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# Get off those edges. - Page 7

I am late to the conversation, having just now taken the time to read the last three pages, but isn't centripetal force what skiers and boarders are trying to create, and isn't this is the purpose of tipping the board on its inside edge?
Nolo, this is spot on imo, both in terms of intent and sequencing.

If centrifugal force is thought of as the problem to be managed (a reaction rather than an action), it marginalises the intent and thereby the control the skier exercises. Skiing is all about shaping these forces to ones own purposes which is why it is a caress rather than a bracing against external foe.

Centrifugal force may actually exist, but it is bad psychology!

The standard centrifugal force vector diagram also suggests an equilibrium to many people which belies the essential imbalance in a carved skiturn.
Quote:
 Originally Posted by daslider If centrifugal force is thought of as the problem to be managed (a reaction rather than an action), it marginalises the intent and thereby the control the skier exercises.
Centrifugal force is a byproduct of the intent (to turn). If not managed properly our intent will not be achieved. Lack of management is what marginalises skier control

Here's the real sequence:

1) We decide we want to carve a turn, for what ever reason.

2) To achieve that intent we tip our skis on edge and allow them to engage.

3) The carving ski creates centrifugal force

4) We relocate our CM so as to remain upright through the duration of the turn.

It's really that simple. If understood, the concept of centrifugal force and resultant force vectors is nothing to be intimidated by.

Quote:
 Originally Posted by daslider The standard centrifugal force vector diagram also suggests an equilibrium to many people which belies the essential imbalance in a carved skiturn.
The goal is lateral force equilibrium while in motion. Tipping the ski empowers the mechanics of the ski to produce a direction change, which changes the forces acting upon us. The lateral CM movements we make allow us to maintain lateral force equiibrium as those forces change and we execute the desired turn. It's called dynamic balance.

The only imbalance is found in the lack of resistence that allows gravity to create motion.

FASTMAN
Quote:
 Originally Posted by Rick 1) We decide we want to carve a turn, for what ever reason. 2) To achieve that intent we tip our skis on edge and allow them to engage. 3) The carving ski creates centrifugal force 4) We relocate our CM so as to remain upright through the duration of the turn.
Daslider & Fastman, I don't think there's too much daylight between your two viewpoints! (Not much more than the theoretical depth of track of a non-sidecut ski on an infinitely hard surface!)
I would just say, instead of 3) above, you could also state, more precisely:
3) The carving ski creates centripetal force (i.e. the ski tries to turn us), causing our body's inertia to create centrifugal force (i.e. the body tries to resist any change to its speed or direction).

Daslider, "Centrifugal force may actually exist, but it is bad psychology!"
If I'm teaching a recreational skier about carved turns, I would be remiss if I were not to tell them how to prepare for the inevitable centrifugal force that they will generate. Of course I would also inform them that they can themselves greatly influence how much CF they'll generate, by speed and/or turn shape (although the latter obviously depends a lot on the sidecut). But if I'm coaching a racer, I'll have to tell them that they'll have to deal with however much CF is dictated to them by their turn radius (decided by the course setting) and their speed (hopefully as fast as possible, otherwise it's not really racing - although of course I acknowledge there's a place for 80 or 90% runs from time to time).

Otherwise I agree totally with what you guys say!
Martin,

The way you phrased #3 makes the most sense to me.
The way #3 reads sounds like your skis are skiing you. I would submit you should be skiing your skis!

When skiing your best you are capitilizing on and controlling all these forces as needed to continue down the hill on "Your" chosen path, not the skis!

Your description to me sounds like being out of control?
A racer going around a GS gate may be able to "control", in the sense of "resisting", the centrifugal force acting upon him, (ie. He makes sure his legs don't give way, by spending hours in the gym beforehand, and by assuming a strong position of skeletal alignment). But the only way he can ALTER that force is by going slower (not the aim) or by skiing a wider radius (sometimes possible in downhill but rarely in the other disciplines if you want to stay in the course).
Non-racers can of course vary their turn shapes and path down the mountain to suit any purpose they may have. I had assumed that what we are talking about is what happens, once a particular skier decides to carve a particular turn shape.
Quote:
 Originally Posted by Atomicman The way #3 reads sounds like your skis are skiing you. I would submit you should be skiing your skis! When skiing your best you are capitilizing on and controlling all these forces as needed to continue down the hill on "Your" chosen path, not the skis! Your description to me sounds like being out of control?
The skis are in control in the sense that for a given edge angle we have no control over the shape of the turn.

