Augment SC and some thoughts about ski suspension

GregK

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Have you tried the '23 Blizz Hustlers?
No, but I bet they’d be decent for their weight like the Enforcer Unlimited are. The Unlimited are similar longitudinal flex to the regular versions but softer torsionally without the metal and would think the Hustlers will be similar. Won’t be as damp but a similar feel as it keeps the track proven shape of the Rustlers.
 

Tony S

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No, but I bet they’d be decent for their weight like the Enforcer Unlimited are. The Unlimited are similar longitudinal flex to the regular versions but softer torsionally without the metal and would think the Hustlers will be similar. Won’t be as damp but a similar feel as it keeps the track proven shape of the Rustlers.
Oh. I get it now. Rustler -> Hustler. Clever.
 

cantunamunch

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Oh. I get it now. Rustler -> Hustler. Clever.

For the Side country. Yes. I am still trying to find someone else who's tried them 'coz my slush-and-shadeice based opinion is crazy good. In a "they nailed a semisoft suspension feel" way.
 

AlexisLD

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Side note on vocabulary: I've always used "damp" to describe the variable Bruno is calling "suspension". But some folks apparently use "damp" to mean "lacking in pop". Personally, I have found a fair number of skis that are damp but still have pop, and I have sometimes resorted to calling these skis "strong".
Perhaps "suspension" is a better word -- although how would one rank "suspension"? It's a category, not a descriptor.

Relevant to this discussion only in the sense that words only mean something if everyone understands/agrees on the meaning. I'd love more finely-tuned adjectives.

I think defining words is really important. I see at least three different things:
1. Damping... the capacity to reduce vibrations over time.
2. Pop... how much it pushes back on you.
3. Suspension.

Blister ranks some skis in their Gear Guide according to their suspension. They have a good podcast about it too. They spend a lot of time saying similar things to what has been said here: suspension is related to stiffness and mass. But the more interesting question to me would be "why is that"?

People talk about a ski being push around or a lot of the terrain being transmitted to your leg. This can give us insight about how a ski behaves. Imagine that the ski is moving flat on snow. Imagine that the ski tip is a mass and that the rest of the ski is a vertical spring that connects the tip mass to your foot. If the tip hits a bump, it will be pushed up. Your feet will feel the tip being pushed up through the stiffness of the ski (displacement x stiffness = force). You will also feel a lack of control when the tip is up in the air.

You can make a few hypothesis about exactly how the ski is being pushed up. One of them is to assume that a constant impulse will be transmitted to the ski. This might not be the case depending on the snow and the ski, but let assume that it is true and let's see where that brings up. If you have a constant impulse, this means that a heavier tip will be pushed up at lower speed compared to a light tip. This means that the lighter tip will have more kinetic energy (because the squared velocity term in E = 1/2*m*v^2). For the same ski stiffness, the lighter tip will be pushed higher due to its higher energy and will transmit more force to your foot (Force = stiffness x displacement). This is why light and stiff skis create harsh rides.

The problem is that if you lower the stiffness of the light ski to feel less of the terrain, the tip will go higher up in the air and spend less time with the snow. This lowers the speed at which you feel you are loosing control of the ski, i.e., this is the speed limit of the ski.

The heavy tip might also "destroy" the snow instead of being pushed back by it, thus reducing the impulse created. This is fun when charging around.

Heavy and soft thus create a nice suspension, but it is heavy and soft! Heavy is not good for touring, and a heavy tip at the end of a soft ski will be harder to control as it flaps around without you being able to drive it. It won't feel like a race car. You need some stiffness.

An important thing to remember also is that all of that is happening within half a cycle (goes up and comes back onto the snow). Damping, as defined by engineers, won't do much during that little bit of time. This is specially true at the damping level that is present in skis (i.e., very little... on the order of 2-3% per cycle). Damping should not be called suspension. They are different things.

The description given by @Bruno Schull is spot on for what has been referred to on this forum as "digital" carbon feel - and we've had several dozen skis tarred with that brush.

The challenge with carbon is it specific modulus (i.e., stiffness divided by mass). It is 4 times higher than fiberglass. If you replace the fiberglass in a ski with carbon with a 1:1 weight ratio, you will get ski that is 4x stiffer. This is no good. If you try to keep the same stiffness, you will have a ski that is much lighter. It is pretty hard to get the same suspension with such different material. But done properly, with some understanding of the physics, it is possible...
 

markojp

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No mention of boots (and plastics) in the suspension equation?
 

Noodler

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No mention of boots (and plastics) in the suspension equation?

