It’s not Stupid

[SSSdave]

BINGO!

Glad you discovered this as a teaching method. I’ve begun to use more skating in beginning lessons. Get your student on short skis and start playing. People learn by doing and the more doing you incorporate into your lesson the faster people learn. Short skis (120 to 135 cm), flat terrain or very gentle terrain, then skate. They will feel how the ski interacts with the snow. I’m a big proponent of direct to parallel and allowing wedges to happen.

Not an instructor nor familiar with what ski instructors are doing with beginners in this era. Never heard instructors are now starting with skating though unclear what that actually is however that sounds like stepping sliding around. Years ago trained an athletic friend to ski linked turns on the first day by first spending quite some time walking around on skis at a resort's uneven though generally flat base area. I did that because I wanted him to naturally discover by himself how skis and edges while confined in ski boots feel by stepping movements. So we went up and down slight hills stepping about in all ways that soon led to being familiar with adding increasing sliding with each step.

I also had him practice side stepping using edges as a way to climb up inclines. I didn't need to explain how he needed to do anything with his ankles to keep an edge because that was discovered naturally. The human foot and ankle make many subconscious movements to maintain balance as we step over uneven surfaces and a person can become familiar with how skis react on their feet likewise. At first for awhile it is just like getting on ice skates for the first time as a person wobbles around discovering the awkward feelings.

After that I went to taking the left right left stepping to slight downhills where I made him step slide straight down the hill keeping his body oriented forward as we do when walking continuing and slowly adding the feeling of bouncing on the skis like one would do at the center of a trampoline. Only bouncing at the center of a trampoline or with kids at the center of a 2x4 spanning bricks at each end gives an up centered balanced bounce. After that I had him follow in back of me as I did likewise adding increasing turning. He had to work through other things of course and recall leaving him at that point on the beginner lift, but the key thing is I had him making linked turns bouncing on the rebound of his skis while usually facing down the hill that requires lower and upper body separation. I didn't need to explain his lower and upper body were twisting as that developed naturally.

 

[karlo]

Not an instructor nor familiar with what ski instructors are doing with beginners in this era. Never heard instructors are now starting with skating though unclear what that actually is however that sounds like stepping sliding around. Years ago trained an athletic friend to ski linked turns on the first day by first spending quite some time walking around at a resort's uneven though generally flat base area. I did that because I wanted him to naturally discover by himself how skis and edges feel by stepping movements. So we went up and down slight hills stepping about in all ways that soon led to being familiar with adding increasing sliding with each step.

I also had him practice side stepping using edges as a way to climb up inclines. I didn't need to explain how he needed to do anything with his ankles to keep an edge because that was discovered naturally. The human foot and ankle make many subconscious movements to maintain balance as we step over uneven surfaces and a person can become familiar with how skis react on their feet likewise. At first for awhile it is just like getting on ice skates for the first time as a person wobbles around discovering the awkward feelings.

After that I went to taking the left right left stepping to slight downhills where I made him step slide down the hill keeping his body oriented forward as we do when walking continuing and slowly adding the feeling of bouncing on the skis like one would do at the center of a trampoline. Only bouncing at the center of a trampoline or with kids at the center of a 2x4 spanning bricks at each end gives an up centered balanced bounce. After that I had him follow in back of me as I did likewise adding increasing turning. He had to work through other things of course and recall leaving him at that point on the beginner lift, but the key thing is I had him making linked turns bouncing on the rebound of his skis while usually facing down the hill that requires lower and upper body separation.

I think learning off-ski’s is great and the best. Unfortunately for instructors, parents are typically looking on at the beginner area and expect to see their kids on skis. Adults also expect to be on skis. I’d spend an entire morning off skis if I could.

 

[Chris V.]

Skis and CoM travel along different paths. Skis go farther left-right, and speed up and slow down when doing that. The slowing down of the skis happens when they travel across the hill in the bottom half of the turn.

We can allow our CoM to continue to travel across those skis as they slow down. Then the line the CoM takes is shorter and less "offset" than the line the skis follow. The question is whether it maintains its speed or not as it goes across and then down then across the hill.