We are in control in the sense that we can choose the edge angle we employ, and therefore the turn shape we produce.

FASTMAN
Martin,

I want to add my agreement to nolo's concerning your restating of Fastman's point #3. The ski is a tool that I use to move my body where I want it to go.

yd
Fastman,

I hear what you're saying but doesn't more than just edge angle affects turn shape.

For example duration of a particular edge angle & where on the ski you are applying pressure and for how long. I decide when I am finished with a turn and beginning the next regardless of edge angle only. Isn't this true? I can continue all the way back uphill on a particular edge angle or right at the fall line decide to retract my legs crossover before and begin a new turn.
Yep, I agree Atomicman.

The predominant determinant of turn radius is edge angle and sidecut, but it can be tweaked in the means you mentioned (fore/aft distribution), and lateral distribution has some affect also. And yes, you definately can alter edge angle during the turn to alter radius. And finally, while start and finish points of the turn don't necessarily have influence on the radius, it sure has influence on the line of travel down the hill.

From one control freak to another, good post!

FASTMAN
Quote:
 Originally Posted by Martin Bell I would just say, instead of 3) above, you could also state, more precisely: 3) The carving ski creates centripetal force (i.e. the ski tries to turn us), causing our body's inertia to create centrifugal force (i.e. the body tries to resist any change to its speed or direction).
Sure, Martin, I have no problem with that.

I see it as a chicken and egg thing though. The two (centrifugal and centripetal) are codependent (Remember PM's carnival ride example), and it's the act of tipping the ski on edge that causes them to simultaneously spring into existence.

But I'm all for whatever description best promotes understanding.

FASTMAN
Fastman:

Thanks for the reply! Makes sense to me.
What never did make sense to me though is the premise daslider started this thread on.

I don't know about you, but my goal is to always be balancing on "ONLY" my edges. Except when neutral between turns or if I am intentionally using redirection.

By the way where & who do you coach?

Over & out!

A-man

Ski with the Wind MF!!!
Quote:
 Originally Posted by Rick Sure, Martin, I have no problem with that. I see it as a chicken and egg thing though. The two (centrifugal and centripetal) are codependent (Remember PM's carnival ride example), and it's the act of tipping the ski on edge that causes them to simultaneously spring into existence. But I'm all for whatever description best promotes understanding. FASTMAN
That's the third time the phrase "chicken and egg" has come up in this thread! Which of those was daslider when he gave birth to this classic? In theory, with just your body weight, you could tip a ski, stand on it, and it would begin to turn, generating centripetal force. But yes, as soon as that happens, in the same instant its equal and opposing partner springs to life.
In the real world of ski-racing, there's often some slight rotary to get things started, so in that case the centrifugal force could be viewed as being created "first", but of course its partner is also created immediately.
Quote:
 Originally Posted by Atomicman What never did make sense to me though is the premise daslider started this thread on. I don't know about you, but my goal is to always be balancing on "ONLY" my edges.
We're beginning to cover old ground here, but I think what he meant is that, once your ski has cut its "trench" into the snow, the main factor that prevents it from skidding out is actually the base pressing against the outside "wall" of the trench, rather than the edge itself.
I know, I don't agree.
Fastman

you'll need to explain dynamic balance to me. What I understand is that we deliberately create an imbalance by leaning inside and tipping our skis causing the skis to turn and produce a countervailing force which we shape to make the turn. We do something similar every time we walk forward. Stability yes, lots of it hopefully, but balance? There is no equilibrium, there is a net resultant force created by the imbalance of forces.

Don't centrifugal and centripetal forces have to act on different bodies and by their nature aren't they unable alone to produce equilibrium?

The practical implication of this theoretical stuff surely is the confusion in proclaiming the importance of balance and then urging skiers to dive down a hill outside their line of support in blatant disregard of their balance! This is surely one of the biggest barriers from intermediate skiing?

Atomicman, doesn't this preoccupation with edges hinder a conception of skiing beyond the groomed and perfectly prepared race piste?
We've heated up again Eh? This always seems to break down at some point and move from science to emotion. I think Nolo's right. Centripetal force creates the turn, and it's managing the balance between the oposing forces that allow us to shape and then release our turns and move to the next one.

