Here is the Fly Baby cowl ready for moulding. It has been sealed and sanded.
1. First run a length of masking tape along the desired part line with one edge of the tape on this centre line.
2. Cut sections of cardboard to match the curvature of the plug and glue them to the centre edge of the masking tape (I use medium or thick Cyano and accelerator to cure it quickly). This forms the vertical part line. The masking tape helps you remove the cardboard and glue later without damaging the plug.
3. Use self-adhesive tape ('sellotape' or 'magic' tape) to seal/bridge the joins in the cardboard. The part line may be a bit wavy but this is not usually important.
4. Add a few domed 'mirror screw' covers to create male/female mating surfaces in the flange to help ensure accurate alignment of the two halves later (the hollows created in this way are more obvious on the next photo).
5. Now wax the first surface to be moulding with ordinary household floor polish wax (the simplest, cheapest polish in a tub).
6. Using paper towels, rub it down and remove all surface wax (except in little corners/gaps which you want the wax to fill gaps). A perfectly smooth surface should polish up to a bright shiny blemish-free finish (you essentially end up leaving an extremely thin and invisible layer of wax). I personally hate the special silicon-based moulding waxes, and the water-based PVA ones work no better than what I have described and are a magnet for dust as they dry.
7. Now apply gelcoat and allow to become touch-dry or harder. It will remain sticky for weeks to aid adherance to the next layer.
8. Add about three layers of medium-weight chopped strand cloth with resin (the finished mould should be about 1/8" thick to be durable). Woven cloth is fine as well; it is more expensive but goes round curves better. If you use chopped strand, cut edges with scissors where they go into a corner (such as at the part line). Tear the cloth by hand for other areas (instead of using scissors) to create a 'feathered' edge which is easier to blend with overlapping pieces.
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