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convex ski bases

post #1 of 15
Thread Starter 
What would cause a ski base to become convex? A guy at Waterville said it could be caused by too many passes with an iron while waxing the ski, making the base too hot. Can anybody verify this?
Thanks
post #2 of 15
What brand / model of ski? Seems it would take a lot of abuse to warp a ski with an iron. I'd be more inclined to believe it was manufactured that way.
post #3 of 15
I've never done/experienced/seen any of the following, but I would think that you'd delam the ski before causing the base to become convex through too much heat from an iron...You'd burn/seal the base structure before getting the ski hot enough to do any of the aforementioned damage anyways.
post #4 of 15
There's almost no way the base can become convex with iron abuse. It would literally delaminate first! The most common way a ski base becomes convex (assuming it started out flat) is by too much flat filing. Your hands tend to pressure the file right over the edges and over time, it will take more edge away and leave the base high. To keep this from happening, you should get them machine ground once in a while, rather than always hand tuning.
post #5 of 15
Thread Starter 
Quote:
Originally Posted by DropCliffsNotBombs View Post
There's almost no way the base can become convex with iron abuse. It would literally delaminate first! The most common way a ski base becomes convex (assuming it started out flat) is by too much flat filing. Your hands tend to pressure the file right over the edges and over time, it will take more edge away and leave the base high. To keep this from happening, you should get them machine ground once in a while, rather than always hand tuning.

The skis are my wife's Volkl Pink Stars. I've never done anything with the bases but wax them. I keep the edges sharp with a moonflex. The iron never gets hot enough to smoke any of the wax I use. They are convex from the tip for about 4 -5 inches and from the tail maybe 3 -4 inches. Had them stone ground last year and pointed it out to the guy so he could try to fix it but they were still convex off the machine. I've also noticed it a bit with my 5 Stars but not as pronounced or as long from the tip. Wonder if it's a Volkl thing?
post #6 of 15
Sounds like poor finishing at the factory.
post #7 of 15
Are you sure they are "convex" (base high), and not "concave" (edge high)?

If it's really convex, is it towards the center of the base, from side to side, or closer to the edges? How high?

Before the grind, how many days were on the skis?

After enough days all skis will become a little convex on the tips/tails and will need a grind to get them flat again...This is normal and shouldn't take more than a pass, or two, on the Winterstieger.

Does the ski feel "hooky/grabby/locked in the turn", or does it feel "squirly/loose/wandery" or hard to initiate turns with poor edge hold?
post #8 of 15
Thread Starter 
Quote:
Originally Posted by memosteve View Post
Are you sure they are "convex" (base high), and not "concave" (edge high)?
Yup. I know the dif, but thanks for the thought:

Talked to a guy at Summit racing. He seems to think its bad handling of the machine. I'll know when I take it to him.
Thanks for the replies.
post #9 of 15
From what I've seen they either came that way or the last machine the tuned the ski was not set up correctly.

Concaved areas on fatter skis is not that uncommon. You can't feel that when skiing them.

The shop should be able to fix like it was said above.

Pink Stars, she must be a good skier.
post #10 of 15

Skivision base planer

This works pretty well at fixing convex bases. A little pricey though, but it works a lot faster than sandpaper wrapped around a couple of old files.
post #11 of 15
A new ski can sometimes be concave, convex or both at different points along its length. Although manufacturing quality control has improved a lot in recent years among most manufacturers, it is still not always as good as it could be.

Often what happens is that the ski base is ground and finished and the skis shipped before the glues in the ski have fully cured. As the glues bonding the ski components continue to cure the base can distort losing the flatness it had when it left the factory. A convex base could also be caused by other aspects of the manufacturing process.

As memosteve points out, skis will tend become somewhat convex as the P-tex material at the edges wears down. This occurs with use or improper base edge filing which is a pretty good reason to only sharpen your ski's side edges except to knock down burrs. For that matter, concave edges at the tips and the tails can often be felt by skiers-at least on hard snow. The rule of thumb is to get concave tips and tails flat at least 1/3 the way in from the edges if you are not prepared to have them ground totally flat. Elsewhere along the ski should be flat-neither convex nor concave. It's generally not a good thing to have convex bases anywhere along the length of the ski.

If your iron was too hot, either the P-tex would blister or the skis delaminate.
post #12 of 15
Quote:
Originally Posted by deanie View Post
The skis are my wife's Volkl Pink Stars.
This happened to my Volkl Pink Stars as well, and for no discernible reason. I noticed it as I was waxing them, and on ice and hard snow boy did I have difficulty holding an edge. I figured that the last shop that had ground them must have messed them up. I took them to a new shop to stone ground them back to flat, but they said there was little ski left after they flattened them out. They said they were so thin they no longer had any life left in them.
I went out and skied them, and they were right. It's possible that this shop could not have done anything better with these skis, given the condition they were in when I brought them in. Anyway, be careful who you give them to when you get them fixed.

I bought new skis.
post #13 of 15
Thread Starter 
OK. I took my 5 stars and my wife's pink stars to a guy named Mike DeSantis after talking with him by phone. Had a factory refinish done after chatting with some of the guys there. He did a beautiful job. He'll be getting my biz from now on. Interesting that LF's skis were shot after being flattened. Mike says that a slight concavity on the base is a part of the design, something I had been wondering about since every new Volkl seems to have it. He did this to both our skis and the Pink stars are certainly not shot even after being convex before. I'll be bringing my other skis to him before heading to Canada and will see if he has an answer to why that happened to LF'd pink stars.
post #14 of 15
Concavity is clearly a result of modern ski design, namely the wider tips and tails. I've never heard that concavity is designed in. Anyway, Mike de Santis has World Cup credentials and knows Voelkl products having worked for them in various high level capacities. He posts here sometimes as "skidoc."
post #15 of 15
Quote:
Originally Posted by deanie View Post
Interesting that LF's skis were shot after being flattened. Mike says that a slight concavity on the base is a part of the design, something I had been wondering about since every new Volkl seems to have it.
Just a note: I had bought the tools and started waxing my skis myself for a few months before this convexity showed up. I'd probably skied them 60 - 100 days by the time I noticed this happening. I still suspect the shop that ground them last.

Glad yours survived the whole process.
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