skiing. Especially when the slopes we ski on may be narrower to start with. In any case the longer I extend the transition period across the hill the more likely I am to get clocked by an unguided missile coming down from above. This conflict of usage patterns is frequent topic of discussion here on the forum.

That's it. Carry on.

 

[Sanity]

I watched the vid. Don’t recall anything about angular momentum.

When one part of a body is going faster than another part, there exists a velocity gradient that necessitates angular momentum. In other words, if all parts of a body have the same instantaneous velocity there will be no angular momentum, so saying your skis are going faster is an equivalent statement as stating there is angular momentum, but in an easier way to understand.

 

[geepers]

In a fast, sharp turn with high edge angles the skier has angular momentum around their COM. That angular momentum puts the skier aft. This is more pronounced with quick releases. Stated plainly, the skis are going faster than the torso, and the skier has to work to catch up. Did you watch that video I posted earlier? Not just my theory.

https://videos.usskiandsnowboard.or...14701222001/phil-mcnichols---turn-shape-model

Yep - the relevant bit to your case was where the guy said the feet are going faster than the body - or words to that effect. Angular momentum didn't crop up (IIRC).

Any case, just trying to reconcile your concept with my experience on snow. Theories are wonderful when they help explain what we experience. And I'm not feeling that one. There's a range of other factors at play: snow conditions (which affects the friction); pitch, turn radius, speed, line (which affects the amount of any difference in feet/CoM speed and the size of the virtual bump); speed of transition, type of transition (which affects the change in friction and the time for any compensation)...

And we haven't discussed various points on technique.

In any event does it matter if the feet are going faster? They are about to go the wide, long route out whilst the torso takes the shorter line. We're in dynamic balance.

 

[geepers]

This is great observation. I'm posting here not to disagree with its substance, but to add some context for recreational skiers on many days in many parts of the world, notably including here in the American NE when there is not much snow or trail acreage to go around, but plenty of people there to use it.

The implied idea that racers are the only ones constrained to a narrow corridor is false. More significantly for this discussion, perhaps, it's very notable how these hot skier demos take place on slopes that tend to be quite wide and are invariably virtually empty. This "arena" disparity presents a very real practical challenge for those of us who like to practice arc to arc turns, but are not yet retired and/or are otherwise constrained as to when we can go skiing. Especially when the slopes we ski on may be narrower to start with. In any case the longer I extend the transition period across the hill the more likely I am to get clocked by an unguided missile coming down from above. This conflict of usage patterns is frequent topic of discussion here on the forum.

That's it. Carry on.

Yep - these guys are making vids for an audience and as a promo. They make enough vids to pick the very good ones.

Well, mostly....




Also...there's a vid of a Korean lady instructor demo-ing short turns at an Interski. She said they focused on short turns in her country due to slope crowding.

 

[JCF]

This is great observation. I'm posting here not to disagree with its substance, but to add some context for recreational skiers on many days in many parts of the world, notably including here in the American NE when there is not much snow or trail acreage to go around, but plenty of people there to use it.

The implied idea that racers are the only ones constrained to a narrow corridor is false. More significantly for this discussion, perhaps, it's very notable how these hot skier demos take place on slopes that tend to be quite wide and are invariably virtually empty. This "arena" disparity presents a very real practical challenge for those of us who like to practice arc to arc turns, but are not yet retired and/or are otherwise constrained as to when we can go skiing. Especially when the slopes we ski on may be narrower to start with. In any case the longer I extend the transition period across the hill the more likely I am to get clocked by an unguided missile coming down from above. This conflict of usage patterns is frequent topic of discussion here on the forum.

That's it. Carry on.

+1
And not to mention the surface variations that have to be negotiated. Love skiing those glaciers in Europe with wide open consistent surfaces. But here in the NE we have dumps, bumps, lumps, ice, humps, ruts, nuts - all within the space of a few turns... You have to adjust on the fly and be reactive. Theories and formulas don't work very often.

 

[Sanity]

In any event does it matter if the feet are going faster? They are about to go the wide, long route out whilst the torso takes the shorter line. We're in dynamic balance.

The point is that there are forces pushing the skier back in performance turns both in the moguls and in the race course. This is why you hear so many top skiers talk about getting forward. It takes constant work. Like I said once before, a US ski team mogul skier told me that he takes a higher line on the bump, because if he drops lower it's more work to get forward again. That's his statement. The physics of it is the deeper the trough, and steeper the front face, the more the skis have to point up, which means the more the feet have to come forward. All that distance then has to be made back up again in a split second after cresting the bump which takes work. In the race course and in the bumps for performance turns that have to happen on demand (not when you feel like it) you need pressure on the tips. So, in every turn that mantra rings out, get forward, get forward.

 

[Zirbl]

In the race course and in the bumps for performance turns that have to happen on demand (not when you feel like it) you need pressure on the tips. So, in every turn that mantra rings out, get forward, get forward.

Have I missed something, or is the disagreement in this thread with the mantra of stay forward, not get forward?

 

[geepers]

The point is that there are forces pushing the skier back in performance turns both in the moguls and in the race course. This is why you hear so many top skiers talk about getting forward. It takes constant work. Like I said once before, a US ski team mogul skier told me that he takes a higher line on the bump, because if he drops lower it's more work to get forward again. That's his statement. The physics of it is the deeper the trough, and steeper the front face, the more the skis have to point up, which means the more the feet have to come forward. All that distance then has to be made back up again in a split second after cresting the bump which takes work. In the race course and in the bumps for performance turns that have to happen on demand (not when you feel like it) you need pressure on the tips. So, in every turn that mantra rings out, get forward, get forward.

Scratching head...

So what's the difference in foot to CoM speed in a reasonable turn? Let's take 12m radius turn with a speed of 16.631m/s. (Picked those 'cause it gives centripetal accel of 1.414g which is roughly a 45 degree inclination of the CoM.) Let's say CoM is 1 m to the inside so the CoM speed is 16.63*(12-1)/12 which is near enough to 15.245m/s.

So that's a difference 1.386 m/s.

Is that significant? A typical soccer player's foot is moving about 20 m/s when they kick the ball. Typically they don't fall over because they automatically compensate and I'm guessing skiers generally do too when their feet (wrt to their CoM) are moving over 14 times slower.

Have I missed something, or is the disagreement in this thread with the mantra of stay forward, not get forward?

Not sure why there's this huge focus on forward/forward/forward once we get past the beginner/intermediate phase of tentative backseat skiing. I'm with the US Team guy in that what goes back has to return. And vice versa - what goes forward also has to return. There's an interesting part in a Tom Gellie vid where he drylands the difference in his fore and aft positions in a carving turn. It's very small and yet he's quite capable of high edge angle turns on a variety of pitches.

Perhaps we should be more like Feutz who apparently is center of the ski top to bottom. (That's Sam DuPratt's opinion on Feutz and presumably a guy whose been on the USA ski team a number of times has some insight.)