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Inside ski pressure ? weight on inside ski - Page 2

post #31 of 121
Quote:
Originally Posted by epic View Post
What I have been looking for is to get him to push the base of the outside ski into the snow instead of chopping the sidewall down onto it.
I have seen skiers that end up pushing too hard and causing the ski to wash when we talk about pushing the base into the snow. Sometimes changing the focus to pushing the sidewall edge into the snow fixes that problem.
post #32 of 121
I think it is less confusing if discussed in terms of active and passive pressure. To apply pressure requires an application of a force. In the case of a skier, the force that drives the pressure created on the snow by the ski either comes from the weight of the body pressing down onto the ski(passive pressuring), or it can come from the use of the musculature in the legs and feet to apply pressure(a force) to the ski while un-weighted, or partially un-weighted- active pressure. Passive pressure is necessary for balance - it acts as the platform on which all active pressure movements take place. Active pressure is necessary for control.

A dominant weighted ski acts as a platform to control the application of active pressure in the partially un-weighted ski. If both skis are weighted, it is more difficult to apply active pressure to both skis simultaneously in the proper amounts to retain control in a turn.

I would try to reason with the student in this manner. Active pressure is something you apply to the inside ski to keep control, or the outside ski to tighten up the turn. Passive pressure is simply the static weight of the ski/skier combo pressuring the snow. As the outside ski is acting as he platform, you don't need a lot of passive pressure on the inside ski to keep control and balance - the outside ski is keeping you on your feet.
post #33 of 121
Thread Starter 
Quote:
Originally Posted by Max_501 View Post
I have seen skiers that end up pushing too hard and causing the ski to wash when we talk about pushing the base into the snow. Sometimes changing the focus to pushing the sidewall edge into the snow fixes that problem.
Maybe, but that's not the problem we were having.
post #34 of 121
The other variable here is speed. Slower turns you need to be more two footed.

I guess we all know that. The weight on either ski varies between 50/50 to 1/99.

I like your second paragraph MojoMan.
post #35 of 121
Words in English are very versatile, more versatile than most single individuals.

A "weighted" average has nothing to do with the force of gravity, though it may affect the gravity of your report card.

A force is a push or a pull.

Pressure is force divided by area, pounds per square inch for example, but many non-physics-type people use "pressure" as a verb meaning to increase the pressure on a surface by applying a force.

Force is a vector; the net force applied to the ski will act in a certain direction. Like any vector it can be broken down into cartesian coordinate directions, with a vertical component and a horizontal component. When considered this way, the vertical component is seen to be directly affected by weight, which is strictly speaking the pull of gravity that always acts in the vertical direction.

However many people substitute the term "weight" to mean total force without regard to direction.

In order to communicate with your client you have to figure out what he means by the terms or make sure he understands you definitions. It's more important that you understand each other than that your usage is strictly correct.


It could be he was being "physically" correct and meant that with no weight at all on the ski it would not have enough grip on the snow to decamber without sliding. Who knows?
post #36 of 121
Pressure or weight? I try to not use either if I can avoid it. Instead I focus on how to move the body to produce an effect. Even then we cannot avoid the terms completely.

For example: A weighted release is a common term that has been around for a long time. What is most important in this maneuver is that there is no unweighting of the ski. It is important to note that we aren't really talking about static weight though. Nor can we say that the pressure remains the same once the edge is disengaged.

Another example is the idea of allowing the pressure to build up during the turn(s). Common idea but is it just pressure or is it weight being modified by g-forces?
post #37 of 121
Quote:
Originally Posted by michaelA View Post
Skier219 - nice breakdown. You mention 'pressure' as being the wrong word to use. Is there any other term that might work? Perhaps the real issure here is 'pressure' aganst the Base vs. 'pressure' against the Sidewall of the ski (on that inside-ski)?
I think we have to be careful using the words pressure (force per unit area) and weight (force), just because they mean different things in their most fundamental definition.

