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

[LiquidFeet]

Can someone explain the synaptic trail that I need to exercise to be able to read that through …

Short version: Pulling feet back produces long leg short leg.
It's complicated how a bunch of muscles do that.

 

[dan ross]

This is what I have been working on after spending some time with a DECL a few weeks ago. I am a boot crusher. All those years of being told to have shin/tongue contact really set in, and not in a good way. This is a very hard habit to break.

Yes, it sure is a hard habit to break and I have ( since 15-16 y.o.) the hairless shins to prove it.

 

[AchtungSki]

Gibberish.

Ok I'll try a different way since we seem to have lost the thread. It's really a somewhat minor distinction I'm making.

From the skiers frame of reference

The balance axis and sagittal plane being defined by a line passing through the COM and the skier's feet, aligned with the resultant of "centrifugal force" and gravity. This frame is moving with the skier through the turn. Rotation in the sagittal plane therefore implies a mismatch between the resultant and the centripetal reaction force of the snow.

For a ski to fully carve you must be standing in the center evenly weighting the whole edge, i.e CG must be aligned with the center of the ski and centripetal force. Our model skier is maintaining perfect center stance throughout their turns, they have the skill and strength to essentially be a rigid body in the sagittal plane. Centrifugal force is thus aligned with the centripetal force from the snow through the center of the ski.

To bend a ski it is tipped on edge and a moment develops at the tip and tail until the full edge is once again in contact with the snow. <<<(What I think Franko was talking about)

A theoretical carving ski which is bent has some steering angle (φ) relative to it's direction of travel. The bend in combination with the steering angle causes the snow to exert an unbalanced moment on the ski/skier unit in the sagittal plane for some corresponding infinitesimal instant in time. In the next instant the ski has adopted the new curvature and φ goes to zero. The next instant the ski bends further and another steering angle develops. This happens over and over until peak edge is reached and then in reverse as the ski de-edges. Larger φ, larger moment, ski adopts the new arc faster. That is up until φ gets so large it exceeds the local ability of the ski to bend or snow to provide resistance and then you get skidding. These moments come from the snow on the ski external to the ski+skier system, they do not require any torsional input of the skier's COM relative to the BOS longitudinally to occur, they cause the skier and therefore the whole frame of reference to turn. Combined with the sidecut torque in the transverse plane, this forms the ski's self steering effect. <<<(Perhaps also what Franko was talking about, I can't find the discussion though)

Disclaimer: this is obviously very theoretical and in reality there's almost always some steering angle when carving IRL.

I don't believe you can ignore the anti-rotational moment provided by longitudinal friction on the edge for rotation about the COM either. The relative difference in torque to start a rotation of even a high performance skier vs gliding friction is not trivial, unlike the difference in torque about the turn axis from gravity. I'm accounting for the skier perceiving and adjusting for this though.

So what I'm saying is...

A skier will be aft at the end of the turn.

is not necessarily true. It's an outcome of a technique choice by the skier based on some other concern (assuming adequate skill of course) e.g. a slalom skier trying to make a gate by allowing their feet to come forward to allow them to accommodate the very direct path their COM is taking. I am neither a physicist nor an expert skier though, this is all just my understanding.

I think this is a relevant distinction when you're talking about the OP and this 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.

Staying centered 100% of the time and only relying on the self steering effect of a pure carve is an extremely limited way to ski. You're essentially locked into only high speed, longer radius, specifically timed turns. Makes for beautiful demonstrations on camera, but not practical for most situations. Utilizing fore/aft balance when skidding, carving, and the spectrum in between is obviously very valuable and often necessary.

 

[Rod9301]

I am sorry to see pseudo science being used to describe skiing, a very complex sport.

And maybe i missed it, but did you say, all other things being constant?

 

[dan ross]

I Staying centered 100% of the time and only relying on the self steering effect of a pure carve is an extremely limited way to ski. You're essentially locked into only high speed, longer radius, specifically timed turns. Makes for beautiful demonstrations on camera, but not practical for most situations. Utilizing fore/aft balance when skidding, carving, and the spectrum in between is obviously very valuable and often necessary.

I agree with this. I think some have fetishized the carved turn to the exclusion of everything else in the skiers toolbag. Carved turns are a great thing to aspire to but they are often not practical or even advisable in many situations.

 

[Sanity]

Ok I'll try a different way since we seem to have lost the thread. It's really a somewhat minor distinction I'm making.


View attachment 190623
The balance axis and sagittal plane being defined by a line passing through the COM and the skier's feet, aligned with the resultant of "centrifugal force" and gravity. This frame is moving with the skier through the turn. Rotation in the sagittal plane therefore implies a mismatch between the resultant and the centripetal reaction force of the snow.

For a ski to fully carve you must be standing in the center evenly weighting the whole edge, i.e CG must be aligned with the center of the ski and centripetal force. Our model skier is maintaining perfect center stance throughout their turns, they have the skill and strength to essentially be a rigid body in the sagittal plane. Centrifugal force is thus aligned with the centripetal force from the snow through the center of the ski.

