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Soft Powder Skis = Increased ‘Float’?...

post #1 of 26
Thread Starter 
I get that soft longitudinal flex in a powder ski has a roughly similar effect to RC/rocker. That is, in deep snow it allows for the ski to be easily bent and thus makes it easy to turn (esp. at slower speeds, tight trees, etc). And also gives the ski a nimble, maneuverable, slarvy-fun kind of personality in powder snow.
 
My question is; Does the soft flex, or RC/rocker for that matter, actually increase the ‘float’ of a ski? ‘Float’ defined as purely the extent to which a ski rises to the surface in 3D snow.
 
I would have thought the flex might only have a very minimal effect, if any, on just extent to which a ski rises to the surface in powder.
Float being a function of;
  • Skier weight (increased weight = decreased float)
    • Also weight distribution along ski surface area – i.e. sitting back allows the tip to rise more than a centered stance.
  • Skier speed (increased speed = increased float)
  • Ski surface area (increased surface area = increased float)
    • Distribution of ski surface area (a 135mm underfoot R-R ski would rise to the surface better than a rockered traditional sidecut ski with the same total surface area?). That is surface area directly underfoot floats more than surface area at tip or tail.
  • Snow density (increased density = increased float)
 
So should flex or camber profile fit in that list at all?
 
If the list above (flex not included) holds then, all other things remaining constant, a HT (185cm at 140-115-130) should rise to the surface marginally quicker than an Elan 1010 (183cm at 140-110-140)?... Although the HT might not be quite as nimble in short turns/tight spots due to a stiffer tip profile, it should, in theory float to the surface marginally quicker? I know that 5mm underfoot isn’t a whole heap of extra surface area and thus won’t make much of a discernable difference – but just using as an example to illustrate the question.
 
Alternatively, would the stiff tip of the HT ‘punch’ or slightly ‘sink’ compared to the softer tip of the 1010? Maybe comparing with something like the Obsethed is a better example given its soft and slightly rockered tip/tail.
 
Thoughts?
post #2 of 26
 youve oveer thought this.


simply put yes, softer skis float better the difference will be more pronouced the slower you go, the lighter you are, and the shorter turns you make.

you can easily ski both the HT and the 1010 and the 1010 will float more due to its softer tip(and softer overall flex).

another easy test is to ski a Nomad 181 and and 181 Nomad SFT and youll quickly find that the SFT(soft) floats better than the normal nomad.

also mounting point has alot to do with float as well but thats another thread.
post #3 of 26
Soft ski will float more easily in soft snow.

Torsionally soft ski will also be deflected more easily in chopped up snow, and probably not hold as well on the pack.  The Icelantic Nomad references above are a great example.  Read the test reports on these 2 skis by comparable weight skiers & that is what they will often tell you.

It is challenging for a ski maker to create a soft flexing ski that does not twist. 
post #4 of 26
Thread Starter 
Touche`.. I agree. Definitely overthought

Yup, mounting point obviously influences skier weight distribution along the ski.

Does anyone know what it is exactly about a softer flex ski that increases float? This is out of pure curiosity and really a physics question. Is it that a softer ski will decamber more easily and thus this bent shape actually increases pressure from the snow on the bottom rather than the top of the ski. And thus it rises more easily/quickly?

Quote:
Originally Posted by BushwackerinPA View Post

 youve oveer thought this.


simply put yes, softer skis float better the difference will be more pronouced the slower you go, the lighter you are, and the shorter turns you make.

you can easily ski both the HT and the 1010 and the 1010 will float more due to its softer tip(and softer overall flex).

another easy test is to ski a Nomad 181 and and 181 Nomad SFT and youll quickly find that the SFT(soft) floats better than the normal nomad.

also mounting point has alot to do with float as well but thats another thread.
 
post #5 of 26
Quote:
Originally Posted by Vinski View Post

Touche`.. I agree. Definitely overthought

Yup, mounting point obviously influences skier weight distribution along the ski.

