I do know of a boat built by a friend 26ft plywood double ender, built in 2 months. Admittedly,he is a boatbuilder and knows what he is doing. The secret is to treat it like a job, i normally try to invest 10 hours a day in a project at least over the 5 days, and possibly less over the weekends. It depends if you can build full time or not and have all the materials on hand. We worked 120 hours a week to get a boat re-framed in 8 days, though i would not like to work like that on a continious schedule.....none of us are getting any younger. It takes discipline and commitment to knock out any worthy cruising boat and a certain amount of cash. Anything that takes longer than 2 years to complete is more at risk of being abandoned.