A vessel (10) designed to operate efficiently as both a catamaran and air
cushion vessel can travel at low speed (e.g. Froude number (Fn)=0 0.3) in
a catamaran or displacement mode and at high speed (e.g. Froude numbers
(Fn)=0.3 or more) in an air cushion or dynamically supported mode. The
vessel (10) includes molded catamaran hulls (11, 12) with parabolic
waterlines, a flexible, air cushion seal system (16, 17), surface
piercing propellers (20) and a propulsion system (e.g. combined diesel
and gas turbine). There are preferably auxiliary gas turbines for
generating lift air pressure. Forward mounted independently stabilizing
foils (30), can optionally facilitate ride stabilization and load
compensation at high and low speeds. The foils also generate transverse
roll forces to improve high speed maneuvering.