Here, we tend to used the words as verbs, as in "to pressure the ski" and "to weight the ski". But we're not saying "apply force per unit area" in one case and "apply force" for the other. We're using the words as two different ways to say "load" the ski in a generic sense. In reality, it might not matter at all, as long as weight and pressure don't get confused with their real meanings.

When I looked into the mechanics of edging (which I hope to post here soon), skier inputs are simplified down to two forces on the ski edge (one vertical force aligned with gravity, the other lateral force aligned with the turn radius) and a torque about the ski edge. The vertical force is a function of skier weight, the lateral force is a function of the velocity and radius of the turn (centripetal force), and the torque is a function of ski angle relative to the snow. The skier can vary all of these via muscles.

You could combine the two forces such that there is one resultant force at the edge and then the single torque. Those are the simplest two inputs a skier can put into the edges. Whether you call it weight, pressure, angulation, whatever, it comes down to a single force and a single torque. Those are the things a skier can input to the ski.
post #38 of 121
Quote:
Originally Posted by Max Capacity View Post
The other variable here is speed. Slower turns you need to be more two footed.
I ski just fine going very slow with all of my weight on just one foot.
post #39 of 121
Though I am all for keeping it simple, only if the basic terminology is used accurately can it be kept simple. And I'm sorry to say that even Bob B's dictionary has not seriously improved the common and accurate use of most ski terms. Because even within that tome there are multiple interpretations by each reader.

While it IS engineering, and can be described as a function of basic physics, there are certain facets which contribute to the confusion.
I might guess the primary source of confusion lies in the fact that both weight and pressure tend to be measured using the same unit. Though they might be qualified by "lbs" vs "lbs per sq inch", it's the "lbs" thing which creates the gray area. Most do not fully appreciate the significance of the "per sq inch" aspect.

But in the context of keeping it simple, I have always had luck using a practical description. "Weight" is generally static, while "pressure" is usually dynamic.

In using this description, most of the skiers I have trained have managed to differentiate and become more discerning of how they identify the actions and activities which create either of these two ideas.

Many of the ideals expressed earlier in this thread have merit and I respect them as written, while others are pretty far off the mark and they are what I find comical. Maybe Jay, Conan, Jimmy, and David are still looking for some writers to cross the picket lines?
post #40 of 121
Just as confusing as miles and miles per hour?
post #41 of 121
Quote:
Originally Posted by Max_501 View Post
I ski just fine going very slow with all of my weight on just one foot.

All though that may be true. Do you ski that way all the time?

I didn't think so.

What I'm trying to get across to you PSIA guy's is, don't over think this.

The average skier really doesn't care about all your PSIA theory. I know you guys enjoy discussing it, hopefully as a way to increase your bag of knowledge.

May be what can come out of this discussion is a better way to uniformly teach the difference between the two.

I hope you guy's don't take this the wrong way.

I'm a big fan of people taking lessons to improve there skiing. As a Mt Ambassador I try to suggest taking a lesson whenever it fits into my interacting with guest.
post #42 of 121
Thread Starter 
Quote:
Originally Posted by Max Capacity View Post
What I'm trying to get across to you PSIA guy's is, don't over think this.

The average skier really doesn't care about all your PSIA theory. I know you guys enjoy discussing it, hopefully as a way to increase your bag of knowledge.
Ha HA. I had to quote this and save it for posterity. Max 501 got called a PSIA guy. Carry on people, there is a foot of new snow on top of my car. : See y'all later. :
post #43 of 121
Seems to me that "perception" is another important consideration for this discussion. Many people perceive increased pressure as increased weight on a foot. These discussions imply to me that many skiers AND instructors don't completely understand the "true" difference between weight/pressure/force and furthermore don't always consider that individual perceptions may be unable to differentiate between them (at least until such concepts are better clarified). On slope I would think it's critical to link a skiers perceptions with what they are doing to initially understand what they are saying. There is nothing wrong in working to change those perceptions so that they match the actual case but I would think it is not always necessary or advisable. If you don't consider a poster's perceptions carefully, there is a good chance you will misunderstand what they are saying.
post #44 of 121
Does it help if the focus is on where the skier is balanced...over the outside ski, the inside ski, or somewhere between the two?
post #45 of 121
Quote:
Originally Posted by Max_501 View Post
Does it help if the focus is on where the skier is balanced...over the outside ski, the inside ski, or somewhere between the two?
No. Of course not. Thats just crazy-talk.
post #46 of 121
Quote:
Originally Posted by epic View Post
Ha HA. I had to quote this and save it for posterity. Max 501 got called a PSIA guy. Carry on people, there is a foot of new snow on top of my car. : See y'all later. :
Go ahead Eric, rub it in. :