For point 3, our skis don't create centripetal force our muscles do, using the complex articulations and levers we call our skeleton. Our skis are only an enhanced contact point that allows us to play more effectively on the snow. They have only the energy that our movements create in them. This is a really important point for me. It is our body movements that create and uncreate turns. This is the outside force that moves our mass in a new direction. Gravity is the only constant. As to which force comes first? From a practical viewpoint the body has to be moved away from it's straight line course for it to resist that movement. It requires a new force to act on it, right? To me it's more than a simple chicken and egg thing, but it doesn't need to be complicated?

We tip, we rotate, and blend the two, but once moving, every movement we make effects the direction of travel of our mass because we are moving some part of our mass when we move.

As far as what constitutes balance, maybe we can approach this from the direction of the brains interpretation of it's sensory input. When the sum total of the bodies input to the brain is recognizable, understood, and predictable as to outcome then we feel in balance. A well engaged edge and platform do this for me. But really, I'll agree with someone else who said that it's really the ability to recognize the need for correction or future need for correction, that determines whether the body can maintain that feelng of being in balance or not. Rick stated awhile back that the bodies balance system treats all the forces the same, it doesn't distinguish between them, it adjusts to them. Roberts called this behavioural vertical. I think this is true from everything I've read and felt.

Enough for me for now. Later, Ric.
Whether the ski takes you around the bend or you take it (or this conversation drives you both), may seem like wordplay, but to me it reveals an important aspect of the mindgame. The question is who is really in control. Skiers imo get back very often because they actually need to be infront of events, literally taking the skis and shaping the turns as they intend. This to me is the definition of skillful skiing as opposed to just getting down the hill.
RicB,

Could you be more specific in just how our muscles create the force to turn us. Seems to me that the muscles of our body just aren't strong enough to account for the observed acceleration of our bodies.

An arced ski following a curved path generates a force which can be represented by a vector pointing up from the ski into my foot. I can shear this vector in various ways to move my body around. This force generated by the skis is the most powerful force that exists in my skiing world and I have complete control of it. This allows me to accelerate my body as slowly or quickly as I want to.

yd
Daslider, I think that is a valid point. when we say that in physical science world, or world of natural laws, that when we have certain actions we will get certain results, is true, but if we look at our actions being dependant on the "interpretation" of the sensory input, or we look at one element of the sensory input (I'm including propreoception in this) being blocked, missing, or misinterpreted, then the result changes because the reaction changes. Then we have the other influences on our balance and movements in the form of certain reflex actions which will overide our ability to process and interpret the input. Reflexes that cause automatic contractions or atuomatic relaxing of our muscles. Tis all very complicated isn't it.

I like to approach it from the point of view of where and how we stand over our skis, and the movements we make to accomplish this coupled with our intentions. Using our body power (weight) through our stance and movments to get the most out of our skis while taking us where we want to go.

My tai chi chuan practice has given alot of reinforcement to me for the idea that slow movement seeking perfection practice is the best path to understanding and speed. If we can't do it well slowly, where is the hope in ever doing it well fast? Later, Ric.
Quote:
 Originally Posted by ydnar RicB, Could you be more specific in just how our muscles create the force to turn us. Seems to me that the muscles of our body just aren't strong enough to account for the observed acceleration of our bodies. An arced ski following a curved path generates a force which can be represented by a vector pointing up from the ski into my foot. I can shear this vector in various ways to move my body around. This force generated by the skis is the most powerful force that exists in my skiing world and I have complete control of it. This allows me to accelerate my body as slowly or quickly as I want to. yd
Our muscles move our body. Without movement in our body we either go straight or we stay still. We have to start the arc with muscle movements. Our muscles control how we utilize our body power or weight and what angle we place our ski on. Isn't our ski just a tool we use and manipulate to make our movements more or less effective or get more out of them? How would you control these forces created? To me to suggest otherwise is to say we have no control over any of it. The ability to control where we go and shape our turns is how wecreate more or less force as I see it., but it all starts and ends with a body movement doesn't it? Later, Ric.
Quote:
 Originally Posted by RicB For point 3, our skis don't create centripetal force our muscles do, using the complex articulations and levers we call our skeleton. Our skis are only an enhanced contact point that allows us to play more effectively on the snow. They have only the energy that our movements create in them. This is a really important point for me. It is our body movements that create and uncreate turns. This is the outside force that moves our mass in a new direction. Gravity is the only constant. As to which force comes first? From a practical viewpoint the body has to be moved away from it's straight line course for it to resist that movement. It requires a new force to act on it, right? To me it's more than a simple chicken and egg thing, but it doesn't need to be complicated?
Interesting paragraph Ric. I think much of this stuff is intuitively understood more easily than conveyed with written word. I also think there are various perspectives used by individuals to foster that understanding. In that spirit, I'll offer mine:

