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# What's height got to do with it?

Why is skier's height seen as a parameter in determining appropriate ski length?

I'll ignorantly claim that it's a myth and irrelevant.

The force to turn/flex a ski is the result of weight, speed and turn radius. So, it does not matter if a 200 lbs skier is 5'2 or 6'2.

Who wants to teach me a lesson?

Two things are in play when you are skiing: you move the ski; the ski moves you.

You interact with the ski at the boot.  The snow interacts with the ski all along the ski, including at the tip and tails.

Consider forces acting on the ski from the ski interacting with the snow.  A ski tip 4 feet in front of you digging into the snow with a force of 50 lbs equates to 200 ft-lbs of torque acting at your ski - boot interface.  The same force, 2 feet in front of the boot exerts half as much torque.  A bigger ski acts on you like a bigger wrench.

Your cm 4 feet above the boot, decelerating with a force of 50 lbs will exert a torque at the boot binding interface of 200 ft-lbs.  Your cm 3 feet above the boot, decelerating with a force of 50 lbs will exert a torque at the boot binding interface of 150 lbs.  A taller skier acts on the ski like a bigger wrench.

Taller skiers don't need as much force to affect a long ski as shorter skiers do.

I think Kawo has a good point and I don't think he's suggesting ONLY weight should be taken into account, but I too would agree too much is emphasized on height.  Consider my good friend who is 6'2" and a rail-like 150lbs, vs my other friend who is 6'1" 245-ish.  There's no way in hell they should be on the same ski length.

Another interesting comparison...

Using a stiff 'advanced/expert" level ski like a Volkl Mantra (assuming both are on same ski length):

Skier 1: Level 7, 150lb, 5'10

Skier 2: Level 3, 250lb, 5'10

In this scenario skier #2, who is much less skilled, will probably be able to ski the Mantra properly and better than Skier #1 because his bodyweight will bend that ski like rubber making it feel like a noodly rental (easier to turn) for the 150lb guy.  All other things being equal.

Fore aft balance is one thing that immediately comes to mind. I think it would be easier for someone shorter to stay balanced on shorter skis. Put Yao Ming on 170's and it would be like normal people skiing on snowblades.

Quote:
Originally Posted by kawo

Why is skier's height seen as a parameter in determining appropriate ski length?

I'll ignorantly claim that it's a myth and irrelevant.

The force to turn/flex a ski is the result of weight, speed and turn radius. So, it does not matter if a 200 lbs skier is 5'2 or 6'2.

Who wants to teach me a lesson?

Apparently you are not familiar with the concept of leverage.  As a skier who is 6'5" I can tell you that it is a different game from up here. Your skis do not know how much you weigh, how fast you are going, or how tall you are, only how much energy you are putting into them, and where you are putting it.  When I lean forward it is not the same as when you do because my weight is leveraged a lot differently.  Same boots, same weight skier, same speed, but higher center of gravity, its just physics.

Edited by mudfoot - 12/3/10 at 9:10pm

Weight has to matter some to the ski, it contributes to how much you're able to bend it when it's on edge. It's partly a technique and strength issue, but if you compared the lightest WC skiers to the heaviest you would probably find a preference for a stiffer ski with the heaviest racers.

the leverage and energy are multiplied by technique.

you take what force you have and apply it at correct angles with perfect timing and you will have more of an effect on the ski than a person not using dynamic technique.

therefore a good skier can manage a long ski.

Very true, but all things being equal, if you added 50 lbs to yourself you should be able to bend a ski with less effort. Does stiffness vary with length? You mostly hear people saying that the longer ski is "more ski" but the stiffness might actually be reduced depending on construction.

+1 for the fore/aft stability consideration.  This is really emphasized when you ski wild snow.   There are more factors than just height and weight at work though, especially skier ability and terrain.

