Carving in the Steeps

[Max_501]

Another good shot:

[dewdman42]

All interesting photos... the question is...what was the "intention" or "purpose" for lifting the inside foot in each of those cases?

[Harald]

Have a look at my 12:11 post, end result more edge pressure.

[dewdman42]

so, (a) primarily to remove any doubt that the stance ski is getting all the pressure...and (b) there is a shift of skeletal alignment that happens by lifting the inside foot off the snow which helps move your CM more counter balanced (ie, angulated) more over the skiis ??? yes?

[Harald]

Picking up the ski sets up balance, , it can have the opposite action on the stance leg, extension, in slalom it transfers pressure from side to side faster. Yo get an immediate to the other ski pressure transfer.

[dewdman42]

Understood.

[j.clayton]

Great thread , all these ways of looking at a small part of a technique end up adding to the clarity of the whole . A nice parallel is Proust , a lot of detailed descriptions and digressions adding up to a clear picture of a character .

Another digression is the theme of PMTS being limited while PSIA's umbrella allows for a big bag of "tools" . PMTS is like a surgeons scalpel . With this you can perform works of art on the mountain , you can blend in much more effectively with the terrain and can actually feel this interaction taking place . ( actually I'm putting myself in Haralds , Dianas et. al . place , I still lack many skills needed but I'm optimistic ) . PSIA is like a kitchen knife , you can spread butter , balance peas on it or scrape at the roast beef but surgery , no way . But then Weems smiles a lot when he skis , so do I when I'm playing tiddlywinks with the kids . As for the Diamond system ?? , the biggest load of hot air since the Zeppelin . The most generous thing I could say about it is vacuous , like all that fake Yoga etc practiced in Vail .

Seriously , coming off my soapbox , PMTS has opened up the mountain like I wouldn't have beleived a couple of years ago . It's turned a struggle into a dance .

[François]

On a flat slope all of gravity is straight into the snow, and it's easy to turn a tight turn. On a 90 degree cliff face NONE of gravity is pushing into the hill and you cant carve anything

Au contraire, mon ami. Yes, gravity plays a part, but you can't count out the component vectors of the centripedal force that is causing the turn (i.e. the continuous inward-pointing force that causes you to follow a curved course). The centripidal vector is right up from the ski top thru your leg straight thru the Cg. The two components of the vector are (1) in shear to the surface and (2) normal to the surface. Shear force tries to break away while normal force presses you deeper into the surface. So all those g's you feel in the turn go towards (a) trying to breakaway and (b) digging deeper into the snow. Add in the gravity vector (itself having shear and normal components) and you get the final vector diagram.

At slope angles less than 45 deg the components of the gravity vector predominate "normal" to the surface (helping edge grip), but beyond 45 deg the shear vector get bigger than the normal vector and gravity is working against edge grip. In any event, it's the total shear strength of the surface that's going to determine whether or not you stay upright. But again, you've got to combine all the forces, not just gravity

Said in a simpler way: if "flatter" surfaces allowed "tighter" turns, auto race tracks wouldn't have banked corners.

(As a review, a vector is an arrow whose direction points along a force and whose length is proportional to the strength of that force. The components of a vector may be considered to be the two vectors that form the sides of the rectangle that has the original vector as its diagonal. If the rectangle is drawn so as one of its sides "lies on" a surface, then the "component vectors" measure the individual forces parallel and normal to that surface (this is called a "vector diagram"). Don't bother to bring up vector diagrams on the E..c forum, they'd rather believe in magic, instead).
.

Gravity acts downards.

That centripetal force that is driving up your leg has an equal and opposite reaction force that is pushing the ski, as you say, into the snow.
I do believe, given your knowledge of vectors, that if you consider two orthagonal components of that force, one sideways attempting to dislodge your skis edge, and one normal to the surface, you will discover (perhaps with the aid of a free body diagram of the skier) that the vertical component of that centrepedal force is equal to the gravity force, and on a flat slope this will be the normal force keeping pressing your edge down.

Yes race cars can go faster on banked corners, and you can carve tighter faster turns too provided your are turning downhill.

Long story short, gravity and momentum gang up on you at the bottom of the turn, and you don't have as much normal component of gravity to aid in the grip department on the steeps.


Sorry for the sidetrack.

Great photos!
Picking up the ski also adds an immediate dynamic component to the ege pressure on the other ski.

[NoCleverName]

vertical component of that centrepedal force is equal to the gravity force

Nah, a centripedal force on a flat surface doesn't have a vertical component, it's all inward pointing towards the center of the turning circle (i.e., just like an orbit). The only reason why centripedal is begin broken into components here (because it doesn't have components itself) is to analyze the shear force acting on the surface that's providing the resistance that develops the centripedal force in the first place (whew!). ... but you are correct that you have to add in gravity to figure the total shear (on a non-level surface). But the gravitational vector can't possibly contribute to the turning force since it's pointed the wrong way. It only figures in determining whether or not the snow surface can support the force being developed by the turn. ... My head hurts! Enough of this polluting this thread! But it's been fun.