In turns that are not completed, where the skis barely turn across the hill and do not take the skier very far left and right, I suspect if someone were to track the speed of the CoM it would not slow much, if at all.

The magnitude of oscillations in speed will differ depending on the kind of turn being made, for sure.

One could measure speed at various points in the turn cycle from super slo mo video. But that wouldn't be as much fun as debating.

The COM takes a shorter path than the skis. Nevertheless, the COM's path is also S-shaped, with the the point at which the COM is traveling straight down slope approximately matching the point at which the skis are doing so.

Again, in the top half of the turn, the COM is giving in to gravity pulling the skier down the hill, and there's little to create any slowing force. Hence, speeding up, unless I'm missing something big. Hence, unless the skier is going to reach terminal velocity, something must be slowing the skier's COM in the bottom half of the turn. That's also the part of the turn cycle where we experience greatly increased forces pushing back on our skis. We absorb potions of those forces with our muscles, something we feel strongly when making dynamic turns. If we didn't do so, our COM would vault right over our skis and become airborne. Wait, maybe that's happened to me a time or two. And I think that's what's been behind some of the more spectacular head' first World Cup crashes we've seen.

 

[Rod9301]

ummm no your COM moves inside you BOS on both.....


freeze a picture and prove me wrong.

 

[karlo]

something must be slowing the skier's COM in the bottom half of the turn

The skier’s COM would slow, unless the COM is propelled by such skier, as @LiquidFeet described, over the skis.

See this post and video,

https://www.pugski.com/posts/385514/

The mogul skier’s COM can go closer to constant velocity than one might first imagine. Absent moguls, the control can even be better. Maybe think of it as a long distance runner. COM and the head appears to be going at constant velocity, much more so than when walking or jogging. Though, speed walkers have pretty close constant velocity of COM

 

[Chris V.]

I acknowledge that speed oscillations will be much reduced in linked very shallow short radius turns, as seen at the start of the video.

I've expressed myself the best I know how, so I won't further belabor the point.

 

[Josh Matta]

So COM isnt to the looker's left of the bottom contact point of the wheels? That seems like the COM is inside the BOS in that picture,

 

[karlo]

I acknowledge that speed oscillations will be much reduced in linked very shallow short radius turns, as seen at the start of the video.

I've expressed myself the best I know how, so I won't further belabor the point.

Going back to the OP, both types of linked turns, ones for which COM alternately accelerate and decelerate, and those for which COM approaches constant velocity, the point is that projecting our COM over the ski and down the hill imparts control. Perhaps showing a learner that mogul skiing video, along with that game show video, is a good way of making the point.

 

[LiquidFeet]

...Again, in the top half of the turn, the COM is giving in to gravity pulling the skier down the hill, and there's little to create any slowing force. Hence, speeding up, unless I'm missing something big. Hence, unless the skier is going to reach terminal velocity, something must be slowing the skier's COM in the bottom half of the turn.....

Well, there you go - perfectly logical reasoning without any holes in it that I can find. So, once snow FINALLY gets on the slopes here in New England (it's coming), this is one to play around with ... to pay attention to and feel the oscillations in speed that the CoM experiences during various types of turns.

 

[karlo]

Well, there you go - perfectly logical reasoning without any holes in it that I can find. So, once snow FINALLY gets on the slopes here in New England (it's coming), this is one to play around with ... to pay attention to and feel the oscillations in speed that the CoM experiences during various types of turns.

I know I am perhaps belaboring the point, having mentioned it in other threads. But, there is that indoor ski center opening in NJ.

 

[LiquidFeet]

^^ @karlo, don't go there.

 

[karlo]

^^ @karlo, don't go there.

I can’t help myself. I plan on being there on opening day, or as close as possible to that, December 4. Help me!

 

[KingGrump]

I can’t help myself. I plan on being there on opening day, or as close as possible to that, December 4. Help me!

If you are that hard up for skiing. Take a short drive up to SVT. Most hills in SVT should be open by then.
The long term solution is still get the **** out of Jersey.

 

[geepers]

There's a small a difference I guess. A high slide only occurs when the body did not move inside too much and the tire regains grip - when it does move inside a lot, the low side can't be avoided.

On skis, at least theoretically, you can find grip even when the body is inside a lot, say hip to snow.