I'll be back on snow Saturday AM.
post #47 of 121
Quote:
Originally Posted by Max_501 View Post
I have seen skiers that end up pushing too hard and causing the ski to wash when we talk about pushing the base into the snow. Sometimes changing the focus to pushing the sidewall edge into the snow fixes that problem.
I think this is one of those "A-ha" moments and possibly a "duh" moment for me! To get the edge to really engage and get carving, push the edge into the snow! I think I've been pushing the base out to push myself into a turn and therefore skidding every turn so far.

A little too late to get to a hill today though

(sorry to interrupt )
post #48 of 121
Weight is just that -- I have about 125 pounds to work with, and if I put more weight on one foot, there necessarily is less on the other. Pressure seems to imply whatever is pushing against the bottom of my feet. Weight is one component, but also speed, steepness of the slope, amount of edging, etc.

Even though I'm trying to learn or refine movements, so there's a lot of time consciously thinking "do this", I try to keep aware of pressure while skiing -- how much and where under my feet there is pushing. An awesome ski instructor showed this to my husband and me on a chair lift ride by having us gently slide a ski back and forth on the little support for skis. It was amazing how even with almost no weight on your foot, you could feel through the ski and boot exactly where the little bar was under your foot.

Even with less advanced students, it doesn't seem like a good idea to use weight and pressure interchangeably -- simplification is great, but not at the price of inaccuracy, which is likely to lead to confusion later. It took me an embarassingly long time to understand the difference between balance and weight -- how your body moves downhill at the start of a turn without weighting the downhill ski. It really wasn't until I read Lito's book (which I heard about while lurking here) that a light bulb went off. A part of this confusion was due to only getting part of the picture at a time (like, move your hips downhill across the skis) in the interest of simplification. Kind of like the blind men trying to describe an elephant -- one feels the trunk and says an elephant is like a rope; another feels a leg and thinks an elephant is like a tree trunk; etc.

DEP
post #49 of 121
Well now,how to describe this...

Weight is variable in a dynamic environment. Especially when we start to talk about lateral acceleration and dynamic motion. A high G turn certainly requires us to resist more force than our static body weight.
For example: 125# at 3g's is 375#. Which is why I don't subscribe to the idea of limiting the term to a static measurement.
There are countless terms but the bottom line is that we are moving our body in such a way that we change how the skis interact with the snow. Which in a shorthanded approach means we are changing our stance to change what the skis will do as they slide across the snow surface. It is the movements we should focus on, not the semantics.
post #50 of 121
One drill i like to help get a feeling for and understand how pressure affects skiing is to make a series of turns on an easy gradient. First set of turns are made by focussing on steering by only adjusting edge angles keeping pressure as light as possible. the second set is done by purely adjusting pressure...

By isolating one or the other you "feel" the effects more.
post #51 of 121
Of course you need to weight your inside ski to apply or create pressure. That does not mean you have to reposition your upper body.

Check this out for some good definitions:

http://en.wikipedia.org/wiki/Pressure
http://en.wikipedia.org/wiki/Weight
http://en.wikipedia.org/wiki/Apparent_weight

It's a good place to start.

However, since this is about skiing, where words are plastic, people tend to equate the terms "apparent weight" and pressure. Which is where the confusion begins.

Nonetheless, it is simply not possible to create pressure on your inside ski without transfering some weight to it. Pulling the foot back to pressure the inside ski is similar to insereting a "shim" under the inside leg. It will bear more weight.

