or Connect
EpicSki › The Barking Bear Forums › Ski Training and Pro Forums › Ski Instruction & Coaching › Let's talk about over-angulating
New Posts  All Forums:Forum Nav:

Let's talk about over-angulating - Page 15

and you feel that is like walking?

So here is some meatball measurements. A 10cm base and a 6.4cm base, a point 15 cm above the middle of each gives us the basic shape of an upside down T. By making one edge of each base the pivot (same edge) and scribing a base tipped to a 45' angle and drawing the same two Ts on that line then measuring the distance that point 15cms above the base I got the following results. The point above the figure with the 10cm base moved 12 cm, and the point above the 6.4cm wide base moved 11.6cm. The simple geometry behind that activity seems to support Jamt's conclusion. I suppose Jamt could share the math but that is up to him, all I know is I would believe his opinion about this.
Edited by justanotherskipro - 1/27/14 at 3:03pm

I was trying to find out about the role of the foot arch in balancing on one's toes and came across this.

Talk about balancing on the edge! Kind of insane.

Go to 0:50 for close to start.

http://www.huffingtonpost.com/2013/08/29/dagger-ballerina_n_3830038.html

xray of foot on pointe. Those are the nails in the shank on the right.

http://blogcritics.org/the-science-of-being-on-pointe/

So Tog ya doing this while skiin? Ya must have AT binders,
Quote:
Originally Posted by borntoski683

and you feel that is like walking?

I think more precisely can you see contralateral connectivity in his movement.

tog- that may have been the strangest 3 min of my day.

Quote:

tog- that may have been the strangest 3 min of my day.

Yeah me too.  Can I get those 3 minutes back maybe? (Being a piano player I hoped she'd jump down on the keys, at least make some music after destroying the finish on the thing.)

Quote:
Originally Posted by markojp

LeMaster clearly and concisely covers the conversation of the last 10-15 posts. Pick up a copy if you don't have one, re-read if you do.

I thought her range was rather limited - she was only playing the sharps.....

Surfdog

Quote:
Originally Posted by borntoski683

Jamt, draw the same picture with the skis having the same edge angle and tell me which one is more inclined.

Here they are with approximately the same edge angle. With the super wide ski you have to angulate towards the inside to keep the CoM above the edge.

The moments are proportional to the distance between the joints and the force vector, thus with the wide ski the torques are larger. This is not always the case though.

In the following picture the sideways bending moment is large in the ankle, but smaller in the knee: So for a person using a lot of knee angulation a wider ski may be better for the knees.

Lets talk about resultant force vector for a second. Gravity pulls straight down, ground pushes back straight up. Skier slides down the slope on some vector with momentum, when edges are engaged partially or fully, friction pushes back proportionally in opposite direction along the slope. Those two force vectors combine to create a resultant force vector. To be in balance at a point in time. the BoS and CoM must line up along that vector. To be more precise, the inside edge of the outside ski needs to be in line with that resultant force vector to be in balance. Along with the CoM which is a point that may or may not be inside the body.

If you had zero angulation the CoM is in the core and you lean inside until the CoM is in line with the vector, ie.... Banked, then the resulting force vector does not pass through the inside edge. It passes through the middle of your foot. If you were banked even more to position the inside edge on the vector, then the CoM would be inside and out of balance. The ONLY way to position them both on the vector is to angulate.

With a wider ski, more angulation is necessary. If you angulate less your CoM will be out of balance to the inside should you manage to inclinate enough to place the inside edge in line with the vector.

Maybe this is a terminology issue?
Quote:
Originally Posted by borntoski683

Lets talk about resultant force vector for a second. Gravity pulls straight down, ground pushes back straight up. Skier slides down the slope on some vector with momentum, when edges are engaged partially or fully, friction pushes back proportionally in opposite direction along the slope. Those two force vectors combine to create a resultant force vector. To be in balance at a point in time. the BoS and CoM must line up along that vector. To be more precise, the inside edge of the outside ski needs to be in line with that resultant force vector to be in balance. Along with the CoM which is a point that may or may not be inside the body.

If you had zero angulation the CoM is in the core and you lean inside until the CoM is in line with the vector, ie.... Banked, then the resulting force vector does not pass through the inside edge. It passes through the middle of your foot. If you were banked even more to position the inside edge on the vector, then the CoM would be inside and out of balance. The ONLY way to position them both on the vector is to angulate.

With a wider ski, more angulation is necessary. If you angulate less your CoM will be out of balance to the inside should you manage to inclinate enough to place the inside edge in line with the vector.

Maybe this is a terminology issue?

If the ski is up on edge the force vector originates at the edge. If you are standing still that force vector goes vertically straight up, and if it passes through the CoM you are in balance.

This is the position I have drawn in the pictures. The picture could be a snowboarder.

