So many problems.

Richuk · Post by **Richuk** » Wed Feb 19, 2014 2:17 pm

Thanks chrismp, you explain things better than I.

Can I just check whether the width of the laminates top and bottom are the same or similar? The description of your board seems to suggest otherwise.

The base will become flat when heated because it was flat when it was cured.

BLOODTYPEZX10R · Post by **BLOODTYPEZX10R** » Wed Feb 19, 2014 2:19 pm

This problem has only surfaced when turning to heat for cure.

I appreciate all of your support and feedback. I will keep trying and succeed or will have to quit.

BLOODTYPEZX10R · Post by **BLOODTYPEZX10R** » Wed Feb 19, 2014 2:26 pm

Richuk wrote:Thanks chrismp, you explain things better than I.

Can I just check whether the width of the laminates top and bottom are the same or similar? The description of your board seems to suggest otherwise.

The base will become flat when heated because it was flat when it was cured.

The widths are the same, this is one piece at this time, laminated and cured with layers of cf and tiax fg.

correct, it will become flat when heated to cure temp and return to convex when it cools, over and over again. slow cool, no cool-hot out of the press, moisture stabilize. Why is it not flat after it cools? If it is the cf then why does this not happen to my core?

Richuk · Post by **Richuk** » Wed Feb 19, 2014 2:48 pm

It is not flat because there is residual tension between the mechanical properties of the laminate. If you know about how a bi-metalic strip works (I'm sure you do) then that is the issue you are dealing with.

Curiously, this is not affecting camber ..

In the absence of photo's you are making this a matter of deductive reasoning. It would help to know:

- is core subject to a separate heat cycle prior to use
- are different wood species used top and bottom
- what width is the rebate (this isn't a big issue)
- what ramp rate are you using

MontuckyMadman · Post by **MontuckyMadman** » Wed Feb 19, 2014 2:59 pm

sounds like from your lack of details you are not making a standard sandwich construction and differing composites and weights and a different core layup than standard.
Without details we are just stabbing in the dark.
Most likely we have hit it here...somewhere.
Perhaps by wrapping the sidewalls with composites and the change in the ratio of resin to composite by adding a speeded heat cure your are getting different contraction rates in the laminate-especially with the carbon.
I suggest you return to the resin system used previously and room temp cure and stop being super mega vague with about 10 people trying to help.

IF YOU CANT TELL US THE DETAILS WE CANT HELP YOU

also forget vacuum. step up to the plate with a pneumatic, shit will be squeezed together and the issue will disappear. Alter your process and molds to accommodate your super secret layup. Get an autoclave or somethin. jeez.

twizzstyle · Post by **twizzstyle** » Wed Feb 19, 2014 3:11 pm

If you have different orientations and/or weights of composites on top and bottom, you WILL get changes in camber and/or concavity if you are curing with heat, period. If you cure at room temp, then take the board to the cold mountain - you'll also see issues. Any delta in temperature from the cured temperature will cause an expansion/contraction of the laminate, and the only way to keep the shape the same is to have an identically mirrored layup on the top and bottom.

Problem solved.

twizzstyle · Post by **twizzstyle** » Wed Feb 19, 2014 3:17 pm

Also remember guys, carbon fiber has a negative thermal expansion coefficient. It contracts with heat and expands with cooling.

sammer · Post by **sammer** » Wed Feb 19, 2014 5:29 pm

I'd have to agree with twiz, thermal expansion of the asymmetrical layup.
The easiest solution other than symmetrical layup would be to make your mold convex.
Or cure with no heat, but you might find your skis going convex once they get cold on the mountain.
Also to agree with montucky... too much information is being withheld to give an accurate diagnosis. Although I'd put money on asym layup!

Even though base material warps and distorts with heat it can't over come the stiffness of the rest of the assembly.

sam

MontuckyMadman · Post by **MontuckyMadman** » Wed Feb 19, 2014 9:22 pm

Perhaps the fact that you are useng a woven composite and heat and vacumme and several other rad and random varibles is contributng to the issue. You ever heard KISS? Keep it simple stupid.

Richuk · Post by **Richuk** » Thu Feb 20, 2014 2:28 pm

So I recently pointed someone in the direction of this forum ... but I kinda wish I hadn't. Kicking someone when they're feelng down or confused, just not cool.

skimann20 · Post by **skimann20** » Thu Feb 20, 2014 3:50 pm

Holy Cow, You guys are trying really hard! tons of great ideas here. I think what Bloodtype needs to do is make a spread sheet with two columns. One "Before" and "After". See where everything is different and the same. there is so much info here it is getting quite confusing. Also, I'm a big believer in "a picture is worth a thousands words" maybe if you took some photos of what you are doing or heck even a build journal would be a good thing.

You seem to have all the questions and the answers but no solution. good luck my friend.

Yes M.M. "KISS" I'm a firm believer in this!

chrismp · Post by **chrismp** » Fri Feb 21, 2014 12:13 am

Richuk wrote:So I recently pointed someone in the direction of this forum ... but I kinda wish I hadn't. Kicking someone when they're feelng down or confused, just not cool.

That's not senseless bashing! So many people are trying to help him, but he doesn't give all the information necessary to be able to find the real problem (ie. claims that it can't be the fiber/heat combo and a day later admits that the problems all came when he started using heat)... of course people get annoyed with it. what do you expect?

falls · Post by **falls** » Fri Feb 21, 2014 1:38 am

Sounds like 90 degree oriented fibres contracting upon cooling (or expanding in the case of cf) that is causing things to go convex. Same as when you heat a ski from the top only and you get exaggerated reverse camber.
Agree with the others who have said that asymmetric composites are likely the cause.

Dtrain · Post by **Dtrain** » Fri Feb 21, 2014 1:56 pm

And this is why his journal is titled............SO MANY PROBLEMS.LOL

BLOODTYPEZX10R · Post by **BLOODTYPEZX10R** » Wed Feb 26, 2014 11:49 am

Kinda feels like it. My ribs are bruised. Montucky you crossed the line.

MM I am entitled to secrets, you are a fool if you think that we small time builders are the only ones here looking at designs and ideas of others. I won't loose my ideas to some large company to a patent. I don't feel that the pics that I am keeping from you are of any concern, my descriptions were plenty.

If you actually read my posts and not the tangents that have occurred from that point I feel the problem could be resolved. A decent discussion about my finding, and experiences would have gone a long way.

It was never my intention to get into fights with any of you and KISS is not my style, what is the purpose to build skis or board like everyone else. It is time for something new and I intend to make it work.

Ski Builders Forum

Ski Builders Forum

So many problems.