Following the shaping of the model, a hard composite surface will be created using fiberglass reinforcement and epoxy resin.  The epoxy adheres to the polystyrene foam as opposed to the polyester resin which will dissolve polystyrene.

The first step is to create a proper working environment.  The work table is covered with polyethylene sheet plastic which will protect the table from damage and will not stick to any cured epoxy.  The liquid resin is located close at hand along with the glass, stir sticks, and mixing cups.  Latex gloves should be used to prevent direct skin exposure to the epoxy resin.

start 1

The following step is to begin putting down the fiberglass to the model.  The dry fiberglass is cut to the proper shape before it is wet-out with the resin.  The foam surface must also be wet out for good adhesion.  The two wet surfaces will create the best bond possible.

The glass build on my model started with a layer of 1708 biaxial cloth with the random strand side facing the foam.  This allows for maximum bond due to the increase contact area from the flatter profile.  While this layer was still wet, a layer of 1.5 oz random strand mat was added.  This layer leaves a smoother (flat) finish than the woven fiberglass mat.

These two layers were put down wet and rolled out to remove air bubbles.  Good bonding is created by removing the air pockets between the surface and following layers.

glass 2

Glass along the edge can be trimmed with a utility knive razor blade during a short period of time while the epoxy is moving through the cure process.  The laminate gets hard enough to cut with a razor blade before it gets to full cure.

edges 3 copy


Following cure, the fiberglassed areas are sanded with sandpaper (40 to 80 grit) to remove stray fiberglass strands that are poking up.  The rest of the surface is sanded to allow adhesion of following layers.