Quote:
Originally Posted by Benflow

I think Kawo has a good point and I don't think he's suggesting ONLY weight should be taken into account, but I too would agree too much is emphasized on height.  Consider my good friend who is 6'2" and a rail-like 150lbs, vs my other friend who is 6'1" 245-ish.  There's no way in hell they should be on the same ski length.

Another interesting comparison...

Using a stiff 'advanced/expert" level ski like a Volkl Mantra (assuming both are on same ski length):

Skier 1: Level 7, 150lb, 5'10

Skier 2: Level 3, 250lb, 5'10

In this scenario skier #2, who is much less skilled, will probably be able to ski the Mantra properly and better than Skier #1 because his bodyweight will bend that ski like rubber making it feel like a noodly rental (easier to turn) for the 150lb guy.  All other things being equal.

eh no.

there is not a single L3 out there that should be skiing on mantras no matter how big they are.

150lb at speed and Gs can easily becomes 300-450 lb of force. a Level 3 250lb guy would be lucky to ever get to 300lb of force.

Some previous posters have been setting kawo straight on this.

I'll just summarize once again (seems like this has to be posted at least once every season):

1. Choose the appropriate flex in a ski based on your weight and skiing preferences (speed, style, etc.).
2. Choose the appropriate length of a ski based on your height (due to physics - how your CoM is applied to the length of the ski via force/levers) and skiing preferences (terrain choice, etc.)

And yes, there are plenty of long-time trusted posters here that may argue these points, but they'll never convince me otherwise.

All you have to do is consider the extremes to see how ludicrous it is to base ski length on weight alone.  If you have a 250 lbs. 5' 2" guy you're not going to put him on a 190cm. Likewise, don't put the 135 lbs. 6' 2" guy on a 150cm.

It's also important to note that in my experience almost every ski model available generally gets softer longitudinally as their length increases.  Most manufacturers do not alter the construction of their skis across the available lengths so that each length has the same flex pattern.  Case in point, the Rossi S86 is relatively stiff in 170, but significantly easier flexing in the longer lengths.

Quote:
Originally Posted by chris719

Weight has to matter some to the ski, it contributes to how much you're able to bend it when it's on edge. It's partly a technique and strength issue, but if you compared the lightest WC skiers to the heaviest you would probably find a preference for a stiffer ski with the heaviest racers.

I think  that is true only in the instance of two skiers of the same weight on the same gear going the same speed.  I do not think a ski can tell the difference between a light guy going fast and a heavy guy going slow.  The momentum generated by the speed of the light guy will allow him to bend the ski just as easily as the heavy guy going slow. Obviously there are a lot of variables, but your ski responds to the energy being put into it from several directions, and that energy can be generated in more than one way.  Being tall gives me the leverage to more easily apply pressure to the front of my skis, which is definitely a two-edged sword, but the bottom line is that a longer ski works better for me than it would for a shorter person of the same weight.

skis which are completely different in construction for each length made: (were) dynastar legend pro, rossignol B-Squad, now pro rc112 I believe, as I skied those and know the difference in stiffness and construction.

these skis you can easily see the difference in thickness under the boot and if you drill them you may notice a different amount of metal, number of metal layers and or thickness of layers.

I think it's the only way to make skis, a no-brainer. My 176 legend pro is half (roughly speaking) as stiff as the 184 and again half as the 192 +-, same formula of the b-squad. nothing makes a ski work better for you than having the stiffness and quality of flex dialed to your size and strength and technique.

Quote:
Originally Posted by Ghost

Two things are in play when you are skiing: you move the ski; the ski moves you.

You interact with the ski at the boot.  The snow interacts with the ski all along the ski, including at the tip and tails.

Consider forces acting on the ski from the ski interacting with the snow.  A ski tip 4 feet in front of you digging into the snow with a force of 50 lbs equates to 200 ft-lbs of torque acting at your ski - boot interface.  The same force, 2 feet in front of the boot exerts half as much torque.  A bigger ski acts on you like a bigger wrench.

