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Can Wider Skis Be Optimized with Different Movement Patterns? - Page 3

post #61 of 77

my understanding the PM calculator is that it doesn't take into effect ski's build: certain woods/materials ( bamboo, tintinal,rubber layers, etc) will privide for more flex/rebound, torsional stability, and the biggie: rocker design and camber. Another factor it doesn't take into effect is the quality of snow. Also, it doesn't define float. So a 3% blower snow is going to have much different float than sierra cement. So I will say this diplomatically: It's a nice tool that needs to be "updated".......

post #62 of 77
Quote:
Originally Posted by nolo View Post

It's just physics. Let's not shoot the messenger, whose only fault is to have explained it so well.


The thing is people like you and others on have used it to make a case where there isnt case to be made.  He also never took into account flex and camber profiles which almost matter more than surface area. Lastly speed was never accounted for, the lower the speed the more advantage at wide/fun shape ski will be. THis works for higher as well. You could say that fun shape increase your speed range and not just overall speed.

The thing is in 3d snow there is no such thing as to much float, if your lighter you have an advantage and instead of trying to nullify your advantage by saying oh I only need 85 underfoot, take advantage and go wide.

 

Your credibility will be next to none if you dont give the new stuff a honest try. IE more than one day and more than one condition.

 

I have seen some die hard Ill never ski on those funny clown shoe people give them an honest try and rave about them. Strangely some were examiners on spring day at the bird with not a single bit of powder around.

 

 

 

post #63 of 77
Thread Starter 

I will definitely give them a fair try this season and report back. In the meantime, do you think the rocker ski revolution will have the same industry changing impact that the shape ski revolution had back when those "clown shoes" were in their early iterations?

post #64 of 77
Thread Starter 

It would be interesting if some equally credible* science guy or gal among us would update PM's paper on skier size and powder skis in the light of rocker technology. (I assume we can use the word technology, if not technique.)

 

Moving on, 

 

How wide is too wide for the size of the person? How do you size lengthwise re physical stature and strength?

 

*PhysicsMan has a PhD in physics with both an applied and university teaching background.

post #65 of 77
Quote:
Originally Posted by nolo View Post

I will definitely give them a fair try this season and report back. In the meantime, do you think the rocker ski revolution will have the same industry changing impact that the shape ski revolution had back when those "clown shoes" were in their early iterations?

 

The game is changing in certain places already - huge numbers of people on rockers on a pow day at Squaw (arguably rocker's home mountain), not very many the same day at Northstar for instance.  For the casual groomer skier or if your home conditions are predominantly hardpack I can't really see the point so they'll never be a universal. 

 

post #66 of 77


 

Quote:
Originally Posted by nolo View Post

It would be interesting if some equally credible* science guy or gal among us would update PM's paper on skier size and powder skis in the light of rocker technology. (I assume we can use the word technology, if not technique.)

 

Moving on, 

 

How wide is too wide for the size of the person? How do you size lengthwise re physical stature and strength?

 

*PhysicsMan has a PhD in physics with both an applied and university teaching background.


Not a knock on PM or his paper at all, but people still don't even know why a bike turns, much less why certain ski shapes work well in certain conditions.  For practical purposes, the science behind it isn't as important as what works and what doesn't.  There is already a long-running series of practical experiments between the people who make skis and the people who try them out and give feedback. 

 

You'll get much more practical information by asking people who've spent a lot of time actually working with, or skiing, these shapes, about what works, than you will by assuming the real world away and making some simplified equations.  For instance, a heavily tapered ski will ski very differently at a certain length, width, stiffness, etc.  than a virtually identical ski that simply has a bit less taper.  The company that makes that ski probably has a good idea which size will work for whom, anyway. 

 

Same for early rise -- I've mentioned this several times, and just by tweaking the shovel and tail very slightly, you can affect the handling of the ski tremendously. 

 

Seeking feedback from people who've been on the skis = pretty good results.  Attempting to come up with a quasi-scientific, quasi-quantitative verdict as to a standard length and width based on skier size = mortgage finance.

post #67 of 77
Thread Starter 

 

This is a very good point:

Quote:
...people still don't even know why a bike turns, much less why certain ski shapes work well in certain conditions.  For practical purposes, the science behind it isn't as important as what works and what doesn't.  There is already a long-running series of practical experiments between the people who make skis and the people who try them out and give feedback. 

 

We may not know what makes the bicycle turn, but that doesn't mean we're not still trying: http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics

 

In defense of PM's paper:

 

This being the Coaching and Instructional forum, where else shall we discuss physics in skiing? Do Newton's Laws of Motion not apply? It seems to me that Newton's Third Law is the heart of PM's analysis. 

 

From Wikipedia:

 

Quote:
Third Law: The mutual forces of action and reaction between two bodies are equal, opposite and collinear. This means that whenever a first body exerts a force F on a second body, the second body exerts a force −F on the first body. F and −F are equal in magnitude and opposite in direction. This law is sometimes referred to as the action-reaction law, with F called the "action" and −F the "reaction".

