Tricia

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I know the pattern of a base grind makes a big difference in how the ski performs.
While looking for an image of the AM Bell Grind from @smoothrides I stumbled upon some images from their FB page and I needed to share these here.

Aren't they beautiful?
:drool:

Grind AM Bell.jpg

Grind of the day: AM Bell. We use this wave class grind for most recreational skis in Tahoe. It runs well in a variety of conditions, and is cut as a margin just narrower than the waist of the ski.

Grind SG .04.jpg

Grind of the day. We use this grind for SG skis in typical Tahoe conditions. Even though the structure is very clear, it's actually a medium depth of cut at .04mm. The lower pitch helps to move water quickly at higher speeds, and the margin allows us to run a true .7 base bevel without any structure in the edge.

Grind Tech Wave.jpg

Grind of the day. We use our Tech Wave on most SL and GS race skis. This is also a multi layer structure, with a very fine, high pitch base and a margin wave running slightly narrower than the waist that carries through the tip and tail. It's a center specific structure and a very light cut at 0.02mm. This makes it work extremely well for lots of turning and side to side motion. Even though this pattern is very clear, the real speed in this grind is the micro structure below, which is virtually impossible to capture with the camera. Photo taken straight off the stone grinder before wax or edge prep.
 
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Noodler

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I'd like to see a compilation of the typical different grinds that are available and their primary purpose. Also wondering which machines are the most capable of producing these grind variations. I sure would like to have these kind of high quality grinds on my skis.
 
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Tricia

Tricia

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@Noodler
I can add some descriptions from Smoothrides posts on each of those I posted above. Will edit.
 

ScottB

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I know the pattern of a base grind makes a big difference in how the ski performs.

Picture Deleted
The lower pitch helps to move water quickly at higher speeds, and the margin allows us to run a true .7 base bevel without any structure in the edge.
Picture Deleted
It's a center specific structure and a very light cut at 0.02mm. This makes it work extremely well for lots of turning and side to side motion. Even though this pattern is very clear, the real speed in this grind is the micro structure below, which is virtually impossible to capture with the camera.
Tricia,
Could you add some more information on base grinds and when they are effective? (and when they are not?) I am a race coach on a small hill, and if I am being honest its been my experience that grinds don't have a big effect. This maybe due to being in New England and skiing a lot on boiler plate snow. It may also be on a small hill you don't reach sustained high speeds for very long. Our typical course run times are 30 seconds. It may also be just my lack of experience with grinds and I am missing the boat on this aspect of ski prep.

From what I have heard and it makes sense to me is: grinds effect how water is released from under your ski. So in wet snow, or warm temps, this will be a significant factor. In -10 F temps, I don't believe there is any "non-frozen" water under your skis to worry about. So the higher the speeds (higher friction) and the warmer the temps, the more grinds come into play. I have no personal experience running a smooth ski versus a "ground" ski in wet snow on the same course.

I do have experience with waxing, and that can be really significant, especially if you screw it up and your skis get "sticky". I assume one of the reasons you really need to brush the wax out of a race ski is to let the structure come though again before your run.

I would appreciate any info you can share on the subject, I am in the beginner category when it comes to ski structures.
 
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Tricia

Tricia

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I'll be the first to admit that I'm not as knowledgeable about what type of grind works for what, other than I really like the AM Bell grind for my all mountain purposes.
As for this thread, I'm extremely appreciative of the art and science of base structure.

I believe there are others on this site who can be more informative about structures for specific purposes.
 

LiquidFeet

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If you do put up pictures of grinds with descriptions of what they are especially good for, that would be awesome. That kind of information is not available anywhere.

If it's possible and you do it, please include some bad grinds and explain why they are bad. I just discovered that a pair of skis I couldn't ski were so difficult to handle because the grind was improperly done. Thanks, Mike deSantis, for figuring this out. He knew immediately when he saw the skis. (That's Mike owner of SkiMD in Natick, MA.)
 

cantunamunch

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I just discovered that a pair of skis I couldn't ski were so difficult to handle because the grind was improperly done. Thanks, Mike deSantis, for figuring this out. He knew immediately when he saw the skis. (That's Mike owner of SkiMD in Natick, MA.)
Is this the Kastles with the K12 bindings you had a while back?
 

