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Is Ski Weight Really that important?


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I was having a discussion with someone about lightweight skis and which ski is the lightest and how one ski is 2 pounds lighter then another ski, etc. It got me thinking. Is 2, 3, even 4 pounds of weight really all that important once you put boots and a 180 pound skier on it? When you figure in the whole "package", what is 2, 3, or 4 pounds when the total "package" (ski, boots, and skier) weight is 190 pounds? Does 188 pounds really make much difference over 191 pounds?

 

Just thinkin.

 

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The more important question to ask is about angular moment, what some people call "swing weight." This impacts the amount of energy required to change from skiing in one direction to skiing in the other direction.

 

The short version of it is that mass out at the ends adds a lot more angular moment that mass near the center. So binding weight is not nearly as significant as the weight of the extremities of the ski.

 

That said, I do think weight (or even the more important angular moment) often gets over-rated. Other properties of the material are at least as important, and the shape of the ski is clearly more important. (To see why, consider the extreme of a 0-weight ski in a silly shape compared to an old dense-wood ski in a good shape.)

 

Still, at the margin, lower swing weight is nearly always a good thing. In other words, if everything else were equal, take the lighter ski.

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Weight matters!

 

I'm not sure that Than is right on swing weight. A slalom ski doesn't "swing" very much around the center of the ski (note that a trick ski does). So a light ski at the ends may not show much advantage.

 

The ski does swing against your body's center of mass. The weight is at the end of a long lever (your legs with COM somewhere above the pelvis). So the all up weight of the ski and bindings matters. The light setup will "snap" a turn with much less effort than the heavy ski. Binding weight is a critical factor in the overall ski weight. The all up weight of the ski, because it is way out at your feet, really has a significant effect on your performance.

 

As with anything, there are tradeoffs. Light skis struggle in rough water. Heavy skis are nice and stable. I seem to trade off a bit of consistency for top end scores when I make a lighter version of a ski. The light ski is much better at recoveries from those inevitable form breaks - that in itself makes a light ski better.

 

Skis are reaching a point of diminishing returns on weight reduction. Many other factors determine how a ski feels and performs. Modern skis are quite light. Many modern bindings are reasonably light (but why the plates aren't Nascar drilled out to save free weight is beyond me). Total ski setups from many manufacturers can be light enough to make the weight differences between manufacturers irrelevant. Demo and pick the ski/binding setup that works best for you. Tie goes to the light ski!

 

Eric

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@eleeski wrote: 'A slalom ski doesn't "swing" very much around the center of the ski'

 

Sure it does. You just have to place your coordinate frame on the skier in order to see it. But the physics of rotating while translating aren't much different than the physics of rotating in place.

 

In any case, Eric and I reach the same conclusion. (So we're probably both wrong...)

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I really don't know what I'm talking about but here is my take on it. I'm guessing Than's concept on "swing weight" isn't really the ski swinging about the boots but swinging about your shoulders where you're holding onto the rope. If you're swinging the ski about your shoulders, which you are, I would think this would play a much bigger factor. Are boots important? I would think so, but I don't see them being as important as the ski itself. If you extend out over the buoy, you have to bring all that weight back in front of you.
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I certainly feel a positive difference on a light ski. I see it being similar to unsprung weight on cars. Unsprung weight is weight/inertia that must be controlled and dampened by the suspension system of a vehicle since it is downstream of the suspension components. Wheels, brake rotors, control arms, axles, half-shafts, etc. As an extreme example a solid truck axle with drum brakes is going to be a lot harder for the suspension system to settle down after hitting a pothole than, say, an independent aluminum control arm setup with ceramic brake rotors and forged alloy rims.
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I feel a difference on a light ski as well. But is that due to it being 1 pound lighter or is it because of the quick reactive capabilities of the carbon fibers and the PVC core which make it light? I'm thinking it is because of the materials used. A ski with a polyuethane core weighs more then a PVC core ski. You're going to feel a difference in the two skis but I don't think its because the PVC core ski is a couple of pounds lighter. You're going to feel a difference because polyuethane is 7 to 10 times damper and less reactive then a PVC core ski. Same idea with 100% carbon fiber versus a ski that isn't 100% carbon fiber. Just my thinking.

