I finally finished carving the foam plugs for the side panels on the bike, and started laying up some fiberglass parts for the 750. The resin is still curing, so I don't yet know how they turned out, but I'll edit this post in a couple of hours to show the finished product.
First, I wrapped the plugs in blue painter's tape. The foam is just a mold (technically, a plug -- a female mold is a "mold" and a male "mold" is a plug, as I understand); it is not a part of the finished product, so the tape will help the fiberglass separate from the plug when it has cured. Also, I'm using polyester resin that I bought at Lowe's, and I am using styrofoam that I bought at Michael's. Polyester resin dissolves styrofoam, so the tape acts as a barrier between the two to keep the resin from dissolving my plug. If you want to build a part that incorporates the foam into the finished piece, then you either need to use a non-styrene foam like urethane foam or Divinycell, or you need to use a different kind of resin, for example epoxy or vinlyester.
Once the plugs are covered in tape, coat them with a layer of automotive wax. The tape already has a bit of a wax coating on it, but the auto wax will help the fiberglass release from the plug a little easier. I used Turtle Wax because it was cheap and available; I'm sure other waxes will work, too. Be careful not to buy a wax and cleaner in one, however. I don't
KNOW that a wax and cleaner won't work, but I'd be cautious about getting soap in the fiberglass layup.
Cut a couple of pieces of fiberglass to fit the part, with a little extra around the edges, then, after covering the plugs with wax, lay the fiberglass over the plug. Pour a little resin over the parts, and use a brush, a roller, a squeegee or whatever you have handy to work the resin into the glass fibers and spread it over the entire part. If you see shiny, white patches in the cloth, that is an area that hasn't been properly wetted out with resin. Work some more resin into that area until you can clearly see the blue plug through the glass. Don't forget to work resin into the sides of the part, too.
Here is what the completed layup should look like. Observant readers will notice a long, thin, white streak near the top of the right piece. While it looks a lot like a void (an area that hasn't been saturated properly with resin), I spent quite a bit of time with my paint roller trying to work resin into the "dry" area there, with no effect whatsoever. Considering how easy it was to work out the actual voids in my layup, I'm convinced that this is just something on the plug -- probably an area where I didn't smear the wax around very well -- rather than a void. We'll see when the part is finished...
...which brings me to one of the cool things about working with foam and fiberglass: if you screw something up, it's not the end of the world. Carve and/or sand out the botched area, then rework it until you are happy. If you mess up a piece of foam, you can glue a new piece of foam in place, then carve or sand it until you are happy with the shape. If the problem is in a piece of fiberglass, use a saw, knife, file or sandpaper to carve out the problem area, then lay up a fiberglass patch over the area. When the resin has cured, sand the patch smooth and voila! Problem solved :)
Edit: As promised, the photos of the finished layups:
These two corners will need to be touched up a bit.
Here are the side panels fitted to the bike after some preliminary trimming:
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