Your cm 4 feet above the boot, decelerating with a force of 50 lbs will exert a torque at the boot binding interface of 200 ft-lbs.  Your cm 3 feet above the boot, decelerating with a force of 50 lbs will exert a torque at the boot binding interface of 150 lbs.  A taller skier acts on the ski like a bigger wrench.

Taller skiers don't need as much force to affect a long ski as shorter skiers do.

One of the cleanest teaching examples I've heard. And all correct. Only caveat IMO is that the ski is not an isolated system, but is contact (we hope) with the snow. If the snow is firm, as Ghost's example, most of these forces will rebound back into the system; the edges can push against something. So the example works. Have a feeling we should be thinking about all this as angular, since we're usually turning around an axis, but too lazy to reach for my physics text. Plenty of engineers here to work it out.

OTOH if you think about it, on ice a longer ski's also acting on the skier like a bigger wrench. Including his/her knees, muscles, etc. So a longer ski will require more energy to compensate against that torque. And in theory, if you turn the system on its head - linked lever arms beginning at the ski, forces aimed upward, a taller skier will have more torque operating on his/her knees and hips, for any length ski. So mixed blessing, being tall.

If the snow is soft, there's practically speaking very little rebound. So unclear if height is still relevant. Weight is, since in pow that's what flexes the ski and creates arc to turn.

Weight alone could be considered if we all carried 99% of our weight in our feet, but we're not built like that.  Our weight is distributed and the CoM is what we use as a reference when dealing with fore/aft balancing and ski technique discussions.  CoM positioning and it's relationship to where the ends of the ski reside are practically everything in skiing.

Hey guys, great discussion! I've always found this issue to be odd.

I noticed there's a lot of talk about leverage and how taller skiers can bend skis easier using leverage. It conjures an image of a skier madly flying from front to back of their ski--most people wouldn't call this good or fun skiing! And in doing so, I can envision only the front or back half of the ski bending anyway...

I think I'm stating the obvious so I just want to put out the disclaimer that it's already known to the folks in this thread... but this is where I'm coming from: In typical freeskiing, generally we aim for a centered and mobile stance. If your weight gets too far forward, your tails will wash and you'll start to demonstrate rotation elements. If your weight is too far back, your skis end up taking you for a ride and pivoting becomes difficult. (and backseat bandits tend to be very defensive skiers.)  That's not to say that you never want to or need to shift your weight--in powder you might suddenly need to push your skis way out in front; same thing in moguls. But generally we strive for a centered stance.

So how does leverage bend the ski if we're trying to remain generally centered? (not contesting bending through mass--that's simple physics)

Quote:
Originally Posted by Metaphor_

Hey guys, great discussion! I've always found this issue to be odd.

I noticed there's a lot of talk about leverage and how taller skiers can bend skis easier using leverage. It conjures an image of a skier madly flying from front to back of their ski--most people wouldn't call this good or fun skiing! And in doing so, I can envision only the front or back half of the ski bending anyway...

I think I'm stating the obvious so I just want to put out the disclaimer that it's already known to the folks in this thread... but this is where I'm coming from: In typical freeskiing, generally we aim for a centered and mobile stance. If your weight gets too far forward, your tails will wash and you'll start to demonstrate rotation elements. If your weight is too far back, your skis end up taking you for a ride and pivoting becomes difficult. (and backseat bandits tend to be very defensive skiers.)  That's not to say that you never want to or need to shift your weight--in powder you might suddenly need to push your skis way out in front; same thing in moguls. But generally we strive for a centered stance.

So how does leverage bend the ski if we're trying to remain generally centered? (not contesting bending through mass--that's simple physics)

Marty!  You're just not thinking 4th Dimensionally!

Tall skiers...such as myself (6'5"), do not lean further forward or back from center than anybody else does.  We're not Michael Jackson in Moonwalker afterall.  However, due to the way we were born, our pivot point (knee) is much further from the top of the boot than everybody elses.  So even if we practice all the same mechanicals as everybody else, there is still more leverage acting on the ski when all is said and done.

