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The purpose of angulation? - Page 2

post #31 of 58
Quote:
Originally posted by Warren:
Just to throw something in here to help me understand...

When I'm moving quickly, and want to tighten the radius of a turn, I increase the angulation. (i.e. move more weight out over the skis in order to bend them further) Is this wrong? How would you describe it?
This isn't "wrong," but it does contradict some of the definition and descriptions preferred by others. The problem is that there are any number of ways to define terms that lead to a consistent or clear description of movements, but these different sets of definitions contradict each other. PSIA has one set of definitions, and tries to create a consistent vocabulary to use at least within its own membership for a variety of valid reasons.
Regardless of what terminology we use, no description will give you the motor skills or perceptual awareness to work the ski as we are descibing. These movements and feelings will not be learned without the experience of them, which involves trial and error and, often, falling.
Nevertheless, if a particular description is meaningful to you, or helps you experiment with new movements, by all means use that as starting point for experimentation.

John
post #32 of 58
Lets look at cause and effect in a simple order of events.

From a straight run (no angulation) (inclination zero or vertical over base of support).

We edge our skis. Whether by tipping feet, moving knees, hips, leaning (banking), whatever, is irrelevant for this exercise.

The ski technology engages and creates a turn, which generate a new lateral force component to which we must adjust our balance.

Our bodies balancing reaction moves the CM to the inside of the turn so we do not fall over. This can be done showing angles, or not (banking).

The net is that the angle of inclination (line from CM to base of support) has changed. Maintaining balance is dependant on inclination. Without it I fall over.

Angulation could occur without repositioning the CM to an inside position of balance, so balance does not necessarally occur from angulation (allthough it may), but from inclination.

How inclination is achieved is with movements, that may show angulation, or not, by banking.

Banking and inclination may appear to be the same, but are not.
Banking is a cause (movement).
Inclination is a result. The equliberium of vertical and lateral forces that reflects a state of balance, and changes with the dynamic balancing process of skiing.

I suggest that most of the time we use angulating movements for both edging and for balance, and seldom only for one or the other.

If we are turning, and maintaing balance, inclination results.
While you can alter its "appearance" with more or less accompining angles, and the equalibrium it represents to guide the flow of CM ("falling in to engage" or "falling out to release"), this is accomplished by movements of the body joints that a couple interrelated things: Change edge angles, and as a result the lateral force component, and move the CM laterally or vertically to balance to that changing lateral force component. These actions represent angulating movements.
[img]smile.gif[/img]

[ July 03, 2003, 02:14 PM: Message edited by: Arcmeister ]
post #33 of 58
Quote:
Originally posted by Arcmeister:
...Banking and inclination may appear to be the same, but are not. Banking is a cause (movement). Inclination is a result. ...
Differentiating these two terms on the basis of causation is a new and possibly very interesting twist on the previous discussion, but unfortunately, I think this would be foreign to lots of people since most seem to use these terms as straightforward descriptions of bodily positions at a particular instant of time.

Do you think that your distinction is why nobody responded to my earler challenge to draw stick figures of: (a) A skier that is banked but not inclined; and (b) one who is inclined but not banked? As I said, if they are indeed separate and well defined concepts, it should be possible to do this.

...I suggest that most of the time we use angulating movements for both edging and for balance, and seldom only for one or the other...

I couldn't agree more. This is why I added the PS to one of my posts in which I said,

"...For the record, what Fastman and I are discussing is not an "either-or" thing. There is obviously a continuum between the extremes (ie, no momentum forces vs. lots of momentum forces), and a corresponding continuum in the constraint placed on the mechanics of the skier..."

Most of the time we are somewhere in the middle of this continuum.

Tom / PM

[ July 03, 2003, 02:43 PM: Message edited by: PhysicsMan ]
post #34 of 58
Thread Starter 
Question: In the Venn diagram that PSIA uses to explain the interrelationship of the four skills--with balance the underlying circle within which are the other three circles of edge control, pressure control, and rotary movements--where would you put angulation?

