Kuzmin scraping and structure

What works best and How to

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sandatos
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Re: Kuzmin scraping and structure

Postby sandatos » Mon Nov 18, 2013 5:03 am

Also because the stiffness match is much much more important than the structure match.


that's interesting. Do you have some links on works and tests on this subject ?

Loran
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Re: Kuzmin scraping and structure

Postby Loran » Mon Nov 18, 2013 1:52 pm

There's indeed a lack of data here. We would expect that some scientist or ski manufacturer would have published something already.
Maybe it's too obvious to everyone. Just like wax was.... Sight !

OTOH the beauty of Kuzmin approach could ease collecting data because there is absolutely no wax interference.
I can simply tell that my girlfriend and I have 5 pairs of no waxed skis with different stiffness and no doubt ever on which pair goes better, one day or another. She ends up on it, of course.

m2qItMot
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Re: Kuzmin scraping and structure

Postby m2qItMot » Sat Dec 13, 2014 5:54 pm

I have been reading this and related threads since last winter - and I am pretty much sold on the idea that this is the way to go, at least for me!

So I have some practical questions, for which I have not found good answers:
    1) How does one buy these scrapers in the US - just contact some non-US distributor and plea for mercy?
    2) How do the Kuzmin scrapes compare to the Primateria ones, other than being "cheaper", if one can use such an adjective here :-) Has anyone tried the Primateria?
    3) To get the "full benefit" of steel scraping, one also needs a nylon brush, such as the current HS-014 model. Am I correct?

I wish his website had a bit more of written step-by-step instructions/manuals!

osloskier
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Re: Kuzmin scraping and structure

Postby osloskier » Sat Dec 13, 2014 7:07 pm

I would be surprised if neither http://www.skistart.com/swe/ nor http://www.enklaresport.se/ will ship overseas. Both routinely ship to Norway (neighboring country, but not full EU member, so customs paperwork). *edit* Skistart ships anywhere, but the shipping cost is pretty crazy (SEK 399). Enklaresport also ships anywhere, at half the cost (SEK 200).

I understand the Primateria scrapers are bigger and so slightly easier to work with, plus they produce an even better finish. But after running the high speed brush the ski will be a glistening black anyway. I haven't tried them myself. These guys just got the endorsement of Knut Nystad (Team Norway ski prep boss): http://norskeski.no/. I haven't tried those either.

It's not hard. Tips:

You need to fasten the ski securely. A wobbly table may cause the scraper to jump, and it's a lot of work to get rid of a cut.

Hold the scraper slightly skewed (15-20 degrees or so) and let your fingers slide along the sides of the ski so the scraper doesn't grab and start to go sideways. If the scraper starts to produce an uneven surface, switch the skew to the other side.

Drag the scraper without pushing very hard - a few kg of pressure.

The scraper should be fairly flat against the ski, 30-40 degrees or so. Too close to the vertical may cause it to jump or grab.

Wear thin gloves, particularly when you scrape away the old grind, or your fingers will hurt.

To save on the scraper you can use progressively finer sandpaper up to 1200 before scraping to get rid of the old structure (I haven't tried this myself yet) .

The + scraper cuts much more aggressively and will get rid of the old structure in about 1/3 the time compared to the U. But with some elbow grease the U will do it too. It will dull faster, though, so if you end up doing this a lot, getting the + scraper in addition might be more economical. They produce sufficiently different structures that I wouldn't be without any of them, but I got only the U at first to test. When it worked better than I had expected I bought the other ones too.

To get good glide in melting snow you need an additional structure tool. But if you're skiing on a universal grind now, you will just have the same poor glide that you're already used to in such conditions.

If you don't get the high speed brush (which is a very high quality product) you can still get good glide, but you will have to brush like crazy. If you didn't brush quite enough, you may notice an improvement after skiing for a while. Brushing is less critical for warmer conditions, and when the snow starts melting you might want to hand brush instead to avoid overdoing it. I used a Swix combination nylon/bronze brush followed by nylon before I got the high speed brush, this works, but you will be sweating. I also tried a very fine steel brush, but that did not work as well, even when followed by bronze and nylon.

Good luck, and I hope you will report on the results :)
Last edited by osloskier on Sun Dec 14, 2014 4:17 am, edited 1 time in total.

osloskier
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Re: Kuzmin scraping and structure

Postby osloskier » Sun Dec 14, 2014 4:03 am

If you only prep your own skis you don't really need the HS brush. I prep skis for my wife and two kids too, and then the HS brush reduces the brushing job from about an hour to 5 minutes.

This is a scary powerful tool, so be careful. Pay attention to rotation direction when you get near the ends of the ski so it doesn't grab. If the top of the brush is rotating towards the same end of the ski that you're approaching while the brush is on the ski, it will grab. If you're about to start a brush stroke from the end of the ski, the brush will grab if the top is moving away from the ski.

If the ski does not have enough support from the profile, it may start to buzz and vibrate. Then you need to support it more, it's impossible to get a good finish if the ski is vibrating.

Almost zero pressure, and the brush must be moving along the ski before it touches it. If you put the whole weight of the grinder onto the ski it will be ruined instantly. Pretend the brush is an airplane practicing for the softest possible touch-and-go. As long as you start with as little pressure as you can you will be able to figure it out without ruining anything.

I forgot to mention that if the scraper starts to feel dull, you may have to clean the edge. Wipe it with a cloth, if that doesn't work try cleaning it with ski base cleaner. Each edge should be able to scrape away the stone grind of several pairs of skis before going dull.

