: Thanks for the ideas guys, I knew I could count on you. I think I'll forget
: about the Owens-Corning stuff and experiment with a rubber detail
: mold/fiberglass mother mold and also a gel coat/chopped fiber/glass cloth
: mold laid up in sections. Fiberglast is a great resource, btw. Thanks
: again for your help.

: Jim

I don/t know for sure the relevant advantages of silicone vs urethane for the detail molds, but the sculptor i listened to most carefully used urethane for heavy production, silicone rtv for quick repairs of that and rtv for major smaller detail work. and then polyester screw together casts backing that.

he would sculpt the positive of both foam/modelling clay/regular clay for detail, release, get the mould detail w/ rtv(major 3d) or urethane first mould(for flatter pieces)(sim mat'l to what pete is showing),and for the more 3d:

clay edge where he wanted to make the backup seam bolt flanges,
cast those pieces, remove the clay and release agent the flanges of the already cast partial backup polyester and use those as the mold edges for the last infill polyester backup, drill thru both flanges and attached bolts then separated all. A totally enclosed structural segmented backup of 3d detailed pieces.

-mick