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Not a review just an observation

geepers

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If I remember correctly, and if you listen carefully to what Jurij says, you will find that the level of torsional stiffness is what make a ski suitable for beginners/experts.

Take a look at this for the Mantra M6 and Blaze 86. It is not a perfect comparison (there are a few factors that are changing like the width and the mass), but it gives you an idea. I plotted the short and long length so that you can see how the lengths of each model scale. The Blaze 86 is marketed as an intermediate ski. The Mantra is an advanced/expert ski.
View attachment 157750


The bending stiffness differences between comparable lengths is about 15-20%. That is not very much. Bending stiffness is related to the speed limit of a ski, and if you think about it, the vast majority of people at resort ski at relatively comparable speed (beside a few chosen one).

The torsional stiffness differences between comparable lengths is however on the order of 60%. This makes a ski precise vs playful. A beginner doesn't want a precise ski. They don't have the skills to prevent catching an edge, or deal with the situation once it happens. Expert skier might want either precise/grippy or playful depending on the feel they are looking for.

Thanks, that's good.

Re-listened to the Jurij interview. Just to make sure we're listening to same it's the Tom Gellie one. Seems it's a combination of both. What he says is their measurements showed the torsional stiffness didn't have any influence on how the ski was holding as long as the skier was in the correct fore/aft position. But as soon as the skier was a little forward or back of the binding area then the torsional stiffness made a huge difference.

The relevant discussion is about the 18 minute point in the interview and the bit about measuring the torsional stiffness was around 20 minutes.

Of course Jurij's era at Elan was a while ago.
 

anders_nor

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here we give the slopes normal names, some names after the builders, or a local hero, or the area they are built, or what they do like "run to city center slope"

Also I find weight plays a way to big role in what you like as a skier.

Then you have the really really good skiers, the person that can run a FIS ski on a shitty hill makeing it look like its a perfect firm groomer. pretty much all of them will have a race background or at least serious skibum
 

James

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The 10 mph likely to have much more to do with it than the 130lb. 10 mph is unlikely to require much angle to balance lateral forces and the main determinant to bending the ski is edge angle. Pressure (from weight) has a very secondary effect and only really shows up on soft snow with very significant increases in load.

Quick test - support a ski tip n tail and see how much weight needs to bend, say, 50mm. It will be a fraction of body weight. 130lb would be more than enough to bend a ski more than 50mm. They are skis, not I-beams. If the middle portion of the ski is not supported by a surface, either because it is in a dip or the ski has been tipped, then it will bend.

Ski below is a Rossi Exp 84 the 2017/18 one with the Look binding package. Yellow and black before they went all screwy with that bluey/greeny version. Not the stiffest ski but not a wet noodle. Not a lot of weight resting on that foot,




So what makes a ski beginner/intermediate vs expert?

Jurij Franko (former Elan ski designer) reckons it is the amount the skier needs to change fore/aft balance to cause the ski to lose grip at the tip or tail, a beginner/intermediate ski needing far less RoM than an advanced/expert ski. Which makes sense as beginners/intermediates are less likely to be able to tip skis to higher edge angles and it fits with the idea that more effort is needed to, say, be a little forward on a stiffer ski to unload the tail to displace it.

Personally, don't get to ski enough different skis to know. :huh:
I get the bending thing, but it doesn’t really match real world experience. There’s got to be more to it then “oh look how easy it is to bend a race ski”.

Super stiff longitudinally skis are not the same to ski as soft skis. Maybe it’s the forebody bending in the turn. Stiff tails make a difference. Certainly in 3-D snow too soft skis for the operator are a nightmare on steeps as they fold up.

I don’t know what the answer is, but I just don’t think stiffness doesn’t matter. Weight definitely makes a difference too. So, if skis are so easy to bend, why would weight matter?
 
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cantunamunch

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. Maybe it’s the forebody bending in the turn.

This, particularly the not-steady-state phase of going from a flat to an edged and bent ski, is of the most interest to me.

Steady state analysis of the bent ski in the fall line is just hand waving until we know how to get to that state.
 
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geepers

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This, particularly the not-steady-state phase of going from a flat to an edged and bent ski, is of the most interest to me.

Steady state analysis of the bent ski in the fall line is just hand waving until we know how to get to that state.

