Abstract: A boat having a variable hull configuration. The hull operates as a displacement hull designed for low resistance at sailing speeds and certain operating conditions. The hull includes an aft section having a pair of surfaces displaceable to a position and attitude such that at higher speeds, under power, the hull gives lift to the stern to facilitate a planing action. In the sailing or low speed mode, these surfaces can be stowed against the hull, if in the form of plates, or they may be solid bodies, such as wedges retracted into the hull by hand, mechanical, electrical or hydraulic operation.