Why do carvers have edge hold on ice?

[AngryAnalyst]

I got interested in trying to design custom skis for myself. I would ideally pay someone else to make them, but I am curious about design characteristics.

My idea is taking race stock construction (silver fir + beech or ash + titanal sandwich) and putting it into a shape with a ton of tail rocker. The hope is that the resulting ski would be easy to pivot while having bottomless edge grip which (theoretically) makes it a great east coast hard snow ski for on and off piste.

That plan may be really dumb, in part because nobody makes the ski I'm imagining as far as I can tell.

A key component of the theory behind the ski is that putting a silver fir + titanal core into almost any shape would make it grip extremely well. So, here's the question. If I'm willing to give up a bit of energy out of a turn from skis like the Kastle MX and Stockli AX by throwing a super aggressive tail rocker on to the back (instead of the flat tail), could I still keep (most of the) edge hold?

The only physics constraint I can think of is the amount friction the effective edge of the ski can generate to facilitate a turn. I am giving up some effective edge by heavily rockering the ski. Otherwise I would have thought that a heavy, torsionally stiff ski would bite into ice quite well.

So, what am I missing?

 

[Tony S]

Wow. My super technical answer is that you'll probably end up on your butt at the end of any serious carved turn.

 

[AngryAnalyst]

Wow. My super technical answer is that you'll probably end up on your butt at the end of any serious carved turn.

Why do you think that? Have you ever used a bonafide or brahma? Only difference is (even stiffer) core + more aggressive rocker line.

If you think my idea is stupid and have some reason for thinking that other than a desire to be snarky explain.

Edit: seriously, I’m not trying to be defensive. If this is dumb, great. It saves me $2K plus in custom ski manufacturing costs from wagner, parlor or fulsom.

 

[KingGrump]

How wide?

 

[AngryAnalyst]

How wide?

88-102 is the range of widths similar shapes with less burly cores that actually exist travel. Pretty agnostic in that range.

 

[markojp]

The brahma and bonefide have some tip and tail 'rise', but as soon as they're tipped on edge a bit, you get all edge contact and centimeters of ski you paid for. Their 'rocker' profile is by no means extreme by any modern ski measure.

Have a look at the tail of the current Head iSL RD fis SL ski for fun.

 

[AngryAnalyst]

The brahma and bonefide have some tip and tail 'rise', but as soon as they're tipped on edge a bit, you get all edge contact and centimeters of ski you paid for. Their 'rocker' profile is by no means extreme by any modern ski measure.

Have a look at the tail of the current Head iSL RD fis SL ski for fun.

I have actually looked at race skis once or twice in my life while waiting in lift lines. It's completely flat and very square right?

I agree with you the Bonafide, Brahma and Enforcer series all have much more modest amounts of tail rocker than I am envisioning. They are also much softer. The Kastle MX98/99 have some tip rocker but little tail rocker and the kind of construction I am thinking of.

Is there some reason tail rocker works very poorly on stiff skis?

 

[cantunamunch]

Is there some reason tail rocker works very poorly on stiff skis?

Your front-to-back balance sweet spot becomes much smaller in all edging regimes and you become locked into one turn exit shape with everything else being tail-chattery. The ski stops wanting to adapt to the snow.

And yes, I have skis like you say you want. Just ask @KingGrump - he flexed them over the weekend and just looked at me funny.

 

[markojp]

I have actually looked at race skis once or twice in my life while waiting in lift lines. It's completely flat and very square right?

No, not right. You need to look more carefully. Without better analysis, you'll just get angry.

 

[Wilhelmson]

Kastle FX HP works on ice and works your legs at the same time. Why is it that tail rocker is chattery?

 

[AngryAnalyst]

No, not right. You need to look more carefully. Without better analysis, you'll just get angry.

sorry rocker pics hard to find online, do those have slightly upturned tails?

Like literally just the back 2 cm or something

 

[Lauren]

The only physics constraint I can think of is the amount friction the effective edge of the ski can generate to facilitate a turn. I am giving up some effective edge by heavily rockering the ski. Otherwise I would have thought that a heavy, torsionally stiff ski would bite into ice quite well.

So, what am I missing?

From a physics perspective, edge grip comes from not only the torsional stiffness of the core, but the way forces are transmitted from you, to the ski, to the snow. Generally speaking, I would think a wider ski is subjected to more torque when the same force us applied (due to more distance between the location where you're applying the force, and the location that the ski is gripping on the snow). So with that, I would think, the wide ski would need to be stiffer (torsionally) than it's race counterpart in order to provide the same grip.

Just a thought...I'm no physicist.

 

[Eleeski]

Interesting thought. What are you trying to get? Quick turns on ice? Smooth carving? Versatility? Different goals with different designs.

