Camber Loss

falls · Post by **falls** » Sun Jan 29, 2012 12:20 am

I know this is an old topic, but any thoughts appreciated.
I made my first pair of skis with camber late last year.
The mold had 10mm of positive camber at its highest point.
Layup - base and edges, triax 22oz, bamboo core, 22 oz triax, bamboo veneer. Fibreglass was oriented symmetrically about the core, long fibres away from core.
Epoxy was ski specific sicomin - heat cured from above only - ramp to 80C over 30 minutes, soak at 80C for 1hr 15 minutes, allowed to cool and pulled hot.
Bamboo core was 2mm in tips and 13mm at centre, quite stiff, but not excessively.
The ski pressed to the shape of the mold pretty well and they look pretty flat etc.

PROBLEM: From the moment I pulled them it was pretty clear they didn't have 10mm camber. In fact they looked like they had very little.
Now they are cured and cut out they have pretty much zero camber.

I have heard certainly of camber loss from heating from above only and had purposely gone for 10mm camber thinking I would lose some.

Do you think it is possible to lose all the camber simply from heat from above alone, or do you think the core was too stiff and the composites couldn't hold it in the cambered shape?

Thanks

Dr. Delam · Post by **Dr. Delam** » Sun Jan 29, 2012 1:22 am

I think that it is heat related. I use flat molds and if I do bottom heat only I get one cm of camber and if I do top heat I get one cm reverse camber at tips and tails.

vinman · Post by **vinman** » Sun Jan 29, 2012 3:01 am

Definitely heat related.

Richuk · Post by **Richuk** » Sun Jan 29, 2012 3:55 am

Falls, I think you have two PID controllers, so you can look at a slightly different heat cycle for the top and bottom. In the Crown clip, you'll see them doubling up on the solution and attaching them to a post press mould. I'm assuming they do this as a QC issue to accommodate any residual elements of the cure cycle that will take place at 25 oC

amidnightproject · Post by **amidnightproject** » Sun Jan 29, 2012 6:49 am

With the bamboo if you don't heat from the bottom you wont get anything for camber. And if you don't heat at all, you will end up with early rise.

Switch your heat to the bottom and you should get some camber back. The bamboo is really stiff. So if you don't cure the composites in the shape you want, the bamboo will control the final camber of the ski. It's annoying haha.

When I first started I had no heat in my press. Everything came out flat underfoot with early rise tip and tail. Now I heat both sides and it'll stay in whatever shape I want it to. Granted your core isn't to thick and your's isn't. Your pretty close to my measurements.

twizzstyle · Post by **twizzstyle** » Sun Jan 29, 2012 8:48 am

Definitely the heat. 10mm camber loss isn't extreme at all. On the last skis I did I heated from the bottom and gained at least 10mm camber. They looked ridiculous to me at first, but turned out to be great on the mountain.

I think my plan for all future pairs is if I want camber I heat from the bottom and get a lot, if I don't then I heat from the top, if I want something in between tough. I've tried shimming my mold and it was too much of a hassle.

If you heat at a lower temperature, the effect will be decreased as the entire ski will come up to temp more evenly.

ggardner90 · Post by **ggardner90** » Sun Jan 29, 2012 3:52 pm

i have been having trouble keeping camber with bamboo as well

amidnightproject · Post by **amidnightproject** » Sun Jan 29, 2012 5:37 pm

Bamboo HAS to have heat. Otherwise you will get no camber and it's got to be on the bottom if you can't heat from both sides.

Are you heating ggardner?

ggardner90 · Post by **ggardner90** » Sun Jan 29, 2012 6:25 pm

OOOOOOOO im hot

usually bout 185, that what my girlfriend tells me. she calls me hot stuff.

all joking aside i have been heating from the top but i will call mei tomorrow and see if i can put the blanket in my casset and if they think its all good i will switch to the bottom. i built a mold that has 3x the camber i want because i lost so much last time. how much camber do you loose if you heat from the bottom or do u get more than the mold with bamboo

falls · Post by **falls** » Sun Jan 29, 2012 7:05 pm

thanks all (especially AMP) - sounds like I need to try bottom heating.
(Rich - I only have one PID and one blanket that has been on the top)

amidnightproject · Post by **amidnightproject** » Sun Jan 29, 2012 8:38 pm

Hey no problem falls. I've done enough reading and being quiet I figure it's time to speak up a little.

Gardner. Unless you have a weird type of cassette that MEI blanket will take the pressure you throw at it and the shape. I heat on top and bottom via MEI blankets and 185 degrees @ 78psi. I don't really loose any camber. I gain a little. I can set it back in the mold after I pull it out and its practically identicle now. Before without heat, not even close...

*edit*
Before you go throwing that blanket on bottom I hope you sandwich it between some aluminum to keep it safe! Just being cautious. I don't want to be the reason a blanket got ruined.

falls · Post by **falls** » Mon Jan 30, 2012 12:30 am

Interestingly I sanded the edges and bevelled the sidewalls today on this pair and sat them back to back and they have a little camber now, probably about what I would have wanted (maybe 5mm on each ski).
It was cooler today 27C and humid, compared to 35C and dry the other day.
Who knows?!?!

vinman · Post by **vinman** » Mon Jan 30, 2012 3:34 am

A little post cure love.

ggardner90 · Post by **ggardner90** » Thu Feb 02, 2012 2:33 pm

just pulled my last ski out press and i got camber like i wanted by switching blanket. thanks for the tip

SkiTheNortheast · Post by **SkiTheNortheast** » Sun Feb 05, 2012 11:43 am

do you need to heat the bottom to get camber just with bamboo cores or other types of wood too, like poplar?

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Camber Loss

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