The Venn diagram implies that all movements used in skiing are either primarily or secondarily balancing movements. Is angulation primarily or secondarily a (suite of) balancing movement(s)?

(ski coach, I am a Level III with a long and various PSIA past. In my view, PSIA is what it is and does very well as it is. Don't expect the Queen Mary to enter a yacht race, and don't expect PSIA to be leading any charges. It's a business association, among the most conservative categories of organizations in the USA. In a conservative climate, innovation comes from the fringes not the mainstream.)
post #35 of 58
Arc,

Bravo
post #36 of 58
nolo,

Again, kudos for a thought provoking question. PSIA-RM utilizes tipping, turning, flexion/extension and I'm more comfortable in that parlance.

I'll go out on a limb. Jennifer Metz opened my eyes to the idea that flexion/extension is oft merely a result of terrain as opposed to active pressuring a la the wheel of a vehicle riding up on a curb and the vehicle remaining level.

The simple answer would be to include angulation in all three movements, however, I'm inclined (terrible pun) to say that it is primarily a edging/tipping and rotary/turning.

The tipping is a no brainer and the rotary is based on the biomechanics required to invert the inside foot.

I'm reminded of one more thing as I type. Last night I read something that intrigued me in, "Skiing An Art....A Technique". Joubert stated something I hadn't considered and that was it is easier to angulate while extending as opposed to while flexing. I don't know how that fits in the scheme of your question, however, I thought it of interest.
post #37 of 58
Ok here is my $0.02 worth in two words about angulation in the ski turn it is momentarily:

SKELETAL LEVERAGE.
post #38 of 58
[quote]Originally posted by Arcmeister:
[QB]Maintaining balance is dependant on inclination. Without it I fall over.

Angulation could occur without repositioning the CM to an inside position of balance, so balance does not necessarally occur from angulation (allthough it may), but from inclination.

FASTMAN REPLY:
This is why I prefer the concept of defining inclination as the edge angle. When it is defined as the CM to center of pressure angle these tomato/tomoto debates can be legitimately introduced from both side because both sides of the argument are describing the same thing.

You are absolutely correct in saying that to balance the angle of inclination (by PSIA definition, CM to COP) must be managed by either adding or removing inclination until the angle of inclination is aligned with R (resultant force vector of momentum and gravity). The problem arises in the fact that just as you suggest angulation can occur without the establishment of balance, so too can inclination if not combined with the proper articulation of the joints (angulation) so your argument could be just as correctly turned around and used by your debate opponent.

This is why I think it is so important to bring the discussion back to fundamentals of balance and pursuing an understanding of the principles that influence and create balance. All these terms we're discussing are nothing but movements intended to ski in balance while creating turn shape. Potato/Pototo debates tend to divert attention from the real meat of the subject and leave the reader confused when both sides seem to make sense.
post #39 of 58
FASTMAN SAID:
...This is why I prefer the concept of defining inclination as the edge angle. When it is defined as the CM to center of pressure angle these tomato/tomoto debates can be legitimately introduced from both side because both sides of the argument are describing the same thing. ...

PM REPLIES:

I agree totally.

I think that another way to look at it is that Fastman is in effect saying is that there is a need for a term to describe the net result of lateral motions of the CM and angulation. Since the combination of the two is exactly what goes into making a given edge angle, why not simply call it "inclination" (which then by his definition is effectively the same as "edge angle").

In other words, neglecting constants like the slope angle and needed factors of 90 degrees, I think he is effectively saying:

"angle of inclination or edge angle" = "COM to base of support angle" + "extra angle from angulation"

(Did I interpret you correctly, Fastman?)

Early in the "Formal Definitions" thread, I said that I preferred:

"angle of inclination" = "angle of bank" + "angle of angulation"

Since there are (a) multiple definitions of "inclination" already in use, (b) I was using the less popular one that Fastman prefers, and (c) the term "bank" carries negative connotations in skiing, there wasn't much enthusiasm for my preferred definition, but in fact, all I saying was exactly what I think Fastman prefers, and for the same reasons.