Good call out and I meant to post about this. You cannot ignore the boot (and the bindings) in the assessment coming from any skier. It absolutely plays into the perception of the suspension qualities of a ski.
 

KingGrump

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Imagine that the ski is moving flat on snow.

I ski lots of bumps, my skis are seldom flat on the snow.
My skis stay up on edge when the terrain gets rough. Smooths out the ride a lot.

Not sure the flat ski scenario is a good one. If it is, points to more of a technique/tactic issue.

No mention of boots (and plastics) in the suspension equation?

At the Aspen gathering @Tony S and I were wondering how @mdf can traverse diagonally across a field of smallish bumps with a flat ski at decently high speed. We figured it was a combination of a soft ski (Rustler 9?) and 35 years old boots (SX92). I further posited that the boots were at the end of its service life. Rather than duct tape, he was using the neoprene boot glove to hold the boot together. :ogbiggrin:
 
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Bruno Schull

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Hi Folks! Thanks for al the contributions--nice conversation.

Just some added information:
Boots = Atomic Hawx Prime size 29.5 with booster strap and Mimic liner.
Bindings = Look SPX 12...in a rental version? They said SPX 12, but they were on a sliding rail system.
 
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Bruno Schull

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@ Alexis--thanks for the detailed reply. That makes good sense to me.

I understand and appreciate what you are saying about the difference between suspension and damping.

But I still think it makes sense to stay with the word suspension, at least for general usage.

For example, in the mountain bike world, damping is included in the "suspension discussion." It's true that suspending a bike (holding it off the ground) is fundamentally different damping (reducing vibrations over time) but we obviously talk about dampers and damping circuits as part of the suspension components, because they are ultimately about the same thing--how a bike moves over the ground, and the feel when riding. Should we encourage consistency with the ski discussion?

Also, if we separate damping from suspension, what about propagation? Is that not different yet again from damping? Would we not then need "suspension" and "damping" and "propagation?" Or is propagation just a function of stiffness and therefore suspension?

Thanks again-Bruno
 

markojp

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Bruno, I wouldn't call a Hawx series boot a 'damp' boot at all. Plug boots in traditional 'heavy' plastics take a great deal of vibration out of the equation. Would your experience on the SC be different in a race boot? I'm thinking it would. Significantly.
 

fatbob

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It's an interesting thread but way too complex to my simple mind. I think of skis as damp or not damp.

This season I have been majority using a carbon ski - benefits being it is light for its size and "chuckable" and basically will do what I'm thinking of. The penalty is death rattle when you hit a field of groomer cookies or refrozen crud.

In contrast a similar sized trad construction ski I skied gave a satisfying whomp when hitting such detritis. The expense being needing to work it harder all over.

Funnily enough having skied almost all the skis from this manufacturer the only time I've thought the carbon model superior for me in the way it felt was in the one I have in carbon.
 
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Bruno Schull

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Bruno, I wouldn't call a Hawx series boot a 'damp' boot at all. Plug boots in traditional 'heavy' plastics take a great deal of vibration out of the equation. Would your experience on the SC be different in a race boot? I'm thinking it would. Significantly.
Hi Mark--good point. The counterpoint, of course, would be the difference in feel between the Augment SC, which has poor suspension in my view, and skis like the Atomic Redster S9/G9, Stockli Laser SL/GS, and Folsom skis, which have great suspension, using the same boots. The only difference between my experience on the Augment SC and those other skis is the binding system.

That said, considering any/all skis, I do think that I'd love a boot with more suspension. The hard part is finding one with a fit like the Hawx Prime (medium-to-large volume). I have high hopes for the Head Formula medium last range. The Lange 130 RS didn't fit my feet/legs, although I wanted to love it.

All best, Bruno.
 

AlexisLD

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I ski lots of bumps, my skis are seldom flat on the snow.
My skis stay up on edge when the terrain gets rough. Smooths out the ride a lot.

Not sure the flat ski scenario is a good one. If it is, points to more of a technique/tactic issue.

It is just a way to simplify the thinking by not considering shape (e.g., a ski with the sidecut length extending past the running length could feel harsh in 3D snow). If you compare two skis with similar shape on edge, you can use the reasoning above. Putting the ski on edge also increases the pressure on the tip by "preloading" the spring. This increases the impulse needed from the terrain to push the tip off the snow. This will make for a smoother ride, higher speed limit, etc.

Even on edge, torsional stiffness doesn't really provide suspension. Twisting the tip by 2-3 deg will give you 1-2 mm of suspension at most.