(Note: all my comments are in reference to carving only)

Quote:
 Originally Posted by RicB For point 3, our skis don't create centripetal force our muscles do, using the complex articulations and levers we call our skeleton. Our skis are only an enhanced contact point that allows us to play more effectively on the snow. They have only the energy that our movements create in them.
I see the ski as the dominant element in the process. Make the exact same body movements on a 0 sidecut, inflexible ski and no centripetal forces are created, no change of direction results.

Make the exact same body movements on 5 different pairs of skis, with 5 different sidecuts, and 5 different magnitudes of centripetal/centrifugal forces are generated.

The ski is more than a just a contact point, It determines the magnitude of the forces created when we make the movements we do.

Quote:
 Originally Posted by RicB It is our body movements that create and uncreate turns. This is the outside force that moves our mass in a new direction.
Yes, our body motions set a turn into motion, but I don't see them as the forces that move our mass in a new direction. I give that credit to the snow, and how the mechanics of the ski interact with it.

We use the body movements to which you refer to put the ski on edge. This begins the process. The ski then, because of the sidecut, and our weight on it, bends and engages it's now curved edge into the snow. The engaged, curved edge produces a resistance to our prior straight path of travel. Our momentum pushes it against the snow, and the snow pushes back, redirecting our momentum into a new direction. Centrifugal force is our momentum pushing, centripetal force is the snow pushing back and redirecting. Our body is just the middle man in the process, resisting the centrifugal and centripetal forces impacting us from opposite sides attempting to squash us.

Quote:
 Originally Posted by RicB Gravity is the only constant.
Agree!

Quote:
 Originally Posted by RicB As to which force comes first? From a practical viewpoint the body has to be moved away from its straight line course for it to resist that movement. It requires a new force to act on it, right? To me it's more than a simple chicken and egg thing
My above description is why I think it is that simple. You tip your skis and simultaneously your momentum pushes against the snow (centrifugal force) and the snow pushes back (centripetal force). Neither really comes first, they have to exist in equilibrium. The snow will only push back as hard as it's pushed against.

FASTMAN
Fastman

if the snow really did squash you between 2 equal and opposite forces in equilibrium as you suggest, you would carry on in a straight line (no doubt very fast)!

Luckily neither of us need worry about the other's theory and we can both enjoy what I suspect are very much the same sensations. Is there a precedent for skiteaching which is more sensory based than our hybrid of sensation and popular science?

As Ott very pithily put it earlier, it would be very interesting to know just what ski designers intended us to do with this stuff.
Quote:
 Originally Posted by daslider Fastman if the snow really did squash you between 2 equal and opposite forces in equilibrium as you suggest, you would carry on in a straight line (no doubt very fast)!
If there was no change of direction (as produced by the engagement of an arced ski edge) the equal and opposite forces (centrifugal/centripetal) would not be created. They would not exist.

The forces we speak of here are in nature lateral to the direction of travel. They are the forces we must manage to reamain in lateral balance, they are not the forces which propell us. Gravity is the force that propells us. If the slope upon which we ski comes to an end so will our movement, regardless of the arc we're riding. The carving ski only determines the direction in which we allow gavity to propell us. It's like ydnar says, we sheer the gravity line.

FASTMAN
Quote:
 Originally Posted by daslider Atomicman, doesn't this preoccupation with edges hinder a conception of skiing beyond the groomed and perfectly prepared race piste?

I don't believe so. I make a concerted effort to ski powder or crud with the same edge control and basic body position that I ski a smooth piste, Race or not. (Quite honestly most race courses are in worse condition than most open pistes and you don't have the luxury of turning when or where you choose).

As I reitierate to other folk I ski with when off piste, don't look down, just ski it like the slope is packed! Most of off piste skiing is mental. Unless the conditions are extremly heavy & wet,I believe you should be able to use very similar technique on or off piste including your using your edges.

