Ski length traditions, lack of tall skier options. A rant.

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Cloxxki
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Ski length traditions, lack of tall skier options. A rant.

Post by Cloxxki » Fri Feb 04, 2011 8:43 am

I've posted on this before, but now I've got a nice professional editiorial to pick data from. Responding to a sizing table would have eased my writing, but perhaps less entertaining.
Please look at this nice article, great to read if you deal with Atomic skis as I do.

http://www.nordicskiracer.com/news.asp?NewsID=5082

"A stiff skating ski has diminishing returns."
Thus, I extrapolate, a skating ski is better a bit long at medium flex, rather than short and hard.
In sted of getting a harder ski at length x, a longer medium is advised.
At 180lb, you're already looking to get a stiff(er) 190cm ski, but Atomic now says that's no use. Get the same ski as the lighter guy, even if you're well over 200lb. That's ignoring basic physics, or telling a big guy he's too fat to skate ski, let alone expect a performance product.

Proportions rule our world.
Glide, with a perfectly flexed ski, will be proportionate to the
body weight/(ski length*width) formula.

Since Atomic (as all the competition) seems to only size skis in length, and use one width for a given model, that can be simplified to:
weight/length.

A 190lb skier (I know several, who are quite fit and race marathons) would be on 190cm skis. A relative ski weight of 1.00.
Or, if they are 1m90 (6'3") which is reasonably to expect, a relative length of also 1.00.
Relative length (I am making these things up) would be an indication of how awkward a ski is to skate. For instance, a portly 1m60/5'3" man skier with short legs, at 190lb/85kg, will find his 190cm skate skis a bit of a hand(leg)full. Unfortunately for him, an even harder 184 would offer diminishing returns.

Where our athletic 6'3/190cm/190lb skier uses pretty hard 190 skate skis (by lack of longer mediums), what does a typical woman use?
"WOMEN FROM 140 (pounds) TO THE UPPER 150’s: These women should be on 184 Hards."
Let's make that 150lb average, and let's use 5'8"/173cm as skier height.
Relative ski weight : 150/184 = 0.815. Quite a bit easier glide.
Relative ski length : 190/173= 1.10

Let's take a lower extreme though, for comparison:
"SKIERS FROM 105 (pounds) TO MID TEENS: Place these skiers regardless of gendre on 178 Softs."
Note that 172's exist as an option.
110lb average, we'll use 5'3"/160cm as height.
Relative ski weight : 110/178 = 0.62
Relative ski length : 178/160 = 1.11
Compare that to a 1.0 and 1.0 for the 6'3"/190lb guy on 190cm skis.

Apparently, skis 10% longer than yourself are a non-issue. You see that quite visually displayed on many a race podium. That's 209cm skate skis for a 6'3" fellow. But picture the face of the ski sales rep if he'd dare ask for those.
People who've skated their classic skis know it's totally doable, from an biomechanical point of view. Harder than short ones yes, but apparently shorter folks just try harder, and get taller skis than themselves to work.

209cm skate skis would give our 190cm skier a relative ski weight of 0.91. Notice that he still has significantly MORE weight per ski surface unit than his female teammate. All factors being the same, skis being ideally flexed, he'll dig deeper into the surface, experience more snow resistance at a given speed. Actual glide speed may still be equal or better due to aerodynamic variances between the 2 skiers. On downhills, the extra skier weight also helps.

Why does the regular tall guy, on "outrageously long" skate skis that don't exist, still have so much more weight per ski surface area? Simple proportions. And yes, men weigh a bit more for a given height.

Take a cube, 1 ft tall, 1 wide, and 1 deep. It weighs 1 stone (whatever that is).
It will be fitted with skis 3feet long, 3x more than size. That fit's nicely.
1
└─┘ 3

Now we take a 2x taller cube. 2x2x2=8 weight units.
If we fit it with 3x longer skis, being 6 long, that's only 0.75x it's weight. The skis will sink in way deep compared to the half sized cube's.
■■
■■ 4
└────┘ 6

Body weight on average increases exponentially with height. If you're 6ft tall, and your child is 3ft tall, you'll see it being roughly a quarter of your weight, definately not half. This is because we grow in 3 dimensions, not one.
Skis however are one-dimensional, as the width is fixed, just length is varied. It can never keep up with a skier height increase for weight, although skis are supoposed fitted per weight. Long enough skis just get in the way quickly.
This could be offset somewhat with wider skis. They spread the load. let's say race skis are all (close to) 40mm wide. 50mm skis are not so far-fetched. Some of us have touring skis of that width. This does reduce ski pressure to the snow by 20%. Smaller width variances can already be useful.