I know that it is unlikely we are going to change the definitions that individuals have been using for years, but at least if people realize that there are problems with them, they can then communicate even more effectively with their students.

Tom / PM

[ July 04, 2003, 09:27 AM: Message edited by: PhysicsMan ]
post #40 of 58
The REAL purpose is to look like Stein.
post #41 of 58
[quote]Originally posted by PhysicsMan:

Fastman is assuming a turn with a big carving component, and hence, there is a direct and strong link between the edge angle and turn radius (and hence momentum forces). I am not making this assumption because I am thinking about other skiing situations. For example, (a) standing still or (b) being able to traverse in a perfectly straight line (even on shaped skis)

In each of the two situations that I just mentioned, there is no M force at all (since you are not turning), and hence, no linkage whatsoever between the angle of the R vector (it always is exactly equal to the gravity vector
===============================================

Great post Tom, you have focused on an important element of the topic. The relationship between momentum, gravity and resultant angle (R) applies in all types of turns (carved, steered, scarved, pivoted) or other forms of motion or non motion. During a turn the M grows in strength as speed grows and turn radius decreases regardless of the amount of carving or steering involved.

A 25 meter radius turn at 20 mph will have the same R angle whether steered or carved. The difference comes in the fact that on the same slope steered and carved turns of the same radius will result in different speeds, and thus different M (momentum) values. The slower speeds and resultant lower M value of steered turn produces a more vertical R angle and requires less lateral CM movement to achieve balance.

As you point out when standing still or moving in a straight line M is zero so R becomes aligned with G (gravity). An exception would be when the skis are other than parallel to the direction of travel, in which case acceleration and deceleration create and M element which requires lateral CM relocation, such as during sideslipping and stopping.
post #42 of 58
[quote]Originally posted by PhysicsMan:

I think he is effectively saying:

"angle of inclination or edge angle" = "COM to base of support angle" + "extra angle from angulation"

(Did I interpret you correctly, Fastman?)
==================================

Yes, Tom, that's exactly my position. You offer a very clear description that shines light on another benefit of the defintion, a means for precise recognition of the amount of angulation present.
post #43 of 58
Nolo. To me, angulation fits into the little tiny triangle formed when edging and rotary overlap. I'm way too tired and beer-soaked to extrapolate right now, but I'll try to clarify at another time.

Spag :
post #44 of 58
Quote:
Originally posted by FastMan:
... when the skis are other than parallel to the direction of travel, in which case acceleration and deceleration create and M element which requires lateral CM relocation, such as during sideslipping and stopping.
We are definitely on the same wavelength. That is why in the PS#3 of my post of July 02, 2003 10:34 PM in this thread, I said:

"...Although it hasn't been said explicitly, I think its important to point out that the "momentum forces" that Fastman and I refer to include not only the usual centrifugal forces, but also linear decelerating forces (eg, resulting from a hockey stop)..."

[img]graemlins/thumbsup.gif[/img]

Tom / PM

[ July 04, 2003, 08:30 PM: Message edited by: PhysicsMan ]
post #45 of 58
Thread Starter 
Physics and Fast Men,

Thanks for clarifying some of the confusion for ski teachers like me, particularly concerning that statement in the PSIA Technical Manual about changing the amount of edge angle without changing the amount of inclination. Good stuff--shows me what I get from EpicSki.
post #46 of 58
I am going to agree with you nolo, I am enjoying this very much.
post #47 of 58
>...Physics and Fast Men, Thanks for clarifying some of the confusion for ski teachers like me, particularly concerning that statement in the PSIA Technical Manual ...

Yer welcome. Our next lecture will focus on the surprising excellence at judging skiing exhibited by natives of the Amazon basin. We will try to make this an equally interesting presentation (zzz...zzzz....)

