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05-06-2019, 07:12 AM #1Registered User
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What's the theory on how ski dimensions scale with skier size?
I've been thinking about this a bit for the last month and thought I'd put it out there in case anyone had either off-the-cuff or more-thoroughly-thought-out ideas on the subject.
Say you start with a skier who's a given height and weight (for example, 6', 200#). And say they're very happily skiing on a certain pair of skis (say 110mm underfoot and 190cm length).
Now imagine I scale that person down by 10% (height-wise) to make a new, smaller skier: height of 5'5" and weight of 145# (since weight scales approximately like height^3). I was trying to think about what ski dimensions they should be on to most closely approximate the experience of our original skier. Does the answer depend on whether you're trying to get equivalent performance in powder or hardpack? I know there are concerns about ski stiffness as well (which may or may not scale like the thickness of the ski), but let's start simpler and just talk about what the length and width should be for our smaller skier.
I can't exactly justify it based on first principles, but I had a gut feel that the ski length should scale up and down with the skier's height. Certainly that keeps things in proportion in terms of what fraction of the ski's length the skier can move their center of gravity over. Can anyone justify that more rigorously? Or does anyone disagree (why)?
But let's run with that: so our smaller skier is on 171cm skis. If we think "equal performance" in powder is about "equal pressure under the ski" then we need 30% less ski area for 30% less weight. So that means the width would need to be about 80% as wide as the original, putting our smaller skier on 88mm wide skis.
For hardpack, if we're trying to keep angles the same as our skier tries to edge the ski, the geometry argues that the ski width should scale down linearly with skier height. That would argue (I think?) for only a 10% narrower ski than the baseline (99mm wide).
Is there "theory" on this stuff? Or at least widely accepted intuition? It seems like (almost) every ski out there keeps the same width underfoot for all the sizes in length. I always thought that was very counterintuitive. What do you think? What dimensions "should" our smaller skier be on?
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05-06-2019, 07:46 AM #2
PugSki Jong
www.apriliaforum.com
"If the road You followed brought you to this,of what use was the road"?
"I have no idea what I am talking about but would be happy to share my biased opinions as fact on the matter. "
Ottime
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05-06-2019, 07:47 AM #3
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05-06-2019, 07:55 AM #4
The smaller skier should definitely buy the red ones.
/ end thread.
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05-06-2019, 07:55 AM #5
All of your math ignores on the ground conditions. A short ski is less stable than a long ski, regardless of what size skier is standing on it. A set of moguls is spaced the same, regardless of what ski you're on. Trees don't space themselves out wider for bigger skiers on bigger skis.
Plenty of people have the skill and strength to drive most ski lengths (at least most ski lengths that are actually produced). The length they're on is more dictated by the terrain they're skiing.
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05-06-2019, 08:02 AM #6
If me and dantheman had equivalent skier-mass-to-surface-area/length, I’d have to be on skis so long (if they even existed) I couldn’t fit them in typical ski spaces like mogul troughs or entry chokes and whatnot.
It’s one of the things that sucks about being a large man who also loves “action sports”. I ride a 55 lb dh bike on not-super-rad trails because I had a horrendous wreck when normal mtb stuff folded up under me on a normal landing. I surf a 7’6 standup paddle board because it’s the only thing I can find that has volume and also downrails and rocker. My pow skis are 140 underfoot. All of those things are classicly kooky. It sucks being big....and one thing about being big is that we weren’t born big so we know what it was like not being big.....whereas small people don’t necessarily know what it’s like to be big.
I think I’d give almost anything to be average size. Fit in normal seats...buy a wetsuit on sale....not have to turn every bicycle into a fucking engineering project.
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05-06-2019, 08:18 AM #7
or you can buy the ski that YOU like, and not worry about other people (bigger, smaller, taller, shorter) are using?
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05-06-2019, 08:28 AM #8
A very wise man once told me, short skis suck. Even the red ones.
Move upside and let the man go through...
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05-06-2019, 08:34 AM #9
My eyes glazed over reading this.
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05-06-2019, 08:39 AM #10Merde De Glace On the Freak When Ski
>>>200 cm Black Bamboo Sidewalled DPS Lotus 120 : Best Skis Ever <<<
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05-06-2019, 08:48 AM #11
I prefer the ski that looks coolest in the lift line over what's actually best for the terrain and conditions I'm skiing on any given day.
Here's the formula for coolest looking ski:
Go that way really REALLY fast. If something gets in your way, TURN!
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05-06-2019, 09:05 AM #12
^^^ i think you're on to something
Your wish will come true. It's just a painfully slow (d)evolution... trust me - and it's worse than the growing pains you remember. 20# of mass & 2.5" of height went missing. Never to be found again.
*
Ludicrous thread... there are people (in this thread) that use a ski way longer than you would think appropriate and do it with aplomb.
dis tu "All of your math ignores on the ground conditions"I am not in your hurry
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05-06-2019, 09:34 AM #13
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05-06-2019, 09:47 AM #14Registered User
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Do you like Gladiator movies?
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05-06-2019, 09:48 AM #15Registered User
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- Mar 2008
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- northern BC
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a ski can not tell how tall you are
a ski can only tell how fat you are
its not those stretchy ski pants that make you look fat
its your fork that makes you look fatLee Lau - xxx-er is the laziest Asian canuck I know
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05-06-2019, 09:54 AM #16
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05-06-2019, 10:03 AM #17
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05-06-2019, 10:08 AM #18
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05-06-2019, 10:15 AM #19
Long skis are dangerous. I sold all of mine after a high speed crash. I am very interested in the formula to ensure I am on the proper length ski for maximum safety. Riding long skis to show how cool you are is not for me. Please keep me updated for my safety. Thank you.
I am 5'10 165lbs.
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05-06-2019, 10:20 AM #20
#redraxftw
"When the child was a child it waited patiently for the first snow and it still does"- Van "The Man" Morrison
"I find I have already had my reward, in the doing of the thing" - Buzz Holmstrom
"THIS IS WHAT WE DO"-AML -ski on in eternal peace
"I have posted in here but haven't read it carefully with my trusty PoliAsshat antenna on."-DipshitDanno
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05-06-2019, 10:23 AM #21
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05-06-2019, 10:24 AM #22
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05-06-2019, 10:40 AM #23
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05-06-2019, 10:55 AM #24Registered User
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- Mar 2008
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- northern BC
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05-06-2019, 03:30 PM #25
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