Marine Propulsion Multihull Ship

Abstract

A ship having a length to width ratio smaller than two and including a superstructure and at least two hulls, the superstructure forming a wing able to generate an aerodynamic lift comprised between 20 and 90% of the weight of the ship at a cruising speed thereof, the wing including curved ends connected to each of the hulls and having a developed surface of an extrados of the wing substantially equal to the product of the length by the width of the ship, wherein a point for application of the aerodynamic lift generated by the superstructure is situated behind the center of gravity for application of the gravitational forces on the ship, and a point for application of the resultant of the hydrodynamic forces generated by the hulls is situated in front of the center of gravity.

1 . A marine propulsion multihull ship having a ratio of a length of the ship to a width of the ship that is smaller than two, a longitudinal axis (Z) oriented from the back to the front of the ship that corresponds to a roll axis of the ship, a transverse axis (Y) that corresponds to a pitch axis of the ship, and an axis (X) that corresponds to a yaw axis of the ship, the ship comprising:
 a superstructure; and   at least two hulls;   
       wherein the superstructure of the ship forms a wing that generates an aerodynamic lift of between 20 and 90% of a total weight of the ship at a cruising speed of the ship, and wherein said wing comprises curved ends connected to each of the hulls and has a developed surface of an extrados of the wing substantially equal to the product of the length of the ship multiplied by the width of the ship, and
 wherein the ship has a point of application of the aerodynamic lift generated by the superstructure (A) that is located behind a center of gravity application of gravitational forces on the ship (G), and a point of application of a resultant of hydrodynamic forces generated by the hulls (H) that is located in front of the center of gravity (G). 
 
     
     
         2 . The ship according to  claim 1 , wherein each hull is a planning-type hull, the hulls defining together at least one hydrodynamic center of lift (H 2 ) that is behind the center of gravity (G) and at least one hydrodynamic center of lift (H 1 ) that is in front of the center of gravity (G). 
     
     
         3 . The ship according to  claim 2 , wherein each hull comprises, longitudinally, from back to front:
 at least one rear body having a rear keel line; and   a front body having a front keel line;   
       wherein the keel lines form an angle between them (α) that is between 0 and 6°, and forming an angle of attack with the horizontal (β) that is between −5 and 5° in hydrostatic trim. 
     
     
         4 . The ship according to  claim 3 , wherein each hull further comprises at least one step between the rear and front bodies. 
     
     
         5 . The ship according to  claim 4 , wherein the front body also has:
 a V-shaped cross-section with a half aperture angle (γ) that evolves continuously from the front toward the step, wherein the half aperture angle is a substantially zero angle at the front thereby forming a bow of the hull, and   a prismatic coefficient measured in hydrostatic trim of less than 0.7.   
     
     
         6 . The ship according to  claim 4 , wherein the rear body further comprises an anti-air leak blade that is below its keel line. 
     
     
         7 . The ship according to  claim 1 , wherein the superstructure has a central portion and a leading edge, wherein the leading edge along the central portion of the superstructure is, along the longitudinal axis Z, behind a bow of each hull. 
     
     
         8 . The ship according to  claim 7 , wherein the superstructure also has end portions, wherein the leading edge along each end portion of the superstructure connects the leading edge along the central portion of the superstructure to the bow of each hull following a gradual and curved aerodynamic profile. 
     
     
         9 . The ship according to  claim 1 , wherein the superstructure has a central portion and a trailing edge, wherein the trailing edge along the central portion of the superstructure is, along the longitudinal axis Z, behind a transom of each hull. 
     
     
         10 . The ship according to  claim 1 , wherein the two hulls are arranged symmetrically relative to a median plane XZ, the ship being a catamaran. 
     
     
         11 . The ship according to  claim 1 , comprising a central hull and two side hulls. 
     
     
         12 . The ship according to  claim 11 , wherein the central hull defines a rear hydrodynamic center of lift and the side hulls define front hydrodynamic centers of lift. 
     
     
         13 . The ship according to  claim 1  having a length between 10 and 50 meters.