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Myths about UHMW Base Material and New Base Material Idea

Tony Warren

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I have spent a great portion of my career working with Ultra High Molecular Weight Polyethylene. It is a great wear material for sliding abrasion and has many other wonderful properties.

UHMW does not have a melt-flow point. It requires a lot of pressure to either extrude it or sinter it. Materially there is no difference between the two processes. If one uses the same resin for either process one gets identical properties.

Over the years I have been told that bases need to be heated so that the wax can penetrate its pores. I have seen UHMW under electron microscope magnification. It does not have any pores at all. None, zero, nadda, zilch.

UHMW is not easy to adhere to. There are several processes that are used to increase the surface energy of UHMW. Crown Plastics uses flame treating, others use corona treatment. The object is the same, to oxidize the surface to increase its surface energy and perhaps to create some polar bonding sites.

The best treatment is fluoro-oxidation. It is a specialized process that must be done correctly. It uses Fluorine gas and heat to work. Fluorine gas is the most reactive element in the periodic table. Under the correct conditions it can start steel on fire! To get Fluorine gas one must crack it out of hydrofluoric acid. An HF spill of any size is very nasty because it dissolves the calcium in your body. 250 ml spilled on your body will kill you within a few hours. All that said, done correctly fluoro-oxidation increases the surface energy of UHMW more and more permanently than any other method. Great adhesion to the ski is the result.

Melted wax has very low surface energy. It adheres well to the UHMW of the base. However it simply does not last all that long. Most of the time we are just skiing on the uncoated base.

I am working on an alternative to UHMW ski and board bases. One issue that I find difficult to believe is the idea that 'texturing' the ski base actually makes it faster. Wax may adhere better to these bases but again that wax is so comparatively soft with relation to the abrasive ice crystals in the snow that I doubt it stays on for more than a few runs. I would like to get some comments from more learned community members to demonstrate to me why I should texture my new base instead of polishing it.
 

crgildart

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I kind of shake my head when I hear about people saying they burned their bases too badly so wax doesn't stick as well. Seems like an imaginary problem to me since wax never lasts more than a couple days anyway. Forgetting to scrape or outright ignoring that process only seems to hamper performance for a run or two.

Hot boxing isn't all its cracked up to be if the above is fact right? Would this topic go well in the Mythbusters thread?

As for "texturing" I assume you mean structure?? I've been convinced that structure helps in warm, wet, STICKY suction snow by allowing for some airflow to impair the suction. I agree that wax clogs it, but that's why rubbing on warm weather wax without scraping works well. It creates structure to inhibit suction.
 

crgildart

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To go a little further, I do agree that having the iron too hot, so hot the wax is smoking is not good for the ski. But, I'm more concerned about the structural integrity and weakening the contact cement and resin under the bases and edges, or bubbling the bases than I am about whether I am degrading the ability of the p-tex to absorb wax.
 

skibob

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I agree on texturing with crgildart. I've always questioned UHMW myself for the reasons you list regarding wax. It has good UV resistance in some forms, but then we put that side down, so?

What materials are you considering?
 
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Tony Warren

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I kind of shake my head when I hear about people saying they burned their bases too badly so wax doesn't stick as well. Seems like an imaginary problem to me since wax never lasts more than a couple days anyway. Forgetting to scrape or outright ignoring that process only seems to hamper performance for a run or two.

Hot boxing isn't all its cracked up to be if the above is fact right? Would this topic go well in the Mythbusters thread?

As for "texturing" I assume you mean structure?? I've been convinced that structure helps in warm, wet, STICKY suction snow by allowing for some airflow to impair the suction. I agree that wax clogs it, but that's why rubbing on warm weather wax without scraping works well. It creates structure to inhibit suction.

Because there are zero microscopic pores in the base, the idea of a hot box allowing wax to penetrate further into the base is just plain stupid.

We did some work with the Canadian team a few years ago with the idea of creating a highly abrasion resistant cold weather wax. When we treated the skis with fluoro-oxidation the wax adhered very well to the base, as we expected it to. However in testing on the Men's downhill course at Lake Louise we found the wax was all gone before the end of one run. It did however work very well and it took one racer from the third seed in SG to second place in the first race he used it on.

What we really learned however is that the best wax techs in the world had zero scientific basis for their ideas about how to make skis faster. They did make skis faster but they didn't really know why. They were always guessing.