Proof:

Pressure = Force/Area.

Force = Mass x Acceleration (Where Acceleration as the vector sum of all forces acting on the skier -- the resultant acceleration vector if you will...)

So Pressure = Mass x Acceleration/Area.

Which means that the pressure on a ski is directly proportional to the mass it supports.

QED.
post #52 of 121

which ski turns first?

in a true carved turn, the inside ski turns fist (or they turn simultaneously). so, in my opinion, it should have some weight on it.

if "all" the weight is on the outside ski, where does that weight go
at neutral/transition , ie when starting the next turn? (since the new outside ski is uphill of the old outside ski at neutral)
any "x / 100 - x" values can be debated (90/10, 80/20) but for me
more "two-footed" is better and allow the center mass to flow more
directly down the hill.


as to weight / pressure, i think of weight as what i bring to the equation,
and tends to be directed mostly downward, (and doesnt require the turn
dynamics to stay standing)

and when i think of pressure
i think of either my stance < where the boots hold me "in">
pressure the tips by being taller / forward

or

the forces built up by my inertia being in one direction
and the shape of my skis causing me to move in a different direction.
(and i do need the dynamics to hold my position)

brad
post #53 of 121
E, I'm not sure why you think repositioning the foot is not included in my statement about stance. Any movement that changes the alignment of the body (position relative to the skis or the snow) changes our stance.
It goes without saying that moving the contact point does that.
Brad,
Weight is a measure of gravities attraction, it is pulling us towards the Earth. When we are in contact with the Earth we feel pressure throught the contact patch. While I agree that when we are lying down we still weigh the same, that is outside of the context of skiing (unless you are lying on the snow which we are trying to avoid). Standing on the other hand, requires us to resist that attraction and we do that with our legs because we want to keep our torso off the ground.

So lets move that into a dynamic environment. All of this mass moving create momentum. Both angular and linear momentum. How we manage momentum and the outside forces we encounter while moving defines the turn that is created. So having said all of this the most important questrion has still not been addressed!
How do we manage this? BY MOVING ALL OR PART OF THE BODY. WHEN WE DO THAT WE ARE MODIFYING OUR STANCE UPON THE SKIS OR OUR POSITION RELATIVE TO THE GROUND. So to be more correct we should use momentum as the term to describe what you said in the last paragraph. To me I can do that and if I need to I do exactly that. However, if a student gets the concept without adding another term I need to define I don't see the need. If weight works for them, let it go!
post #54 of 121
Not sure there is a final answer to all of this. Weight vs. Pressure and the words we choose when delivering the idea to others is a matter of personal understanding.

So long as a given instructor mulls over all these ideas and comprehends the various perspectives I suspect they’ll do just fine selecting their own ways to provide instructive information to students. An interesting sidebar to this is yet another interpretation of ‘pressure’ - one related to the perception of pressure that is actually just muscular stress.

From an internal perspective we ‘measure’ pressure by sensing it. The more sensory input we have, the more pressure we perceive. But what happens if we compare our perception of pressure in a structurally strong position to that of a structurally weak position?

A person standing well stacked against their skis in a high G-Force turn will experience the feel of high pressure on the soles of their feet. If that same skier then uses an overly flexed stance they’ll feel tremendous stress on many muscles and probably perceive a far greater pressure than really exists in that same turn.

---
JASP,

I’m in general agreement with the idea that we actively manage pressure by making movements but I think there's one other mechanism we can use without any movement at all: Time. A skier in motion holding onto a given position (making no active movements at all) can permit under-ski pressure to change over time (I believe that still counts as active/conscious management).

We can easily manage pressure thru timing as when the slope-angle is changing and we make no active movement to increase or decrease the pressure-change effect this will have on us. This ties in well with your comments about the role momentum plays. In fact, this ties back nicely to Inside-Ski pressure issues from the “multi-segmented” body point of view.

Each individual leg represents perhaps 20% or our overall body weight. A skier making a turn need not “put” weight onto that leg for it to create pressure (on its own) under that Inside-Ski.

