One must assume this is just a multiple posting of a similar set of questions concerning your desires to start building a plastic 11' sailboat?
If looking into this from a business stand point and interested in eventually making money building boats, you'll need to do some serious research across several subjects. Chemical and structural engineering, yacht design, roto molding or other plastic forming process, would be the first things you should gear up for. If not yourself, then your staff.
The one off build to test a prototype would be best suited with a plywood building technique. Yes, you can use 'glass over Home Depot foam, but it's more costly, tougher to fair, requires more engineering, more building skill and is more time consuming to build. An 11' prototype can be built in less then a week in plywood, ready for testing and fairly cheap. Proof of concept verified (or not), then you can move on to the next stage.
Considering you basic questions thus far, you need a boat designer and an engineer as good drinking buddies. Buy them some beers and pick their brains, maybe some stock options. Other wise, you have a considerable amount of education ahead of you.