However, glide resistance for a given ski surface is lower when the ski is narrow and long. After you've skied one kilometer, you've compacted (one ski all the way) 1000x0.04=40 square meters rather than wider ones. So, we are into skinny skis.
It would be most interesting to see the tallest/heaviest elite skiers to be abllowed to try 200cm long, 47 or even 50mm wide skis that are properly flexed. On hard surfaces I don't expect a glide advantages, especially due to the added with, yet on soft surface I expect them to do better than before, especially with actual race-effeort skating.
Come to think of it, I cannot remember a race with tough snow conditions where a heavy racer did best.

Just as another can of worms, bicycle crank length, with most adults fitting in a range of ~20% height range, they all end up handling cranks within a 6% range (170-180mm). The shorest as well as the tallest riders, more than 20% apart, still end up riding the same 175's. This doesn't make it "right", it just shows that the market limits the options.
As a child you grow into your cranks, and then adjust as you outgrow them. You don't notice a problem until you've had a month of training on a proportionate crank length.
I suspect skis have a similar issue going on. If I'm wrong, I'd love to be explained the physics. so far, I know that when the track is soft, I am pretty much without a change to have a good race, or even relaxed ski. On firm surface, I am immediately with the quickest skiers in a group.

Will logic ever be allowed to disctate ski dimensions, rather than marketing and traditions? Will one ski brand ever make a 21st century attempt to help their tallest racer to gain a little performance edge? Right now, with 190cm and over 6'4" tall, offically you're not even allowed to take part in IBU races. Tall skiers are growing off the minimum allowed ski sizing range! Short skiers would only get in trouble if the rule worked the opposite way.

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Post by kuan » Fri Feb 04, 2011 9:51 am

Jesper Modin does quite OK.

Just looked up a BMI calculator. If you're 6' 4" and 200lbs your BMI is almost 25? Hmm... wonder how accurate that is.
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Post by Cloxxki » Fri Feb 04, 2011 9:58 am

kuan wrote:Jesper Modin does quite OK.

Just looked up a BMI calculator. If you're 6' 4" and 200lbs your BMI is almost 25? Hmm... wonder how accurate that is.
BMI = kg / m / m
BMI = 90.72 / 1.9304 / 1.9304 = 24.344

Modin is a sprint specialst, and indeed quite a manly man.
Being a worldcup xc'er, when does he come across soft snow? Did he take opart in those nasty Praque sprints a year ago? :-)
Biathlonners seem to get more marginal grooming, perhaps due to the length of the events.
Last edited by Cloxxki on Sat Feb 05, 2011 6:13 am, edited 1 time in total.
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Post by kuan » Sat Feb 05, 2011 5:49 am

I'm trying to think through the scaling argument (cube square rule) and apply that to skis.
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Post by Cloxxki » Sat Feb 05, 2011 6:39 am

kuan wrote:I'm trying to think through the scaling argument (cube square rule) and apply that to skis.
I'll attempt to condense, or at least rephrase.

skis between 172 and 190cm (10% range) are designed to fit all humans 1m50-2m00 (33% range) and 110-250lb (100+% range)
Automatically, one will expect relatively short short for the heavier folks.
Those heavier folks however are usually not 100% taller than the halflings.

Purely based on intuition, many skiers will suppose that ideal ski length is something like body height + 10cm. It seems to hold true for smaller and medium skiers, after all.

We can't help it, but a proportionate athlete, 10% taller than they other, will weigh 1.1*1.1*1.1= 37.7% more.

To properly scale the taller athlete's ski's to have the same pressure distribution as the smaller athlete, 37.3% larger skis are needed. As we don't have width sizing, it will all need to be in the length. Yet, for all of adult humanity, just 10% ski length range is available, and if the smaller skiers was already 170lb, he's on 190s already, no way up.