If you balance on the inside ski you can ski angulated the wrong way and still be edge locked. The location of this edge would be the equivalent of the position of the edge on the outside ski if it was extremely wide.

Another example. Say that your feet are straight under your hip joints and that you have a ski that has the width equal to the distance between you hip joints. If you lift one foot the inside edge of the ski on the snow will be exactly under the COM and you are in balance. If the ski is narrower than this you have to angulate to stay in balance. If the ski is wider than this you are still in balance but you are not balancing on the edge.

Quote:
Originally Posted by Jamt

If the ski is up on edge the force vector originates at the edge.

Ok I see where you are coming from there. I have to ponder that some more. It gets a little murky because the conversion of momentum into turn forces originates from momentum of the CoM, so there is an angle there in the way that momentum plows into the snow from an angle and how exactly that converts into some component of the resultant force vector and the angle of the leg compared to the angle of CoM momentum, etc

Often you see diagrams from LeMaster or others where the resultant force vector is pointing out from the CoM rather then in from the edge. Centrifugal vs centripetal. But momentum is not a force, so as you say the force to balance against comes from the edge, created by a conversion of motion energy of the CoM into reactionary centripetal force at the edge. In actual practice I have found angulation crucial for lateral balance on the edge. It has been my experience that wider skis need more, and that has been coached to me as well. I understand the point you are making and will ponder it some more.

In any case this has been an Interesting derail from the points made earlier about skiing vs walking. Walking happens on the bottom of our feet, skiing happens on the edges. The movements and balance are different. Do people still disagree with that?
Edited by borntoski683 - 1/28/14 at 7:28am

When I'm getting after it and arcing on hardpack I can feel more pressure along the inside of my outside foot (ball and arch) then on the outside of it (lte of the outside)...sure feels that way anyways. I see where others are coming from regarding the whole foot but I think a lot of these perceptions depend a lot on what types of turns we are making, what radius they are, what type of snow we are on, skis, boots, etc.....A question to ask I think is how large of a platform have we established? On very hard snow it ain't much.

Same if I do inside ski to inside ski turns. This time it's more lte than bte.

Edit: I have no video proof that I can get after it and arc on hardpack so for all you guys know I'm full of sh*t

zenny

Edited by zentune - 1/28/14 at 7:39am
Quote:
Originally Posted by zentune

When I'm getting after it and arcing on hardpack I can feel more pressure along the inside of my outside foot (ball and arch) then on the outside of it (lte of the outside)...sure feels that way anyways. I see where others are coming from regarding the whole foot but I think a lot of these perceptions depend a lot on what types of turns we are making, what radius they are, what type of snow we are on, skis, boots, etc.....A question to ask I think is how large of a platform have we established? On very hard snow it ain't much.

Same if I do inside ski to inside ski turns. This time it's more lte than bte.

Edit: I have no video proof that I can get after it and arc on hardpack so for all you guys know I'm full of sh*t

zenny

I understand what you are saying but the pressure is still on the bottom of your foot even if it is limited to a portion of it.

Tog is correct! Ya don't ski on the sides of your feet!

tog is correct!

And again, we're reinventing LeMaster.
Not the sides either Aman, the edge!
Quote:
Originally Posted by borntoski683

Quote:
Originally Posted by Jamt

If the ski is up on edge the force vector originates at the edge.
....
In any case this has been an Interesting derail from the points made earlier about skiing vs walking. Walking happens on the bottom of our feet, skiing happens on the edges. The movements and balance are different. Do people still disagree with that?

Yes, still disagree. As does Atomicman.

Maybe it's semantics. I have a 6th toe near the 5th metatarsal. So, clearly there is force on the sides of the feet, or I use the sides. Steering etc. I'm not saying that we don't use the sides, we just don't balance on them. They also can not support any significant weight. Our bodies are not built that way.

When Wcup skiers are doing nearly 3gs in a turn they are not doing it through the sides of their feet. They'd snap the outside knee apart.

(If everything was kosher though, footbed, fit etc. I would not have gotten that 6th toe. I had a footbed that was too slanted to the outside.)

Quote:
Originally Posted by borntoski683

Not the sides either Aman, the edge!

Yes the bottom  edge of the bottom of your foot. approxiamately a line from your big toe back through the ball and arch but on the bottom not the side!

Finally!

We don't do that we when walk.

Quote:
Originally Posted by Atomicman

Yes the bottom edge of the bottom of your foot. approxiamately a line from your big toe back through the ball and arch but on the bottom not the side!
now youre talkin!

zenny
Quote:
Originally Posted by zentune

now youre talkin!

zenny

Quote:
Originally Posted by borntoski683

Ok I see where you are coming from there. I have to ponder that some more. It gets a little murky because the conversion of momentum into turn forces originates from momentum of the CoM, so there is an angle there in the way that momentum plows into the snow from an angle and how exactly that converts into some component of the resultant force vector and the angle of the leg compared to the angle of CoM momentum, etc

Often you see diagrams from LeMaster or others where the resultant force vector is pointing out from the CoM rather then in from the edge. Centrifugal vs centripetal. But momentum is not a force, so as you say the force to balance against comes from the edge, created by a conversion of motion energy of the CoM into reactionary centripetal force at the edge. In actual practice I have found angulation crucial for lateral balance on the edge. It has been my experience that wider skis need more, and that has been coached to me as well. I understand the point you are making and will ponder it some more.