As for on piste, the entire goal of carving is to balance on only the ski edge. If one is not accomplishing this you are smearing or skliding not on a "PURE" carve. One more thing, If you are racing, whoever "PURELY CARVES" the cleanest arcs the mostoften wins the race. Unless you are on the World Cup there is no such thing as a perfectly prepared Race Piste unles you run maybe 1-10 in lower level races.

Respectfully,

A-Man
Quote:
 Originally Posted by Rick Make the exact same body movements on 5 different pairs of skis, with 5 different sidecuts, and 5 different magnitudes of centripetal/centrifugal forces are generated. The ski is more than a just a contact point, It determines the magnitude of the forces created when we make the movements we do. FASTMAN

Yes - that is why I had so much trouble learning to ski on 3 pairs of skis last season instead of just 1....

With 1 pair I can "memorise" what the response is likely to be & be pretty close....

With constant change between 3 pairs I had to learn to "listen" much more to the ski....

VERY different thing for me when skiing... it required skills I did not have, at the start of the season, to adapt to those changes....

Yet my instructor insists I MUST learn to deal with these changes - preferably by myself - if I am to reach my skiing goals
Rick said: We use the body movements to which you refer to put the ski on edge.

RicB asks: How do we tip our skis on edge without some movement to the inside of the turn? I see our movement towards the center of the turn as the centripetal force that starts the turn. We move our CoM lateraly into the turn, or we tip our feet and knees into the turn, or any other way you want to do it. I see no way to turn with out some edge engagement of some kind which to me says we are moving some part of our body into the turn. When we do that we change the direction our body is heading. We alter our course to the inside. We introduce a center seeking force with our muscles. Now maybe some see this force needing to come from outside our body, or a reaction to our movements, but I just can't get there myself. Now we are back to that chicken and egg thing, but if we have to move first????

Five different skis are five different tools with unique characteristics, but none of them will turn without introducing some movement towards the center of the turn.

And I should have said that our skis have only the energy our movements combined with our weight give them.

There are certainly different ways to look at this, but I like to view it from where it starts. I do like the inside to out view over the outside in view with most things. I'm also someone who has come to terms with tools over a long period, and probably have some notions about the operator versus tool partnership that some don't share. I guess I just want to give credit to the operator. I'll give credit to the body movement creating the turn, to the movement towards the center of the turn our body makes.

Sure makes for some interesting thought doesn't it? Later, Ric.
Quote:
 Originally Posted by RicB Rick said: We use the body movements to which you refer to put the ski on edge. RicB asks: How do we tip our skis on edge without some movement to the inside of the turn? .
I engage the edges of my skis by pronating/supinating my feet....
I INCREASE edge angle by moving my body (inclination/angulation etc)

This is what got me all mixed up before.... everyone using their bodies to put skis on edge....

I USE MY FEET

I know that to supinate/pronate my feet the weight distribution changes - but I ski best when the movement "starts" at my feet.... thinking about moving BODY tends to result in feet not being in charge.... thinking about moving feet means that body does what it needs for feet to do their job...

When I walk do I think "project CofM forward & catch it on front foot" or "lift foot & put it down again" (assuming I think about it at all) ...
Watch a tired bushwalker at the end of a hard days walk... talk to them - they are thinking about lifting that foot & placing it forward .... the Cof M moves to allow the feet to work as they must

I think it is far more natural to move correctly if you learn to move from the feet.... thinking of moving the upper body around produces that result
Don't have any disagreement here Disski. I think that this is different than determining what is happening from a physics or natural law standpoint though. Your distinction between pronation and edging movements are important too. Pronation is worhty of a thread all it's own.

On the subject at hand I've got a few question to ask of those who responded to my post below.

Do you see the world of natural laws stopping at the skin?

Do you distinguish between the forces external to and acting on our body and those forces that originate within our body?

If you do, how do you categorize the forces generated from within? Our muscle effort.

Do you see the magnitude of force exerted a determining factor in categorization of the force?

On the subject of the the ski generating force, I guess my take would be more in comparison to a lever, which amplifies the force we imput but doesn't create it in and of itself. Now I'm not saying a ski is a lever, but that it serves us in the same way. It turns our small force which manipulates our mass into big forces. Later, Ric.
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