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Ski Base Structure
It's all about those little grooves on the bottoms of your skis. Structuring is the practice of creating a series of very small, parallel grooves on the entire surface of your ski bases. The purpose of structuring is to make sure that the theoretically proper amount of water is created between ski and snow as you glide. Whether or not this is actually the mechanics involved is subject to much discussion and disagreement...but either way, the deal is simple: Structure needs to be small grooves when snow temps are cold, and they need to be bigger when snow temps start to warm up.
How's Your Structure?
In cold, dry snow you want to increase the amount of water present between ski and snow for maximum glide. You do this by increasing the friction between the ski base and the snow. By increasing the volume of base that touches the snow, you increase friction...so, you want to have lots of grooves. The more, the better. To increase the number of grooves, they have to be small (.5 mm between ridges or less).
The way you create this structure is by taking it to your local stone grinding ski shop. But if you wanted to do that, you wouldn't be reading this article, so here's the deal: You have to hand sand the ski bases with increasingly fine grades of sandpaper...start with 120, and work your way to 220. Use a sanding block to keep the bases flat, and sand from front to back of the ski. Follow up the sanding by rubbing the skis down with a plastic bristle pad such as Scotch-Brite, a cleaning thingy available in most grocery stores. This is done to get rid of the plastic "hairs" created by sanding.
Congratulations, you just saved $45. Now of course the machine operated by the professional will do a better overall job, but unless you're a racer or a finicky skier you probably aren't going to know the difference.
As Winter Ends...
In warm, wet gloppy snow you have the reverse problem. Too much friction creates too much water which sucks your skis to the snow, makes 'em feel "sticky." Now you need coarser structure, we want to try for grooves spaced .75 mm apart or more. Now we work with 80 grit or even 60 grit sandpaper. Another way is to use the edge of a file, or by brushing with a stiff, sharp-bristled steel wire brush. Remember to use the Scotch Brite pad once more.
Some final thoughts...
Before you structure, you want to make sure your ski bases are flat. You can do this with a straight edge, just run it along the base and look for gaps. If you have bumps, remove them with a steel scraper. Always work in one direction, front to back.
Remember that after you structure, you need to wax. Wax naturally fills in all the grooves! Now you understand why you have to use a stiff brush after waxing -- you want to get the wax out of the grooves, in other words, it should "coat" the grooves -- not fill them in.
Structure eventually wears down. How long it lasts depends on the frequency with which you ski and also on snow conditions. You can eyeball your bases and just re-do the structure if it appears to be worn down.
-- Walt Morris
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