Ski Builders Forum

http://epubl.ltu.se/1402-1757/2006/03/L ... 603-SE.pdf

It pretty much changes everything according to old waxing theory.

Somehow I have suspected this, after waxing my skis over and over ten times, just to see them completely dried out the day after skiing. Why do they make sintered uhmwpe at all? Doesn't work!

Thanks for this excellent and informative paper. Are there any reasons the conclusions should not apply to downhill skis? How are "kick" and "glide" waxes different than those used on downhill skis?

If we still make our ski bases with UHMWPE (obviously better than many materials), should we buy a non-sintered version? Are ski shops set up to scrape the bases instead of stone grind them?

Did anybody in the US hear about this in the "news" [radio/paper/mag] recently? I think this is what my girlfriend [who doesn't ski] was telling me about yesterday. But she couldn't remember where she saw/heard it. Maybe she's just psychic.

Not sure where else it was covered, but GetOutdoors blogged about it.

http://www.getoutdoors.com/goblog/index ... wedes.html

More coverage of the issue, but no definitive answers to the alpine ski question - is a raw, scraped UHMWPE base better for downhill skiing?

http://www.economist.com/science/displa ... _na_tran=1
http://www.wildsnow.com/?p=77

If have well understood, they suggest to remove wax from the base and just scrape it: the ski will be faster.

A friend of mine got a pair of secondhand Pocket Rocket 3 years ago. He uses them around 100 days per season, and he never waxed the skis in 3 years: the base is so dry it is almost white. He told me they are faster than brand new skis...

Hello waxers!

I read about this a year ago and started to think about my old Blizzard Firebird Comp wich I scraped with a sharpened steel scraper! Since then I have not had a pair skis with such glide. I waxed them once a year, did not matter I think, and I always had the best glide in all conditions of all I knew.
I do this on my skis now but it is hard work to get that finish. Conclusion: Why have a nice high tech base when trashing it with a stone grinder.
Well, I think wax and grinder companies did a good jobb because they survived with something that belong to wood bases!

Hendryx

@Henrik,

Can you explain the scraping procedure you are talking about. What are you scraping away?

I've been reading just a couple of minutes after I posted this message about the scraping:
http://www.jenex.com/tuning/star_tuning.html

Is the scraping taking a part off from the base? How much and why does it make the ski faster? Are those skis not worn faster than those we don't scrape?

Cheers,

Geoff

Hi, just wanted to share a few thoughts after reading the article.

One comment made “why sintered UHMWPE. It doesn’t work.” (endre). My understanding is the sintering is a production process as apposed to extruding, and makes the material stronger/more durable. So buying and using sintered base shouldn’t be a problem. Its how the base is prepared that makes the difference.
Sinter - to use pressure and heat below the melting point to bond and partly fuse masses of metal particles, or to be bonded in this way.

They also mention that additives like graphite make the UHMWPE less able to resist abrasion. The best stuff to get is the clear pure UHMWPE, which is what was used to conduct the tests.

The test were conducted by an XC pro, so to me that just means he has more interest in that type of skiing. Why would it make a difference for alpine skiing? Glide is glide… isn’t it? I mean their tests were done on a down hill slope on a XC track for 100 m. I don’t see a difference.

The real conclusions to the thesis were in the part about dirt absorption with respect to stone ground (SG) waxed skis and scraped unwaxed skis. The dirt pick up on wax skis and SG skis made them lose their glide advantage, which was slight, within just a few kilometers.

For us I would think that getting the skis ground flat and the edges set to the angles you want is the place to start than take the skis home and scrape them yourself. Look here for a Swedish steel scraper only $6.95 US
http://www.tognar.com/base_flattening_t ... board.html
They also talk about using a rotary steel wire brush after scraping. I’m assuming that it is a structuring tool?

Yes the scraper will remove material. You also need to take care that you don’t flex the scraper as you use it or you can put a concave in the ski base. If the scraper is sharp you should not have to apply too much presser and one or two passes should do the trick. All you would have to do after that is clean the ski once in a while to bring it back to the glide you got when you first scraped it.

This article pretty much throws out all of the stuff I’ve been doing to skis for the past 35+ years. It sure is going to save me a bunch of money on ski prep costs.

Thanks really great stuff!

sintering uhmwpe is done to create pores in the material, the problem is that the pores are to tiny. I don't think sintered is stronger than not sintered because of the sintering, rather opposite i would think, but i might be wrong there.

Actually, sintered umhwpe in general is stronger than the standard method of making uhmwpe (extrusion). I dealt with this issue at work a few months back, and as I recall, the sintered uhmwpe had a tensile strength around 3000 psi, while the best that any supplier could give me for extruded material was about 1800 psi. Additionally, the extrusion process creates a lot of internal stresses in the material, which can really cause troubles when it is cut out. Sintered material on the other hand is generally less prone to this issue as the material starts as fine grains that are then cooked together.

There has been simular discussions about sintered and non sintered inserts, and as many of you might remember Dönek sold their stock of sintered inserts on ebay about a year ago. Sintering allows combinations of materials in orher configurations than what is possible in alloys at lower than melting temperature (f.ex titanium, which has an extremely high melting temperature) Sintering also makes a more or less "spungy" structure, with pores, that can be positive or negative depending on use. In some ball bearings etc. they use sintered parts containing lubricates, when the metal heats up and expands the oil gets squeezed out. I automatically assumed that by sintering UHMWPE, these were the characteristics they were after.

I had time to read the thesis, and I decided to use the electronic scanning microscope to get some pictures.
This is PTEX2000, as I received:



And this is after sand papere griding, waxing and brushing:



It seems the wax fill in the "grooves" on the base.
I will prepare better samples, and I should do some test on scraped samples as well.

Awesome pictures!

AMAZING! Thats really awesome you took the time to do that. The original pics look really defined and has really "sharp" edges. The wax looks much more muted... almost looks like a photoshop filer of sorts.