Model boat hull design notes – hull design and construction is my favorite aspect of building model boats. here are some tips for hard chine and round bilged hulls. The model pt boat site hull 2 – 1/20th skeleton kit. see hull-2 mdf version. 1/20th scale (4′) top and 1/35th scale (27.5") models side by side.. Instant access to 518 different plans – from small wooden boat plans to large sailboat plans – free boat plans.