Fly Baby cowl - first plug (on right) and second attempt (just before final assembly of foam blocks for sanding)...
1. Here I have used polyurathane insulation foam but 'Blue Foam' (Styrofoam IB) is better because it is firmer and more consistent.
2. Take care in choosing the size and position of the blocks of foam. Doing this can help you create symetry or determine centre, panel or part lines later.
3. Once you have the shape, you usually need to firm up and improve the surface. The polyurathane foam takes solvent-based solutions such as sanding sealer but use water-based PVA or Acrylic paint or vanish for most other foams.
4. Sand this lightly to remove high spots, but be careful not to break through the 'skin' as this creates imperfections which are hard to repair. Use a light-weight filler (they are usually soft and easy to sand) to fill the pores and any depressions.
5. A more robust 'skin' is to apply one layer of glass cloth with epoxy resin which would also be sanded and filled before proceeding.
6. An optional step at this time (especially where you did something special with point 2 above) is to apply little blobs of glue (or similar) to mark window or panel lines if you want these to be visible in the finished product.
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