Landing craft with fixed and retractable azimuthing drives

Abstract

A marine vessel used for loading and offloading vehicles and cargo that has both excellent seakeeping and beaching properties. The vessel is provided with azimuthing or steerable thrusters below the waterline at the bow and stern of the ship, with the stern end thrusters being retractable into the hull during beaching operations. Because the vessel is beached “stern first” the bow may be designed with better wave breaking and seakeeping features than are on prior landing craft designs.

What is claimed is:  
     
         1 . A marine craft which is capable of seaward movement and beaching operations, for carrying and landing cargo comprising: 
 a) a boat hull having a waterline, a generally v-shaped bow portion for good seakeeping and wavebreaking capabilities and a stern portion adapted for beaching operations;    b) a first ramp mounted on said bow portion above the waterline for loading and unloading cargo from a dock or other fixed structure;    c) a second ramp mounted on said stern portion for unloading and loading cargo during beaching operations;    d) a least one azimuthing drive mounted below the waterline on the bow portion of the hull; and    e) at least one azimuthing drive mounted below the waterline on the stern portion of the hull, 
 whereby the craft is able to load cargo in the proper orientation for unloading during beaching operations, traverse open seas bow forward with excellent stability and speed, approach a designated beaching area, orient the craft from a bow forward position to a stern forward position by way of the azimuthing drives, beach the stern of the craft and unload the cargo while minimizing the effects of high surf near the beach, and sailing off of the beach with the bow pointed toward open water.  
   
     
     
         2 . The landing craft of  claim 1 , wherein the bow portion contains a deep forefront.  
     
     
         3 . The landing craft of  claim 1  further comprising a keel and means for retracting the stern azimuthing drives above the keel and into the hull, whereby said azimuthing drives are protected during beaching operations.  
     
     
         4 . The landing craft of  claim 1 , further comprising a pair of clamshell doors mounted on said bow, proximal to the bow ramp, whereby the seakeeping abilities of the landing craft are improved and the bow ramp is protected from wave damage.  
     
     
         5 . The landing craft of  claim 1 , wherein the bow below the waterline is fitted with a bulb to reduce calm water resistance.  
     
     
         6 . A marine landing craft comprising; 
 a) a boat hull having a keel, a waterline, a bow and a stern;    b) said bow having a deep forefront adapted for wavebreaking and seakeeping operations;    c) a ramp for loading and unloading cargo on said stem;    d) at least one propulsion drive mounted below the water line at the bow of the hull, said at least one bow propulsion drive being adapted for full rotational movement about a horizontal plane; and    e) at least one propulsion drive mounted below the waterline at the stem of the hull, said at least one stem propulsion drive being adapted for full rotational movement about a horizontal plane and for retraction into the hull above the keel, 
 whereby the landing craft is capable of movement in multiple directions and beaching stem first and extracting from the beach bow first  
   
     
     
         7 . The landing craft of  claim 6 , wherein the means for loading and unloading the cargo from both the bow and the stem are retractable ramps.  
     
     
         8 . The landing craft of  claim 6 , wherein the at least one propulsion drive mounted below the waterline at the stem of the hull further comprises a fixed pitch propeller mounted within a nozzle.  
     
     
         9 . The landing craft of  claim 6 , wherein the at least one propulsion drive mounted below the waterline at the stern of the hull provides 60% of thrust power and the at least one propulsion drive mounted below the waterline at the bow of the hull provides 40% of thrust power.  
     
     
         10 . The landing craft of  claim 6  further comprising an operating draft and an adjustable ballast whereby the waterline of the hull may be adjusted above or below the operating draft.  
     
     
         11 . A method of delivering cargo on a beach or other unimproved land-water interface, the method comprising; 
 providing a marine vessel having a hull, a waterline, a bow end, and a stern end, the marine vessel including steerable propulsion mechanisms mounted below the waterline at the bow and stern ends of the hull respectively, a ramp on the bow end of the vessel and a ramp on the stern end of the vessel;    loading the cargo onto said marine vessel by way of either the bow ramp or the stern ramp;    operating the steerable propulsion mechanisms to orient the marine vessel to a position in which the stern end of the vessel faces the beach;    beaching said vessel upon said beach; and    unloading the cargo onto the beach by way of the stern ramp.    
     
     
         12 . The method of  claim 11 , further including the step of retracting the at least one steerable propulsion mechanism located on the stern end of the vessel into the vessel prior to beaching said vessel.