Tipping the foot inside the boot first - why?

Tony S

I have a confusion to make ...
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mister moose

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You will need to discuss that first sentence with Mr. Newton
Yes, forces need to be aligned but have you considered the origins of the forces at play?
Would you consider Kinetic Ecosystems? My point is the kinetic chain to initiate a turn at low velocity is different from high performance turns.
Not talking about static vs dynamic here. Dynamic Balance in skiing means balance "while on the move" whether it's 3MPH or 40MPH.
What we have been referring to as static is when rotational forces are very small. They of course are still there. And yes of course the kinetic chain has differences according to technique of the skier and as forces present themselves. And while you are nearly there, I don't think you quite have rotational motion down pat.

??? Think you got it backwards
It is the ski/skier generated Centripetal force that creates the phenomenon we know as Centrifugal force. There are arguments regarding what the definition of Centrifugal force really is.
Not really. It's pretty well established.

In the context of skiing, I look at Centrifugal force as being the force that is trying return the skier's mass to a straight-line direction of travel.
This is called inertia. Inertia is not a force.

All one has to do is release their edges to experience that. The energy (velocity) source for both Centripetal and it's resulting Centrifugal component is the pull of gravity in combination with the slope of the hill.
You are double speaking, invoking two reference frames at once. There is no centrifugal component, ever when discussing centripetal.

This goes to my assertion that what many skiers feel is not real.
If we feel it, it's real. You just aren't describing it correctly, and that leads to confusion. Centrifugal is real when in a rotating reference frame, such as the car seat in a turn example. We also feel our mass being accelerated, we feel our inertia. Our fluid in our inner ear flows.(change in velocity can mean change in direction, not speed, both create acceleration).

Those who learn to feel the generated push of Centripetal vs the pull of reactive Centrifugal know what I mean.
Hmmm. I know what you mean, but if you're discussing the 'push', the tangential inward force that changes our velocity vector, then the 'pull' is your own inertia resisting that change in velocity.
 

Chris V.

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In high velocity, linked turns where the developed Centripetal Force is by far and away the most dominant, the gravitational terms Weight and Topple are not in play. When teaching a beginner or instituting a drill at low velocities, the reverse is true. This is why some drills fail to solve a problem.
"Weight" being a function of mass and gravitational force, it's probably more useful to think in terms of mass than in terms of weight, and then to think in terms of the total force experienced by the skier. Mass is one component determining centripetal force. Added to centripetal force is the force that results from gravity--technically, I think, what the skier experiences is the resulting ground reaction force. So the total force pushing up against the feet of a skier in a turn is the combination of centripetal force and the ground reaction force that gravity creates. To put what geepers has said in other words, at any isolated moment in the turn, a blindfolded skier wouldn't be able to tell what fraction of that total force resulted from gravity.

I'm sure everyone participating in this forum is a good enough skier to, without even thinking about it, use the energy of the old turn to move dynamically into the new turn. Beginners aren't typically good at this. If a skier maintains balance fully resisting the forces of the old turn until the last moment, and then releases all at once, the skier's momentum will tend to carry the skier's center of mass in a straight line. The only thing that will start the skier's center of mass moving toward the center of the new turn will be gravity--which as you've noted becomes a relatively weak component of the forces acting on the skier, as velocity increases. In that case, if the skier wants to shorten the radius of the new turn, the skier's only options will be to push off the hill, stem, make a pivoting move, or do some combination of these. These are the movement patterns one typically sees in beginners.

On the other hand, if the skier begins releasing the center of mass from balance against the forces of the old turn, while the skis continue traveling the arc of the old turn, then the center of mass will be able to move more rapidly into the new turn.

This pattern of an early progressive initiation of release has been given many names--toppling, "climbing the wall," "the infinity move," "using the force." I believe they really all amount to the same thing.
 

François Pugh

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@JESinstr is correct when he says that there is no centrifugal force when using his frame of reference that is fixed to the local topography. He is also using the term centripetal merely to define the direction of his turn, just like centrifugal defines the direction of what some might call the inertial force or more properly momentum in his frame of reference, and what we call centrifugal force in a frame of reference fixed to the skier.

@JESinstr , when you say the skier frame of reference is not real, you have trapped yourself into limiting your thinking. If you agree that the earth rotates, and revolves around the sun, and other commonly accepted astronomy (not astrology), then you will agree that your preferred frame of reference is indeed rotating about the centre of Earth, and a non-rotating frame of reference fixed there would be better. Then you could explain why train wheels wear faster on one side than the other, and why you need to invent a coriolis force to explain it in the frame of reference fixed to the earth the train travels over. This coriolis force would just be a another centrifugal force in the skier frame of reference (a very small one).

