Why do skis stay the same width as length increases?

A snowHead

The question is in the title, take a particular model of ski, if a big 190cm / 100kg guy needs a longer ski than a 150cm / 50kg guy, why isn't it wider?
Currently, as a ski gets longer, the width stays the same but the turn radius gets bigger, so the shortest ski in the model with a 16m radius will ski quite differently to the longest with a 20m radius?

A snowHead

@tangowaggon, not always the case. My Head Kore 93s are actually 91 mm wide in the length I've got (171). It's only the 177s that are 93 mm wide. So some manufacturers do change the width with the length. I don't recall what the turn radii are.

There's probably a fair degree of marketing in the selection of widths - if a ski is available in 5 different lengths, and changes width by 2 mm per length increment, what width is it? The Kore 93 could be a Kore 89, or Kore 97. So is it a ~90 mm ski, or a ~100 mm ski? And how would Head justify having a Kore 99, and possibly Kore 87, in their line up?

If the aim was to make each size ski the same, the layup would need to be (subtly) different, core composition tweaked slightly etc. And I reckon there would still be differences - I very much doubt that you and I will ever have the same impression of a ski (in an appropriate size for each of us), given that we're towards opposite ends of the size & strength spectrum. It's probably an unachievable goal.

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@tangowaggon, I think you might be over thinking this.

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In general the thinner a ski the easier it is to flip from edge-to-edge, so the faster you can link your turns. And for the same length a narrow ski puts all the skiers weight on the hill through a smaller area so applies more pressure on the snow.

At one extreme you have a slalom race ski where you want really quick edge switching, so they need to be narrow and the best way to handle different skier weights (for a slalom ski) is to change the length.

At the other extreme you have pure, deep powder skis. Here the need to spread the skiiers weight over as much snow area as possible is much more important than how quickly/tightly you can turn the ski, so you go wide - but you do still need to be able to turn the skis/not have a stance that looks like you're riding an invisible horse to keep the two planks apart so there are practical limits...where you're back to only having length to play with.

That's the logic for the two extremes. For most skis it's probably just cheaper/easier to make a batch of a specific ski in different lengths than mess around trying to balance both different lengths and widths for different skier bodies.

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I'm not sure why you're thinking that the parameters are connected, particularly. Skis (and snowboards) are sold "by length", but really that's just a convenience, in so much as it helps retailers and skiers because if they find a particular ski/board "too short", they pick the size which is "longer".

In reality, you could to some extent build a single model of ski in a single length, varying instead the flex of the ski depending on skier weight. Burton did that with the first generation Burton Fish boards. They produced a single length... in a couple of different flex patterns. That worked great, but confused internet people, retailers and snowboarders, so they went back to ... selling different "lengths". But really they were selling boards aimed at people of different weight.

To some extent width is the same (with some extra complexity for snowboards). If you like a narrow or a wide ski, that's not really much to do with your weight particularly, it's more about what you're riding on and why. There's no reason a heavier racer, for example, would want worse cornering characteristics than a lighter one, or the other way around.

The overall design of a ski is a combination of multiple parameters such as width, length and stiffness. That they typically sell them as a set of "lengths" is just to keep it simple for y'all. The consequence of it... is that some people like some skis more than others, because the particular mix of those characteristics is different, even amongst skis of the same nominal length.

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@phil_w, and same "nominal" dimensions ...

Then you can post your own questions or snow reports...

The waist on Scott The Ski changed with length (I think that's the case with other Scott skis as well)- but whereas there are some skis that do this, I think they are in the minority.

After all it is free

OGSO ski essentially have two ski's a fully rocketed and a traditional camber. they come in a light wight for touring, and a medium weight for free ride. then each model is based on a waist of 10mm eg 70 - 80 - 90 underfoot but within that model its scaled so for example if I ski their 90 underfoot bing tall and having a longer ski it 98 underfoot.

@tangowaggon, it is a reasonable question. Generally a ski character is at least in part implied by it's underfoot (waist dimension). When you keep the waist the same across a range of lengths then if you also maintain tip and tail size then you do affect the turn radius. How much depends on the the disparity between waist and tip/tail, how much that matters depends on the skis other characteristics (camber/rocker/etc).

A couple of examples:

When we made Redeemers they came in 2 lengths, 180 & 190. The waist and widest points were the same, and as the widest points were relatively close together (5 point ski) the two lengths did have quite distinct characters. In anything less than powder the 180 was way turnier than the 190.

We made the gen2 Director in a range of sizes 151-191 with nominally the same tip/waist/tail. Each skis felt similar to those next to it in the range, but the 151 was definitely different to the 191. Additionally the 191 was definitely a mid-fat to a height appropriate rider, the 151 was a pretty FAT ski for someone it fitted height wise.

On some of our later skis we do mess with tip/waist/tail dims to try and keep character more stable across the sizes. So a ski nominally 104 say underfoot may be fractions different one way or the other at that point and at the tip tail to smooth out the differences.

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@under a new name, I think you're seriously "under thinking" this, at least as far as the the theory goes, the question is, does the theory actually appear too highly on your your purchase hierarchy?

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Why do skis stay the same width as length increases?

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