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Commonalities.... - Page 7

post #181 of 202
Quote:
Originally Posted by Skidude72 View Post

 

 

Perhaps it's worth defining what the middle of the ski is. I think this image helps us understand that we are referring to the functional middle of the ski, as opposed to the geometrical middle. NE is correct that the binding and boot are behind the middle of the ski, but are they not in fact placed over the sweet spot, the place where you can engage the entire ski from a centered stance? That is the functional middle of the ski, the center of the radial cut in an asymmetrical design . Hope that's not too fuzzy.

post #182 of 202
Quote:
Originally Posted by Shoebag View Post
but are they not in fact placed over the sweet spot, the place where you can engage the entire ski from a centered stance?

 

No it is not placed over the sweet spot most of the time. 

post #183 of 202

    I agree with The Dude here. The red zone is the middle (but it is not a singular point!) and corresponds nicely with where our balance axis passes through our feet in our turns. Move the Cm over the balls of the feet and we can achieve pressure more towards the forebody of the ski. As our cm's move over the arch and then heel (in some special instances) we pressure the middle and sometimes afterbody of the ski. But the Cm rarely passes into the "green zone" or the "purple zone", so as said above, we move our Cm's within the middle zone...a "playground" (I like that Skidudebiggrin.gif).

 

  But some note pressure on the bottoms of our feet is a more accurate way of describing  it than cuff/spine of the boot pressure because the balance axis, an imaginary line which is drawn perpendicularly from our Cm's through our feet, is directly opposing  the forces that the snow is exerting back at us. Thus, pressure is often noted at the interface (bottoms of feet) between our bodies and the skis (our feet are mini BoS's) The cuff/spine sensation is a result, not the cause--at least as some view it, because our lower legs our confined within often tight fitting and stiff boots, and thus meet resistance at these points (and it's a good thing..in some cases we might just keep going forward or rearward!) That's not say we can't add a little more, though...

 

  The advice to get forward relates to this--but it could be misinterpreted by some as meaning "all the way" forward...as in with our Cm's, into the dreaded green zone so that we can pressure the tip. Also as noted above, forward movements are not necessarily made directly towards the tips of our skis---this is also misconstrued by some ( like me at one point).

LL

   Our points of view/perspectives are very important things to consider when describing such things however...One mans trash is another mans treasure!!

    zenny


Edited by zentune - 4/24/13 at 8:06pm
post #184 of 202
Quote:
Originally Posted by NECoach View Post

 

No it is not placed over the sweet spot most of the time. 

 

If you are correct then you would always need to be fore just to be centered on the ski. Not sure if I'm fully comited to that concept.

post #185 of 202
Quote:
Originally Posted by Shoebag View Post

 

If you are correct then you would always need to be fore just to be centered on the ski. Not sure if I'm fully comited to that concept.

   Can't speak for NEC, but we generally don't stay in just one "spot" on the skis as we move through our turns...In dynamic turns we continually shift our balance.

 

   zenny

post #186 of 202

a ski typically has different flex characteristics front to back.  Where the exact center of the ski is a moot point to some degree.   Any notions about bending from the "middle" of the ski should not be taken absolutely literally that way.

 

Where the binding is located has to do with where the manufacturer feels will provide optimal performance.  In the old days there used to be a formula that more or less attempted to put the balls of your feet right in the center, but these days the manufacturers are all over the place, some even providing bindings you can slide forward or back as you feel like.  

 

There was a period of time around 10 years ago, when a lot of manufacturers were specing binding mounts a bit forward compared to normal, in an effort to make it easier for typical recreational skiers to init their turns, since a lot of rec skiers are often not forward enough.  There was a period of time where some people were even insisting on remounting the bindings back from that location.  My impression is that this was a temporary fad and is no longer happening but I really don't know.

 

Ski designs are getting quite elaborate now with interesting flex patterns, interesting sidecuts, early rise, rocker, etc..

 

In short, you can't really make very many conclusions by the location of the binding other than that the manufacturer is trying to locate it where they believe it will perform most optimally with a good stance.  I think its fair to simply say...bending from the middle means, try to make the bottom of your boot feel like the middle of the bent ski.

post #187 of 202

Start here

 

http://www.epicski.com/a/ski-binding-placement-fore-aft

 

There are many threads on this and most setups are reported at 1.5 to 2cm too far back.

post #188 of 202
Quote:
Originally Posted by borntoski683 View Post

There was a period of time around 10 years ago, when a lot of manufacturers were specing binding mounts a bit forward compared to normal, in an effort to make it easier for typical recreational skiers to init their turns, since a lot of rec skiers are often not forward enough.

