OK to sand a ski to get it flat?

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JeffOYB
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OK to sand a ski to get it flat?

Postby JeffOYB » Mon Jan 25, 2016 6:49 pm

I'm a little leery of sanding my new (old) Fischer SCS skate skis to get them flat. But someone here said it was OK. I recall we used to do this.

So what I would do is put a 120/150 sheet on a block and do the rough flattening until it's very close. Then I'll go to 220 til it's perfect. The link below says that's good for blue/purple conditions. Then I'll peel with a sharp heavy cabinet scraper. Then do a few waxings with hardwax to prune hairs, then a few with soft wax to get a good soak.

Is this an OK plan to improve glide?

Or should I just fuggitaboutit and ski with factory rilled skis with concave middle third length?

Right now I see daylight under a scraper for the middle third length of the skis.

Oh, also I plan to do this sanding only to the portion which isn't flat. Hopefully the final smooth will merge nicely in with the unsanded portion -- I suppose the sanded portion will be a bit lower, eh? So I'll taper it into the factory-flat area.

Here's a link that shows what I'm up against: http://fasterskier.com/forums/topic/can ... el-scrape/

More cool info under the "Preparing for Sanding" header: http://www.skiwax.ca/index_tp.php
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Magnus Johansson
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Re: OK to sand a ski to get it flat?

Postby Magnus Johansson » Tue Jan 26, 2016 3:05 am

I recommend avoiding sanding and try steel scraping instead, not with a cabinet scraper but with Kuzmin's, Primateria's or Skigo's base scrapers. Then you do not have to wax at all.

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Re: OK to sand a ski to get it flat?

Postby TooHeavy » Tue Jan 26, 2016 9:36 am

Go ahead tip to tail. A poor mans stone grind.

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Re: OK to sand a ski to get it flat?

Postby MN Hoser » Tue Jan 26, 2016 1:27 pm

It's fine to sand it and safer than taking a steel blade to the ski. Use a sanding block with a slight curve, more than the camber of the ski (so you're just using a portion of the block to sand) and move tip to tail. Also start with a fine grit (like 200 or 240) since it will just sand just the high portion. A course grit (like 100) will sand the full width of the ski. I use a black sandpaper (when I sand). Remove material slowly, and after you have the ski flat enough, then move up in grit to as fine as you have (to remove hairs) and then a razor blade and finally warm scrapes with a sharp scraper. You' have to figure out how to structure the ski. I guess you could make a pass with sand paper, and I'd do that after polishing with a really fine grit paper. You could also use an imprint tool. If you grind, I think the shop would prefer to do the flattening. If the ski is not too far out, I'd leave it since the center of the ski (not flat) will have less effect on handling.

Jay

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Re: OK to sand a ski to get it flat?

Postby JeffOYB » Tue Jan 26, 2016 2:44 pm

OK, I jumped in. Started with a few passes of 150 grit waterproof. I wrapped the sheet of fresh paper around a heavy square steel block. Then did a hotwax with red. Did a sample scrape with my sharpened steel scraper. Left a lot of red wax near the groove. Concave!

Then I tried 80 grit. I saw mention of a water mister in the skiwax.ca info so I've been sprinkling some water on the bases now'n'then. I would make a ballpoint pen mark across the ski then sand it until it disappeared. I would test here'n'there with the ballpoint pen mark and make a few passes til it disappeared. Test again. Seems like that means the base is flat. ?? Then red hotwax and steel scrape. Still not getting all the wax! I would scrape and a long puddle of untouched wax would remain!

I don't know the performance effect of a flat ski. Or if concavity makes a slow ski. But I *DO* know a flat ski makes for funner and easier wax scraping! I like peeling off all a waxjob in just a few passes. I hate scraping half a base at a time or worse. Tilting a plastic scraper to get all wax out of a concave base region is LAME. Heck, then there's IRONING -- some of my skis are so concave -- that's ALWAYS the issue! -- that the iron doesn't even heat and melt evenly and I have to make tilted runs! Lame!

So I've been sanding both skis now for about an hour. At first I'd do it with 80 > 150 > 220 then hotwax and scrape. And it still left wax near groove.

Now I've just been sanding with only a fresh sheet of 80. I wanna get these bases flat! It finally seems like one base is flat. One is still being a pill after a good working over with 80 grit! What's up? I don't wanna sand away the whole dang base! (OK, it's finally behaving now.)

Maybe this black paper isn't removing as much base as I'd think. I don't see tons of black dust around. Some black in the wax shavings. It does make scratches in the bases that are coarse then fine...

After I finally get both flat I'll go over them with 150 > 220 and sharp-scrape on green hardwax to get rid of hairs. Then 5 waxings with red wax for soaking.

I'm surprised how long it has taken to get these things flat! I'm using a flat form. I'm not pressing real hard. I have a square sanding block. Why was the concavity so stubborn?

So they're pretty flat now. I'll go over with reducing grits now, etc.

OK, did that. On with the green and then warm hotwaxes. The IRONING is already so much nicer and pleasing! That alone is a very nice perk. Hope they're fast!
Last edited by JeffOYB on Tue Jan 26, 2016 3:37 pm, edited 1 time in total.
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Magnus Johansson
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Re: OK to sand a ski to get it flat?

Postby Magnus Johansson » Tue Jan 26, 2016 3:07 pm

In the following video Leonid Kuzmin is seen working on a ski with both a concave and convex base: https://www.youtube.com/watch?v=Wy5EAETYASE


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