How Do I Turn?

[GrimSurfer]

I agree @lowangle al I also didn’t learn to Telemark on double camber skis or leather boots.

So Fish, you didn't learn on leather boots? That's all they had when I started in 85'. Coming from a xc backround I went with double camber skis. I had a couple pairs of single camber skis, but didn't have the experience to feel their benefits so I didn't stick with them. Same for the cable binding.

It took about 15 years to be able to make turns without needing enough momentum to flex the skis into an arc. Then I switched to a single camber ski with a cable, quit working (in the winter) and put it all together. It still took another 15 or more years to get over that overweighting of the rear ski and finally get perfectly centered.

It doesn't have to take 30 years to learn. With the right gear, good instruction and a season pass you could figure it out in a season. The good thing is, like sex, you don't have to be an expert to enjoy it. At least that's what I've heard.

I first went in 1971. IDK what I was on, but they felt like low top converses and they could have been on quadruple camber skis for all I know. We shuttled to a pass somewhere in Colorado and by the time I got to the bottom, I'd sat down so much I finally put my legs through the arm holes on my down vest to cover my butt, it was so cold!

You needed this… ha ha

[tkarhu]

Tip Pressure. IDK if this is an accurate term. After all, isn’t it easier to use weight to apply pressure to the ski tip on a double cambered ski?

Ball of foot pressure would be more accurate than tip pressure in my understanding. ”Tip pressure” has nothing to do with ski tips, more with toe tips, or what do others think.

With good technique you would pressure the ball of your rear foot, but with my stiff foot soles and NNN-BC tip pressure somewhat describes how the posture of rear foot feels. If binding is installed at balance point, rear foot will pressure ski base evenly.

Also, as a disclaimer, I just started to work on this just a few weeks ago, but tried to learn from others’ posts here.

Btw good that you ask @GrimSurfer. That lets us avoid misunderstandings, in cases we have different understandings of what words mean.

[TallGrass]

From Pictures, Pictures, Pictures…
viewtopic.php?f=1&t=527&start=1390#p55213

Why are the skis at different angles?
Why is there more “spray” from the inside ski?
Inside boot look not very pressed to the ski?
What is the significance of the skis being at different edge angles?
Just curious…

That's how you turn.
If both skis were parallel and equal in all aspects*, you'b be going "straight."

* Or opposed, opposite such as in a snowplow/wedge/pizza.

Are the front and rear tires of you car, bicycle, ... at the same angle (direction), same tilt (lean), and so on when they turn?

The "significance" is unequal forces, un-aligned factors leads to a direction change, an upsetting of inertia, the direction of momentum, what ever words you like.

For comparison, the front wheels on a car can differ in caster, camber, angle (toe-in), tread, tire pressure, rolling resistance (bearings or brakes), ... which can cause it to drift or turn or otherwise go non-straight.

How many can you list for skiing? And not just the skis (angle, direction, ...), but the skier too (muscles, joints, CG, ...).

And then there's all the surface (road or snow) factors like slope, resistance, ... and how the two interact.

It's kind of impressive that humans can tele ski like they do, especially if one tried making a robot do it and had to break it down to sensors, code and servos. Sometimes when they attempt things like that, it brings to light the actual mechanics involved when what they "thought" it took doesn't work with the robot until they discover what does or what was missing.

[GrimSurfer]

If this were a car, the inside ski would be angled into the turn more than the outside ski because the inside line is of a smaller radius than the outside line.

This is what is revered to as Ackermann in automotive applications.

https://en.m.wikipedia.org/wiki/Ackerma ... g_geometry

Insufficient Ackermann explains the spray from the inside ski… we’re looking at evidence of “scrub”. This is just like a car with insufficient Ackermann (which is common then the wheels are at full lock) will skitter one of the front wheels across sandy pavement.

So why is this happening, or effective, in skiing? Because that scrub on the inside ski is a form of “skid steering” (which is how tanks turn). Greater drag on the inside ski, relative to the outside ski, causes torque. This helps with the turn.

A snowplow turn works on the same principals I’ve described above.

The other thing that is certain is that there is no significant pressure being placed on the tips of either ski. If there were, more spray would be evident. Besides, look at the skier’s hips. That gives a clue where the weight is being applied along the ski.

[TallGrass]

Insufficient Ackermann explains the spray from the inside ski… we’re looking at evidence of “scrub”. ... scrub on the inside ski is a form of “skid steering” (which is how tanks turn). ... A snowplow turn works on the same principals I’ve described above.

Reminds me of "farm trucks" where the tie rods are loose, tires don't match, one brake occasionally drags, and so on, and yet despite all these things being off you're able to steer it where you want it to go and even go to town to pick up more supplies.