Tom / PM
post #48 of 58
Thread Starter 
Tell me, PM, could you judge a beauty contest?
post #49 of 58
(...I just know I'm walking right into something, but WTH... so he proceeds innocently onward with a straight face...)

Sure! Why? You got a job for me? For work like that, I wouldn't even charge my normal consulting rate.

Tom / PM

PS - Don't forget, I did jump right aboard on your side in that earlier thread after you introduced your gedanken experiment about the natives . I certainly hope you didn't take my recent reference to that thread wrong. It was an attempt at a self-referential, self-deprecating dig that I thought you would enjoy.

[ July 07, 2003, 11:53 AM: Message edited by: PhysicsMan ]
post #50 of 58
Thread Starter 
I just dug ya back, PM. I know you could judge a beauty contest.
post #51 of 58
Sz'okay.

... and all the time I thought you had a fun job lined up for me .

Tom / PM
post #52 of 58
Quote:
Originally posted by FastMan:
A 25 meter radius turn at 20 mph will have the same R angle whether steered or carved.
With this a a point of referance, I'll continue to season this stew a little with another example, on the other end of the skiing buffet from where our ultra-carve appitites have led our thoughts to indulge and feast.

Imagine we were to make a turn of constant radius, at some fairly moderate and constant speed, but using the absolute minimal amount of edge angle possible to accomplish the task. If we use the suggestion that inclination creates/represents our angle of edging, given the angle of the slope, in the bottom of the turn we could concievibly be inclined to the outside of the turn from vertical, as we used "reverse" angulation to maintain the minimal edge, yet still balance our CM enough to the inside of the turn against the lateral force component, however slight, that would be generated.

This example shows that the definition of inclination as the line of dynamic balance from CM to base of support as per its vector geometry/physics definition, and the suggested interpretation that inclination represents/creates our edge angle to be mutually exclusive concepts. This mis-interpritation of sameness results from a perspective unique, and limited to, high energy carving analysis, where they just happen to appear to represent the similar angles.

Similar logic(?) would imply the fahrenheit and celsius are always the same just because they are at -40.

So, my story (lacking any logic to warrent changing it) is:

Angulation reflects causing movements (to edge & balance).

Inclination as the resultant outcome (CM dynamically balanced).

:

[ July 07, 2003, 07:25 PM: Message edited by: Arcmeister ]
post #53 of 58
I was trying to find earlier articles in the archives for a friend to read and came upon something written by Bob Barnes;

"Another point, Rick: I don't think Harald would agree with you that he lets his center of mass dictate the tipping of his skis. I don't. Perhaps that's not what you meant to imply, and forgive me if I've misinterpreted you. But while the position and movements of the center of mass certainly do have a large effect on the edge angle of the skis, these are not something you can adjust for edge control! For any given moment in any given turn, there is a precise amount of inclination of the center of mass (tipping of the body) into the turn that results in balance. Any more or any less, and you are out of balance--it isn't something you have a choice in, and it isn't something you can control.

As you know, Harald is (quite rightly) big on movements that originate low in the "kinetic chain." That is to say, edging/tipping movements that begin with the feet and ankles--not with the center of mass!

So again, you are right that the location of the center of mass--the degree you are leaned into a turn for balance--has a large effect on tipping the skis. But it is angulation movements, primarily in the feet and ankles, knees, hips, and spine (preferably in that order) that CONTROL edge angle.

Best regards,
Bob Barnes

I thought this was an interesting perspective!
post #54 of 58
Quote:
Originally posted by Arcmeister:

This example shows that the definition of inclination as the line of dynamic balance from CM to base of support as per its vector geometry/physics definition, and the suggested interpretation that inclination represents/creates our edge angle to be mutually exclusive concepts. This mis-interpritation of sameness results from a perspective unique, and limited to, high energy carving analysis, where they just happen to appear to represent the similar angles. [/QB]
Arc, the similarity I was referring to was not a corresponding of R angle (resultant angle of force as dictated by existing levels of gravity and momentum) and edge angle. I definitely agree that there is typically a variance between R angle and edge angle. Even in carved turns alignment of the two is a rare occurrence restricted to very high speed turns. In most carved turns the R angle is less inclined than the edge angle, and some measure of joint articulation must be employed to move CM such that the R force vector is directed at the desired base of support so efficient balance can be achieved.

