Ptex -- tough vs waxable?

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JeffOYB
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Ptex -- tough vs waxable?

Postby JeffOYB » Mon Dec 18, 2017 11:03 am

Who knows how ptex bases play out?

What is the very best? What is the quality we're looking for?

Are there trade-offs? Like you can have toughness and waxability but not both?

I think with climate change and the new sport of trail-skiing that we need ski makers to innovate and deliver a base that is both tougher than ever before and also still super-fast.
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Triarii
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Re: Ptex -- tough vs waxable?

Postby Triarii » Tue Dec 19, 2017 3:10 am

I think you are looking for any sintered UHMWPE base (as P-Tex), all variations inside this category should be extremely minor compared to other parameters. All sintered UHMWPE bases have great toughness and waxability and of course there are tradeoffs.
I agree that most evolution (if any) will happen for wet conditions.

The perfect base material will depend on the conditions, and I think this may see some evolution in the future with cold/plus skis. We may see a PTFE base in a high end plus ski some day. Maybe a base with cross linked PTFE for a more universal or even a cold ski.

I guess that may result in a continued divergence between professional and consumer equipment (as with wax and skins) with PTFE bases having lower friction while having lower wear resistance and higher cost. This is the only way I see that friction can be reduced significantly.
More experiments with white and other carbon-less bases. Also for cold conditions.
For consumer gear with UHMWPE, I think that as wear resistant as possible is the ideal direction. I would expect to see someone come out with a skin ski with a steel scraped base (i.e. Kuzmin) marked as "zero maintenance", which will be a revolution for the average skier that has never touched a waxing iron.

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Re: Ptex -- tough vs waxable?

Postby Loran » Wed Dec 20, 2017 1:19 pm

Hi,

Since you're mentioning Kuzmin, he brought to our attention that there's no such thing of "waxability" didn't he ?
No "pores" into sintered UHMWPE base. A very small amount of wax will "dilute" into amorphous parts of the p-Tex, once and forever...
We're eagerly waiting for PTFE & cross-linked PTFE bases.
Its worth mentioning that apparently SLEGAR of Asiago tested PTFE bases many years ago and came to the conclusion that too low friction has an adverse effect. No data, no paper for backing their conclusion though. only http://www.slegar.com/index.php?option= ... Itemid=131

Cheers

BTW : The owner of "P-Tex" trademark is CPS Gmbh : http://www.cps-gmbh.net/en/gesintertes-uhmwpe.php

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Re: Ptex -- tough vs waxable?

Postby Triarii » Thu Dec 21, 2017 3:04 am

Hi! Yeah I figured it was enough with a mention. His name tends to open a completely different discussion (which I enjoy very much, but for the sake of the topic). Kuzmin did prove that there were no pores to absorb wax, but I don't think this means that all UHMWPE bonds to wax in the same way so I don't think that eliminates "waxability" as a term. But of course, for us who believe in his findings it is a moot point.

Thanks for the link, the conclusion is interesting and as the article mentions, almost paradoxical. It would be great to see some data on their tests, especially the conditions tested in. I would believe that PE to PTFE is such a big change that it would need some rethinking of the ski profile. If the ski is too slippery to create a sufficient water film, why not reduce the contact area to increase the contact stress? And was the test with pure PTFE or with some additive to increase thermal conductivity (the black stuff in ordinary bases)? As always on the topic of glide and snow, too many variables.

Loran
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Re: Ptex -- tough vs waxable?

Postby Loran » Thu Dec 21, 2017 4:07 am

There is this paper, which is about testing different polymers on snow : https://www.research-collection.ethz.ch ... 160-02.pdf

Conclusion abstract : "In this study, polymer slider soles of a wide range of chemical compositions and surface structures were explored for their tribological properties on snow at near constant conditions (snow temperature -2.6 to -4 °C). An optimum surface roughness of the soles - in the range of 0.2 to 1 μm - is detected for which friction is minimal, essentially independent of the surface topology, and, most remarkably, for which the influence of the chemical composition of the sliding surface becomes virtually negligible."

If I get it well, when the roughness is not optimal, then PTFE is always better though.

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Re: Ptex -- tough vs waxable?

Postby Triarii » Thu Dec 21, 2017 6:16 am

Thanks again, very good read.
That temperature range is very conveniently the range where the lowest friction coefficient typically can be seen. The biggest expected advantage for a PTFE base would surely be in higher temperatures with thicker lubrication film.
Surface roughness is very into Kuzmin theory which states that the high surface roughness of a stone ground ski is negative, while this report seems to suggest otherwise.

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Re: Ptex -- tough vs waxable?

Postby Loran » Thu Dec 21, 2017 12:59 pm

I think that Kuzmin says that stone grinds leave lots of hairs that must be dealt with : Either shaved or "glued" by wax.
Also, he says that a stone grind can only produce short straight patterns, which is not necessary the best pattern. Maybe, maybe not.

I think that a pure straight pattern, in the range of 0.2 to 1 μm is typically what we is achieved by using cutting tools.
Kuzmin came later with the advice of using a riller (macro structure) for wet conditions.

I read (I don't remember which paper) that a bit of transverse pattern helps gliding by creating turbulence.
What is the optimal transverse pattern : stone grind, Kuzmin's, or other riller?


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