In any case this has been an Interesting derail from the points made earlier about skiing vs walking. Walking happens on the bottom of our feet, skiing happens on the edges. The movements and balance are different. Do people still disagree with that?

BTS I think the source of the misconception is that since it takes more effort to angulate when using wide skis you need have more...

Quote:
Originally Posted by Jamt

BTS I think the source of the misconception is that since it takes more effort to angulate when using wide skis you need have more...

See post above. It is the distance the skiers ankle is from edge that makes a wide ski more difficult.  Because it is farther from the source of the force from the snow ,  more susceptible to the torque force trying to flatten the ski

Quote:
Originally Posted by Atomicman

See post above. It is the distance the skiers ankle is from edge that makes a wide ski more difficult.  Because it is farther from the source of the force from the snow ,  more susceptible to the torque force trying to flatten the ski

Sorry to say but I don't like that part of ultimate skiing at all. The force on the ski boot causes torque on the ski boot, not the ankle. I may have a totally relaxed ankle and oppose the torque with muscles higher up. For the ski boot to be in balance the forces need to balance but the snow doesn't care if the opposing forces come from under the foot or higher up in the shaft. The snow doesn't care what causes the boot to be in balance or have the appropriate platform angle.

'There are other reasons why tipping the foot joint is a very good idea, but it has little to do with what Ron says.

Quote:
Originally Posted by borntoski683

In any case this has been an Interesting derail from the points made earlier about skiing vs walking. Walking happens on the bottom of our feet, skiing happens on the edges. The movements and balance are different. Do people still disagree with that?

BTS walking doesn't happen across the entire surface of the bottom of the foot at any point in the gait cycle, so it is as dynamic as skiing. The balance requirements are obviously different but the ability to manage the ground reaction force in either also requires whole body integration.

So BTS, the vector S in those diagrams passes through a magical math point and the base side of that metal edge and a few mm of the plastic base do not bear our weight? I understand perfectly what you are trying to suggest but it doesn't hold water my friend. Skidding or carving it really doesn't matter, to have any centripetal effect the force coming up through the snow must act on the body and the ski from an outside to inside direction. Nor is it accurate to say we are "balanced" or in a state of equilibrium when a direction change occurs. English being a messy language doesn't help here. Inclined but not inclinating, balancing but not balanced, there just are so many similar terms that don't mean the same thing. But I'm spiraling and want to share my view of what your argument would imply. In what you described the outward fleeing forces would include the reaction forces coming up from the snow and this would cause the skis to move away from the intended turn.

or the "push" coming from the sidewall side of the trench I mentioned would then be equal to or greater than the "push" from the base side of the trench. And angulation to create that equilibrium would mean no inward acting force would exist. It's really that simple, the base side of that platform must bear more weight and the reaction force must come from a direction below the base of the tipped ski for the reaction force to have a centripetal effect. A separate but very relevant idea is that the reaction forces involved in booting out are outward fleeing and cause the ski to move out and away from the turn.

Without centrifugal forces being applied to the snow, the reaction force would not be centripetal. We do that with the base of the ski no matter how thin the platform we create happens to be..

Edited by justanotherskipro - 1/28/14 at 10:46am

Wow, so finally we're on the same page about the bottom of the foot? Even if it's ball to heel side?

Like I said before, in Pilates, at least the one I went to, they emphasize walking on ball of foot to heel side. - The so called "edge" according to some, You train yourself to do it. Just like you train your legs to not splay out on the lift but go straight ahead. An issue for some more than others.

Also, skates are not necess on the center line. For fig skates that can all be custom made how much offset there is.

jamt, I agree about the torque on the boot and not the ankle, so...

If you have a wide ski edged on hard snow, is not that torque always present on the boot? Even if angulating? How does angulating effect the torque from the ski edge? The force is still at a point beyond the boot edge so there is a torque there no?

But BTS, I hope all of us disagreeing with you doesn't make you feel we are picking on you. It actually gives all of us an opportunity to refine how we describe the process of getting the skis to turn. For my part I see the assumption that we can develop centrpital reaction forces without applying some centrifugal forces to the snow as where your theory breaks down.

New Posts  All Forums:Forum Nav:
Return Home
Back to Forum: Ski Instruction & Coaching
EpicSki › The Barking Bear Forums › Ski Training and Pro Forums › Ski Instruction & Coaching › Let's talk about over-angulating