Does anyone know what it is exactly about a softer flex ski that increases float? This is out of pure curiosity and really a physics question. Is it that a softer ski will decamber more easily and thus this bent shape actually increases pressure from the snow on the bottom rather than the top of the ski. And thus it rises more easily/quickly?
 


 

exactly.....well the ski is more likely to be decambered regardless of snow type, a decambered ski is a floating ski.
post #6 of 26
I was a little weary of a fully rockered ski, so I ended up getting a pair of Sir Francis Bacons that are a pretty soft fat ski with traditional camber and sidecut. I can fully feel the decamber in 3D snow and they float amazing really surfy. I was little weary of tip dive due to my experiences on a shorter stiff ski. But once I let the Bacon's go I was blown away by the float I experienced. Soft ski's are fun, but I still want a stiffer ski with a rockered tip for charging.
post #7 of 26
Quote:
Originally Posted by Vinski View Post

Does anyone know what it is exactly about a softer flex ski that increases float? This is out of pure curiosity and really a physics question. Is it that a softer ski will decamber more easily and thus this bent shape actually increases pressure from the snow on the bottom rather than the top of the ski. And thus it rises more easily/quickly?


I think it's like this:

Soft snow has two ways to move when a ski tip is moving through it:  it can follow the curvature of the tip and go under the ski, or it can spill over the edges and go around/over the ski.  Snow that spills over the edges and goes around/over the ski does nothing for flotation.  A soft ski decambers easily by both rider weight and the pressure of the snow following the curvature of the tip, the latter of which decambers the ski even more when it reaches a certain speed to basically turn the entire ski forebody into one large shallow ramp that facilitates a lot of snow moving under the ski.  OTOH, the tip of a stiff ski kinda batters through the soft snow.  I mean, the motion-facilitated decambering might still happen to some extent, but it might require so much theoretical speed that it never really happens.  So the snow just moves around/over the tip.

*edit* BWPA beat me to it.
*edit* I guess I also restated Vinski's original post.
post #8 of 26
Dt pretty much covered the science. I'll say the same thing differently, however. The softer flexing (longtitudinal) ski pats the snow softly, allowing the snow to form under it and create float. The stiffer ski hits the snow with a smashing blow, compressing and displacing the snow before the snow can provide float.

All the stuff about binding placement and stance is irrelevant to the question. Planing the tip up by sinking the tails is more like a boat reaching plane speed.  It's not floating, and it's not powder skiing. The idea that you have to have the tip up to ski powder is simply not true. Get that and your getting somewhere in powder. Rocker and Reverse Camber are not designed to plane up, they are designed to arc in the powder, at various levels in it. IMHO, of course. (Except maybe the pontoon, and all skis like it, which seem to surf around like a overgrown duck sliding the mountain on her web feet riding way in the back seat.)
post #9 of 26
Thread Starter 
V. Interesting.

Q;
Given a ski will decamber to some extent with skier weight, at slower speeds would I possibly experience more float on my HT's (as of yet unriden) as a heavier guy (~210lbs) vs a lighter guy (~150lbs) who is not decambering the ski as much as that speed? Or, as I suspect, is this effect much more than negated by the fact that overall weight decreases float?

Sounds like I may find the HT a bit more maneuverable and nimble at slow speeds in tight spaces than lighter skiers due to more decambering?

Quote:
Originally Posted by DtEW View Post

I think it's like this:

Soft snow has two ways to move when a ski tip is moving through it:  it can follow the curvature of the tip and go under the ski, or it can spill over the edges and go around/over the ski.  Snow that spills over the edges and goes around/over the ski does nothing for flotation.  A soft ski decambers easily by both rider weight and the pressure of the snow following the curvature of the tip, the latter of which decambers the ski even more when it reaches a certain speed to basically turn the entire ski forebody into one large shallow ramp that facilitates a lot of snow moving under the ski.  OTOH, the tip of a stiff ski kinda batters through the soft snow.  I mean, the motion-facilitated decambering might still happen to some extent, but it might require so much theoretical speed that it never really happens.  So the snow just moves around/over the tip.

