Thread: Carbon fibre/epoxy gurus help please

I was making topwater stick baits for a while (Epoxy over cedar). And have had many go wrong and a couple go alright.
99% of my problems always came from not mixing properly and not letting the resin cure in the right temp & humidity.

Mixing rules I followed:
Use syringes to measure (never kitchen scales)
Mix in ‘pot A’ for 2minutes, pour epoxy into ‘pot B’ and mix again for 2mins.

Curing conditions need to be dry and warm.

I’ve had the milky thing happen when rain has hit an un-cured project. But not sure if this is the same as your problem.

We see whitening of carbon finish kayaks...my understanding is that its water getting under the UV stable clearcoat. You won't see it with a pigmented paint job.
My stab in the dark is that you let an epoxy layer get to dry and because of the amine blush mentioned earlier it couldn't fully bond with the previous layer. As a result water has penetrated between the layers and has now dried out. It will be interesting to see if those blemishes peel off easily with sanding.

So I finally got round to looking at this. I started to sand it with dry paper and it quickly got gunked up. The deformed patches were actually really soft. So much so I could scrape it off with my fingernail! I changed to a knife and scraped as much as I could off, then cleaned up with some wet paper. I think I have most of it off now. I have put it in the hot water cupboard to dry overnight, then I’ll give it some more epoxy layers. I’m guessing I must have either gotten the mix wrong, or not let it cure long enough? It’s weird though as when I finished it the first time it all seemed hard.
It’s good though, a couple more layers of epoxy will be good to fix some of previous imperfections.
The main one being I originally made the LOP too short, so as you can see I have lengthened it to the correct LOP. I’ll paint it black before I epoxy and that should blend in nicely

It was easy to find and fix the soft patches. I just ran the whole thing under the hose and watched the whiteness appear. It was actually quite widespread, but particularly on the butstock.