 

A smaller body exerts less force than a bigger body. Surely rocker ski designers take this into account?

 

 

Quote:
Seeking feedback from people who've been on the skis = pretty good results.

This is what the thread is attempting to do, but--and there's a big but--we have to consider the source. Science has certain rules that account for bias, whereas it's extremely difficult to control the bias out of a qualitative opinion. 


Edited by nolo - 7/9/10 at 8:05am
post #68 of 77

Frankly, I'm not too sure of the value of physics most of the time to coaching or instructing skiers or snowboarders in any way, much less in terms of recommending skis.  Not the physical laws don't apply to the sport, but that it's not a valuable exercise to try to suss that out most of the time.  I actually liked most of PM's posts, and this is not directed at him, but most of the times that I see people try to apply a general background in physics/engineering, etc. to motion sports, they get it wrong.

post #69 of 77
Thread Starter 

Touche.

 

Still, I'd argue that 'tis better to base instruction on science than on perceptions. I've noticed over the years that learning to ski (i.e., to balance on a sliding surface) is not particularly intuitive. That's why we have so many skiers trying to get 100% out of the half aft of their skis. Certainly these legions of half aft skiers could benefit from learning to use the whole ski.

post #70 of 77
Quote:
Originally Posted by nolo View Post

Touche.

 

Still, I'd argue that 'tis better to base instruction on science than on perceptions. I've noticed over the years that learning to ski (i.e., to balance on a sliding surface) is not particularly intuitive. That's why we have so many skiers trying to get 100% out of the half aft of their skis. Certainly these legions of half aft skiers could benefit from learning to use the whole ski.


So many skier who have never know other wise are trying to get 100 percent out of their aft half of their skiers. You ve never had the person come up to you say to you 'someone told me I should feel my calf in my boot" well i have.

 

A good benefit of rockers is there is no true backseat on harder pack snow, you cna ski them aft but never hanging on the tail like you will see so much. 

 

Full rockered skis are the greatest teacher of fore and aft balance there is.

post #71 of 77
Quote:
Originally Posted by nolo View Post

Touche.

 

Still, I'd argue that 'tis better to base instruction on science than on perceptions. I've noticed over the years that learning to ski (i.e., to balance on a sliding surface) is not particularly intuitive. That's why we have so many skiers trying to get 100% out of the half aft of their skis. Certainly these legions of half aft skiers could benefit from learning to use the whole ski.


Nice description
 

post #72 of 77

The trouble with using physics to explain skiing is that it only works if the person you are explaining it to has some understanding of physics.  Many people don't, the people who don't know how a bike turns for example.

 

The trouble with feedback, is feedback from someone who doesn't know and understand enough about skiing isn't worth as much as feedback from someone who knows how to ski.  You have to get a feeling for what the person giving the feedback is able to do and usually does with their skis.  The benefit of this form is after you have been here a while you can get a sense of that.

 

It's not about feeling the back of your calf on the boot.  It's also not about feeling the boot tongue on your shin, pressuring this nor pressuring that.  It's about feeling the snow through your skis and pressuring your ski tips, or tails as you see fit, tipping your skis, feeling and applying pressure through your skis' tips, tails, edges, what ever.  The ski is part of you and you move it and feel with it. 

post #73 of 77

Skiers are made by.spending countless hours in different conditions and the desire to improve.

post #74 of 77

http://www.surfline.com/blogs/talking-design-the-board-blog-with-rusty-preisendorfer/rusty-and-friends-on-the-physics-of-aspect-ratio-in-surfboa_41287/

 

Some analogous discussion of design issues and physics for boardsports in 3d environments (snow's not water, so the overlap is far from complete and in some ways the issues skis present are more complex).  In terms of actual end product, one interesting thing is that even on the shaper/manufacturer end of things there is no consistent level of attentiveness to the "book learning" part of design, and seemingly no real direct linkage between reliance on book learning and the quality of the end product.

post #75 of 77
Quote:
Originally Posted by nolo View Post

 

 

Anyone besides me ever seen a chute full of pristine powder fouled by a sideslipping snowboarder or skier? Heck yeah I dislike it when someone does that. 



A set of skins and some touring gear will largely eliminate this problem. smile.gif   

post #76 of 77
Quote:
Originally Posted by Finndog View Post

my understanding the PM calculator is that it doesn't take into effect ski's build: certain woods/materials ( bamboo, tintinal,rubber layers, etc) will privide for more flex/rebound, torsional stability, and the biggie: rocker design and camber. Another factor it doesn't take into effect is the quality of snow. Also, it doesn't define float. So a 3% blower snow is going to have much different float than sierra cement. So I will say this diplomatically: It's a nice tool that needs to be "updated".......



It's a nice tool that doesn't even bother doing any of the things you mention - since it is a purely geometrical analyzer with a built-in fudge factor that can be set by the user to match observed performance of real-world skis.   

post #77 of 77
Quote:
Originally Posted by slider View Post

Skiers are made by.spending countless hours in different conditions and the desire to improve.



...and an awareness of one's own motion...and an intuitive need to find new intent.

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