*edit* BWPA beat me to it.
*edit* I guess I also restated Vinski's original post.
 
post #10 of 26

The stiffer ski makes sense (in deep light powder) for a bigger skier. you can decamber it and make it perform, whereas a lighter skier might not.  However, to compensate for that problem, some ski models are made in a softer flex (thinner core and/or different construction) in the shorter lengths, the inverse on the longer skis.


The width of the ski doesn't exactly make it float on the snow, it makes it capable of  doing various maneuvers in the snow, of which coming up is one.

post #11 of 26
Thread Starter 
Like patting a small dog?..
If you could measure the force of skier x doing 30mph on a soft pow ski vs a stiff pow ski (take Nomad example from earlier) I couldn't imagine that the actual force on the snow would be wildly different? The shape/bend of the ski on the other hand.

Definitely not stating that you have to have the tip up to ski powder. Just want to understand the attributes which make a ski float more or less. I would have thought stance/mount point can make a difference to float. E.g. - If, from a centred stance, I apply subtle aft pressure my skis will rise more than if I apply subtle fore pressure, no? Similar story with mount posi.

I like the overgrown duck analogy - nice image.

Quote:
Originally Posted by davluri View Post

Dt pretty much covered the science. I'll say the same thing differently, however. The softer flexing (longtitudinal) ski pats the snow softly, allowing the snow to form under it and create float. The stiffer ski hits the snow with a smashing blow, compressing and displacing the snow before the snow can provide float.

All the stuff about binding placement and stance is irrelevant to the question. Planing the tip up by sinking the tails is more like a boat reaching plane speed.  It's not floating, and it's not powder skiing. The idea that you have to have the tip up to ski powder is simply not true. Get that and your getting somewhere in powder. Rocker and Reverse Camber are not designed to plane up, they are designed to arc in the powder, at various levels in it. IMHO, of course. (Except maybe the pontoon, and all skis like it, which seem to surf around like a overgrown duck sliding the mountain on her web feet riding way in the back seat.)
 
post #12 of 26
If you aren't able to bend the ski... you will not be able to ski it effectively in powder or anywhere else. Rockered skis are pre-bent so this is less of an issue... but still important if you want to vary your turn shape.

Think about newtons physics. Each action has an opposite reaction. When you stand on the skis in snow it is the snow that is holding you up. Stiffer skis do not bend as much and when slidign forward less snow goes under the tips. This means more snow goes over the tips and this creates drag becuase your boots are in the way. 

Softer skis are take less pressure to bend. As a result the tip sits higher in the snow. When sliding forward, More snow is going under the ski as the ski slided forward the snow is pushed down and compresses under pressure. This firmer platform under your base holds you up in the snow. This leads to less drag on your boots and you can go faster, which will lead to even more float...

As for the HT... if you want a powder ski I would try somehting else, if you want a stable fat ski for skiing fast in all soft snow conditions and thats good but not great in pow try the HT.
post #13 of 26
exagerate the concept: a 2" X 4"  pressed into the snow. a piece of 1/4" by 4" wood pressed into the snow. you wouldn't even be able to sink the 1/4".

Asking DT, does this experiment tell us anything.
post #14 of 26
Thread Starter 
Thanks tromano - nice explanation.
Exactly what I got the HT for!

Quote:
Originally Posted by tromano View Post

If you aren't able to bend the ski... you will not be able to ski it effectively in powder or anywhere else. Rockered skis are pre-bent so this is less of an issue... but still important if you want to vary your turn shape.

Think about newtons physics. Each action has an opposite reaction. When you stand on the skis in snow it is the snow that is holding you up. Stiffer skis do not bend as much and when slidign forward less snow goes under the tips. This means more snow goes over the tips and this creates drag becuase your boots are in the way. 

Softer skis are take less pressure to bend. As a result the tip sits higher in the snow. When sliding forward, More snow is going under the ski as the ski slided forward the snow is pushed down and compresses under pressure. This firmer platform under your base holds you up in the snow. This leads to less drag on your boots and you can go faster, which will lead to even more float...