LiquidFeet

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Yes. I thought it was the funky plate under the binding that was causing the problem. The ski: Kastle MX 78. Mike is taking off those old bindings and putting Attack 13 demos on. I already had these Attacks so even though he pointed out that the problems were caused by the grind I am still changing the bindings. You remembered.
 
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fatbob

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OK so I'll ask, after a terrible experience with a snowboard decades ago where the shop totally took about 5 years off the lifespan of the board by overgrinding I've totally sworn off shop grinds unless my bases are totally FUBAR'd without.

How much life does each of these structural grinds take off the skis - if you restrutured say twice annually how many years would an average retail ski last (assuming no other wear n tear - appreciate that heavy rental stock designed to be butchered my last longer, an FIS base shorter)
 

slowrider

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Tricia,
Could you add some more information on base grinds and when they are effective? (and when they are not?) I am a race coach on a small hill, and if I am being honest its been my experience that grinds don't have a big effect. This maybe due to being in New England and skiing a lot on boiler plate snow. It may also be on a small hill you don't reach sustained high speeds for very long. Our typical course run times are 30 seconds. It may also be just my lack of experience with grinds and I am missing the boat on this aspect of ski prep.

From what I have heard and it makes sense to me is: grinds effect how water is released from under your ski. So in wet snow, or warm temps, this will be a significant factor. In -10 F temps, I don't believe there is any "non-frozen" water under your skis to worry about. So the higher the speeds (higher friction) and the warmer the temps, the more grinds come into play. I have no personal experience running a smooth ski versus a "ground" ski in wet snow on the same course.

I do have experience with waxing, and that can be really significant, especially if you screw it up and your skis get "sticky". I assume one of the reasons you really need to brush the wax out of a race ski is to let the structure come though again before your run.

I would appreciate any info you can share on the subject, I am in the beginner category when it comes to ski structures.
Interesting article on ice/snow reaction with skates, skis.

https://www.comsol.com/blogs/why-is-ice-slippery-enough-for-skiing-and-skating/
 

Doug Briggs

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OK so I'll ask, after a terrible experience with a snowboard decades ago where the shop totally took about 5 years off the lifespan of the board by overgrinding I've totally sworn off shop grinds unless my bases are totally FUBAR'd without.

How much life does each of these structural grinds take off the skis - if you restrutured say twice annually how many years would an average retail ski last (assuming no other wear n tear - appreciate that heavy rental stock designed to be butchered my last longer, an FIS base shorter)
If the grind is done properly, and I know it is at @smoothrides , you'd wear out the core before you wore out the base with tunes. I structure my skis regularly and don't have any trouble with thin bases. Of course, I do them right. ;)
 

Doug Briggs

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Maybe @smoothrides or @Doug Briggs could add some insight to some of these questions.
While I can put a good structure on skis I am by no means an expert on different structures or playing with them. Peter, my shop mate, on the other hand is really getting his hands dirty with the Scout. Maybe we'll have some new structures this season. These photos look kind of deep compared to what we do in CO. We have different snow than Tahoe so we use different parameters for our structures.

Our race structure is similar to the second image from the top of this page. Our structure is the mirror image, though. ;) Usually we do edge to edge (not a margin structure like this one). I'm eager to learn, though so maybe we'll try margin on the race skis. Our speed ski structure is also a layered structure.

We can do wave structures with margins. Many times it is what the customer asks for that determines what we do.
 

cantunamunch

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Yes. I thought it was the funky plate under the binding that was causing the problem. The ski: Kastle MX 78. Mike is taking off those old bindings and putting Attack 13 demos on. I already had these Attacks so even though he pointed out that the problems were caused by the grind I am still changing the bindings. You remembered.
I remember thinking the tune was the problem; what was off with the grind?
 