An even better frame would be the sun-fixed frame of reference, since Earth revolves around the sun. But wait, there's more. The sun revolves around the centre of our universe. What does our universe revolve around? Our galaxy?

The scary (to some) truth is there is no "REAL" frame of reference, the only difference is one frame of reference makes the math easier for the problem at hand, as astronomers discovered when they decided to have things revolve around the sun instead of using the earth as the fixed point.
 

JESinstr

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^^^^^^^^^

Boy, you guys are tough :geek: !

It is interesting how you picked up on that phrase "what you feel is not real" and took it literally. Hmmmm Topple? Weight?

That phrase popped up in the golfing world because the "Muscle" between your ears is initiating movements based on mis interpreted or misunderstood forces. If you do not understand the physics (small p) of creating Centripetal Travel, then the resultant Centrifugal force that you feel (which can be created unintentionally) will have a high chance of being misinterpreted resulting in defensive, bracing movements vs offensive movements.

I appreciate the constructive comments of @geepers , @Chris V. and @François Pugh.
 

markojp

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Centripetal = real
Centrifugal = perceived

(much as in sailing, True wind angle vs. apparent wind angle.)
 

geepers

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You need to move the mass where it needs to be to control the ski to put them in the right position at the right time and pressure them correctly to move your mass where you want to be.

So... in other words mass tells the skis how to curve and the curve of the skis tells the mass how to move. That it? :P
 

François Pugh

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^^^Yup, pretty simple eh? ;)
The interaction between the mass and the skis is a two-way street controlled by tipping and pressure, or as Warren Whitherel said fifty years ago, "If you apply correct edge angles and pressure to a ski, the ski itself will provide most of the required turning forces." Or was it, "Tip and pressure the skis correctly and they will take you where you want to go." My memory ain't so good as I remember it once was.

If your mass ain't in the right place, you can't tip and pressure the skis correctly; it got there because you didn't tip and pressure the skis correctly.
OR
You are in the right place to tip and pressure the skis correctly because that's exactly what you did.

That's all there is to it.
 

Dave Marshak

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I haven't read this whole thread but it seems to me that's there's some "tip-your-new-outside-foot NO extend-your-old-downhill-leg NO flex-your-new-inside-ankle" going on. Why make a choice? Do all of those things and figure out what effect that each has in your skiing. When you learn that you will have more skills to apply in any situation.

Also things are completely over the edge when the discussion goes to whether gravity and acceleration exist in different universes.

I'm feeling better today because I skied yesterday. I suggest you all do the same.

dm
 

razie

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Sorry y'all didn't mean to troll this and swim away, got distracted with non-skiing matters... and some in-person skiing matters as well.

Some data from carv:

Suggests that increasing edge angle while under load is not really a thing (at least for Ted :) ).

Tedblog-edgeangle.jpg



Tedblog-osp.jpg

I’m out. I’m not interested in arguing. When you put up a graph that shows the opposite of what you intend to prove there’s no point discussing it further.

Carry on.

dm

@Dave Marshak the graph clearly shows that the edge angle never increases as pressure goes up. It only decreases a bit. To say it proves your point that you can increase it under load because it shows it changes is... uhh... :geek:

I think what's missing in the discussion is how additional edge angle is added under load by shortening the inside leg. You'll only ever get so much by foot tipping alone. And believe me, I'm a huuuge foot tipping advocate.

Good point.

The issue is that saying you can change the edge angle from subtle foot tipping under heavy load is like trying to do ballerina things while lifting 400 lbs. The inside foot can tip all it wants at the apex, the angle won't change anymore. And trying to tip the outside foot when planted on it and lifting the weight of 2 of youse on it is asking this guy:

1669074262813.png


To lift and then do this:

1669074311515.png


P.s. those were supposed to be gifs

As to SL turns not being carved I agree, for most skiers and pros - they can't hack it, let alone teach it... if that's what you meant. It is the ultimate test of skill. Especially on a black run. But that does not make that an universal truth. There's enough of us that can manage it :ogcool:

 
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Rod9301

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I haven't read this whole thread but it seems to me that's there's some "tip-your-new-outside-foot NO extend-your-old-downhill-leg NO flex-your-new-inside-ankle" going on. Why make a choice? Do all of those things and figure out what effect that each has in your skiing. When you learn that you will have more skills to apply in any situation.

Also things are completely over the edge when the discussion goes to whether gravity and acceleration exist in different universes.

