Beautiful grinds

[S.H.]

Yeah, thanks for clarifying that. The tread allows the water some place to go; not just up, but out to the side as well. The tread ventilates the contact patch allowing the water a path to escape. Another analogy where we see something similar is stepped boat hulls. And the marine industry has learned that hull steps only work if they have adequate ventilation from the side.

But ski structure doesn't provide ventilation so I struggle with understanding how it helps that much to break up the film of water. I think ventilation is key to better performance, at least in wet snow. Next time your skiing this spring, run through a wet patch with the skis flat. When you feel the grab, put the skis on edge and you should feel the grab release almost immediately.

Hey! Spring ski design idea: Drill a bunch of holes in the ski to ventilate the heck out of it. Make it look like a reverse cheese grater. Seriously, somebody try this.

I've skied a completely flat, blanked (unstructured) ski before.
Next run, an identical ski with the grind my coaches/techs chose.

There was a massive difference.

Snow skis aren't designed for running through standing water, they're designed for winter snow. So your spring skiing "wet patch" analogy is flawed, IMO.

 

[James]

Next time your skiing this spring, run through a wet patch with the skis flat. When you feel the grab, put the skis on edge and you should feel the grab release almost immediately.

Yeah, that only works to a point. When the spring glue is deep, putting the ski “on edge”, tilting it, works briefly but then the whole thing is still in the glop so it doesn’t matter.

I’ve tried this technique too many times at Abasin in the warm May glue below Black Mt lodge. Eventually, you realize nothing works to stop the herkey jerkeys. Nothing except deep structure apparently.

 

[KingGrump]

Nothing except deep structure apparently.

And HF10.

 

[tomahawkins]

Yeah, that only works to a point. When the spring glue is deep, putting the ski “on edge”, tilting it, works briefly but then the whole thing is still in the glop so it doesn’t matter.

Exactly. It works as long as you can get some of the ski up into clean air. It stops working when the glue gets too deep to ventilate.

So why does a saturated film of water over the base cause so much drag? What is the consensus as to why that happens?

Theory: The front half of the ski up to the boot pushes water down into the snow and out the side. The back half of the ski then tries to lift off the snow, but can't because of suction. Just like an F1 diffuser, it generates a lot of downforce on the tails. Plausible? If so, maybe the solution is to ventilate the back half.

 

[Erik Timmerman]

You ever see a Marine Ka-Bar? It has the deep blood slots on the sides so it doesn’t get stuck in a person. Like the center groove that skis used to have.

 

[Dakine]

Exactly. It works as long as you can get some of the ski up into clean air. It stops working when the glue gets too deep to ventilate.

So why does a saturated film of water over the base cause so much drag? What is the consensus as to why that happens?

Theory: The front half of the ski up to the boot pushes water down into the snow and out the side. The back half of the ski then tries to lift off the snow, but can't because of suction. Just like an F1 diffuser, it generates a lot of downforce on the tails. Plausible? If so, maybe the solution is to ventilate the back half.

Good question.
I'm a hydrodynamicist by trade but have not thought about this a lot.
Once there is enough water in the snow that we are talking about hydrodynamic drag and not mechanical friction.
My first thought is that there is a ~100 time greater drag when pushing an object through water as opposed to air.
I don't think downforce is involved significantly but I'm guessing that the greater the wetted surface, the greater the drag.
If you floated the ski on an air cushion with a blower like a hovercraft, you wouldn't have much drag. (or control)
In drier snow structure helps by allowing water to escape thus reducing the wetted surface.
In really wet snow, the structure could help by allowing air to get beneath the ski.
TFE based waxes help by repelling water from wetting the base and allowing more air under the skis.

I can already see a bunch of stuff that's questionable about this argument but, hey, it's a shot.
I'm betting that if you continuously injected polyacrylamide goo solution at the front of the ski you could reduce the drag a lot just like drag reducing agents work on ships and pipelines.
That's a really bad idea.....

 

[BC.]

Thread bump….

Structure courtesy of Guenther’s (Elk)….

 

[ihocky2]

Yeah everytime I want a deep structure for spring I get talked out if it by the shop. What would be cool is a glue on skin type layer that has deep channels. Edges would be an issue.

Going back on an old thread that had a recent bump but this caught my interest. I skis east coast with lots of man made snow and can get into spring crud for 4 or 6 weeks some years. I'm wondering how adding a pair of used skis for spring skiing would go. I'm thinking something narrow to reduce surface area and have a deep structure ground.

 

[cantunamunch]

I'm wondering how adding a pair of used skis for spring skiing would go. I'm thinking something narrow to reduce surface area and have a deep structure ground.

That's a fine idea BUT a) fatter skis work better and b) you really want a medium deep with cross because deep structures become massively difficult to turn.

The WS09 pattern shown here works really well on PA manmade/slush, is older than a lot of the patterns shown above^ , and is about as deep as you ever want to go.

https://starthaus.com/wordpress/tag/race-grind/

 

[Philpug]

Augment AM98 factory structure.

 

[BC.]

^^^Awesome

 

[ihocky2]

That's a fine idea BUT a) fatter skis work better and b) you really want a medium deep with cross because deep structures become massively difficult to turn.

The WS09 pattern shown here works really well on PA manmade/slush, is older than a lot of the patterns shown above^ , and is about as deep as you ever want to go.

https://starthaus.com/wordpress/tag/race-grind/

Thanks for the tip on the width and grind depth.

 

[James]

That's a fine idea BUT a) fatter skis work better and b) you really want a medium deep with cross because deep structures become massively difficult to turn.

Better at what? I thought his concern was suction.

 

[Erik Timmerman]

Augment AM98 factory structure.
View attachment 153235

It's certainly unusual.

 

[James]

Hard not to be cynical about grinds when tuning in general is poor even on skis $1k +

 

[Tricia]

@Philpug and I stopped by Wintersteiger to check out the new Jupiter
Here are some drool worthy grinds.

 

[cantunamunch]

@Philpug and I stopped by Wintersteiger to check out the new Jupiter
Here are some drool worthy grinds.

View attachment 156478 View attachment 156479

Is anyone else thinking 'Wintersteiger / Pirelli calendar collab? ' Pirelli, you listening?

 

[Tricia]

Is anyone else thinking 'Wintersteiger / Pirelli calendar collab? ' Pirelli, you listening?

I seriously thought of a tire tread when I saw that grind on the Stockli

 

[Henry]

Some of us are old enough to remember getting our name etched into the skis' top sheet. I'm waiting for the next version of the grinding machine that will etch the skier's name into the bases as part of the structure.

 

[Tricia]

Some of us are old enough to remember getting our name etched into the skis' top sheet. I'm waiting for the next version of the grinding machine that will etch the skier's name into the bases as part of the structure.

David Ingemie's retirement gift from Völkl after more than 45 years as the President of SIA.