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Ski Width, Weight, and “Quickness”

Intro

If you’ve read through some of the Comments Sections of our reviews, you’ll have noticed that we get quite a few good questions and comments from our readers.

And we often find that a reader has brought to light an interesting point about the piece we’ve tested, or has raised a broader question that’s worth considering and discussing.

But some of these comments and questions can get buried deep down in a particular thread, so we’ve created this series to feature some of the conversations that are taking place around Blister.

This week, we’ll highlight a question about a ski’s “quickness” that appeared in the Comments Section of our review of the Atomic Vantage Theory:

You talk about how quick the ski is from edge to edge, and imply that a narrower ski will be quicker edge to edge then a wider ski. I thought this made perfect sense, but no matter how wide or narrow a ski is, as soon as you angulate your leg/foot, the ski will respond, more or less, instantaneously to correspond with this angulation. But the wider the ski is, the more work you need to do to make the movement. But this is a function not of width per se, but of weight. So, all things being equal, a wider ski will be slower edge to edge, but if my reasoning is correct, a lighter ski, even if wider, should be quicker edge to edge. In your opinion, does experience bear this out?”

Will Brown’s Reply:

Good question, Eric.

The short answer is: Sometimes, but it depends.

The much longer answer is:

I think you’re right that the width of a ski doesn’t change the physics of how one of its edges is engaged. In terms of the angle of your leg and the amount of movement involved, I don’t believe there is a difference between setting a 115mm-underfoot ski on edge at 30 degrees vs. setting a 85mm-underfoot ski. So in that sense, I suppose me talking about “quickness” and how fast a ski is edge to edge isn’t technically accurate. I think you’re right that it is more a matter of the amount of effort required to put a ski on edge. Requiring less effort translates to the ski feeling “quicker” – the ski is easier to put on edge more quickly.

In any case, your comment got me thinking about why that is, and what the most significant factors are—weight vs. width, etc. I’m not so sure that how quick a ski feels isn’t a function of width, at least in part, and I’m not sure it’s only a function of a ski’s weight, either, but you’re right in that weight definitely plays a role.

Tipping a 115mm-underfoot ski on edge to 30 degrees (or from one edge to the other) seems to take more effort / leverage than it does on a 85mm-underfoot ski. Why? I’m no engineer, but it would seem to have something to do with the distance between the center of your boot sole to the edge of the ski. If you put a candle on a holder with a very narrow base, it will take less force to tip it over than if you put that same candle on a holder with a very wide base. (All you scientifically-inclined readers out there, please feel free to chime in with a better, more sophisticated explanation, as I’m sure there is one.)

So I don’t think we can rule out width, but you’re right in mentioning weight because (in keeping with my weird candle analogy) the weight of the base of the candle does affect how easy it is to topple the candle. So at what point does the weight of the base play more of a role in keeping the candle upright than the width of the base? What’s going to feel quicker – a narrower, heavy ski, or a wider, lighter ski?

At 124mm-underfoot the 188cm Line Magnum Opus is going to feel quicker than the 108mm-wide 188cm Armada Invictus, in part because the Opus is lighter (+1 for weight). Would a very heavy, 68mm-wide slalom ski with a race system binding on it feel quicker than, say, the 110mm-wide Volkl V-Werks Katana? Probably (+1 for width).

So lighter (but wider) can be quicker, but it’s not always the case. Weight and width are only two of many more variables in ski design. Sidecut, effective edge, length, flex, swing weight (how the weight is distributed on the ski, which is different from a ski’s overall weight), not to mention snow conditions, all play a role in how quickly and easily you’re able to get a ski from one turn to the next, or how hard it is to do so.

That’s why we really do try to communicate the particulars of a ski, keeping in mind all of these factors. But, clearly, even then, we’re still liable to misspeak now and again. In any case, thanks for prompting this little thought experiment, and helping me stay on point. :)

10 Comments

  1. Michael Latta January 8, 2015 Reply

    A wider ski requires more force as you are pivoting on the edge while your body weight is in the boot area. The skier weight has to be lifted to place the ski on edge. The narrower ski has less travel distance for the skier weight so it should be quicker. Since skier weight overrides ski weight in this, the width should be a much larger factor than ski weight.

  2. Dm January 8, 2015 Reply

    From an engineering point I think three factors are in play.

    Width as Michael Latta says should dominate in most situations as there’s a jacking effect on wider skis – you are literally lifting your body weight as you edge.