 

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I had a friend that used a spacer under one boot due to a motorcycle accident that left one leg about an 1" shorter than the other.

 

I think the lighter skis make a difference in skiing. Other than that I sure prefer carrying around my weighs nothing new carbon ski vs. the old heavy skis.

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I think weight does matter, but I think of it differently.

 

First of all, when the ski "swings" in the turn, it is actually carving, the shape of the ski is pushing against the water and the water is pushing against the ski. This is quite different than of you were swinging around a pole with the ski in the air.

 

Second, I think when the edge change happens there is a moment of unweighting. At this moment I think ski weight makes a big difference.

 

Anyhow, seems most of is think light is good.

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There are a lot of opinions on this subject. The thing that separates light skis from heavy skis is the materials. These materials have a lot of properties besides their weight. Lighter is most likely an advantage but is it THE key to more balls?

 

A ski that is 50% fiber glass and 50% carbon is different from a 100% carbon ski in a lot of way besides pure weight. A 100% carbon ski that has 55% resin is going to be different from a ski that is 40% resin. In both cases the weight is a secondary factor.

 

Flex and rebound totally change as these materials change. I say that weight is a byproduct of materials and better materials make a better ski

 

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The thing that most folks do not realize is that R&D skis can be heavy. I know for a fact that 41 off has been run this year on a 10 pound ski. When skis get cut up, reshaped, Bondo added and then glued back together do you think the ski is still super light?

 

 

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Radar will have three skis out of the same mold for 2013

Strada - light weight everything

Vice - not all Carbon and heavy-ish core

Vice C that is somewhere in between. All carbon and heavier core I think.

 

If I had to guess, the Vice C will be a chunk faster off the ball than the normal Vice and feel almost exactly like the Strada.

 

The cool thing about the standard Vice is the it flows out off the second wakes extra nice. Is that because of weight or materials? I do not know but it feels really good. The downside to that ski is if you bobble at the ball it is not as fast to accelerate back to the wakes.

 

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I think Eric was on to something with the lighter ski "snapping" a turn. When I first went from a older HO to my first Goode (9500), My eyes practically came out of my head with the first turn (how quickly it came around and out in front of me). I would have to think that has something to do with weight.
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Insert Sam Kinison voice: Aaaaaaaaaa Aaaaaaaaaaaaaa Aaaaaaaaaaaaaaa

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@Boody do you really want a faster edge change? The faster the ski goes from one edge to the other, the narrower you will be. Ever heard of a guy named Nate Smith?

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I am going to say that the spacer Bob is using is not for leverage, but to equalize leg length. If I am not mistaken he had a hip replacement a few years ago. Almost always the surgical leg is purposefully lengthened to tighten the lateral tissues and stabilize the joint as you are loosing the normal stability of the ball and socket. I am guessing he had his left (rear) hip replaced and needed the spacer to level things out.

 

Personally I would prefer a lighter ski. Easier to pick up and carry to the dock.

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I have a 5mm difference (short right) and am RT foot fwd. I have an inlay in my hardshell under the liner.

 

With out the spacer it is difficult to shift my weight enough onto the front foot.

 

BUT - that hunking spacer seems a bit extreme, would seem to concentrate stress at the front or rear of the block.

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I agree it's a big plate, but depending on the surgeon, etc there can be very large differences in leg length that a simple lift in a shoe will not correct sufficiently. It's not uncommon to see LLD's of 3/4". Or maybe it is for some unknown skiing purpose.
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@DanE and @Mr.Jones thanks for messing up sales of the new "Smart Spacer." It is an advantage. Everyone needs to buy one from me. They are only $349 per binding. If you have a single plate, like G10, they are discounted to $689.

 

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it may be that the heavier skis are also the skis with less advanced, potentially "soft" materials and flex mor, but I believe the more novice a skier you are you will benefit more from a lighter ski than some of the stronger, more advanced skiers. Skier strength may play a role in that too but IMO advanced shortline skiers have to be strong.