 

I think you meant the binding mount mark was back.

 

http://www.realskiers.com/ski-bindings.htm

post #189 of 202

I think this study was published in 2001 or thereabouts

 

http://www.hiihtoliitto.fi/@Bin/5120/Binding%252Bposition%252BBenno.pdf

post #190 of 202
Quote:
Originally Posted by NECoach View Post

I think this study was published in 2001 or thereabouts

 

http://www.hiihtoliitto.fi/@Bin/5120/Binding%252Bposition%252BBenno.pdf


very interesting thanks for sharing!

post #191 of 202
This whole binding thing is endless you realize. Before I get into it I'll say that it makes little difference hearing the clinician's whole holding up the ski and pointing out the center etc. it may help some to think about it , but this "info" is hardly new.
Bindings aren't suddenly in different locations and the Demo team decided to make a presentation about it.
So I'm with skiDude and the middle is not a single point. When we say " bend the middle of the ski" are you measuring if its exactly symmetrical? Most ski flexes are def not symmetrical so even if you point load the exact middle it won't bend evenly.

The old standby of mounting was ball of foot on center of running surface and many people go back to that still making their own marks.

Everyone, ie ski makers, now pretty much uses the center mark on ski boots and puts a mark on the ski to align. With the exception of "center mounted" park skis for spinning,
these binding mark locations from manufactures are usually done by ski testers who say put it at x. It is not done by a set of super computers running sims. ( though who knows maybe they've started).

The effect of this is that binding positions for similar dimensioned skis from different makers can vary quite a bit. Nordica sponsored a test of this some years ago- '07 I think. What they discovered were large variations in marked position for different manufactures.

Lou Rosenfeld was involved in that and presented a lot of the data at ESA Big Sky in '09. I don't have the full paper I thought it was online but there is a smaller one.
The upshot was a difference of like 7 cm sometimes amongst similar skis. That is one ski could be say +3 and another-4 from a calculated point.
The other interesting thing was a study he worked on for Atomic where they moved binding position and mapped out the force input from the skier. The world cup skier's pressure curves are basically the same through the turn whereas the Provincial team skier can not make the adjustment.

Abbreviated paper on Binding Position:
http://www.lous.ca/sg_userfiles/BindPosArticle09.pdf

Lou's Shop (he's in ask a boot fitter forum)
http://www.lous.ca/index.html

Edit: I see NEcoach has linked a very similar study! It looks like it's at least partly the Atomic one.
Edited by Tog - 4/24/13 at 10:06pm
post #192 of 202
Quote:
Originally Posted by Shoebag View Post

If you are correct then you would always need to be fore just to be centered on the ski. Not sure if I'm fully comited to that concept.
Shoebag I agree with your interpretation. I change nothing from my earlier view. I wish I'd taken in that whole binding presentation she did to address it earlier.
It's looking more and more that it could just be one big justification for the dogma that " thou shalt have thy shins pressed firmly into the tongue and keep going further"
post #193 of 202
Quote:
Originally Posted by Kneale Brownson View Post
My take on her presentation is that there's too much emphasis on forangle movement. I THINK she was after moving forward along the length of the skis while creating tipping with the feet and legs. We need to not only move forward but stay forward, balancing on the outside ski, to bend it from the middle. I found my efforts to follow this direction helpful.

 

This is what he said was the content of the clinic.  If you ask me, that is not bending from the middle of the ski, so I will say flatly I hate that ism as much as foraganol-fever.  

 

BTS over and out.

post #194 of 202
Quote:
Originally Posted by Tog View Post


The other interesting thing was a study he worked on for Atomic where they moved binding position and mapped out the force input from the skier. The world cup skier's pressure curves are basically the same through the turn whereas the Provincial team skier can not make the adjustment.

Abbreviated paper on Binding Position:
http://www.lous.ca/sg_userfiles/BindPosArticle09.pdf

Lou's Shop (he's in ask a boot fitter forum)
http://www.lous.ca/index.html

Edit: I see NEcoach has linked a very similar study! It looks like it's at least partly the Atomic one.

Interesting article Tog, thanks for sharing.

 

I found it interesting that distribution of pressure throughout the turn was very similar for the WC skier, but that the curves were shifted with more or less the same amount as the binding was moved, i.e. the pressure center on the skis shifted when the binding was shifted.