    However, sidecut for a given width will make most difference, shorter radius, quicker ski…

    Assuming similar torsional rigidity. If the ski is as soft as a noodle, it will never feel quick as the edges will never fully engage.

    So super quick = skinny underfoot + short radius + torsional stiffness = slalom ski

  3. John January 8, 2015 Reply

    I just did a on snow comparison of boot stiffness vs. binding stiffness by AB testing 2 identical Movement Shifts mounted with Dynafit FT-12 w/ power towers, and Marker Kingpins. The 2 boots used were the La Sportiva Spectre and the Scarpa Freedom SL. The skis are 1400+ grams, an approxiamately 99mm underfoot.

    The first thing I noticed was how much more power I had skating with the Kingpin with either boot. Ultimately the stiffer binding allowed the ski to be pushed harder, and increased turn initiation and power out of a turn. the same ski was more lively, carved better, and did not chatter at speed.

    Maybe with a better ski/binding interface, though it may be a little heavier, a lighter boot with greater articulation may be the better way to go. The whole package of skis boots and bindings is lighter.

    I felt like what was a light nervous ski on hard snow is now more powerful, stable, and predictable.

  4. Bill den Broeck January 8, 2015 Reply

    If changing edges is a muscular feat then ski weight matters. If you use primarily muscular feats to ski, maybe your skiing isn’t as refined as it could be. Edge change speed depends on ski width and little else. Get a ski at 105mm and a ski at 85mm (waist sizes) with comparable weights and you’ll find the narrower ski changes edges faster. Make the narrower ski heavier and the same result will be found. I’m not sure that physics discussions will help here, though the physicists (both real and shade-tree) may insist they would. Just go run some gates on an easy citizen NASTAR/beer league course, you won’t need a physics lesson to verify your findings.

  5. Alan January 9, 2015 Reply

    Wouldn’t you have to move your hips a further distance with a wider ski to get the same angle of the ski on the snow as both your foot centres are further (higher) up from the ground?
    So the slightly increased distance the hips have to move from turn to turn, if the angulation is constant, has got to take longer to cover?
    Not sure if weight makes much difference as the forces are wanting to go sideways promoting edge change while in a carve and being held at bay by the edge and in a carve the ski is always touching the ground so the perceived weight is probably more noticeable in the twisting effect ala the swing weight more I’d say.

  6. Adam January 9, 2015 Reply

    Take it to the extremes… If you skied on ice skates, the action is a simple pivot on the blade itself… The physics require no lifting of the skier, specifically as the skiers weight pressing downward during a carve. Then ski on a board two feet wide… The force required to lift the skier onto the skis edge is significantly more than the skiers weight. You have to generate a force equal to the skiers weight ” in motion”. Think of the force required to lift a stationary car versus the force required to resist the impact of a car collision while going 60 mph. Then torsional rigidity and ski stiffness and rebound energy and radius etc all become a factor as the ski is bent which create a force vector in direct opposition to the skiers downward weight. So one skis properties might create an easier situation to “get on edge” than another ski. In other words, it’s complicated. Fun stuff.

  7. Bill den Broeck January 9, 2015 Reply

    Turn to turn isn’t the same as edge to edge. Turn to turn is affected by inherent turn radius, torsional flex, and skier technique.

  8. Mike January 9, 2015 Reply

    Width and weight are just two parts of the equation. Width, or distance from the center of the ski, acts as a lever. In the case of a wider ski, it takes more force (effort) to overcome the greater lever. Thus, exact same skis except width, the narrow ski would be quicker. Same is true for weight. Additional factors include: side cut, materials, torsional rigidity, dampness, tail stiffness, overall stiffness, stand height, ski length, swing weight, Thickness, “stiffness” of binding. I did not include boot stiffness as it would be constant for a given skier. All these (and more?) contribute to what we perceive as “quickness”. I don’t think any one factor can be identified as the “quick” factor as it is clearly multi factorial.

  9. eric January 9, 2015 Reply

    Hey, I am just happy that my semi-coherent sense of puzzlement could elicit such a thoughtful and considered set of comments! Yea to the Blister readership, who not only can out-ski most, but apparently out-think most too!

  10. Spokane January 9, 2015 Reply

    Rocker
    Width
    Sidecut
    Camber
    Length
    Weight is probably the last thing related to quickness.

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