Design a Concrete Sailboat

Сезон 1, серия 6: It may sound suspiciously like a lead balloon, but a concrete boat can be made to float. Your engineering challenge is to create a concrete sailboat that can operate safely in 10-mph winds. Hydrostatics comes into play in designing a hull with sufficient buoyancy, and aerodynamics enters the picture in designing a sail that doesn't cause too much heeling in the wind.