Skis are pretty torsionally rigid nowadays. No real downside to a torsionally stiff ski so it's easy to add enough material to resist the twist. Lots of ways to do this that aren't limited to race construction.

Controlling where the edge pressure intersects the snow is the art. Camber and the stiffness profile along the ski control that.

Rocker makes a ski effectively feel shorter while keeping area for soft snow. For the edge holding, ignore most of what is outside the rockering. Make the edge area lively (stiff?). I'd avoid getting super stiff in the rockered area.

It will be a complex core/layup. But not particularly difficult.

A lot of what we think doesn't translate into a real ski's design. Trial and error is very useful. Don't be afraid to grind the ski to try to change characteristics.

A lot of good design work has been done. Examine and measure skis you like. Also look at some exotic designs (Anton Gliders?) for ideas on alternative ways to generate edge power.

Do you have access to presses, ptex, edges, composites and cores? If so, experiment and tell us what works!

Eric

 

[KingGrump]

Kastle FX HP works on ice

Are we talking about the same Kastle?

 

[Ken_R]

I got interested in trying to design custom skis for myself. I would ideally pay someone else to make them, but I am curious about design characteristics.

My idea is taking race stock construction (silver fir + beech or ash + titanal sandwich) and putting it into a shape with a ton of tail rocker. The hope is that the resulting ski would be easy to pivot while having bottomless edge grip which (theoretically) makes it a great east coast hard snow ski for on and off piste.

That plan may be really dumb, in part because nobody makes the ski I'm imagining as far as I can tell.

A key component of the theory behind the ski is that putting a silver fir + titanal core into almost any shape would make it grip extremely well. So, here's the question. If I'm willing to give up a bit of energy out of a turn from skis like the Kastle MX and Stockli AX by throwing a super aggressive tail rocker on to the back (instead of the flat tail), could I still keep (most of the) edge hold?

The only physics constraint I can think of is the amount friction the effective edge of the ski can generate to facilitate a turn. I am giving up some effective edge by heavily rockering the ski. Otherwise I would have thought that a heavy, torsionally stiff ski would bite into ice quite well.

So, what am I missing?

A well tuned (1/3) stiff ski with full rocker should do what you want. When on edge the ski will offer grip but when flat it will pivot easily. Several existing skis come to mind.

 

[Josh Matta]

So they already make this ski.

https://www.evo.com/skis/black-crows-daemon


I also use to own the Katana which was a full reverse ski as well at 112mm under foot. That ski was actually crazy easy to ski on hardpack during steered slower speed turns, it was like the little bit of contact underfoot was driven in the snow and then as edge angle built into the turn the ski grew in length

Your idea would work, it just pointless to give it extreme tail rocker. Long and low rise would work fine. The rocker should be slightly less than what angle it need to be to get edge contact at that angle and it would work fine. IMO Volkl and Rossi had this figured out years ago with the Volkl Katana and full reverse camber mantra, as well the Rossi Sickle and Schimitar.

The issues with full on reverse camber is can feel fairly unstable when on a flatter ski, and lacks "pop". IMO though your idea is sound and if it was me and I wanted something narrower than the Daemon, I would model the katana shape and tail rocker and just bring it down to the size you want.

 

[Tony S]

Why do you think that? Have you ever used a bonafide or brahma? Only difference is (even stiffer) core + more aggressive rocker line.

If you think my idea is stupid and have some reason for thinking that other than a desire to be snarky explain.

Did not intend to be any snarkier than I ever am - which isn't saying much - and I certainly did not mean to imply that your idea was stupid.

I was just reflecting on the skis that I have been on, that have a lot of tail rocker. (As others have said, the Brahma doesn't qualify for "a lot" in my view.) The Rossi S8 -> Super 7 comes to mind. My experience carving firm snow on those skis is that you have to get off the edge really early before it just stops pushing back and leaves you in no-man's land. The traditional carving model of pressure that moves from the toepiece to the heelpiece during the course of the turn doesn't work with those skis IME - it's like stepping on a banana peel. If I want a hard snow carving experience I want to hang onto that turn long enough to finish it properly, even to the point of coming back up the hill a bit. Having a bit of pop at the end to help me get weightless during transition doesn't hurt either. My two cents.

 

[cantunamunch]

So they already make this ski.
. IMO Volkl and Rossi had this figured out years ago with the Volkl Katana and full reverse camber mantra, as well the Rossi Sickle and Schimitar.t.

Don't forget the old style RTMs.

 

[Wilhelmson]

Are we talking about the same Kastle?

Yup, they were on sale so I wanted to try them out. They grip great. What was your experience?

 

[Dwight]

hmm, I think I have pair, unless you don't want any front rocker.