Unless we actively lift that leg to transfer its weight to the other ski, the Mass of that leg & gear will be supported by its own ski. This means that 20% of our body weight is automatically on our Inside-Ski - unless we actively prevent it by lifting that leg/ski thru muscle activation!

So, I’ve a question for those of you who advocate 100% (or 99% or even 90%) on the Outside-Ski… Do you actually activate a bunch of muscles to lift weight off that Inside-Ski in every turn? Or do you just not ‘put’ any extra weight on it (leaving that ski with only leg & gear weight on it)?

Seems to me that activating a bunch of muscles to lift (or lighten) that leg/boot/binding/ski would not be as efficient as just letting that leg and gear rest on that ski.

.ma
post #55 of 121
Quote:
Originally Posted by michaelA View Post
So, I’ve a question for those of you who advocate 100% (or 99% or even 90%) on the Outside-Ski… Do you actually activate a bunch of muscles to lift weight off that Inside-Ski in every turn? Or do you just not ‘put’ any extra weight on it (leaving that ski with only leg & gear weight on it)?
Its depends on what part of the turn we are talking about. At release I do one of two things...(i) in a SL turn I'll actively pick the ski up or (ii) in a larger radius turn I'll simply relax the stance leg muscles. After the release I actively retract the inside leg to get it out of the way for the angles I'm creating by tipping. So, yes, muscular movement is involved with the way I manage the inside leg, yet I can ski all day, so I don't think of it as being inefficient. I think the key is that I let the long and strong outside leg carry the majority of the forces generated during the turn.

As far as pressure vs weight. What happens if we ask the student to increase pressure on the ski?
post #56 of 121
Max you still need to tell them how.
Mike not responding to terrain variations works as long as we remember that we are not seeking a static position on the skis. So IMO not continuing to move would not be something I would use very often. Mostly because I firmly believe in constant movement.
post #57 of 121
Hmmm... guess that sounds reasonable Max. Didn't mean to imply that an inside leg-lifting movement was 'inefficient' - rather just not as efficient as not doing so.

If a necesary gain in 'lateral toppling speed' is achieved to a specific purpose then I've no issues with the idea.

In a short SL turn I can see where a skier might want to actively lift that new inside leg to use that leg-Mass to help pull them over (laterally) if they're not quite in the best starting position to get far enough over fast enough to deal with the CF in that next turn.


JaSP, I neither seek a static position nor do I seek to 'always keep moving' just to be moving. Movements I make are (hopefully) to a desired purpose. If upcoming terrain will provide all (or most) the re-positioning of Mass I will need, then more power to it. Letting Centrifugal Force transfer my weight onto the new Outside-Ski well after turn entry lets me lollygag into that new turn while remaining on my old Outside-Ski. Nice way to catch quick catnaps while skiing...

.ma
post #58 of 121
Mike, Allowing the terrain to do most of the work is a great idea. It goes along with learning to read the terrain on the fly and exploiting what the mountain gives us. What's most important to me is that they understand the variability of each turn and that to remain static at any part of the turn require us to be more active subsequent to the "nap".
post #59 of 121
I've recently started initiating my turns using the inside ski; i.e. if I want to turn left, I tilt the left ski onto it's outside edge, and then follow a fraction of a second later by rotating the right ski onto it's inside edge.
Doing this I've been able to initiate my turns much faster, with more control, and shift back through a neutral position to turn in the opposite direction much faster, with less effort.
This is the opposite of what I've been doing for years.

As far as pressure vs weight; when I put pressure onto one ski I'm invariably putting some of my weight onto it. Maybe that's just a problem I have with my balance.
post #60 of 121
I will try not to ramble
Ski on your outside ski. It should get all your weight. Both skis should do the same thing in the snow, skid or carve. Pressure happens between the ski and snow interaction. To feel that pressure your inside ski needs to be controlled and under your center. Too far ahead and you lose shin contact hence pressure. Too far back and you get too much. The problem happens when you try to put weight on your inside ski the tendency is to shift your body inside and hence you loose balance against your outside ski.
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