My friend Vincent is a true professional when it comes to composites. He has been very helpful with all my bodywork and fiberglass questions (e.g. What’s the best way to bond X to Y?). When I told him my plan about bonding my shell to the chassis with urethane caulking, he had lots of suggestions. The first one was to use 3M 5200. It’s typically used for marine applications, but it is incredibly strong and stays flexible.

His next suggestion was to “bog” the mating surface between the shell and the chassis (I learned that in the fiberglass realm, the term “bog” refers to a resin filler that fills gaps between materials). We started out by using double sided tape as a spacer. Then we layered pieces of packing tape over the double sided tape. The double sided tape creates a space for the caulking, the packing tape helps release the bog.

We also used some “magic” mold release liquid on the packing tape as an extra layer of insurance.

After that, we glued some regular fiberglass mesh to the chassis using 3m 77 spray adhesive. Then we mixed up the bog. The bog was a mixture of two part fairing compound (similar to Bondo, but much better) and short fiberglass strands. This made the bog quite stiff and less likely to drip all over the place. We spread the bog onto the fiberglass mesh, then placed the shell onto the chassis. We clamped it in place to get everything level.

After 24 hours, we popped off the body. The bog stuck to the shell very nicely and released from the chassis with almost no effort. This is the result:

Now I just need to clean up the edges of the bog and then prep both surfaces for the 5200. Next week we should have the shell mounted.