Physics debate

[Telerock]

This discussion (ad infitium) has a basic assumption that I contest. In my limited experience, using extreme leather boots and 3_pin bindings, with and without spring cables, the tip (Bent up forward end) of the ski has no bearing (no pun intended) on a turn. Instead, it is the center of the ski, when one puts his/her weight on it (excepting my 2.5 camber 210 straight skis); and the left/right angle (cut or carve) that forces the turn, with the primary force applied by my bent toes under the foot and extending the length of the ski (apologies for the run-on sentance). That is, ideally, with even weight between the skis, my forward foot, flat on the ski starts the turn, and the back foot, toe-only, presses down and towards the outside of the turn. In my best form, the skis are close and near (not precisely) parallel to each other; leaving a “sible track’.
The form and forces are the same, reguardless if cables are used or not. Cables do help by providing lateral (Sideways) force for the carving by enguaging the heel, as well as the semi-flexible toe/vibram sole.
That said, I have not used other bindings.
However, since the rear foot, which is “up” and connected only by the toe/ball of the foot needs only to apply force down, and sideways to the outside of the turn; I do not see the advantage to “ active bindings”as various defined here, except to support the heel in twisting/sloping/bending/carving the ski so it edges.
In short, the sole (no pun) pupose of the front of the ski, with telemark, it to prevent diving into the snow. The turning is controlled by the edging near and under the foot. Downward and outward pressure with the toe/ball of the foot is sufficient unto the day.
Happy Trails.

[DG99]

No offense to Tom, and I understand the "I like to think there's a bit of magic* " appeal, however a ski with a scale on either end being 1. pulled into a wall by 2. a person pulling a tether who's standing next to it, is not going to get "closed system" results due to said "open system" interference. Similar results would occur with an alpine binding (fixed heel), or 6-foot 2x4 with a string pulling forward on a 1-foot block bolted to the middle. Barring single-ski teleskiing, a better set up would be four (4) scales supporting the front and rear of each ski of a skier, linked to a computer graphing in real time each scale's reading which at any point of rest should be the same sum, and for any "event" (jump, squat, shift), be the same average sum over the duration.

It’s so elementary that there’s downward force from the skier’s weight. The only thing is that we can also pressure the front more than the back end of the ski by leaning forward against the cuff of the boot, if the binding has some resistance, either a fixed heel, a cable pulling downward, etc.

It’s seems the simplest thing, why such a convoluted discussion? Very weird.

[DG99]

I’m going to ask my daughter about all this. She’s a high school physicist, does very well at it. Lately she’s working on replicating the Cavendish experiment. Or some variation on it.

https://en.wikipedia.org/wiki/Cavendish_experiment

I’m sure she can tell us the correct answers. Like, is there spring tension in a cable binding?

If you ask the question properly, like “what is the difference between tension and net force”, she might be able to explain it to you. Because the issue isn’t about whether there is tension… of course there is. It is whether that tension imparts a net force on its own, which it does not.

Yes. Of course there is. And everyone knows the cable isn’t pushing down on the front of the ski by itself.

[Telerock]

My point simplified; what is the need to push down the front of the ski?

[GrimSurfer]

This discussion (ad infitium) has a basic assumption that I contest. In my limited experience, using extreme leather boots and 3_pin bindings, with and without spring cables, the tip (Bent up forward end) of the ski has no bearing (no pun intended) on a turn. Instead, it is the center of the ski, when one puts his/her weight on it (excepting my 2.5 camber 210 straight skis); and the left/right angle (cut or carve) that forces the turn, with the primary force applied by my bent toes under the foot and extending the length of the ski (apologies for the run-on sentance). That is, ideally, with even weight between the skis, my forward foot, flat on the ski starts the turn, and the back foot, toe-only, presses down and towards the outside of the turn. In my best form, the skis are close and near (not precisely) parallel to each other; leaving a “sible track’.
The form and forces are the same, reguardless if cables are used or not. Cables do help by providing lateral (Sideways) force for the carving by enguaging the heel, as well as the semi-flexible toe/vibram sole.
That said, I have not used other bindings.
However, since the rear foot, which is “up” and connected only by the toe/ball of the foot needs only to apply force down, and sideways to the outside of the turn; I do not see the advantage to “ active bindings”as various defined here, except to support the heel in twisting/sloping/bending/carving the ski so it edges.
In short, the sole (no pun) pupose of the front of the ski, with telemark, it to prevent diving into the snow. The turning is controlled by the edging near and under the foot. Downward and outward pressure with the toe/ball of the foot is sufficient unto the day.
Happy Trails.

^^This.^^

Whatever weight shift forward/back is needed is easily managed by the skier. It is not analogous to “pressure on the tip”, which is a ridiculous overstatement that ignores the fact that most of the ski in contact with the snow actually bears whatever weight/force is exerted by the skier.

[lowangle al]

Telerock, somewhere about twenty pages back we discussed that the "tip" is the front half of the ski. You don't need tip pressure to make skis turn. Like you said, you just need to weight them.

Also, it will be a lot easier to feel what tip pressure does for your skiing with a plastic boot and a ski with a lot of sidecut, but I still like it and feel it with leather boots. Just because you don't use it or feel it doesn't mean it doesn't exist.

[lowangle al]

My point simplified; what is the need to push down the front of the ski?

More effective edge in contact with the snow allows you to make tighter turns with better edge hold. It's good for controlling speed on steep hardpack, among other things.

Like you said though, you don't need it. As long as you have that edge underfoot working for it. It doesn't replace the need to have that middle of the ski carving.

[DG99]

My point simplified; what is the need to push down the front of the ski?

I also ski alpine, which is a bit simpler. You can just tip the skis sideways and engage the edges to turn. But pushing on the front also shortens the turn, ie a tighter turn radius by bending the ski.

Or, you can pressure the ski using gravity and muscles and shorten the turn that way, reversing the camber more, but that only goes on for so long. It’s the downweighting portion of the turn.

In a tele turn, having more pressure on the tip of the trailing ski helps tighten its turn. Also it doesn’t flop around as much. Trying to ski Switchbacks in free pivot mode really shows how helpful it is to have at least a little of this resistance! And more active is more helpful, to a point. You could theoretically just ski on a free pivot, especially if you could design a boot with very soft forward flex but great torsional and lateral rigidity. It might be a bit tough though.

AFAIK!!!

My 2 cents….

[DG99]

Oh… I see there are other answers already.

[lowangle al]

Oh… I see there are other answers already.

We basically said the same thing.