I read a book once on how to mold a fiberglass canoe. You'd have to be a masochist to try this type of construction. The mold is much more difficult to make than the canoe. Why? Because the mold has to be just about perfect. A boat is a hydrodynamic shape. Every curve, surface and dimension imparts characteristics to the finished boat. Any imperfections in the mold will show up in the finished hull. Muscle powered boats with too many shortcomings get old in a hurry.
Could you build a boat using your idea? Certainly. Would it float? Probably. Would it be a desireable boat to paddle? That depends on how many years of your life your willing to spend to get it right.
On the other hand you could learn to build using some existing technology and have some fun.
Bibliography: For those that think I'm overstsating the case read "Building Your Kevlar Canoe" by James Moran.
Charlie