 

Also interesting to notice that the pressure center is shifted about 15 cm forward early in the turn compared to towards the end of the turn. On my foot that corresponds to the distance between the center of the ball to the center of the heel, i.e. he is working with the CoM under the foot but he is using pretty much all of that range.

Also interesting to see that he has a part in the turn where the fore-aft is more or less constant, about in he 50-70% range into the turn. 

 

Would have been interesting to also see a graph of the boot flex angle.

 

The provisional skier seems to have some fore-aft balancing problems with some binding settings.

post #195 of 202
Quote:
Originally Posted by NECoach View Post

I think this study was published in 2001 or thereabouts

 

http://www.hiihtoliitto.fi/@Bin/5120/Binding%252Bposition%252BBenno.pdf

 


Quote:
Originally Posted by Tog View Post....
Abbreviated paper on Binding Position:
http://www.lous.ca/sg_userfiles/BindPosArticle09.pdf

Lou's Shop (he's in ask a boot fitter forum)
http://www.lous.ca/index.html

Edit: I see NEcoach has linked a very similar study! It looks like it's at least partly the Atomic one.
 

Finally, some science.  Thanks for the links.

post #196 of 202
Quote:
Originally Posted by Jamt View Post

Quote:
Originally Posted by Tog View Post

The other interesting thing was a study he worked on for Atomic where they moved binding position and mapped out the force input from the skier. The world cup skier's pressure curves are basically the same through the turn whereas the Provincial team skier can not make the adjustment.


Abbreviated paper on Binding Position:
http://www.lous.ca/sg_userfiles/BindPosArticle09.pdf


Lou's Shop (he's in ask a boot fitter forum)
http://www.lous.ca/index.html


Edit: I see NEcoach has linked a very similar study! It looks like it's at least partly the Atomic one.
Interesting article Tog, thanks for sharing.

I found it interesting that distribution of pressure throughout the turn was very similar for the WC skier, but that the curves were shifted with more or less the same amount as the binding was moved, i.e. the pressure center on the skis shifted when the binding was shifted.

Also interesting to notice that the pressure center is shifted about 15 cm forward early in the turn compared to towards the end of the turn. On my foot that corresponds to the distance between the center of the ball to the center of the heel, i.e. he is working with the CoM under the foot but he is using pretty much all of that range.
Also interesting to see that he has a part in the turn where the fore-aft is more or less constant, about in he 50-70% range into the turn. 

Would have been interesting to also see a graph of the boot flex angle.

The provisional skier seems to have some fore-aft balancing problems with some binding settings.


That summary sounds very similar to what SkiDude has presented!

Time to go ski...
post #197 of 202
Quote:
Originally Posted by cgeib View Post


That summary sounds very similar to what SkiDude has presented!

Time to go ski...

Yes, it is also aligned with my beliefs, but it is always nice to have some "proof".

 

I don't know if Skidude touched upon the distribution throughout the turn in this thread though.

 

The start fore and then move back as racers often do is not very aligned with the OP's "not only move forward but stay forward"

post #198 of 202

Agree with the pressure distribution being what SkiDude was saying.

In terms of this rather lengthy thread, it doesn't address the flexing into the boot issue.

SkiDude had multiple times talked of using plantar flexion - ankle open as pressure in the

 

beginning.

042c635e_campbellfig1.jpg

The thing about these graphs is that they don't match the Wcup turns.  The graphs have the max pressure at the top of the turn - before 20% of the turn.

In all the wcup photos, the max pressure is undeniably at the bottom of the turn, possibly late middle for some but not the beginning!

So...what's up with that??

 

Thankfully the world doesn't depend on the ski industries science or surgeons would still be laughing at germ theory and we'd all be riding horses to work. (maybe not so bad)

More links:

geez, we have a wiki on this!

http://www.epicski.com/a/positioning-ski-bindings-using-the-campbell-balancer

 

2005:

http://www.epicski.com/t/30475/how-to-determine-binding-position#post_353235

 

2010 discussion

http://www.epicski.com/t/92938/binding-mount-position-is-99-of-ski-performance

 

 

 

 

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post #199 of 202
Quote:
Originally Posted by Tog View Post

Agree with the pressure distribution being what SkiDude was saying.

In terms of this rather lengthy thread, it doesn't address the flexing into the boot issue.