As for the HT... if you want a powder ski I would try somehting else, if you want a stable fat ski for skiing fast in all soft snow conditions and thats good but not great in pow try the HT.
 
post #15 of 26
Thread Starter 
That's got almost entirely to do with weight rather than flex doesn't it?

Quote:
Originally Posted by davluri View Post

exagerate the concept: a 2" X 4"  pressed into the snow. a piece of 1/4" by 4" wood pressed into the snow. you wouldn't even be able to sink the 1/4".

Asking DT, does this experiment tell us anything.
post #16 of 26
 I'm pretty sure I said I was done posting this link on threads like this. But I lied. Here's 95% of what you need to know about the topic, courtesy of Shane McConkey's vision...

http://www.fuzeqna.com/evogear/consumer/kbdetail.asp?kbid=61

Obviously flex has an impact in terms of how easily a ski decambers & planes as it moves. But the McConkey piece really frames the discussion well in terms or sidecut & camber. And Keith's discussion on the Praxis site echos the same themes: http://praxisskis.com/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=4&category_id=1&option=com_virtuemart&Itemid=29
post #17 of 26
Quote:
Originally Posted by Vinski View Post

That's got almost entirely to do with weight rather than flex doesn't it?

 



 


no, probably it's just dumb.
post #18 of 26
Quote:
Originally Posted by davluri View Post

exagerate the concept: a 2" X 4"  pressed into the snow. a piece of 1/4" by 4" wood pressed into the snow. you wouldn't even be able to sink the 1/4".

Asking DT, does this experiment tell us anything.

Not really, per Vinski's reason.  In fact, given the same centralized load (ie a skier) on these pieces of wood, the flexier piece of wood might actually sink a couple of millimeters lower when measured at the load.

The model of float must involve forward motion and a tip that acts as a ramp.  Imagine a purely flat powder ski without a tip.  (Or, think about skiing switch in powder without twin-tips.)  It might offer some support if you just stand on it, but the moment it starts to move, there is nothing to keep the flat tip from progressively augering into the powder and getting less support by the moment...  until it hits bottom.  Whether the ski is soft or firm doesn't really come into play as there is nothing to push the tip up to form the shallow ramp that is necessary for float when moving.

A ski's flex is very important, but it can be argued that the tip design is even more important.  The overall angle of the tip (and if you really think about it, the curve shape) and the tip frontal area determines the amount of "tip lift" force that it will provide at whatever speed you're going.  In theory, you can have a stiff powder ski with a giant-ass tip that can provide enough "tip lift" force to form the forementioned shallow ramp even at slower speeds with the stiffer ski.  Come to think of it, this is pretty much the definition of tip rocker if you think about the rocker area as an extended tip.  Ergo, tip rocker can allow you to build a stiffer ski (which obviously has many benefits on harder snow) without completely compromising float.  I think I just recapitulated the design of the K2 PE, LOL.

All theoretical per my understanding of a ski traveling flat in powder, of course.  When you tip that ski over to turn, I think spindrift's link to McConkey's idea becomes the dominant issues.
Edited by DtEW - 2/4/10 at 1:03am
post #19 of 26
I have found that a ski with a stiff tail tends not to float as well as a ski with a softer tail.
post #20 of 26
Stiff tails in powder = ruddering instead of arcing turns.  Wrong tool for the job.

A long even flexing ("big smile") ski on the softer side allows you to relax in the middle, with the biggest fore/aft sweet spot.  Powder can be skied on almost any kind of boards, but it is hard to reach the "zone' without the right ones.
post #21 of 26
Dt, the Legend Pro XXL is exactly a fairly stiff ski with a huge-a$$ tip. Have you seen that tip? wow. some like it, some don't.

So talking tips, what's up with Fisher's hull design? deflects snow to the side a bit? I'm looking at the Watea 114, a wide, soft ski with the hull tip design. Would that be to give it some crud capability? Or better powder float?