Tangent
I remember working a summer job in high school while riding in one of the work pickups, I asked why the window crank was sitting in the middle of the dash against the windshield and offered to attach it looking at the bare shaft on the passenger door. Co-crew moved his leg to the side a bit so I could see his door panel and said, "Then what would I use to roll my window?"

We then rolled up the windows (one at a time) as it was starting to rain, when some other crew pulled alongside in the other Ford yelling something, so I opened the door a crack (to avoid re-installing the crank) to hear that driver yell, "We need the window crank!!!"

The lone Dodge pickup was nice -- it had two cranks, and they weren't Ford compatible.
Well, it was until a new guy, despite being told to slide it in, tossed in a sheet of 4x8' plywood on top of the others which went quasi-aerofoil on the cushion of air, and instead of nosing in to the end of the bed it rose up and took out the rear windshield.

It's all physics, folks.

[Stephen]

If this were a car, the inside ski would be angled into the turn more than the outside ski because the inside line is of a smaller radius than the outside line.

This is what is revered to as Ackermann in automotive applications.

https://en.m.wikipedia.org/wiki/Ackerma ... g_geometry

Insufficient Ackermann explains the spray from the inside ski… we’re looking at evidence of “scrub”. This is just like a car with insufficient Ackermann (which is common then the wheels are at full lock) will skitter one of the front wheels across sandy pavement.

I understand Ackerman (catamaran rudders).
Skis are so close to each other that I think this is a specious assumption.
Also, if what you say is true, then the inside, back ski would have more spray to the INSIDE of the turn, rather than to the outside. So, even though the inside ski has too much “toe in” the skid is not throwing snow in such a way as to support that theory.

So why is this happening, or effective, in skiing? Because that scrub on the inside ski is a form of “skid steering” (which is how tanks turn). Greater drag on the inside ski, relative to the outside ski, causes torque. This helps with the turn.

I doubt that comparing ski turning to tank turning bears much fruit.
One can’t slow down or speed up the speed of the ski to cause turning.
Again, fully understand from twin engine catamaran - same as treads on tank or track dozer.

A snowplow turn works on the same principals I’ve described above.

The other thing that is certain is that there is no significant pressure being placed on the tips of either ski. If there were, more spray would be evident. Besides, look at the skier’s hips. That gives a clue where the weight is being applied along the ski.

Agree there seems to be not much tip pressure, maybe more heel pressure?
Back foot tip pressure would be generated by an “Active” binding. I can’t make out what the binding is, but the skier seems to be more on his toes than ball of foot. To me, this would imply less weight on that ski, and or that the binding is less Active and not resisting the boot hinging at the toes. An active binding will resist lifting the boot heel and cause the boot sole to bend more and the bellows to compress (causing “tip pressure”).
Also, it looks like the outside ski has more arc to it and the inside ski is less bent (more weight front foot, less weight back foot). As best I can tell, anyway.

[GrimSurfer]

Your specious assumption is just an example of simple geometry.

It is also betrayed by the photo. Look at the spray from the inside ski. It is greater than the outside ski. Why? Because it’s scrub angle (angle between where it is pointed and the direction of travel of the skier) is greater.

Simple geometry.

Perhaps more heel,pressure? Yes. I suspect so given the stance of the skier.

The truth is it takes many subtle things to turn. Including an imbalance of weight and an imbalance of forces.

[Stephen]

I think the inside ski has more spray because it is flatter, has less weight, and is skimming across the snow, which brush’s the snow to the side (skidding in the turn).
The outside ski looks like it has more weight, more edge angle, more curve, and like it is carving more than skidding, so throwing less snow spray.

The inside ski is pointed more down the fall-line.
Even though the two skis are in a wedge, like a snowplow turn would be, there is no snowplowing going on here.
The outside edge of the inside ski is engaged, not the inside edge of the inside ski, like in a snowplow.

[Stephen]

Because it’s scrub angle (angle between where it is pointed and the direction of travel of the skier) is greater.

Are you sure about that?
I don’t think so.
The skier is turning right, across the fall-line.
The inside ski is pointed relatively more DOWN the fall-line, not more across the fall-tine.

[GrimSurfer]

Because it’s scrub angle (angle between where it is pointed and the direction of travel of the skier) is greater.

Are you sure about that?
I don’t think so.
The skier is turning right, across the fall-line.
The inside ski is pointed relatively more DOWN the fall-line, not more across the fall-tine.

Uh huh. I’m sure.

1. Look at the picture… don’t forget that the skier is in motion. The left ski is leading the arc. The skier is turning right.

2. Look at the spray. The right ski is throwing up more snow. This is a sign of friction because the scrub angle of that ski is larger. Why? Because the right ski is pointed down the fall line but the skier is in a turn… in other words, the skier is in the process of crossing the fall line.

3. The inside arc of the turn is, by necessity, smaller than the outside arc. Yet the right ski isn’t angled into the arc of the turn as much as the left. Hence, the scrub. Hence the difference in spray that we observe.