Beautiful grinds

[KevinF]

It is no doubt we have an extreme number of high performance skiers here in the community. But for the other 90% of the skiers out there, can they really feel the difference between a different type of grind?

YES! I don't know that they could tell the difference between good and great, but definitely bad from good. They wouldn't know that's what they are feeling, but they'd feel it.

I can definitely feel the difference between a good tune and a bad tune (i.e., with the edges, if there's a hanging burr or whatever). I can feel if the base edge angle has increased beyond what I like. I can feel if a ski's base structure has been worn away, especially in "wetter" snow conditions.

But I'm not sure I could feel any distinction between two different base grind patterns on otherwise identical skis.

 

[ScottB]

It is no doubt we have an extreme number of high performance skiers here in the community. But for the other 90% of the skiers out there, can they really feel the difference between a different type of grind?

If by grind you mean bevel angles or "tune" I think its easy to tell that. Exactly what Kevin says.

If by grind you mean Pattern or Structure put into the Ptex on the bottom of the ski, I personally have never felt a difference between any pattern that was put on the bottom of my skis. I have never had a "bad" pattern put on any of my skis. I do believe in wetter snow a difference can be felt due to pattern, but I find wax makes a much more noticeable difference.

My 2Cents and why I asked about it earlier.

 

[ScottB]

Two to three times per year. Maybe should do it a little more. You can lose that base bevel without really knowing it. I'm not made of money though. Obviously grinding every time is way beyond excessive, and I think would actually be detrimental to performance, but it won't wear out your skis.

Are you having the base bevels ground to zero and then re-applied 2-3 times per year??? Or just putting new structure into the bottom? That seems fairly frequently if re-beveling. I use SkiMD for my grinds and I have gone 2-3 years on a ski I use for race coaching without the base bevel getting larger. I measure them occasionally just to see where they are. Of course, how the ski is used is really the determining factor on wear and necessity to re-grind. I sharpen my side edge angle about every other ski day, but almost never touch the bottom angle. On my "tree skis" I get so many edge ding's that one grind at the start of the season would really be needed to keep them pristine. I don't bother doing it that frequently, but it wouldn't hurt.

 

[Doug Briggs]

@Mike Thomas has a story about the shop manager in shop he used to work at in NH who would tune his skis literally every time he skied. He'd go skiing, then come back into the shop and be like "tune these skis", so the skis would get like 30 grinds a year and they were fine. So my answer is if the shop is any good, din't worry about it.

If someone brought their skis in on a regular basis, where I work, and said "tune these skis" I'd look at the skis to see if they actually needed a grind and recommend to get or not get a grind based on the condition of the skis. We quite frequently will 'downgrade' a tune after communicating with a customer to let them know the skis don't need a grind, just edge tuning. I'd hope any shop worth its salt would do the same.

 

[Doug Briggs]

Are you having the base bevels ground to zero and then re-applied 2-3 times per year??? Or just putting new structure into the bottom? That seems fairly frequently if re-beveling. I use SkiMD for my grinds and I have gone 2-3 years on a ski I use for race coaching without the base bevel getting larger. I measure them occasionally just to see where they are. Of course, how the ski is used is really the determining factor on wear and necessity to re-grind. I sharpen my side edge angle about every other ski day, but almost never touch the bottom angle. On my "tree skis" I get so many edge ding's that one grind at the start of the season would really be needed to keep them pristine. I don't bother doing it that frequently, but it wouldn't hurt.

I don't doubt you, but most race coachs' skis are heavily rounded, thus base bevels shot, when I get to them. They all say it is from slipping courses, which I get.

 

[Uncle-A]

If by grind you mean bevel angles or "tune" I think its easy to tell that. Exactly what Kevin says.

If by grind you mean Pattern or Structure put into the Ptex on the bottom of the ski, I personally have never felt a difference between any pattern that was put on the bottom of my skis. I have never had a "bad" pattern put on any of my skis. I do believe in wetter snow a difference can be felt due to pattern, but I find wax makes a much more noticeable difference.

My 2Cents and why I asked about it earlier.

This is not about the "tune" it is about "structure" I think most of us can tell a bad tune but structure is a different story.

 

[tomahawkins]

For me, "structure" just doesn't pass the smell test. We cut these miniscule patterns in our skis, fill them in with wax, and now our skis perform better? We equate "structure" to treaded tires for wet conditions, but treads are designed to increase, not decrease, traction. And once I saw a race tuning video where the turner's last step in the process was to lightly run a horsehair brush along the bases of the skis to "bring out the structure". Come on! Once that ski has traveled 3 feet on a race course under load it will have undone anything that brush accomplished.

Sorry, but I have to call BS on structure.

But I could be wrong. Show me some data. Has anyone A/B tested structured vs. unstructured bases; preferably on the same run with structured on one foot and unstructured on the other? (I've tried that with waxed vs unwaxed on a few days. Results: Not much difference, at least in the conditions I tested.)

 

[S.H.]

For me, "structure" just doesn't pass the smell test. We cut these miniscule patterns in our skis, fill them in with wax, and now our skis perform better? We equate "structure" to treaded tires for wet conditions, but treads are designed to increase, not decrease, traction. And once I saw a race tuning video where the turner's last step in the process was to lightly run a horsehair brush along the bases of the skis to "bring out the structure". Come on! Once that ski has traveled 3 feet on a race course under load it will have undone anything that brush accomplished.

Sorry, but I have to call BS on structure.

