Mixing Adheasive

[Dan]

I am ready to bond the core into the fiberglass. The existing core was not adhered to the fiberglass as well as I had originally thought. The core wasn?t stuck at all. I ripped it out using a hooked tool and the vacuum to pull it out of the gap and then used the air hose to blow the rest out. It blew out like confetti.

I have cut and fit the new core pieces so that they can be slid into the gap. The new pieces are 4mm okoume, .160? thick. The original plywood was .140? thick. The pieces have been coated with un-thickened epoxy to let it soak into the wood.

The surfaces that will be next to the wood, the inside of the fiberglass panels, look like the surface of the moon. When the sides were originally bonded, it was done exactly like Tim said. ?Blobs of resin or putty here and there.? Which left a lot of voids. I want to fill as much of these voids as possible.

I am going to brush un-thickened epoxy on the fiberglass surfaces and on the wood. I have made a small tool that can reach into the gap and mop the epoxy onto the surface. While the epoxy is still wet, I can trowel some thickened epoxy into the largest gaps. Then I can slide the core into place. Then inject epoxy into the remaining gaps as well as I can, then clamp the sides together. I have the clamps set up to stop at 5/8?. This way the walls will be uniform 5/8?. As well as I can tell 5/8" is the original thickness. The epoxy will not be thicker that 1/8? anywhere so I don?t think exothermic heat will be a problem.

I am also going to use the slow hardener to give me more time to work the epoxy into the gap. It?s a long gap and the filling and the clamping will take I?m guessing around 30 min. or longer provided I take the time and do a good dry run. Planning and going through the motions with clamping will be critical.

Obviously I want a strong adhesive for bonding the core to the fiberglass laminates. What would be the best mixture for this process? I have fumed silica, and microfibers. I have used the fumed silica by itself for filling holes and gaps and general bonding, but I haven?t used the microfibers yet. Will the microfibers thicken the epoxy enough that it will not sag and the epoxy will not drain from the thickener before it sets?
I will need to inject the goop into the joint with a syringe to fill the gaps, so I will need the mixture to flow well, but stay put once it?s in there.

Does this sound like a good plan? Any advice will be greatly appreciated.
As alyways, a few pictures to help with the confusion.
http://home.wmis.net/~dhapp/gap/gap.html
Dan

[Tim]

Microfibers can add additional strength to an adhesive mixture, but epoxy mixed with cabosil alone is also a fine choice for adhesive strength. You will likely need some cabosil as a thixotropic additive anyway, to smooth out the mixture and increase its viscosity into a nice paste for your job.

Use a combination of the two, or just cabosil; either will be fine. Be sure to mix it nice and stiff for this job, or you run the risk of running or draining.

That's quite a jigsaw puzzle you've created there! I'm sure that was a tedious job...