I blowup my anchor rode locker hatch this winter. Going to build a model from the old one and make a mold.
What did you use for mold materials? What do you use for a release agent of the model? I've done some hatch repairs and vacuum bagging but never built a mold.
If I was going to pull a gelcoat part it would have been much different as you are making a final product. Since I'm painting I didn't spend a lot of time on the mold.
If you only have to make the hatch cover and you want gelcoat I would do it one of two ways.
Option 1:
Melamine sheet - you really don't even need to wax it, but I always do. I don't even use a partial paste and just go with a standard auto wax. If you add any recessed pieces like you see in mine those should get a heavy coat as the wood will soak up the poly/expoxy. You could also use PVA if your worried. It can be applied with a spray gun or even a preval sprayer. You really don't need to with melamine unless its old and banged up.
Take non-air curing modeling clay and push it in all your corners to make a radius. I use a tongue depressor or a bead to remove the excess. The bead in my pic was something I grabbed from my daughter and ran a drywall screw into it.
Add your non-waxed gelcoat 2-3 coats and let it setup.
1.5oz CSM
1708
Either 1.5CSM or putty and add core on top
1708
1.5 CSM
Cut the excess glass while its in the mold. If you screwed the mold together correctly you should be able to just take it apart. Since it's a one off its very easy to remove.
Option 2:
MDF Mold - you really need to seal up the MDF or it makes a mess. Not a big deal if you are painting the part, but if you want something close to a finished the mold will need to be coated. My receiver will be done this way and I'll try to take more pics. I'll be covering it with Epoxy bilge paint-----because I have some.
You could use gelcoat or any epoxy paint. I would use wax and PVA on a MDF.
If you don't need a mold with routed edges I would go with melamine. It works much better as the lamentation won't stick. I build everything with epoxy except for parts.