Camber Issues

[JonC]

I’ve been building for the past few years and have had a fairly consistent issue that I have not been able to nail down the cause of in order to try and solve it. It exists in varying degrees and doesn’t seem to cause any real issues with the function of the ski. The skis work well, give positive energy from the camber profile, and no one has had any complaints specific to the issue while skiing. I had noticed the issue and not thought much of it, but a friend brought it up who works at a tune shop and it’s just not consistent with commercial models. I would like to remedy it if possible.

When holding the skis together, base touching base, when you press the mounting zone together, the entire base does not sit flat against one another. They touch in the center, open up 1-2mm on both sides and then touch again at the tip and tail. When I do this with commercial skis they press flat and uniform against each other.

I thought the issue was the flex profile, that the epoxy was curing too fast from too much heat in the press, or that it was specific to the epoxy, but I don’t believe any of those are the root cause. (That doesn’t mean I am correct...) I am using a fairly standard construction. Ash/popular core, triaxial glass, Entropy super sap, both uhmw sidewalls and wood sidewalls, carbon stringers on about half of the skis, 4001 bases, vds over edges, all veneer top sheets, some with nylon over top, some with epoxy and varnish, and after changing these variables, including my ramp rate, the issue persists.

Pressing in a fairly standard press, I beams, pneumatic firehose bladder, 2k watt mats top and bottom with a pid setup. I press at 50psi with 1/8” mdf top and bottom outside of the .060” aluminum cassettes.

If anyone has any thoughts about what may cause this or how it could be fixed, let me know!

[vinman]

MY first thought would be some kind of irregularity in your molds. If your molds are routed by hand from a template. I'd guess you don't have a consistent arc on your camber.

[JonC]

MY first thought would be some kind of irregularity in your molds. If your molds are routed by hand from a template. I'd guess you don't have a consistent arc on your camber.

Molds are cut on a CNC, but not by me. The molds appear to be accurate as far as my eye can tell. They are 1" MDF with 3 pieces of 1/4-20 rod. The camber is a fair curve when not flattened, it just doesn't completely flatten when you press them together by hand.

[mammuth]

a pic would help

[JonC]

Here are a few pictures. It’s pretty much what Moment has branded as “mustache” camber. I believe Shaggy’s also brands something similar.

[mammuth]

So both skis have the same deflection?

[mammuth]

Check the deflection of your lower I beams if the molds are good (check it with the molds and skis inside as well)

[JonC]

The camber is a fair curve when it’s not being flexed.

Edit: I do get about 3/32” of deflection in my press at 50 psi.

[chrismp]

I just did this test on a few big brand production skis we have lying around in our shop and some of them showed the same behaviour, so I wouldn't worry about this too much.

However, I think this comes down to the flex profile of the ski. My guess is that if the cambered part of the ski is rather stiff, the camber still remains when the skis are only clamped in the middle. I tried the same test with an old really stiff snowboard with loads of camber by pressing it against a flat surfave (CNC working surface) and it showed the same behaviour.