If you ski bump extremely smoothly (i.e., the tip of the ski is never "impacting" a bump), then the mass of the tip is irrelevant to the suspension of a ski. You should only care about stiffness (and shape) in that case...
 

AlexisLD

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I understand and appreciate what you are saying about the difference between suspension and damping.

But I still think it makes sense to stay with the word suspension, at least for general usage.

I am not sure I was clear, but I think suspension is a better word than damping for skiing if we had to only use one word. I think most skiers will be able to feel the suspension of a ski. I think most skiers won't be able to feel a change in the damping of a ski (even if it is something that exist). I think the level of suspension between skis changes by a lot (mass and stiffness) but that the damping between skis doesn't change by much. That being said, I think we should use different words. It is more precise/efficient!

For example, in the mountain bike world, damping is included in the "suspension discussion." It's true that suspending a bike (holding it off the ground) is fundamentally different damping (reducing vibrations over time) but we obviously talk about dampers and damping circuits as part of the suspension components, because they are ultimately about the same thing--how a bike moves over the ground, and the feel when riding. Should we encourage consistency with the ski discussion?

I don't like that analogy with mountain biking. Yes, we are talking about spring-damper-mass, but they are not configured the same way or operate in the same range. It is not that same spring-mass configuration, it is not at all the same level on damping, the travel of a bike suspension is much longer and a bike suspension take all the load going to your body.

The bike can be modelled as a spring/damper (tire), mass (wheel), spring/damper (suspension) and mass (skier) system. The ski is more like I described, a mass (tip) and a spring (the front part of the ski) attached to the ground (the tip moving won't make your foot go up and down).

My bike suspension is close to critically damp (zeta around 1) while my ski is barely damped at all (zeta around 0.03).

The tire (spring) on the bike makes for elastic impact with the ground while the snow creates mostly inelastic impact with the ski.

Also, if we separate damping from suspension, what about propagation? Is that not different yet again from damping? Would we not then need "suspension" and "damping" and "propagation?" Or is propagation just a function of stiffness and therefore suspension?

I am not sure I understand this properly. I think this is trying to split even further damping into sub-components (i.e., how damping is created instead of what it effectively does) and is only relevant at much higher frequencies that we should care about. I think people using this are talking about the propagation of waves within the material, which means we are talking about the speed of sound (5000 m/s in wood).
 

cantunamunch

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I am not sure I understand this properly. I think this is trying to split even further damping into sub-components (i.e., how damping is created instead of what it effectively does) and is only relevant at much higher frequencies that we should care about. I think people using this are talking about the propagation of waves within the material, which means we are talking about the speed of sound (5000 m/s in wood).

I'm not sure skiers are actually sensitive to propagation.

My working notion is that they're trying to use 'propagation' to talk about modes , particularly if there are multiple sizes of the same ski being talked about.
 

Tony S

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I ski lots of bumps, my skis are seldom flat on the snow.
My skis stay up on edge when the terrain gets rough. Smooths out the ride a lot.

Not sure the flat ski scenario is a good one. If it is, points to more of a technique/tactic issue.



At the Aspen gathering @Tony S and I were wondering how @mdf can traverse diagonally across a field of smallish bumps with a flat ski at decently high speed. We figured it was a combination of a soft ski (Rustler 9?) and 35 years old boots (SX92). I further posited that the boots were at the end of its service life. Rather than duct tape, he was using the neoprene boot glove to hold the boot together. :ogbiggrin:
Note that I finally got over my uncharitable resentment about this and decided that he was just better at it than I was. I also eventually found my own approach but it took me about six runs over those heinous micro bumps to do so.
 

cantunamunch

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Note that I finally got over my uncharitable resentment about this and decided that he was just better at it than I was. I also eventually found my own approach but it took me about six runs over those heinous micro bumps to do so.

Well, at least you didn't blame the (lack of?) preload :D
 

mdf

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At the Aspen gathering @Tony S and I were wondering how @mdf can traverse diagonally across a field of smallish bumps with a flat ski at decently high speed. We figured it was a combination of a soft ski (Rustler 9?) and 35 years old boots (SX92).
My skis were NOT flat. There is no way I could do that on a flat ski. And my boots aren't alll that soft (they have an adjustment). The key is to stay on edge, put a little more weight on your boot cuff than normal, and keep "loose knees". And my skis ARE soft (Navigator 85) and longish (186 cm),

I like to play a game to see how long I can wait for the first mogul turn. As the bumps start to grow, you can often extend a little by looking for the best path -- the core part of the game is to just ignore the bumps.

You also have to be going fairly fast and have an acute angle to the mogul-ette spines.
 
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