This brings me to the structured base idea. One of my other professional areas is in the ultra-high pressure lay-flat hose business. I invented a 6 inch to 12 inch hose that bursts at 2,250 psig and operates at 1/3 that pressure. We flow various liquid fluids through the hose; from Jet fuel to potable water. All of the scientific research on the flow of fluids tells us that the smoother the inside of a hose or pipe, the greater the flow will be at any given pressure. This is because the friction of the hose against the fluid at the inside of the hose serves to reduce the laminar flow and in a sense reduce the internal diameter of the hose and thus the flow.

The question then is, do skis act like hose or pipe. In other aspects of my career I have worked at bulk material flow of everything from iron ore to coal to pulp. In all cases flow is proven better on smooth surfaces than nubly surfaces. I think the same holds true for skis. Consequently I doubt there is any fluid 'suction' change that is better with structure than without.

However I agree with you that waxing skis for warm weather works well. I just hot wax and scrape and repeat that every day I ski on non-winter snow.

Thank you for your input. It is most helpful in my thinking through this issue.
 

skibob

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The question then is, do skis act like hose or pipe. In other aspects of my career I have worked at bulk material flow of everything from iron ore to coal to pulp. In all cases flow is proven better on smooth surfaces than nubly surfaces. I think the same holds true for skis. Consequently I doubt there is any fluid 'suction' change that is better with structure than without.
.
I don't think you can calculate a Reynolds number for a ski. If you want to look at fluid dynamics, you need to consider more complex movements than a pipe. Bulk flow models like glaciers and lava probably helps think about it, but with skiing you are flowing a "solid" over a viscous material, not the other way around.
 
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Tony Warren

Tony Warren

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To go a little further, I do agree that having the iron too hot, so hot the wax is smoking is not good for the ski. But, I'm more concerned about the structural integrity and weakening the contact cement and resin under the bases and edges, or bubbling the bases than I am about whether I am degrading the ability of the p-tex to absorb wax.

The key with heating epoxy subsequent to cure is to avoid going past the glass transition temperature Tg as well as the heat deflection temperature. Smoking wax will change the characteristics of the wax. Heating the ski above 130 C to 200 C can pass the Tg of most epoxies. Of course the Ptex is not great at transmitting heat, so for short periods of time it is unlikely you will break down the epoxy structure. That said, hotter p-tex is in my opinion not relevant for wax absorption anyway.

Keeping the base cooler when waxing will completely eliminate the potential for disbondment of the epoxy from the base, so you are on the right track.
 
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Tony Warren

Tony Warren

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I don't think you can calculate a Reynolds number for a ski. If you want to look at fluid dynamics, you need to consider more complex movements than a pipe. Bulk flow models like glaciers and lava probably helps think about it, but with skiing you are flowing a "solid" over a viscous material, not the other way around.

Exactly correct. However I think that the PV would also come into play. However it was not all that long ago that many yacht racers tried to coat the hull of their boats with nubly, spray applied polyurethanes and polyureas. The idea was that a turbulent barrier between the hull and the water would add speed. The results were at best mixed and of course now they make their hulls as slick as possible.

Thanks for your input, again your advice has helped mold my thinking.
 
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Tony Warren

Tony Warren

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I agree on texturing with crgildart. I've always questioned UHMW myself for the reasons you list regarding wax. It has good UV resistance in some forms, but then we put that side down, so?

What materials are you considering?

I have in mind a proprietary thermoset that I have developed for pultrusion applications. It is a very tough hybrid material with some very cool magic pixie dust that gives it high abrasion resistance, very high hardness, and coefficient of friction only slightly higher than teflon like materials. If it works I think it may be a game changer.
 

jmeb

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Please excuse me if this is a stupid question -- I'm genuinely curious...

If wax disappears within a run or two as stated above, why do my skis with black bases (after multiple wax cycles) turn noticeably lighter after--not 1 or 2--but a dozen or two dozen days of skiing? Why causes the color difference?

Waxing takes them back to the deep black, and that color takes a while to wear off.

I'm not making a claim that the black bases are faster etc, just wandering what besides wax being on/in the base could cause the color difference.
 
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Tony Warren

Tony Warren

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Please excuse me if this is a stupid question -- I'm genuinely curious...

If wax disappears within a run or two as stated above, why do my skis with black bases (after multiple wax cycles) turn noticeably lighter after--not 1 or 2--but a dozen or two dozen days of skiing? Why causes the color difference?

