For years I've had grand delusions of building a kitplane like a Lancaire or Glassair, which is partly pre-fabricated. Completion time can take a couple thousands hours. I don't know how many hours it would take to single handedly build a 100 foot yacht from scratch, but one very determined craftsman took up the gauntlet and built this behemoth in his backyard. The yacht is a catamaran called 'Kaleidoscope'. It is 100ft long, took 5 years to complete and countless blisters...
I met that guy and saw the boat on the Great Loop when I did it in 2008. Real nice guy. He had a Doberman that loved eating Bonita's, whole. It was on the Tenn Tomm, we stayed at the same marina one night side by side.