Blah
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Re: Kuzmin scraping and structure

Postby Blah » Sun Dec 14, 2014 9:38 am

I would think that if we looked at the structure put in with a high speed brush that it wouldn't be nearly as clean as it would be with a scraper like the Primatera (spelling?) or from a stone grinding machine? I've looked through microscopes at the difference between some companies factory grinds or certain grind machines vs others and you can definitely see a difference in how "clean" the grind cut is.

osloskier
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Re: Kuzmin scraping and structure

Postby osloskier » Sun Dec 14, 2014 10:12 am

The HS brush has very thin and soft nylon filaments. They would be too soft for a hand brush, I think. I imagine all those tiny, high speed impacts hammer and massage the cut structure into a more rounded shape on the microscopic scale instead of scratching it.

Blah
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Re: Kuzmin scraping and structure

Postby Blah » Sun Dec 14, 2014 7:21 pm

Ok that makes sense. I thought what you were describing was a metal brush that was cutting structure in the ski.

Loran
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Re: Kuzmin scraping and structure

Postby Loran » Mon Dec 15, 2014 5:37 am

You can order directly from kuzmin. Shipping costs are minimal (9 euros for our recent order of 3 scrapper and one HS brush, shipping to France)

BTW, HS brush are a brilliant idea. Thin nylon allowing a deep polish and high speed to get the strength.

If you 're into quitting wax and nevertheless wants the 2 or 3% fluoro gain, FP finishing (HS brush and drum) is also a brilliant idea of his.

Blah
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Re: Kuzmin scraping and structure

Postby Blah » Mon Dec 15, 2014 7:57 am

Personally if I played around with this I would have no intention of quitting waxing. I would use it to open fresh base material or to change the structure of the ski. My only concern would be as I stated before that the cut from one of these scrapers is not going to be nearly as clean as waht you get from a stone grinder.

Loran
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Re: Kuzmin scraping and structure

Postby Loran » Mon Dec 15, 2014 9:43 am

As a matter of fact measured by Kuzmin, a (sharp) steel scrapper will render a much cleaner and better gliding surface than a stone-grind which leaves plenty of hairs and roughness. A stone-ground ski must be either be waxed or "shaved" to glide correctly.

Steel scrapping will actually be a post-processing to shave and decrease roughness of a stone-grind process.
The skis he tested had been ground by Lars Svensson.

At least greyish areas on my ski bases are gone. Forever.

After Kuzmin measured that fact, the stone-grinding process has maybe increased in quality, though.
Yet the very process of (relatively) high speed rotating emery stone has not changed, so the physical effect of creating hairs because of the tensile strenght of UHMWPE is still there.

Beside hairs and roughness, Kuzmin then questioned the kind of grind done by a rotating stone. Which is *always* small and straight patterns. They can be a dirt magnet, especially if you put in there soft wax acting as a " bond" for fluoros. When fluoros are gone, you're left with that " glue" inside the structure. Hence his research to produce different structure generating aeration without the adverse effect of collecting dirt. (Xriller). At the World Cup, they don't care much on that, as stated by Knut Nystad, because they are allowed to swap skis... (Every 8km for a 50km event).

osloskier
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Re: Kuzmin scraping and structure

Postby osloskier » Mon Dec 15, 2014 6:50 pm

"Scraper" is a misnomer, I think. They don't scrape, they cut, and the result is better than with sandpaper. They are not just used for skis: http://www.stewmac.com/How-To/Online_Re ... shing.html

Chris
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Re: Kuzmin scraping and structure

Postby Chris » Tue Dec 16, 2014 7:16 am

Loran wrote:At least greyish areas on my ski bases are gone. Forever.

Beside hairs and roughness, Kuzmin then questioned the kind of grind done by a rotating stone. Which is *always* small and straight patterns. T


Isn't the greyish area believed to be wax residue that has worked out of the base? If you are not applying waxing then there wouldn't be greyish areas by definition. I don't think this either proves or disproves waxing versus scraping

Don't the scraping and brushing process also leave a straight pattern? A grinder or a scraper can make something large depending on how the stone is cut or the scraper manufactured. Again I'm not sure how this proves or disproves grinding versus scraping.

Loran
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Re: Kuzmin scraping and structure

Postby Loran » Tue Dec 16, 2014 9:08 am

Chris wrote:Isn't the greyish area believed to be wax residue that has worked out of the base?

No. These are raised lamellae or "hairs". A wax residue would not stick like that.
Anyway, "working out" the base means reverse dilution, due to base cooling. It's a one time process for a small part out of the 2g wax that dilutes into the base. Don't rely on that.

Chris wrote:Don't the scraping and brushing process also leave a straight pattern? A grinder or a scraper can make something large depending on how the stone is cut or the scraper manufactured. Again I'm not sure how this proves or disproves grinding versus scraping.


A cutting tool (let's call it like that) will leave a straight pattern, but much much less deep. Also much much longer due to pure translational movement. A manual, deeper, structure is required in very wet condition.

I'm not saying that manual tools are always better than a stone-grind. But stone-grinding is definitely limited to short and straight patterns and this is not necessary the best for all conditions.

m2qItMot
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Re: Kuzmin scraping and structure

Postby m2qItMot » Tue Dec 16, 2014 7:21 pm

So, regarding the brushing after steel scraping - what exactly does it achieve?

How bad is it, if one does not brush or brushes not much?

How do you know when you are done brushing - just by the shiny finish on the base?

Last, but not least, can one use a cheaper (well ... er, previously purchased :-)) nylon roto brush? E.g. the Swix fine blue nylon one? Or the apparently discontinued, stiffer, less fine, black nylon brush?


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