I had some friends helping me change the hub on my car a few years ago.  Both dudes were much stronger than me...and heavier...but topped out at 5'10".  Neither of them could get a bolt off one of the hubs with an average sized Ratchet no matter how hard they tried.  I remembered a story a friend told me about working on a hummer in the Army.  They had a guy attach something like an 8 foot pole onto the end of a torque wrench to try and get a bolt undone.  It ended up snapping the bolt.  So I offered up the same suggestion with my grand am.  We added about a 18" pipe onto the wrench, and wahlah, bolt comes right out with only my strength pulling on it.

Moral of the story, don't underestimate the force that can be added to your skis with only an extra few inches of height on the skier.

test

Fujative: that's true about turning; however, I'm wondering about how a  taller skier in a centered stance could bend a ski more.

It's not just about bending the ski.

Sometimes you need a little extra pressure to press the tip into the snow so that it gets a good bite and doesn't slip, so the ski will bend.  Going into a turn, the radius is decreasing and the tip needs a little extra grip as compared to the tail.  Accelerating out of a turn with the tip having a larger radius than the tail, the tail needs a little more grip.  Managing fore aft pressure will result in less movement from home base of the cm if the cm is higher.  Remember it's F=ma at the cm needed to torque the boot forward that affects acceleration, some of it unwanted but necessary, of the cm.

At the apex of a turn, the bend in the ski is the same with higher cm or lower cm.

Also consider the affect on fore-aft stability when encountering bumps and crud piles.  Lower skiers don't need as long a ski to manage these forces without over-pressuring the tips.

When a tall skier leans into his boot to the same degree as an equal weight skier with shorter legs the taller skier applies more force on the front of the ski because his/her weight is being applied from a higher knee/lever point.  The opposite side of that equation is that the taller skier has to move their knee farther forward to apply the same angle of force to their boot.  Fortunately, most of these factors can be equalized by modifying your boot flex.

Edited by mudfoot - 12/6/10 at 7:51am

the most significant factor is the skier who uses technique to apply pressure on the front of the ski (or the tail). since few skiers get the weight shift through the turn, or ride the sweet spot very well,  technique trumps stature as a factor of power into the ski.

Do you think 164cm would be too small for me? I'm 5'6" and 150-155lbs depending no the time of day

I'm a level 7-8 skiier. I'm looking to buy a 1Q all-mountain ski. I Ski mostly eastern frontside but I'm looking to practice tackling bumps and off piste a little more often.

My advice would be to avoid the temptation to go wide (or the pressure from the sales guys).  As a level 7-8 skier you're still working on developing a solid carved turn that you can use in all conditions.  Wider skis will make getting to that point more difficult (i.e. learning to really tip your skis).

So my "i-Advice" would be to pickup something in the mid 160s for length and the mid 70s for width.  Don't go beyond 85mm underfoot no matter how tempting it might be.  You would only be doing yourself a disservice.  Also be careful of skis that are too stiff for you to be able to bend them at lower speeds.

As far as your desire to ski bumps and ungroomed - that's more about skills than skis.  Good skiers can take any ski anywhere, but of course some tools are better for the job than others.  A little extra width doesn't really buy you all that much on the ungroomed - a lot more width will allow you to get away with poor technique by letting you use pivoting moves and poor releases without getting hung up.  Consider your desire to become a better skier over the desire to look cool on the latest fat skis.

My thinking is that Kawo's OP is a fair challenge to a traditional, but much overrated, criteria in ski selection. I've not read an convincing argument presented that would affirm the simple proposal that tall skiers benefit from the longest skis or short skiers need the shortest skis. Everyone who has posted describes the complexities of selecting a modern ski, no need to reopen that issue. On a scale on 1 to 10 in considering a ski purchase, I'd rate length, as a stand alone criteria about 1. When was the last time you heard someone state they want to buy a 175 cm ski? That's not to say that getting a correct length for you in a specific ski is unimportant. But that's more like fine-tuning.