In that interview Franko (a physicist) says when he started at Elan he asked how skis work. They said "We don't know." Said he was to later find out no matter the industry, the only ones who had the theory worked out were associated with the military.
 

geepers

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I get the bending thing, but it doesn’t really match real world experience. There’s got to be more to it then “oh look how easy it is to bend a race ski”.

Super stiff longitudinally skis are not the same to ski as soft skis. Maybe it’s the forebody bending in the turn. Stiff tails make a difference. Certainly in 3-D snow too soft skis for the operator are a nightmare on steeps as they fold up.

I don’t know what the answer is, but I just don’t think stiffness doesn’t matter. Weight definitely makes a difference too. So, if skis are so easy to bend, why would weight matter?

If I understand what Franko's saying it's response to input. How far will a ski rotate when the CG is moved fore/aft a given amount. He says racing skis are made to rotate very slowly as it is made for higher loads - difficult to ski at low speeds. Beginner ski made so it rotates much faster for the same input - easier to ski with low loads.

So bending stiffness (and weight) matter in what effect a change in CG has. A stiffer ski requires a bigger movement for the same weight. A heavier skier is able to bring a bigger change with the same movement. At least that's what I'm thinking it means.

But :huh: . Don't get to try enough skis. Want some-one to post The Definitive Answer. Who's in the military?
 

James

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Beginner ski made so it rotates much faster for the same input - easier to ski with low loads.
As another matter, mount point influences this. It’s one reason I hate center mounted skis, a little goes too far. But I have little experience with them. I think it’s better for kids to learn with directional skis before branching out because they too easily rotate them. But it’s almost as pointless as having a pole length discussion with most kids and parents.

Like the two siblings I had who are quite good skiers. Eleven years old. They ski probably 2 weeks out west. Yet they’re in rental boots and progressive mount twin tip skis. Can not get them out of whole body tipping. No way can they bend the inside leg.
It’s likely the boots are two shells too big. Their shins are bolt upright.

Multiple instructors have had the boot conversation. On the second day I was told by the dad he monkeyed with the boots. No change. They’re beyond fixing.
 
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AlexisLD

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I get the bending thing, but it doesn’t really match real world experience. There’s got to be more to it then “oh look how easy it is to bend a race ski”.

Super stiff longitudinally skis are not the same to ski as soft skis. Maybe it’s the forebody bending in the turn. Stiff tails make a difference. Certainly in 3-D snow too soft skis for the operator are a nightmare on steeps as they fold up.

I think it is important to remember that even if it is "easy" to flex a ski, it doesn't mean that nothing is different on the snow between a soft ski and a stiff ski. Here are a few thoughts:

- Pressure at the tip/tail is gonna be higher for a stiff ski. More pressure = more friction/grip at these points. This means that a stiff ski will be harder to pivot. As almost all turns are initiated by pivoting (even for experts doing carving turns), you will feel some difference between soft/stiff skis during turn initiation. It will be harder to initiate a turn with a stiffer ski because it will be harder to pivot the ski and create an "angle of attack" that makes it easy to flex the ski.

- This is a little bit more of a far fetch idea, but you also have to think that skiing is not a static motion. It is easy to flex a ski when standing on it, but there are some moment of weightlessness during skiing. It is easy to create the load necessary to flex a ski during the final phases of a turn, but much harder to do so early in the turn... Not too sure about this one though...
 

mdf

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Personally, I like softer but longer skis. They still carve if they have camber and a real tail, but they are friendlier for the same length in bumps. (When I demo stiffer skis, I can make them work after a run or two of adaptation. But I still don't like them as much.)
 

cantunamunch

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Personally, I like softer but longer skis. They still carve if they have camber and a real tail, but they are friendlier for the same length in bumps. (When I demo stiffer skis, I can make them work after a run or two of adaptation. But I still don't like them as much.)

We had a thread some time ago about whether there was a minimum forebody stiffness that would reasonably work in bumps, below which the ski was basically a lazy tip noodle without control authority. Not sure what the conclusion was. Maybe @Erik Timmerman remembers.
 

mdf

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We had a thread some time ago about whether there was a minimum forebody stiffness that would reasonably work in bumps, below which the ski was basically a lazy tip noodle without control authority. Not sure what the conclusion was. Maybe @Erik Timmerman remembers.
I know that when my previous pair of Navigator 85s wore out to a state of full-length reverse camber, skiing bumps with no tip engagement was difficult.
 

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