 Poster: A snowHead
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I worked 15 years at ICI as a polymer chemist.
Ski bases and ptex are made from ultra high molecular weight polyethylene which has a molecular weight of 3 - 7million
Milk bottles are made from high density polyethylene which is chemically identical but shorter molecular chains with a molecular weight of 10,000 - 100,000.
When ptex is burned, the molecular chain unzips so the material that actually lands in the hole in your base has a molecular weight little better than wax, I would guess not much more than 1000.
Whilst ptex is actually quite cheap, in the absence of its availability ther may be alternatives.
Do not mistake semi opaque hdpe bottles with clear pet bottles! Or glass for that matter, youll never get it to light 
Blue plastic water pipe and yellow gas pipe are also made from hdpe.
Any other thoughts?
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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@tangowaggon, plausible, and I don’t doubt your expertise.
Not sure when a base repair would be such an emergency though? Itadarod?
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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Proper milk bottles are made from glass so I doubt this would work.
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@tangowaggon, interesting. Is a ptex candle actually burning ptex though? I'd assumed and/or been led to believe that it was ptex mixed with some kind of fuel, and it was the fuel that burned to generate just enough heat to melt the plastic? Would that still unzip the molecular chains?
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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| Tubaski wrote: |
| @tangowaggon, interesting. Is a ptex candle actually burning ptex though? I'd assumed and/or been led to believe that it was ptex mixed with some kind of fuel, and it was the fuel that burned to generate just enough heat to melt the plastic? Would that still unzip the molecular chains? |
Surely the ptex (plastic) is the fuel? I assume it started its life as oil.
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@Tubaski, I expect it's the heat that unravels the chains, in fact, isn't it important to prevent the candle from burning too hot and charring, but just to have enough of a blue flame to allow it to melt? Burning for me means it's reacting with oxygen and becoming a different sort of molecule. (Too long since my chemistry days, and not sure I'd have known the answers even then!)
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| Tubaski wrote: |
| @tangowaggon, interesting. Is a ptex candle actually burning ptex though? I'd assumed and/or been led to believe that it was ptex mixed with some kind of fuel, and it was the fuel that burned to generate just enough heat to melt the plastic? Would that still unzip the molecular chains? |
Ptex is pure pe what actually burns is unzipped pe
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@tangowaggon, thanks.
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You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
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Just for example ptex is a chain of millions of carbon atoms, each with two hydrogens sttached, diesel fuel is a chain of typically 15 carbons, each with two hydrogens so you can see how much the ptex has to unzip before it will burn.
I have a nice core shot in my black based skis so im going to roll up some bin liner
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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Thinking about it further (can you tell I'm bored on nyd?) There is little point in making ptex from uhmwpe because it will not melt & flow without unzipping it. It would probably be better to use a lower mw pe that could be used in a hot glue gun at a temperature that would not degrade it and get it into the base without being unzipped.
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And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
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Bit of a core shot
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You know it makes sense.
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Rolled up builders dpm
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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Filling in progress, keep the "pen" as close as possible, lift slightly if the flame starts to flicker as this is usually a sign that it's about to go out.
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Poster: A snowHead
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Finishing with sanding mesh and flat sanding block
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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Job done, ready for waxing.
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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Actually looks pretty good, do you think it’ll be hard enough.
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| SnoodlesMcFlude wrote: |
| Actually looks pretty good, do you think it’ll be hard enough. |
Just as hard as ptex but past experience of ptex suggests that it's best to keep this as an outer edge.
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Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
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Ptex only bonds to ptex so won't bond to the core of the ski or the metal edge so that repair will soon crack and fall out.
The only way to repair a core shot like that is to weld in a metal grip foundation layer first.
Most proprietor ptex candles have a paraffin additive to help the burn as ptex tends to self extinguish. The paraffin additive plus the carbon and other contaminates from the burn make the repair softer then the existing base as opposed to a proper base weld with paraffin free rods with no flame.
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| spyderjon wrote: |
The only way to repair a core shot like that is to weld in a metal grip foundation layer first.
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or you cut out a rectangular section and super glue the same size ptex sheet into the whole, at least that's what we don in the Alps.
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@davidof, done that in the shop plenty of times
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@spyderjon, out of interest, does a proper ptex repair absorb wax as normal, someone a while back said not, but I've always felt it takes ok?
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You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
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+1 for metalgrip!
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@spyderjon, I'm inclined to agree with you, whilst I think milk bottle or dpm is just as good as ptex, ptex itself is not that brilliant.
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snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
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| davidof wrote: |
| spyderjon wrote: |
The only way to repair a core shot like that is to weld in a metal grip foundation layer first.
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or you cut out a rectangular section and super glue the same size ptex sheet into the whole, at least that's what we don in the Alps. |
It's faster & therefore a lot cheaper to do a proper welded repair on damage like that but many shops don't know how to do it &/or have the tools (even though they're inexpensive). Most patch repairs require a base grind & therefore a full service so it's a way of bumping up the cost plus most shops don't care about doing unnecessary base grinds. A metal grip/welded repair can be done in isolation quickly & cheaply (I'd charge £10) with no other work being required unless necessary.
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And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
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| KenX wrote: |
| @spyderjon, out of interest, does a proper ptex repair absorb wax as normal, someone a while back said not, but I've always felt it takes ok? |
KenX, there's two different types of absorption in to the ptex, the absorbtion in to the voids/pores created from the sintered production & absorption in to the solid. A 'melted-in' repair doesn't have the sintered cavities so you'll loose that absorbtion but wax can still be disolved in to the solid. However you'll get a lot less absorption in to the solid with a candle repair due to the carbon/inpurities within the repair material caused from the burn, which isn't present with a true welded repair using tools like the Kunzmann Base Doc II or a Skimender repair pistol.
As you, like me, use a good welding technique you'll still see/get good wax absorption whilst those that don't will most certainly be using a candle repair.
Note that I'm not an industrial chemisty so my terminology may not be correct but in laymans terms that's how the modern sintered ptex made for ski/snowboards works. I've a friend who did his chemistry Masters & Phd specifically in this field who could give an afternoons presentation on this stuff but his explanation to me that ptex is 'magic' stuff works for a numpty like me. He's also confirmed that everything detail here is correct: http://www.dominatorwax.com/technical-education
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| spyderjon wrote: |
It's faster & therefore a lot cheaper to do a proper welded repair on damage like that but many shops don't know how to do it &/or have the tools (even though they're inexpensive). Most patch repairs require a base grind & therefore a full service so it's a way of bumping up the cost plus most shops don't care about doing unnecessary base grinds. A metal grip/welded repair can be done in isolation quickly & cheaply (I'd charge £10) with no other work being required unless necessary. |
That's good to know.
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You know it makes sense.
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@spyderjon, for most of the fairly average piste skiers (like myself) would you notice a huge difference if (say) a 1 inch square but of base didn’t have wax properly absorbed?
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Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
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| SnoodlesMcFlude wrote: |
| @spyderjon, for most of the fairly average piste skiers (like myself) would you notice a huge difference if (say) a 1 inch square but of base didn’t have wax properly absorbed? |
Nope.
Forgot to add to my above post that the one advantage of ptex patch repatch is that you'll still get both types of wax absorption in to the repair site.
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Poster: A snowHead
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@spyderjon, thanks for that, confirms what I thought
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Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
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Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
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You need to Login to know who's really who.
You need to Login to know who's really who.
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