To bend a ski it is tipped on edge and a moment develops at the tip and tail until the full edge is once again in contact with the snow. <<<(What I think Franko was talking about)

A theoretical carving ski which is bent has some steering angle (φ) relative to it's direction of travel. The bend in combination with the steering angle causes the snow to exert an unbalanced moment on the ski/skier unit in the sagittal plane for some corresponding infinitesimal instant in time. In the next instant the ski has adopted the new curvature and φ goes to zero. The next instant the ski bends further and another steering angle develops. This happens over and over until peak edge is reached and then in reverse as the ski de-edges. Larger φ, larger moment, ski adopts the new arc faster. That is up until φ gets so large it exceeds the local ability of the ski to bend or snow to provide resistance and then you get skidding. These moments come from the snow on the ski external to the ski+skier system, they do not require any torsional input of the skier's COM relative to the BOS longitudinally to occur, they cause the skier and therefore the whole frame of reference to turn. Combined with the sidecut torque in the transverse plane, this forms the ski's self steering effect. <<<(Perhaps also what Franko was talking about, I can't find the discussion though)

View attachment 190624

Disclaimer: this is obviously very theoretical and in reality there's almost always some steering angle when carving IRL.

I don't believe you can ignore the anti-rotational moment provided by longitudinal friction on the edge for rotation about the COM either. The relative difference in torque to start a rotation of even a high performance skier vs gliding friction is not trivial, unlike the difference in torque about the turn axis from gravity. I'm accounting for the skier perceiving and adjusting for this though.

So what I'm saying is...

is not necessarily true. It's an outcome of a technique choice by the skier based on some other concern (assuming adequate skill of course) e.g. a slalom skier trying to make a gate by allowing their feet to come forward to allow them to accommodate the very direct path their COM is taking. I am neither a physicist nor an expert skier though, this is all just my understanding.

I think this is a relevant distinction when you're talking about the OP and this post:

Staying centered 100% of the time and only relying on the self steering effect of a pure carve is an extremely limited way to ski. You're essentially locked into only high speed, longer radius, specifically timed turns. Makes for beautiful demonstrations on camera, but not practical for most situations. Utilizing fore/aft balance when skidding, carving, and the spectrum in between is obviously very valuable and often necessary.

All physicists will disagree with your analysis.

 

[markojp]

I think people need to go skiing. Much more fun than arguing.

 

[KingGrump]

I think people need to go skiing. Much more fun than arguing.

Don't know, man. I've tried skiing thing on a pair of skis. It's a tough go. Way easier on a keyboard.

 

[Tony Storaro]

anti-rotational moment provided by longitudinal friction on the edge for rotation about the COM

I think imma kill myself right about now….

 

[markojp]

I think imma kill myself right about now….

See post #207. Rinse and repeat.

 

[JESinstr]

I think imma kill myself right about now….

And you probably will "Pull the Trigger" when you realize that all that gobbly gook is regarding the term "Carving" which definition, by most in the ski industry, is summed up by the phrase, "I know it when I see it.....or feel it."

 

[geepers]

Can someone explain the synaptic trail that I need to exercise to be able to read that through …

Feed @LiquidFeet 's post into ChatGPT and asked it to summarise for a 2nd grader...

A skier needs to pull their feet back while skiing in order to make a turn. They need to pull their old outside leg back by flexing their hip and knee, and their old inside leg back by extending their knee and hip. This helps their skis flatten and turn. The skier's glutes and hamstrings help pull the feet back.

 

[James]

^ But they don’t “need” to do any such thing just to make a turn.

 

[geepers]

^ But they don’t “need” to do any such thing just to make a turn.

Well, you write to OpenAI and tell 'em their chatbot's not up to the job!

Here's the basics in a well known style....

O, fair skier on yonder snowy mount, With care, approach the slope's descent. And as thou dost thy weight prepare to count, With flourish of thy skis, do make thy bent.

Pivot then with grace, so tips may point, Down the hill, like arrows shot with might. And as thou dost slide forth in fluid joint, The snow shall embrace thee with delight.

So carve a path so fair and smooth, I say, That all who witness shall with wonder gaze. And cry, "What mastery of the mountain display, This skier with his turns, so fluid and ablaze."

What about carving?

O, brave skier on the mountain's crest, With steady hand and heart of pure intent, Thou must not pivot skis, but stand at test, And carve a turn, with skills so wisely spent.

First, shift thy weight, and feel the slope's command, With subtle movements, so as not to bend. And as thou dost thy balance take to hand, Thy skis shall glide, without a pivot's trend.

Now, lean and press, so edges slice the snow, And carve a turn, with grace so rare and bright. Let rhythm flow, like harpstrings soft and slow, And all who see, shall marvel at thy sight.

So make this turn, with style that's truly thine, And show the world, the art of skiing divine.

 

[JCF]

Feed @LiquidFeet 's post into ChatGPT and asked it to summarise for a 2nd grader...

A skier needs to pull their feet back while skiing in order to make a turn. They need to pull their old outside leg back by flexing their hip and knee, and their old inside leg back by extending their knee and hip. This helps their skis flatten and turn. The skier's glutes and hamstrings help pull the feet back.

What I love about poetry is that most of the important stuff is not said with the words