How to Mold RC Boats

Prepare your plug. The plug is an exact model of the finished piece you'd like to cast. You can actually use a finished boat for the plug or create one out of any variety of materials. However, the finished surface of the plug must be completely smooth, clean and defect-free. Any defects or debris will be imprinted in your mold and reproduced when you cast your boat. Use mold release wax on the plug, per the manufacturer's instructions. If your plug is not properly waxed, your mold will stick to it and you may damage the plug and/or the mold when you remove the plug, after the mold has cured.

Create the mold separation flange. Hot glue a strip of Minicel foam along the length of your plug, where your two mold pieces will separate. Align one edge of the foam strip with the mid-line of the boat. Cover this side of the foam strip with PVC tape. Apply mold release wax to the PVC tape-covered side of the flange.

Apply gelcoat to one half of the plug. Following the gelcoat manufacturer's directions, mix the gelcoat and catalyst. Apply gelcoat to the surface of the half of the plug and flange, on the side with the PVC tape on the flange. Use a disposable paintbrush, to create an approximate 1/2-mm thick layer. Be sure the gelcoat is evenly applied to prevent wrinkling in the final mold. Allow to cure until slightly tacky.

Apply fiberglass to the gelcoat-covered half of the plug. Mix the fiberglass resin and hardener, per the manufacturer's directions. With a disposable paintbrush, apply a layer of resin to the gelcoat-covered half of the plug and flange. Cut pieces of fiberglass matte and lay into wet resin on the plug and flange, overlapping edges of other pieces. Paint another layer of resin over the matte, wetting it completely without overwetting it. Use the fiberglass roller and paintbrush to ensure the matte is completely embedded with resin and all air bubbles are removed. Allow to cure until slightly tacky and repeat the process to add another layer of matte. Allow to cure completely.

Create the other half of the mold. Carefully remove the flange from the plug and first half of the mold, ensuring the plug does not separate from the mold. Apply mold release wax to the new fiberglass separation flange. Repeat the gelcoat and fiberglass process you used on the first half of the mold, for the second half. Allow to cure completely. Separate the two mold pieces and remove the plug. Check the mold for any imperfections and sand if needed.