But I could be wrong. Show me some data. Has anyone A/B tested structured vs. unstructured bases; preferably on the same run with structured on one foot and unstructured on the other? (I've tried that with waxed vs unwaxed on a few days. Results: Not much difference, at least in the conditions I tested.)

world cup ski techs have done / do this on 100s to 1000s of skis per year.

it makes a difference.

a completely unstructured ski will be very slow.

 

[tomahawkins]

world cup ski techs have done / do this on 100s to 1000s of skis per year.

Yes, but how many of those techs cut structure because all the other teams do? I just want to see the evidence that supports the case for structure, because looking at it from first principles, that case is not clear.

I am skeptical because ski tuning, and the industry as a whole, has a history of following pseudoscience. E.g. "wax permeates a base", when electronic microscope imaging shows it does not.

 

[Erik Timmerman]

I have had skis transformed by a grind. Not changing the bevels, but changing the grind pattern.

 

[S.H.]

Yes, but how many of those techs cut structure because all the other teams do? I just want to see the evidence that supports the case for structure, because looking at it from first principles, that case is not clear.

I am skeptical because ski tuning, and the industry as a whole, has a history of following pseudoscience. E.g. "wax permeates a base", when electronic microscope imaging shows it does not.

a few minutes of googling yields:

https://www.researchgate.net/publication/255569185_Comparison_of_Ski_Running_Surfaces_Machined_by_Various_Stone_Grinding_Equipments

Changes in the cross-country ski base properties resulting from the ski use - Sports Engineering

In this work, changes in the cross-country ski base properties resulting from stone grinding, skiing, waxing and re-stone grinding have been investigated. The surface topography, crystallinity, wettability and sliding properties of cross-country ski bases were recorded using a selection of...

link.springer.com

https://www.researchgate.net/publication/245481341_Cross_Country_Ski_Base_Tuning_with_Structure_Imprint_Tools

Snow Engineering 2000: Recent Advances and Developments

This volume presents the background to the recently developed European standard (CEN standard) on snow loads. Many of the papers on "structural engineering" describe results from a European snow project that was completed in 1999.

books.google.com

 

[dbostedo]

For me, "structure" just doesn't pass the smell test. We cut these miniscule patterns in our skis, fill them in with wax, and now our skis perform better? We equate "structure" to treaded tires for wet conditions, but treads are designed to increase, not decrease, traction. And once I saw a race tuning video where the turner's last step in the process was to lightly run a horsehair brush along the bases of the skis to "bring out the structure". Come on! Once that ski has traveled 3 feet on a race course under load it will have undone anything that brush accomplished.

Sorry, but I have to call BS on structure.

But I could be wrong. Show me some data. Has anyone A/B tested structured vs. unstructured bases; preferably on the same run with structured on one foot and unstructured on the other? (I've tried that with waxed vs unwaxed on a few days. Results: Not much difference, at least in the conditions I tested.)

I can't comment on structure - I've never experimented with it.

But I can point out a possible flaw in your analogy. Tread doesn't exist to provide traction directly (at least not in wet conditions) - it's there to give the water some place to go so that parts of the tire contact the pavement and you don't get a hydroplaning effect. That gives you traction. Likewise, on a ski, the structure is meant to break up a thin layer of water and let the skis contact the snow better. In this case the water layer or hydroplaning is sticky and slow (same reason you wax - to shed that water better). So potentially the same effect, but in one case it gives traction, and in the other case provides better gliding.

 

[James]

When was that crisis in Norwegian cross country where the techs/team blew the grinds, the skis were slow, and the whole country was outraged? Sochi?

 

[Tony S]

Sorry, but I have to call BS on structure.

But I could be wrong. Show me some data. Has anyone A/B tested structured vs. unstructured bases; preferably on the same run with structured on one foot and unstructured on the other? (I've tried that with waxed vs unwaxed on a few days. Results: Not much difference, at least in the conditions I tested.)

I think you need to keep experimenting.

 

[James]

I want to try a spring ski with a super deep structure for glue snow. That might be about the only condition where I question if it’s worth being out.
The question is would it be skiable in the more normal spring ir even winterish conditions higher up?

 

[Dakine]

world cup ski techs have done / do this on 100s to 1000s of skis per year.

it makes a difference.

a completely unstructured ski will be very slow.

I agree, the amount of study and track testing done by wax companies proves the worth of structure beyond any doubt.
Not much is published for propriatary reasons.
However, IME, a completely unstructured and unwaxed base is tough to beat in really cold, dry snow.
You will burn up the base though.

 

[Erik Timmerman]

I had a pair of FX94s with a super deep structure that I used just for spring. They were so much easier that I felt bad for the people getting herky-jerked all around me. On cold snow they were not fast but they were usable.

 

[James]

I had a pair of FX94s with a super deep structure that I used just for spring. They were so much easier that I felt bad for the people getting herky-jerked all around me. On cold snow they were not fast but they were usable.

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.

 

[tomahawkins]

But I can point out a possible flaw in your analogy. Tread doesn't exist to provide traction directly (at least not in wet conditions) - it's there to give the water some place to go so that parts of the tire contact the pavement and you don't get a hydroplaning effect. That gives you traction. Likewise, on a ski, the structure is meant to break up a thin layer of water and let the skis contact the snow better. In this case the water layer or hydroplaning is sticky and slow (same reason you wax - to shed that water better). So potentially the same effect, but in one case it gives traction, and in the other case provides better gliding.

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.

 

[KingGrump]

Edges would be an issue.

The new margin type base grind on a auto feed machine would be great for a deep spring structure. Always had issues with the edges on a deep spring structure. The base bevel do not remove all the structure on the metal edges.
Definitely need a base grind at the start of the following season to get rid of the spring structure.