I never meant to suggest a similarity in R angle (PSIA's angle of inclination when skier is in balance) and edge angle, as seems to have been your interpretation of the material I presented. As you point out, such alignment seldom exists.

I believe your erroneous interpretation came from the following prior conversation:

===================
ARC SAID:
Angulation could occur without repositioning the CM to an inside position of balance, so balance does not necessarally occur from angulation (allthough it may), but from inclination.

FASTMAN REPLIED:
This is why I prefer the concept of defining inclination as the edge angle. When it is defined as the CM to center of pressure angle these tomato/tomoto debates can be legitimately introduced from both side because both sides of the argument are describing the same thing.
====================

Let me expand on my statement to provide clarity. The "SAME THING" I was referring to was the movement necessary to relocate CM to a position of balance (direct R to an efficient base of support). Whether called angulation by one camp, or inclination by the other, it's the same bio mechanical movement.

I think the important challenge is to move beyond nomenclature for the time being and get a firm grasp on the purpose for, and efficiencies of, the movements we are assigning names to. If the instructor clearly understands the relationship between turn shape, sidecut, speed, edge angle, gravity, momentum, R angle, body bio mechanics, and balance then developing efficient movement patterns in students becomes a much easier task, regardless the nomenclature PSIA or the individual determines appropriate to assign to the movements.

[ July 07, 2003, 09:27 PM: Message edited by: FastMan ]
post #55 of 58
Quote:
Originally posted by nolo:
Tell me, PM, could you judge a beauty contest?
OK, lets see if I can fiqure this one out. Natives of the Amazon Basin can identify expert skiing but they can't personally display it. PM can identify attractiveness but he can't ........... what??? :

Ohhhhhhh, I get it!!!

Better have some rounds under your belt if your going to hop in the ring with Nolo! [img]graemlins/thumbsup.gif[/img]

I'm keepin on her good side!
post #56 of 58
Tom, I did remember the Amazon discussion and got a healthy laugh out of your reference to it. I think Nolo was just joining in on the fun, she's has a good sense of humor and is pretty level headed, not prone to anger or emotional retaliation, as displayed often in her unbelievably patient interaction with Gonz. How many could do that?

Do keep up your occasional inserts of humor, your pretty good at it. This heady stuff does need lightening effect of humorous interjection every so often, it does tend to get rather dry. Someone has to provide some balance for the DESIRE TO NAP my presentation style creates!
post #57 of 58
Thread Starter 
post #58 of 58
She probably thought she was still dukin' it out with Gonz, and forgot that I completely supported her in her Amazon native analogy, so that if I was putting it down, I was putting myself down as well.

In any case, for those who might be puzzled about how Amazonians made it into the discussions on a skiing forum, here is the original reference:

Quote:
Originally posted by PhysicsMan on April 18, 2003 07:59 AM:

Nolo:> "...I could bring a resident of the Amazon rain forest to the base of any major ski area in the world and ask him to point out the best skiers on the hill and he would be able to do it with the same reliability as a Level III (maybe better, being unclouded by bias)..."

PM:> "I agree totally. I also think that the same native (as well as the rest of us) could rank order (ie, tell you which is the best, next best, etc.) a group of skiers with good reliability...
Actually, all I was trying to do by mentioning it in this thread was to generate some humor by hinting at some really obscure / academic-sounding topic that she and I both were familiar with, but which would sound absurdly / humorously / crazily / borrrringly academic to everyone else.

So much for my yard-sale like attempt at internet humor. I think I better just stick to physics and leave the humor dept. to Fox. Hey, at least I got the "obscure" part down pat.

Tom / PM

[ July 08, 2003, 12:45 AM: Message edited by: PhysicsMan ]
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