I was talking about the new Rossignol Pro model, a very stiff ski, that is a change of design from the Bandit Squad 108 in that it has tip rocker, and a squared tip design. I agree that it is to be stiff enough for heavy crud and high speed, but some rocker for light powder float.

Mud, I have learned from what you said about sweet spot. That (way stiff) may be why the Burgundy Explosiv (first design re-released) has such a miniscule sweet spot. People say: hard to ski, but when you master it, so rewarding. I say: total BS, just an inept design compared to other skis.
post #22 of 26
Quote:
Originally Posted by davluri View Post

Mud, I have learned from what you said about sweet spot. That (way stiff) may be why the Burgundy Explosiv (first design re-released) has such a miniscule sweet spot. People say: hard to ski, but when you master it, so rewarding. I say: total BS, just an inept design compared to other skis.

davluri:

The two biggest issues with skiing deep snow are the weighting between your skis, and the fore/aft balance.  Wide skis take care of the first one, and soft (or rocker) long skis take care of the second one.  I am always puzzled by people who go short and fat for their powder skis, they are solving one problem, but increasing the other, and as you noted, stiff skis and soft snow are never a good combo.  MF
Edited by mudfoot - 2/4/10 at 11:44am
post #23 of 26
Quote:
Originally Posted by davluri View Post

So talking tips, what's up with Fisher's hull design? deflects snow to the side a bit? I'm looking at the Watea 114, a wide, soft ski with the hull tip design. Would that be to give it some crud capability? Or better powder float?

To tell you the truth, I'm not sure.  The design of a v-shaped boat bow is to do precisely the opposite of what you would want with a powder ski: it's so that the boat does not climb out of the water as high upon forward motion.  Boats that are supposed to have lots of lift (ie airboats) have flat bows, much like the flat ramp of a typical ski tip.  OTOH, v-shaped boat bows are supposed to be more efficient at moving through the water at slower speeds (not dependent on pushing the boat out of the water, instead facilitating the movement of water around the boat), while providing some lift (not as much a flat-bottom, though) at higher speeds.

Maybe it's a gimmick, or maybe the hull tip of the Watea 114 gets you moving faster on shallower slopes, who knows.  Its dimensions puts it in the pure powder category, and may not need much tip lift to function fine in powder.  Haven't tried one.
post #24 of 26
Thanks for running that through your computer (brain) Dt.

My thought was that the ski mostly floats and rides up over the snowdue to being wide and soft. But to keep it from totally sucking in heavier cut up snow, the hull tip design.

when you examine that hull tip, it is clearly a very expensive feature, therefore, IMO, not a gimmick. In fact, I'm guessing that if it's good, and if I want it, I'd better grab it fast as I can't believe they can continue to add such an expensive structual element to their skis when no other skis do, and remain at a competitive price, 699 ish.
post #25 of 26
Thread Starter 
Interesting. On face value it sure doesn't sound like it's much more than a gimmick.
Think of all the other factors and variables which influence the personality of a ski and how it skis in deep snow; flex pattern, camber, sidecut, width, etc. I find it hard to believe that a hull on the tip of a ski could make any meaningful difference to its performance in soft snow. I'm making assumptions here sure; certainly open to any logical counter-arguments..

Quote:
Originally Posted by davluri View Post

Thanks for running that through your computer (brain) Dt.

My thought was that the ski mostly floats and rides up over the snowdue to being wide and soft. But to keep it from totally sucking in heavier cut up snow, the hull tip design.

when you examine that hull tip, it is clearly a very expensive feature, therefore, IMO, not a gimmick. In fact, I'm guessing that if it's good, and if I want it, I'd better grab it fast as I can't believe they can continue to add such an expensive structual element to their skis when no other skis do, and remain at a competitive price, 699 ish.
post #26 of 26
 Didn't dynastar experiment with the hull tip back on the Nobis' skis? I remember a rippin skier saying he could feel it. 
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