Scruffy

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Here: https://pdfs.semanticscholar.org/8c92/69fe7426bd8237c77dad1ecd6235556d17ea.pdf

is probably more technical info than most want and does not answer the basic question about what structure is best for what conditions, but there is some interesting things to glean from it.

This is interesting:
Along the ski there may exist solid-to-solid contacts at the front of the ski and towards the tail of the ski, due to frictional heating, mixed conditions, and finally solely wet friction. Therefore, the friction coefficient varies along the ski too.
 

LiquidFeet

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I remember thinking the tune was the problem; what was off with the grind?
It was cut deep, the grooves were wide, and the pattern was simply straight lines going tip to tail. Mike deSantis said they didn't finish the grind I think. He scraped his fingernails across the skis and said "Hear that?"
 

AmyPJ

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OK so I'll ask, after a terrible experience with a snowboard decades ago where the shop totally took about 5 years off the lifespan of the board by overgrinding I've totally sworn off shop grinds unless my bases are totally FUBAR'd without.

How much life does each of these structural grinds take off the skis - if you restrutured say twice annually how many years would an average retail ski last (assuming no other wear n tear - appreciate that heavy rental stock designed to be butchered my last longer, an FIS base shorter)
If the grind is done properly, and I know it is at @smoothrides , you'd wear out the core before you wore out the base with tunes. I structure my skis regularly and don't have any trouble with thin bases. Of course, I do them right. ;)
I was going to say what Doug said :)
 
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Tricia

Tricia

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Grind of the day. We use this grind for SG skis in typical Tahoe conditions. Even though the structure is very clear, it's actually a medium depth of cut at .04mm. The lower pitch helps to move water quickly at higher speeds, and the margin allows us to run a true .7 base bevel without any structure in the edge.
Our race structure is similar to the second image from the top of this page. Our structure is the mirror image, though. ;) Usually we do edge to edge (not a margin structure like this one). I'm eager to learn, though so maybe we'll try margin on the race skis. Our speed ski structure is also a layered structure.
As noted, the structure you're talking about in the second pictures is the grind used for SG Skis.
 

GregK

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Was going to guess if the ski is hard to turn, a course, linear grind would cause that and those aren’t often done because the ski wants to just go straight. In some machines, the Pre Grind stage will produce a deep and wavy looking(and feeling) pattern that is then flattened out before the actual structure is applied. Sounds like it went through the Pre Grind stage and that’s it!

In regards to how many times you can grind-a lot if the machine operator knows what they are doing. The big problem with grinds is that there are “base grinds” and “stone grinds” and they often don’t mean the same thing. A base grind could just mean a kid taking the ski free hand without auto feeder on a sandpaper belt taking who knows how much material off in order to take out scratches or marks.

An auto feeding system puts more uniform pressure over the ski passing over the belt and will remove far less material per pass. Often sandpaper belts used to flatten the base quicker and then a stone used to fine finish the base and then finally add structures like shown above. There are places that do base grinds with only belts and the finish would be rough and without structure.

There was a video a few years back where a shop took an auto feeding machine using med grit sandpaper belt to see how many passes they could do before they hit the core on a snowboard. They did 250 passes and still had base left. I never let a belt hit my skis as they don’t finish as well and should only be used if more material needs to be taken off. I get stone grinds only on auto fed machines.
Most stone grinds I get take 4-10 total passes per grind depending on condition of the skis so you can grind LOTS of times before issue on an stone ground, auto fed system.

Some info on structures. Colder snow-smoother and finer structure and warmer snow-deeper and courser structure.

https://www.racewax.com/base-structure-theory/
 

LiquidFeet

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Was going to guess if the ski is hard to turn, a course, linear grind would cause that and those aren’t often done because the ski wants to just go straight. In some machines, the Pre Grind stage will produce a deep and wavy looking(and feeling) pattern that is then flattened out before the actual structure is applied. Sounds like it went through the Pre Grind stage and that’s it!/
Thanks for the description. That must be exactly what was going on with my Kastles.
 
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