I'm feeling better today because I skied yesterday. I suggest you all do the same.

dm
But why reinvent the wheel?

This is the purpose of instruction, so everybody doesn't have to figure out out by themselves.
Or going to school for that matter
 

Chris V.

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Sorry...got distracted with...some in-person skiing matters as well.
Much the best plan for improvement...more of that, less reading and arguing.
And trying to tip the outside foot when planted on it and lifting the weight of 2 of youse on it is asking this guy:

View attachment 183747

To lift and then do this:

View attachment 183748
Good one. Every movement has its place.
As to SL turns not being carved I agree, for most skiers and pros - they can't hack it, let alone teach it... if that's what you meant. It is the ultimate test of skill. Especially on a black run. But that does not make that an universal truth. There's enough of us that can manage it :ogcool:
If you say "short radius turns," I'll ask, "How short?" IMHO, it's best to learn brushed turns first, then progress to perfecting carved turns. The similarities between excellent brushed and carved turns much outweigh the differences. Then get good at longish carved turns, and start tightening them up more and more. Actually carving turns of the radius found in a WC slalom course, on a pitch found in a WC slalom course, requires highly refined movements. We all have our limits. Most of us won't get there, but with practice we can get closer and closer.
 

markojp

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Much the best plan for improvement...more of that, less reading and arguing.

Good one. Every movement has its place.

If you say "short radius turns," I'll ask, "How short?" IMHO, it's best to learn brushed turns first, then progress to perfecting carved turns. The similarities between excellent brushed and carved turns much outweigh the differences. Then get good at longish carved turns, and start tightening them up more and more. Actually carving turns of the radius found in a WC slalom course, on a pitch found in a WC slalom course, requires highly refined movements. We all have our limits. Most of us won't get there, but with practice we can get closer and closer.

But all those WC'ers we're never trying to brush turns when they were kids at their local clubs. The only goal was to get from start to finish as fast as possible. There was only one way to get their, and even from a young age they knew what skill they had to master to get the outcome to win... carved turns.
 

Dave Marshak

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The issue is that saying you can change the edge angle from subtle foot tipping under heavy load is like trying to do ballerina things while lifting 400 lbs. The inside foot can tip all it wants at the apex, the angle won't change anymore. And trying to tip the outside foot when planted on it and lifting the weight of 2 of youse on it is asking this guy:

View attachment 183747

To lift and then do this:

View attachment 183748
That's exactly what you need gto do in high g turns. You're balancing a load greater thaan your body weight on an a narrow edge. That requires subtle fine adjustments, not gross body movements. At the gym when I have my body weight on a bar on my shoulders I can easily articulate my feet enough to move the center of press left or right or forward or back on one or both feet. The reason that is possible is because the path is at a right angle to the movement I need to make with my foot. It's the same inside a ski boot.

This was your original statement that I responded to:

Put another way, you can do two things to your skis: tip them or pressure them, but not at the same time.

That's demonstrably false. Of course you reach maximums of pressure or edge angle, but theat doesn't mean you can't tip and extend at the same time within those limits. Andeven at the limit of highest pressure a skilled skier is still able to use fine movements to control edge.

dm
 

Dave Marshak

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But why reinvent the wheel?

This is the purpose of instruction, so everybody doesn't have to figure out out by themselves.
Or going to school for that matter
Everyone has to figure it out for themselves. The purpose of coaching is to help you avoid dead ends and to keep you on the right path. My coaching method was to have you do what I did so you can ski the way I ski. I never thought of it as reinventing the wheel.

dm
 

razie

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@Dave Marshak activating mucles to feel the ground left or right while you're supporting the weight on your heels is fine. How about tilting your tibia significantly while your lifting? That's generally what it takes to tip a ski since we have tall boots. And that generally takes relaxed muscles (as opposed to co-contracting muscles) and flexion in the knees. Which is why it won't work when the leg is long and strong. All you can do is to hip in more by angulating or shortening (or well... tipping the other one, but not going there). Just ski facts - you know, alternative truths.

As to my absolute statement, which I still like, it is true. And false at the same time. Maybe we can add the word "meaningfully" to make it appear less false to some. Or underline that both of those things, tipping and pressure, grow from min to max and intersect, neither is an on/off switch... and trying to do both is pointless, as one is trying to increase angles and the other to decrease them...

1669122193153.png


What is false is that you can tip and extend at the same time, when the leg is already extended to support that Olympic bar full of weights. You can't do either of those things... but of course someone could stay low to the apex and then extend under pressure, just to prove me wrong, perhaps for the sake of an argument. What that has to do with actual skiing is less clear.
 
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