I think the surface starts to oxidize which will cause the colour change. When we tested skis we started out with a deep grind of the base so that there simply was no wax on the ski. When we ran the skis we used a high-temperature wicking material and heated the base to about 150C. We got back less than 3% of the original wax applied, often less than 1%. Keep in mind though that we were testing on the World Cup course at Lake Louise which was entirely bulletproof top to bottom and I assume therefore more abrasive than skiing on nice snow.
 

crgildart

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When I don't scrape, there is noticeable thick and gooey wax down the centers of the bases for several, at least 3+ ski days but the edges and about 1/2" in on each side are squeaky clean by then.
 
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Tony Warren

Tony Warren

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When I don't scrape, there is noticeable thick and gooey wax down the centers of the bases for several, at least 3+ ski days but the edges and about 1/2" in on each side are squeaky clean by then.

We never run a flat ski anymore. We are always on edge and turning. So what you are seeing is the working surface of the base being entirely denuded of wax. My guess is that you spend a fair amount of time on hard snow on piste.
 

skibob

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I have in mind a proprietary thermoset that I have developed for pultrusion applications. It is a very tough hybrid material with some very cool magic pixie dust that gives it high abrasion resistance, very high hardness, and coefficient of friction only slightly higher than teflon like materials. If it works I think it may be a game changer.
Sounds like fun. I've often had the random thought (when I look at my phone on the mtn) that gorilla glass is probably getting durable enough for some ski applications. Internet of things anybody :).
 
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Tony Warren

Tony Warren

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Sounds like fun. I've often had the random thought (when I look at my phone on the mtn) that gorilla glass is probably getting durable enough for some ski applications. Internet of things anybody :).

Way too brittle for ski applications. Fun to think about though isn't it?
 

fatbob

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Because there are zero microscopic pores in the base, the idea of a hot box allowing wax to penetrate further into the base is just plain stupid.


The question then is, do skis act like hose or pipe. In other aspects of my career I have worked at bulk material flow of everything from iron ore to coal to pulp. In all cases flow is proven better on smooth surfaces than nubly surfaces. I think the same holds true for skis. Consequently I doubt there is any fluid 'suction' change that is better with structure than without.

.

So are you saying hot boxing is a complete waste of time as there is no way to saturate the bases? Presumably it means that hot scraping is worthless other than to clean the surface.

Re base structure I'd always thought that the mechanism was one of dispersal like a Wet Tyre allowing the ski to plane on the "normal" amount of water rather than dragging in the flood.
 

Eleeski

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At a small enough scale any surface will get rough. Wax does get thinner with temperature so hot waxing has value. However, I don't think that wax thins out too much with excess temperature (it's pretty thin once it melts) and something that thin is going to penetrate fairly completely quickly. The benefits of hot box are pretty marginal.

With that said, I cannot feel wax on the ski - certainly after the first run or two. So maybe I'm not one to evaluate waxing techniques. However, a better waxless base will really help me.

Of course, I prefer klister to slow me down through the bumps.

Eric
 

neonorchid

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http://www.penroseoutdoors.co.uk/pg/65/Ski-Buyers-Guide
Extruded Base
To make an extruded base the pellets are melted together, opposed to a sintered base where the pellets are crushed together under high pressure to form a ski base. The extruded base is cheaper to make and is found mainly in cheaper skis. This base is very durable and holds up well to the knocks and scrapes that comes when learning to ski.

Sintered Base
A sintered base, being crushed to gain its' form, has small holes and is slightly porous because the pellets have not been fused together. These holes allow a far greater wax absorption, and as a result the ski is a lot faster than a ski with a extruded base.

Ski-Base-Diagram.jpg
 
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Tony Warren

Tony Warren

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So are you saying hot boxing is a complete waste of time as there is no way to saturate the bases? Presumably it means that hot scraping is worthless other than to clean the surface.

Re base structure I'd always thought that the mechanism was one of dispersal like a Wet Tyre allowing the ski to plane on the "normal" amount of water rather than dragging in the flood.

I think the only advantage of hot boxing is to make the ski universally warm so the wax is better dispersed on the base. However, if there are zero 'pores' in UHMW, the stuff p-tex is made of, then there is nowhere for the wax to go, other than to cook off the surface of the base. Wax is volatile, so the wax carrier will evaporate and leave just the solids lightly adhered to the surface. This makes people think that the wax has gone deeper into the ski, rather the answer is that it has vapourized from the surface.

I have heard tons of stories about why ski base structure is important. However I would think if the case were as you claim, then all of the elite sailing yachts, all the race cars etc. would use this technique to create a turbulent flow on the skins of their devices. They don't. What do they know that we don't know.
 

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