Blade sail

Abstract

It is an object of the present invention to provide a boat sail with a greater forward thrust (per sail area), a reduced heeling load, and a more wieldy size. It is another object of the present invention to provide a boat sail with a more perfect reliability in its aerodynamic shape, a tighter control of the angle of attack between the airfoil and airflow, and the possibility of near-fingertip-control for “feathering” of thrust (among forward, neutral, and reverse). It is yet another object of the present invention to provide a boat sail that is—by virtue of its shorter overall height—safer near suspended power lines, in storms, in lightening, and under bridges. It is a further object of the present invention to provide a boat sail that is safer from boom hazards. The Blade Sail accomplishes these objects by providing a collection of vertical blades, controlled by a central “pitch-feathering” system.

1 . An aerodynamic propulsion system (a “sail”), wherein a collection of “blades” (aerodynamic surfaces) are assembled and “feathered” to adjust pitch:  
     
     
         2 . A sail as claimed in  claim 1  wherein the blades are mounted vertically about the structure of a boat, connected for pitch control by a central system (such as “line and cam”), thus providing both forward and aft thrust to the boat and a “boom-less turn” (where no large boom must swing around the passenger area of the boat).  
     
     
         3 . A sail as claimed in  claim 1  wherein the blades are mounted vertically on a “boom”, connected for pitch control by a centralizing system (such as a “rack and pinion”), thus providing both forward and aft thrust to the boat and boom yaw adjustment to optimize aerodynamic and hydrodynamic effects—including a “spinnaker” effect.  
     
     
         4 . A retrofit as claimed in  claim 1  wherein a collection of blades (a “Blade Sail”) is attached to the existing traditional sailboat structure (such as mast and booms,) to produce a “multiple blade” sail within a region (and hardware) where a traditional sail typically exists.