SkiDude had multiple times talked of using plantar flexion - ankle open as pressure in the

 

beginning.

042c635e_campbellfig1.jpg

The thing about these graphs is that they don't match the Wcup turns.  The graphs have the max pressure at the top of the turn - before 20% of the turn.

In all the wcup photos, the max pressure is undeniably at the bottom of the turn, possibly late middle for some but not the beginning!

So...what's up with that??

 

Thankfully the world doesn't depend on the ski industries science or surgeons would still be laughing at germ theory and we'd all be riding horses to work. (maybe not so bad)

More links:

geez, we have a wiki on this!

http://www.epicski.com/a/positioning-ski-bindings-using-the-campbell-balancer

 

2005:

http://www.epicski.com/t/30475/how-to-determine-binding-position#post_353235

 

2010 discussion

http://www.epicski.com/t/92938/binding-mount-position-is-99-of-ski-performance

 

 

 

 

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How so? Standard theory of racing is get most of your turn done before the gate and use the flex of the skis to accelerate you at the end. So early pressure up high which is what he graph is showing. what you seen in the WC photos is the second hump in the graphs right before extension/retraction. The non-WC athlete shows a less steep curve indicating that he's probably a little late and has to "fight" the turn a little bit longer, those spikes could also be some chattering...

--EDIT--
 

Actually, check that! those graphs have nothing to do with the amount of pressure exerted on the skis!!! Those graphs show the position on the point of application of pressure in reference with the zero/mid-point of ski!

post #200 of 202
Quote:
Originally Posted by Jamt View Post

I found it interesting that distribution of pressure throughout the turn was very similar for the WC skier, but that the curves were shifted with more or less the same amount as the binding was moved, i.e. the pressure center on the skis shifted when the binding was shifted.

 

Full paper here

 

http://www.lous.ca/sg_userfiles/Bindingposition_indepth.pdf

post #201 of 202
Quote:
Originally Posted by jzamp View Post

How so? Standard theory of racing is get most of your turn done before the gate and use the flex of the skis to accelerate you at the end. So early pressure up high which is what he graph is showing. what you seen in the WC photos is the second hump in the graphs right before extension/retraction. The non-WC athlete shows a less steep curve indicating that he's probably a little late and has to "fight" the turn a little bit longer, those spikes could also be some chattering...

--EDIT--
 

Actually, check that! those graphs have nothing to do with the amount of pressure exerted on the skis!!! Those graphs show the position on the point of application of pressure in reference with the zero/mid-point of ski!

Yes, 100% right!  doh! And I knew that too. Carrying on....

 

Ok, don't have time to go into these next ones, Haven't even digested them..

 

Jamt you'll like these two articles I found because the first one has lots of formulas. It does seem to have enough readable material for non -physicists to enjoy without glazing over completely or frying the brain.

Second article is about injury, but maps out turns in GS comparing course sets.. It's simpler but has angle which is the angle of com though.

Anyway, enjoy!

 

Not sure if this has what we're looking for, but it's the big Kahuna so far:

 

Dissertation for the Swiss Federal Institute of Technology,Zurich

Finite Element Simulation of a Carving Alpine Ski

Peter Andreas Federolf

2005

Body of paper approx 130 pgs

http://e-collection.library.ethz.ch/eserv/eth:28070/eth-28070-02.pdf

 

 

"Course setting and selected biomechanical variables
related to injury risk in alpine ski racing: an
explorative case study"

British Journal of Sports Medicine Sept 2012 7pgs

pdf version:

http://bjsm.bmj.com/content/46/15/1072.full.pdf+html

 

html version, graphs can pop out in window and get very large

http://bjsm.bmj.com/content/46/15/1072.full

post #202 of 202
Quote:
Originally Posted by Tog View Post
.
042c635e_campbellfig1.jpg

 

I just skimmed through the article.  Briefly, what's going on here is that the ex-WC skier (S1) maintains the same relationship between the ski and his/her body, independent of binding position.  ["The elite skier acted on the skis to keep a constant relative position between body and skis."] Thus, with the binding forward, his/her weight is more forward; with the binding back, his/her weight is more back. By contrast, here's what they said was going on with the good recreational skier (S4), which seems also to apply to S3, who is an ex-junior Canadian racer:

"The good skier reacted to the change in the turning characteristics of the ski by altering the relative body position in response to the change in binding position. The results were inconsistent because, for each of the different binding positions, the skier had to find a different body position to best turn the ski. "

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