:: View topic - Heated Press and camber issues

After the first 2 skis came out with too much camber (Kaffienes and Daddies little girl), I modified the mold to have only about 5-6 mm of camber. We were able to try out the new mold this past week and lo and behold, the camber doesn't change. Our new skis still have way too much camber (>25mm). We are thinking the thermal expansion of the materials, especially the edges, is causing the camber to increase as the edges cool and contract after pressing. One pair has titanal on the bottom and the camber is much greater than the pair without.

Is anyone else having the same problems? One thought is to reduce the temperature. Another idea is to build a negative cambered mold and hope some of camber cancels out. Other thoughts on the issue?

-kelvin

Are you allowing the skis to cool in the press?

I just pulled a board out of my press and had the same issue. Maybe I should try letting it cool in there too?

In my heated blanket press, I haven't experienced this issue at all. I am throwing a ski in there tonight, and I will get a thermometer in there to find out how hot it actually gets.

We rip them out of the press smoking hot.

I'll definetly try letting them cool before taking them out. However, it seems that the epoxy is already at a full cure and everything is set in place at the extended lengths.

-kelvin

I'm no expert on the issue, but I have definatly heard that boards/ski's in heated presses should go through a heat/cool cycle before you take them out. I would guess that you should let them cool under pressure for approximatly the same amount time as you have them heated. I have also heard that the longer they cool under pressure the better the result.

what about using symmetrical metal layup like in the karhu video? maby this will "balance" the thermal expansion?

I heard some factories use diferent temperatures at the top and the bottom. maby to compensate?

Hello!

I cure my skis at room temp and have 10-15 mm camber built in to my moulds, the amount of camber varies with length. Sometimes I speed up the curing process by heating to ~35-40 celsius and I gain more camber, about 5 mm.

I think it is the steel edges that expand and contract different from glass laminates. The steel is the only part that my skis that are assymetrical with respect to the camber. Top sheet and base material are to soft to contribute to thermal relaxation tensions, probably.

My tip is: If you go for a heated press, optimize everything for a certain temp and stay to a certain material configuration. As soon as you differ material and/or temp you do not know what happends to your final product.

Henrik

Henrik

Hi Henrik,

At room temperature cure does your ski come out with the designed in camber or does it relax a bit? I am building 170cm skis and the mold has 15mm camber but I want the final ski to be no more than 10mm.

Thanks Tony

Hi Tony!

Yes they do, they relax 5-10 mm depending on length. I have a soft light core that does not contribute to the flex very much so you may experience differeces from my relaxation. But otherwise it sounds good with 15 mm of camber in your mold! Though I have a little less camber for a 170 cm ski, ~10-12 mm.

Good luck!

Henrik