I would say there's quite a big difference between falling a couple of feet on to the road (even if it is going by at 88ft per second or more) and being pole vaulted upside down over the motorcycle and smashed down on the road with an extra helping of angular momemtum.

I notice that some of the MotoGP riders have managed to recover from their elbow/knees/bike dragging on the ground. Seems to have become SOP for Marquez...

 

[razie]

yeah,

I would say there's quite a big difference between falling a couple of feet on to the road (even if it is going by at 88ft per second or more) and being pole vaulted upside down over the motorcycle and smashed down on the road with an extra helping of angular momemtum.

I notice that some of the MotoGP riders have managed to recover from their elbow/knees/bike dragging on the ground. Seems to have become SOP for Marquez...

cool video... they recover by separating more from the bike and allowing the bike to stand more upright and regain traction - you seem him doing just that in the slow mo... good separation is key

he's shifting the hips more inside and has to release the outside foot to allow that and the bike to stand up more. I have to do the same, not because of the big angles, but because I've never adjusted my pegs properly - they're in a standard/adventure position

I know they sometimes are also able to pickup the bike with the sliders, I never got so low , so that would be a theoretical discussion for me... I could never save a low side on a bike, but I see it - I saved quite a few on skis though, same principle: increase separation, except on skis you want bigger angles to regain grip, so you move the body outside, not inside

cheers

 

[geepers]

Actually, in mtb you move the com (butt) to the outside of the turn, to lean the bike.

We incline the bike

yeah,

cool video... they recover by separating more from the bike and allowing the bike to stand more upright and regain traction - you seem him doing just that in the slow mo... good separation is key

he's shifting the hips more inside and has to release the outside foot to allow that and the bike to stand up more. I have to do the same, not because of the big angles, but because I've never adjusted my pegs properly - they're in a standard/adventure position

I know they sometimes are also able to pickup the bike with the sliders, I never got so low , so that would be a theoretical discussion for me... I did not have to save a low side, but I see it

cheers

Back when I rode bikes (70's/80's) the limit to lean angle, assuming adequate tire grip, was whatever came in contact with the road. Typically foot rests, exhaust pipes and on some of the inline 4 cylinder bikes, the engine. I wore a hole in the crank case of one of my bikes just going around corners. Was a pita to repair as aluminium welding was not that common in those days.

To some extent the contact could be delayed by moving body parts inside the turn - dangling inside knee, butt on the inside of the seat - although we didn't do it as much as they do today. It was also possible to stretch the envelope a little by jacking the rear wheel around on whatever was in contact with the road - as long as the road was smooth enough!

@Rod9301

So COM isnt to the looker's left of the bottom contact point of the wheels? That seems like the COM is inside the BOS in that picture,

The CoM has to be inside the turn otherwise the rider wouldn't have any centripetal force to counter momentum.

Yes it may be possible at low speed to keep some part of the body vertically above or outside the contact line of the tires if the speed is very slow and the body is contorted enough. But Center of Mass has to be inside the turn for any speed above zero.

 

[razie]

@geepers I only play hard with bikes in the dirt now - it's easier on the body and the bike...

having said that, it's very interesting that, when looking for grip, we lean body inside and bike outside for road bikes and body outside/bike inside for dirt (and skis). The difference is how traction is created and how acceleration and torque/leverage affects that. It's a nice puzzle.

 

[geepers]

@geepers I only play hard in the dirt now - it's easier on the body and the bike...

When I was 25 it generally hurt every time I came off a motorcycle. Road or dirt. Conversely seemed to be able to take a tumble on snow and generally come up laughing.

Some decades later it seems to hurt enough falling over on skis - not every time but often enough - and I have no desire at all to see how much it hurts coming off a motorbike!

 

[Rod9301]

Here's a picture that shows the butt and your body on the outside of the turn, and the bike leans

Of course, to counteract the centrifugal forces, the entire body has to be on the inside of the tire patch.

I was just saying that noonish biking is different than skiing.

In skiing, the hips are more inside, while in mountain biking, they have to be more outside, to get the bike to lean.

The angulation is 180 degrees different.

Can't upload the pictures but here's a video.

 

[karlo]

and this is inclination?