: Sounds like a fast way to make a boat?

None of the methods shared on this site are what I'd call fast.

If you truly wanted to go to a fast prototyping method, you'd design the boat in the computer, output the design to a multi-axis CNC cutter and produce tools in stacked laminate particle board, knock-out a couple of sets of thermo-formed decks and hulls, glue them together and go test the dude for fulfillment. The right outfit could do the whole thing for you in less than a day and if you were slick with the design software, you could get a pretty good cutting file in a few hours.

That is fast.

If you are tactile kind of guy who is good with his hands, you can hand shape a chunk of lighter weight machinists foam (and yes, even the blue or pink stuff you can get at HD) in no time, surface the whole thing in Bondo and take it to a sorta smooth finish so that you can pull deck and hull parts. The parts can be vacuum bagged to keep them very light and stiff. Then, glue them together for the proto boat and test until it hurts. Hardly any investment in time or materials and you get to paddle the thing to see how it performs. It doesn't need to be glorious to look at.

There are, literally, dozens of methods for doing this and all of them will work if you understand the process. To hear people shoot on your concept when it is entirely workable is tiresome.

After all, it's your project, you can define it in any way you want and the adventure is yours to contemplate during the process, as well as afterward. Don't let the naysayers turn you off to the potential.

If you want to have some backup on all this... a close friend in Tasmania is building his own sportscar body in fiberglass. He has chosen to shape the sections of his bodywork in low density foam and glass them over. Once the glass has cured, he pulls the glass parts and puts them back together as rough bodywork.

This guy has spent a lifetime fabricating large scale fiberglass parts for auto, aircraft and various commercial interests and really knows what he's doing with the material.

Try it, see what you learn and don't be afraid to experiment.