We are really very close to saying the same thing, just quibbling over what for the moment really isn't an important detail.

At least people here actually care about proper analysis. Over on CIPE (I call them that because if you reverse what is said over there you get a fundamental truth) they'd invoke something mystical. They also have a hard time with long sentences.

[Harald]

Welcome back J.Clayton

[François]

Nah, a centripedal force on a flat surface doesn't have a vertical component, it's all inward pointing towards the center of the turning circle

Enough of this polluting this thread! But it's been fun.

I think we can agree. The force along the leg has a horizontal component causing the centrepetal accelerartion, and a vertical component resisting gravity. And I will stop polluting the thread now too.

[Harald]

Just wanted to clarify this point. When you can't see the forest for the trees you take after and talk about the nuances, not the glaring problems.

This example tells the story: Part of a long post I put up earlier.

When I was director of training at Winter Park, I had a whole fleet of PSIA trainers and examiners on my staff. They were constantly skidding and pushing the skis in the upper part of the turn. I told them to stop pushing the feet out to the side. They told me that they were instructed to get angles by getting the feet out away from the body as far as they could. I responded by telling them that you don?t get angles by pushing the feet away, you develop angles by tipping the feet and dropping the body into the arc. This was a huge deal. After some further coaching they began to understand and realized PSIA had been telling them everything backwards.

This is a major technical misunderstanding within PSIA. Do they repair or fix the damage? No they talk about whether or not we use steering in PMTS. This is again, I keep using this when referring to PSIA ?Ridicules?. Whether or not we use steering isn?t the issue, the issue is, if you are teaching it and it?s screwing up your own best skiers and teachers, why don?t you address it? They are a baffling organization and I know they have a back door escape just as esoteric in definition as the rest of their explanations of technique they don?t use. They can't even tell you what they do use and its affects.

By the way Level 6 in the PSIA progresion still has a wedge. And you have to practice it if you take a lesson from level 2 through 6 to perfect it before you can move on to parallel. We've come a long way baby.

[François]

Just wanted to clarify this point. When you can't see the forest for the trees you take after and talk about the nuances, not the glaring problems.

This example tells the story: Part of a long post I put up earlier.

When I was director of training at Winter Park, I had a whole fleet of PSIA trainers and examiners on my staff. They were constantly skidding and pushing the skis in the upper part of the turn. I told them to stop pushing the feet out to the side. They told me that they were instructed to get angles by getting the feet out away from the body as far as they could. I responded by telling them that you don?t get angles by pushing the feet away, you develop angles by tipping the feet and dropping the body into the arc. This was a huge deal. After some further coaching they began to understand and realized PSIA had been telling them everything backwards.

This is a major technical misunderstanding within PSIA. Do they repair or fix the damage? No they talk about whether or not we use steering in PMTS. This is again, I keep using this when referring to PSIA ?Ridicules?. Whether or not we use steering isn?t the issue, the issue is, if you are teaching it and it?s screwing up your own best skiers and teachers, why don?t you address it? They are a baffling organization and I know they have a back door escape just as esoteric in definition as the rest of their explanations of technique they don?t use. They can't even tell you what they do use and its affects.

By the way Level 6 in the PSIA progresion still has a wedge. And you have to practice it if you take a lesson from level 2 through 6 to perfect it before you can move on to parallel. We've come a long way baby.

I'm not familiar with any lesson system. I think I may have looked at a book way back when I first started,written by a woman perhaps, published prior to 1970 (I don't know how old it was when I got it). I think I used a "snowplow" between shusses on my first day on skis, and then a stem christie? for maybe a day and then on to banking turns on the third day adding in a "comma" shape for making turns at slow speeds.

Please tell me, is PSIA "Level 6" the typical PSIA student after two days on the hill?

[Harald]

A typical PSIA student even instructors, at level six or seven still have remnants of a wedge in their turns, they have probably skied three to five years, for some its twenty years, averaging about fifteen to twenty times a year. At least that's what we encounter with folks that come to PMTS, Harb Ski Systems camps.

With PMTS, beginner skiers are skiing level 4 or 5 by the second day. The third day they are parallel on blue terrain. This is from a survey done by Ski Area Management Magazine at Sol Vista three years ago.

Customer satisfaction from prior lessons, in this case PSIA lessons, to PMTS lessons, went up three fold.

[NoCleverName]

And I will stop polluting the thread now too.

We might want to start another thread where we explore some of the physics of skiing. I was just up to my ski club for a few days and amonst other things brought up my Feynman Vol 1 to refresh my dynamics which is very, very old and rusty.

Getting back into it a bit, I am beginning to see where some of HH's intuitive notions about how to ski probably have some solid physical reasons. Also, I think I see a possible program that would refute some of the CIPE "magic" ideas (in particular, rotary and steering). I believe it also might be important to study the "Harb Carver", which, while I believe it turns for a different reason than a ski, might provide a simpler model for studying the skier's energy budget.