A very large printer.. http://www.thermwood.com/lsam_home.htm http://www.thermwood.com/lsam_home.htm Technically they printed it for a mold but that's because

A very large printer.. http://www.thermwood.com/lsam_home.htm http://www.thermwood.com/lsam_home.htm Technically they printed it for a mold but that's because fiberglass is better and while you can can print with glass reinforced materials the fibers have to be quite short which reduces their tensile strength compared to composite sheets. That said if you really wanted too you could print a functional hull, but it's not a good application for it. Not every manufacturing method is appropriate we can CNC mill a car from a single block of aluminum too but it's not exactly a good manufacturing process for this task. EDIT: HanseYachts AG apparently prints a 10m (~33ft) hull for one of their Yachts using a cellulose composite filament.