When I started skiing on the old pencil skis in the 70's, the mantra was that a ski length should be at the palm of your hand when extended over your head. I would argue this height/length relationship, once established, got carried over into modern ski selection but is no longer relevant. From a practical standpoint, skiers first select a type of ski desired which will be defined in a modern ski more by width at the waist. Manufactures generally make 3 or 4 lengths available. From there, my guess is that 80% are manufactured and sold in the middle sizes, the sweet spot for a typical skier attracted to that ski. There are atypical skiers, so, to each his or her own. Demo away on size in a certain model and see what it tells you.

Exactly.

Quote:
Originally Posted by Living Proof

My thinking is that Kawo's OP is a fair challenge to a traditional, but much overrated, criteria in ski selection. I've not read an convincing argument presented that would affirm the simple proposal that tall skiers benefit from the longest skis or short skiers need the shortest skis. Everyone who has posted describes the complexities of selecting a modern ski, no need to reopen that issue. On a scale on 1 to 10 in considering a ski purchase, I'd rate length, as a stand alone criteria about 1. When was the last time you heard someone state they want to buy a 175 cm ski? That's not to say that getting a correct length for you in a specific ski is unimportant. But that's more like fine-tuning.

When I started skiing on the old pencil skis in the 70's, the mantra was that a ski length should be at the palm of your hand when extended over your head. I would argue this height/length relationship, once established, got carried over into modern ski selection but is no longer relevant. From a practical standpoint, skiers first select a type of ski desired which will be defined in a modern ski more by width at the waist. Manufactures generally make 3 or 4 lengths available. From there, my guess is that 80% are manufactured and sold in the middle sizes, the sweet spot for a typical skier attracted to that ski. There are atypical skiers, so, to each his or her own. Demo away on size in a certain model and see what it tells you.

Quote:
Originally Posted by Living Proof

Demo away on size in a certain model.

Easier said than done.

I am sorry, but IMO anyone who thinks that ski length is an overrated criteria in equipment selection must be talking about skiing on nothing but groomed runs.  If you are dealing with terrain and snow condition transitions a short ski is a deficeit, and the taller you are the more of a deficit it becomes.  Imagine hitting a condition that unexpectedly pitches you forward.  A taller skier with a higher center of gravity will need more ski to handle it as smoothly as a shorter person.

The trend is now towards longer rockered skis.  Why, because length is a definite asset anywhere but on packed snow, assuming you have the skills to use it properly.

Edited by mudfoot - 12/6/10 at 9:27am
Quote:
Originally Posted by mudfoot

I am sorry, but IMO anyone who thinks that ski length is an overrated criteria in equipment selection must be talking about skiing on nothing but groomed runs.  If you are dealing with terrain and snow condition transitions a short ski is a deficient, and the taller you are the more of a deficit it becomes.  Imagine hitting a condition that unexpectedly pitches you forward.  A taller skier with a higher center of gravity will need more ski to handle it as smoothly as a shorter person.

The trend is now towards longer rockered skis.  Why, because length is a definite asset anywhere but on packed snow, assuming you have the skills to use it properly.

Example:  I have for quite some time been skiing on K2 Public Enemies and Fujatives.  I've often heard people describe them as good all mountain skis, because they are skinny enough to carve, and fat enough to float (at the time...obviously not compared to the new crop of skis).  Well at 6'5", I've only skied the longest version available....a 179.  The 179 Public Enemy comes up to my mouth.  Too short by most standards.  I've always felt these skis sank like a rock in powder...contrary to what other people were saying about them.  I only continued to ski them because I spent most of my time in the park, and they were cheap and durable.  But I most definately could have benefitted from a longer version.

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