 

I know after skiing on the Vice vs the Strada the vice skied like a log for me at 34.2mph 22-32off. the strada was noticably more agile, quicker and I could feel the weight difference in trying to move the ski outbound and maintain leverage off the 2nd wake. the Vice "bounced" around more, and was not as smooth through the wakes or the edge change. Materials could have had an effect as well of course. I don't think its any coincidence that the highest end skis are also the lightest in their respective lineups. my 2cents

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@Killer

Insert Sam Kinison voice again: Aaaaaaaaaa Aaaaaaaaaaaaaa Aaaaaaaaaaaa

 

The skis feel different but how can you say the difference is literally the "weight"? Those two skis have different flex and rebound characteristics because they are built from different stuff.

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@Horton, had to look up this Sam Kinison reference :) I agree, different skis, but the shape is the same and even you have said the shape is what the pros play with the most.

 

If it was lighter it would have to be made up of some more carbon or other advanced materials so the makeup would change and we're back at square1 (no pun intended). For me the difference between the 67 vice (the exact ski you tested which I picked up from a baller) and a new 67 strada was mind blowing and I'm not a heavy skier or running it through deep shortline passes. Every ski that comes out of the factory has a slightly different flex so that variable may be lower on the list IMO.

 

 

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If you want a certain stiffness out of a fiberglass ski, it will weigh a certain amount. Advanced materials like Graphite will allow the same stiffness at a greatly reduced weight. Or you can go stiffer and still be lighter than old glass. Note that fiberglass is a wonderful engineering material in itself, has uses in modern skis and is able to create skis that ski well.

 

@Horton is too dismissive of the effect of weight on a ski. It is a real effect. It is not the only variable that matters by any means. And light weight will not make a bad design ski well. But it might make a good ski better.

 

Stressing over a couple of grams will not have any effect on buoy count. A couple of pounds will.

 

Conventional thinking for waterskis is that you want your soles of your feet as low as possible. Very different from snow ski racing where more lift means more angulation and more edge pressure is possible. My personal experiments have found no benefit and a bit of adverse effects from foot lifts. But these were not extensive tests. Removing the heel lifts from my trick ski helped a tiny bit (a few years with lifts, since then none) but that effect is quite subtle. I do cant the boots a bit forward.

 

Keep it light!

 

Eric

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Since stiffness was added to this conversation, I'm going to throw one more monkey wrench in the issue of weight/stiffness. Yes you can use more fiberglass to equal the same stiffness as carbon fiber and yes the fiberglass will weigh a little more. The problem is that the two composites structures will not have the same strength. So they may bend the same when measuring a flat sheet but the ski as a whole will be different because the bottom skin is primarily loaded in tension and it's much stronger than the carbon version. The dampening will also be drastically different, regardless of the core.

 

Now here's where it gets really complicated. Fiberglass and carbon fiber are typically measured in tension and bending. These composites works great in tension because the fibers take all of the load but when you're loading the composites in compression, the resin takes the load. So in a hard turn, the bottom of the ski is being pulled in tension and the top of the ski is being loaded in compression. This means that the top and bottom skins of the ski may be made exactly the same as the bottom but will have greatly different strength properties in the given application.

 

All of that schoolboy theory mumbo jumbo and I think the real thing to consider may just be the ski as a complete package. I doubt a 3lb walmart ski made with carbon fiber and a pvc core will carve well or explode out of the turn nor will a 10lb Strada be quick and turn well with a wood core and fiberglass mat.

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You totally forgot rebound

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Dampening would be what controls the rebound, unless you are thinking in shock absorber terms of compression and rebound forces and tuning them individually. My logic in the comment is rebound being either the return force during/after the compressive loading, say in the turn, or perhaps the velocity of the rebound action and the damping would be as you noted the rate of decay of the oscillations or even the initial oscillation. I tend to think that a ski with a lot of rebound and maybe even little damping would be one that feels very lively and vice versa for the other end of the spectrum.
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