Questions from first time mold maker

I am helping a group of teenagers work on making a mold for a half submarine hull (top half). It’s a little bit like the blind leading the blind, though I’m apparently better at doing research and figuring out what we need to test first…and I don’t have homework to do at night, so I can play. This is primarily a self-funded project, so we are on a limited budget.

So, I’ve watched some excellent plug/mold making videos (Total Boat and Fiberglast come to mind) and read through lots of recumbent bike projects, gotten my hands on composites books, etc. Here are my questions:

-If you make a plug out of polystyrene board, must you fiberglass over it? Is it sufficient to fair the foam, fill in and smooth any voids, then coat it with gelcoat? If you think this is poor procedure, why?

-Can you hand lay up carbon fiber or must you vacuum bag it? We are first time carbon fiber users (it was donated) with experience doing hand lay up of fiberglass. We have never vacuum bagged. Our shape is about 9 ft long and 2 feet across in the mid-section with complex curves at each end, the more challenging being at the stem. What problems might we encounter if we attempt a hand lay up? If we were to add a core, how does that change the equation?

I know I’ll have more questions, but let’s start with these.
Thank you for your help.:smile: