Evan / Jim - Question on inconsistent adhesion to clear gel

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#1

I seem to be having this problem with patchy gel coat adhesion. It seems like the gel coat and carbon are not fully bonding (see pic). Any thoughts? :?:

What I usually do is spray down a layer of clear gel (50/50 mix of clear gel and Duratec high gloss additive help to make more transparent) and let it cure. This way the mold is set when I need to use it. Then I infuse using VER and let cure overnight under vacuum. I have seen this on a couple parts, but this did not happen with Evan and I used epoxy. I am wondering if it has something to due with the VER on the cured gel coat whereas the epoxy has better adhesion properties. I could switch to epoxy but I am trying to keep the costs down.

The nose of the engine cover had the same problem.

#2

My thinking is that using PER or VER is “B” staging too fast and with the epoxy, you have a longer time to fully pull the resin into place.

#3

The VER that I am using is the FiberGlast stuff and it requires a 1.5% catalyst. If I backed that down to say 1%, do you think that might help? The only caveat to that is I tried this on a limited sample and I experienced incomplete cure in some areas even after an overnight bagging. I cannot attribute it to that exactly, but I thought it might be not enought catalyst or poor mixing. I think I will see if I can replicate the problem with some thin epoxy resin I have. Thanks

#4

VER is pretty tempermental when it comes to catalyst ratio. Just stick to the 1.5%. It looks like the resin failed to penetrate that sections of the part for whatever reason. Did you have that honeycomb like core material on the back of that part?

#5

None of the honeycomb core on that part. Me thinks it has to due with the VER as I pulled a part last night using epoxy over a cured, clear poly gel coat and it was perfect. Guess I will burn through what remaining VER I have and start moving towards more epoxy. No big deal as I was having problems with the usable pot life with VER anyway and really wanted a longer cure time. Thanks