Skis being 2-dimensional (a surface interface with mother earth's divine whiteness, width*length), narrow skis being the norm (making them effectively one-dimensional), yet humans being sized two-dimensionally and weighing 3-dimensionally (the 3rd dimension doesn't get in the way for the heavier skier, but the ski does notice), there will be a narrow range or extreme end of the sizing table where ideal ski fit is reached.

It is my hypothesis that smaller skiers are able to compete with taller ones, for a large part because the concept of the ski, but especially the way manufacturers traditionally size them, negating the David vs. Goliath race.
A walking giant will always be faster than a running small man, as long as the surface is firm. The giant has all the muscle and lungs (3D) to support his weight. He can endure walking pace (10mph) all day. The short man willl need to be an ultra athlete to manage 8mph all day. The giant however might as well be an ultra athlete himself, and then we're looking at 25mph all day.
We don't have a factor-3 height range in humans fortunately, but the David vs. Goliath dynamics do apply.

How does David beat Goliath in a distance race the giant choose? He picks skis as the mode of transport.
The Giant's conceptual advantage is -1D, yet ski manufacturers boost it further to -2D.
Skiing commerce favors short, light humans.

Perhaps this adds to the whole junior thing being so big in skiing. Lightweight skiers are already so high up the ranks for natural speed. Yet as they grow, their conceptual advantage diminsihes, gaining taime on the top adults gets harder quickly.

If Atomic were to do a ground-up design of a skating ski for a filthy rich MBA star (220cm, 110kg), Discovery Channel style, it would not be simple 190cm in stiff as used for a 180cm 170lb skier. Not if they are taking their mission seriously.
The 110kg (250lb or so) MBA star wpon't care about sub-kg pairs of skis. He's got the might of the world, he use lift railtrack bars if he needs to.
At his height, he can handle 240cm skis just fine. in 40mm narrow though, that's going to be huge challenge to design to last. Width and even height will need to be built in to span the length, as with a river bridge. I bet the outcome could be a 55mm wide, 240cm long skating ski. The surface pressure won't beat a featherweight woman's, but his glide and skate speed over soft soil will be hugely better than on the otherwise perscribed 190cm hards.
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Post by MN Hoser » Sat Feb 05, 2011 8:38 am

A couple thoughts. One, it's hard to ski in packs with long skis. So a number of people perfer a little shorter ski for the control and the ability to ski in packs. I think long skis are a more universal ski for different snow conditions.

I think Fischer made 185, 190, 195, 200 and then shortened the tip so the skis went 3 cm shorter. I never see 197, so I didn't know they still made those. But, tall guys usually have an advantage in classic races because they have a longer stride. For some reason, short guys are very competitive in skate races. If the snow is soft, the tall guys suffer. I remember Husby (a big strong guy) simply had no chance at Nationals one year because it snowed 5-6 inches.

Jay

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Post by Cloxxki » Sat Feb 05, 2011 10:24 am

Thanks Jay, that for now confirms my experience and suspicion.

I can appreciate the short ski argument for packs, and perhaps that was somehow a reason for minimal ski rules to be implemented. Quite puzzling otherwise.

MTB racing was long a short guy sports, wheels being taken from kids bikes in the 70's, and not upgraded until in 2004 the UCI allowed for 700c/29" wheels. huge diffference in proportionality, although also short riders benifit from it.

Fischer told me they sold their old 197's all to Russia. In Europe, the big thing is always "we've had no demand for it". Shoe comps will even say this of shoe sizes, which all the competition make, and sell, and don''t get stuck with. JUst saying no to money to not accomodate certain customers.
Then they added the RCR Vasa Skating in 197 for last winter's season. A nice mid level ski for racers on a budget. Being labeled Vasa though, implies it being used in packs of thousands.

Big sports comps usually like to keep customers dumb, let them think sizing is well figured out. It reduces tooling costs (4-5 molds to serve all), and SEEMS to optimize profits. But what if that one or 2 sizes up with steal sales away from most of the competition...?
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