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Decambering when ski is warm

post #1 of 11
Thread Starter 
I have noticed that, on more than one pair of skis, that the ski tails decamber while they they are warm from hot waxing. Has anyone else noticed this?
post #2 of 11
I've been told that it was normal and a sign that the skis are up to appropriate temperature. Dave Peszek, I believe, said that sometime a while back. I personally have never payed attention enough to notice.
post #3 of 11
That happens to skis with sheets of metal in them. Race skis decamber a huge amount. The type of alloy they use changes properties when heated.
post #4 of 11
takes you back to Blizzard Thermo, taking a property of a ski (camber changing in different temperatures just like the bimetal strip in high school physics) and marketing it as a feature....
post #5 of 11
I think this primarily affects skis with a metal layer *near the base* (normally right under the ptex). With heat, it expands and lengthens. Being near the bottom of the ski, it ends up curling the ski opposite to the camber. I imagine that if you could heat the upper surface of a ski with a metal topsheet, it would curl the opposite way. Cool stuff.
post #6 of 11
That's natural. That's why it's important to NEVER leave a ski clamped in a vise while it heats and then cools. You should to let it cool naturally and slowly. In other words, unclamp them from the vise and don't throw them out in the cold while they are still hot from ironing. That will hurt them. Let them cool down slowly...unclamped... inside.
post #7 of 11
As a rule I never clamp skis or snowboards while hot waxing. It has never seemed right to fix a ski and heat it up.
post #8 of 11
Quote:
Originally Posted by skier219 View Post
I think this primarily affects skis with a metal layer *near the base* (normally right under the ptex). With heat, it expands and lengthens. Being near the bottom of the ski, it ends up curling the ski opposite to the camber.
Interesting theory. Have a look at some actual numbers:
http://www.engineeringtoolbox.com/li...ents-d_95.html

We notice the TCOE for

polyethylene - 72 EE-6 in/in*(degF)
ABS - 55 EE-6 in/in*(degF)
aluminum - 12 EE-6 in/in*(degF)
epoxy - 10 EE-6 in/in*(degF)
wood (oak) - 3 EE-6 in/in* (degF)

So, your theory could be fairly correct for the case of Aluminum/oak core mismatch. The ski would be build as a base(matching layer)metal(epoxy)wood.

If the core is some sort of (non-epoxy, non-crosslink) plastic foam, the expansion of a uniformly heated ski with metal near the base would go the other way (making more camber).


Quote:
I imagine that if you could heat the upper surface of a ski with a metal topsheet, it would curl the opposite way. Cool stuff.
I'm surprised Phil hasn't tried this yet with FMJ Volants. Oh, wait, steel's pretty low on the list. Well, if he gets some Dynamics or Atomics with the magnesium topsheet it could work.


I'm getting several interesting thoughts from this thread.

One of them is that maybe we should sinter PE into bases with some sort of fiber reinforcement in the bases (steel whisker?) running along the bases. I vaguely remember something like this being done somewhen but can't remember where.

The other thought is that the PE number may not be for HDPE, which might conceivably be lower, but I am not happy about the thought of putting PE into 'cutting board' binding lifters anymore, not without metal backing sheets.
post #9 of 11
Quote:
Originally Posted by Alpinord View Post
As a rule I never clamp skis or snowboards while hot waxing. It has never seemed right to fix a ski and heat it up.
Advantage- binding vise, lasso vise, or any other vise with one clamping point per ski. If you're using a boot dummy in a binding, the decambering net force is taken up by the heel forward pressure spring.
post #10 of 11
BTW, notice that pine is distinct from oak, but only across the grain:
http://www.forestry.caf.wvu.edu/prog.../wdsc340_7.htm


So, are true bars relevant for fat skis only at snow temps?
post #11 of 11
Quote:
Originally Posted by Voltron View Post
I've been told that it was normal and a sign that the skis are up to appropriate temperature. Dave Peszek, I believe, said that sometime a while back. I personally have never payed attention enough to notice.

Happens to me all the time, see, I'm perfect...

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