modlers i need your help! after modelign trains for a few years i have ventured out into modeling ship (gasp) however i was wondering any one else here has doen that because i need to know how to fiberglass my hull. I have never done fibergalss work before, the hull is wood construction with white foam on the outside, i followed plans while doing this, however the fiberglass seems to reacte with the foam and eats it away. shoudl the foam be painted/priemd first? soory if it’s off topic here but i have no where else to turn.
Anything that has solvents will dissolve Styrofoam. Prime the foam with a thick coat of latex paint first.
The easiest way around the problem is to use Epoxy Resin rather than traditional fiberglass resin (polyester) which contains solvents that attack the foam as you have discovered. Some years ago I built a tugboat for my boys using a plug carved from foam. It is applied in the same way as traditional fiberglassing with a couple of changes. Do not put resin on the foam and then lay the cloth, but rather lay the cloth dry on the foam and then brush the resin onto the cloth to hold in place. Use a fairly heavy cloth for the first layer and follow up with one or two layers of successivly lighter cloth, applying each layer dry and brushing on the resin after. This method uses considerably less resin as the foam is very pourous and absorbs a lot. After the last layer of cloth use one or two coats of resin as neccessary to get a smooth finish.In my case I later removed the plug by carving a hole in the foam and pouring in a cup of Acetone. I then installed balsa and plywood formers to hold everything in place inside.If you do want to dissolve the foam be sure to do this outside as it produces a lot of bad (potentially harmful) fumes. This will result in a hull that is very strong and durable. Install your prop and rudder shafts/tubes before applying the resin.
I used a product called Cold Cure Resin which is used in the boat industry. This stull will set up in very low temperatures and even underwater. It has been used to patch holes in boats before they were refloated. It’s other big advantage is that it has very little odor and won’t get you thrown out of the house.
I built a hull like that once and I used wood putty over the styrofoam and then sanded it smooth before I laid the fibergass on. Worked like a charm!