Abstract:
A planing boat&#39;s primary hull has an adjunct hull surface rotatably connected thereto near its forward end. The adjunct hull surface extends along the hull of the planing boat to aft of amidships and is constructed of a rigid material that conforms to the shape of the hull of the planing boat. A position controller is coupled to the adjunct hull surface to selectively position the adjunct hull surface relative to the hull of the planing boat. When the adjunct hull surface is spaced apart from the hull of the planing boat, the position controller also absorbs shock loads experienced by the adjunct hull surface.

Description:
This is a continuation-in-part of copending application Ser. No. 08/701,365 filed on Aug. 21, 1996, now abandoned. 
    
    
     ORIGIN OF THE INVENTION 
     The invention described herein was made in the performance of official duties by employees of the Department of the Navy and may be manufactured, used, licensed by or for the Government for any governmental purpose without payment of any royalties thereon. 
     FIELD OF THE INVENTION 
     The invention relates generally to adaptive hulls for a boat operating at planing speeds. More specifically, the present invention relates to a system for reconfiguring the shape of a boat hull during operation to mitigate shock loads in rough water and improve performance during planing in smooth or rough water. 
     BACKGROUND OF THE INVENTION 
     The typical planing boat hull for use in rough water makes use of a deep vee shape that tends to cut into the waves instead of violently impacting the water&#39;s surface as is the case with a flatter hull bottom. This deep vee hull design reduces some of the shocks, but at high speed in rough seas the shocks can still cause injury to personnel and damage equipment. The typical deep vee hull also requires more propulsion power than a shallower vee hull of equal weight for a given speed. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a boat hull configuration that will reduce shock loads on the boat and its occupants when operating at planing speeds in rough water. 
     Another object of the present invention is to provide a boat hull configuration having the ability to plane at greater speed for a given hull weight or be able to carry more weight at the same speed. 
     Still another object of the present invention is to provide a movable means for controlling planing and shock impact of a boat hull moving through waves in various sea states. 
     Finally, it is another object of the present invention to provide a boat hull configuration that is user adjustable to reduce shock load to the hull and its cargo when operating at planing speeds in rough water. 
     Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings. 
     In accordance with the present invention, a planing boat&#39;s primary hull has an adjunct hull surface rotatably connected thereto near its stem, i.e., the forward-most end of the hull. The adjunct hull surface extends along the hull of the planing boat to aft of amidships. The adjunct hull surface is constructed of a rigid material that conforms to the shape of the hull of the planing boat. A position controller is coupled to the adjunct hull surface to selectively position the adjunct hull surface relative to the hull of the planing boat. When the adjunct hull surface is spaced apart from the hull of the planing boat, the position controller also absorbs shock loads experienced by the adjunct hull surface. The adjunct hull surface is positioned during operation for optimum load isolation and/or planing performance by the position controller. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the present invention will become apparent upon reference to the following description of the preferred embodiments and to the drawings, wherein corresponding reference characters indicate corresponding parts throughout the several views of the drawings and wherein: 
     FIG. 1A is a side view of a planing boat hull shown with the shock mitigating system of the present invention in its retracted position; 
     FIG. 1B is a side view of the planing boat hull shown with the shock mitigating system of the present invention in an extended position; 
     FIG. 2 is a cross-sectional view taken along line  2 - 2  of FIG. 1A; and 
     FIG. 3 is a schematic view of the position controller used to control both position and reactive movement of the adjunct hull surface in the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and with simultaneous reference to FIGS. 1A,  1 B and  2 , several views are shown of a planing boat  10  equipped with the shock mitigating system of the present invention. Planing boat  10  is representative of any high-speed planing boat having a hull  12  with the forwardmost portion of its bow known as the stem indicated at  14  and the stern indicated at  16 . While the present invention is based on the shape of hull  12 , it is to be understood that the particular choice of hull  12  is not a limitation on the present invention. 
     Pivotally attached to stem  14  planing boat  10  is a movable secondary or adjunct hull surface  20 . More specifically, the forward end  22  of adjunct hull surface  20  is hinged at point  24  to hull  12  to allow rotational movement of surface  20  towards and away from hull  12 . The movement and/or positioning of adjunct hull surface  20  will be explained further below. However, at this point in the description, it is sufficient to note that adjunct hull surface  20  can be fully retracted against and nested with hull  12  (FIG. 1A) or selectively positioned in a spaced-apart relationship with hull  12  (FIG.  1 B). 
     Adjunct hull surface  20  is typically made from rigid sheet material such as fiberglass, aluminum, steel or any other rigid material suitable for use in boat hull construction. All along its length, adjunct hull surface  20  is shaped on its top surface  20 A and bottom surface  20 B to conform to the shape of hull  12  as is apparent in the cross-sectional view shown in FIG.  2 . In terms of its length, adjunct hull surface  20  extends to a location on hull  12  that is aft of amidships of planing boat  10 . In the present invention, adjunct hull surface  20  must be more than half the length of hull  12 , but considerably less than the full length of hull  12 . This is because adjunct hull surface  20  must support approximately two-thirds of the hull&#39;s weight when planing, but not all of it because some weight must be present at the aft end of hull  12  to provide longitudinal stability in the vertical direction. Typically, the length of adjunct hull surface  20  is approximately two-thirds the length of planing boat  10 . The width of adjunct hull surface  20  is also not limited to a specific measurement. However, for many high-speed planing boats, the width of adjunct hull surface  20  is approximately two-thirds the chine width of hull  12 . Note that the width of surface  20  could be the full width of hull  12  for a heavily loaded hull while for a lightly loaded hull, the width of surface  20  may only need to be one-half or less the width of hull  12 . 
     To control both the position of adjunct hull surface  20  with respect to hull  12 , and control the shock mitigation afforded by the present invention, a position control and shock absorber system  30  is coupled to adjunct hull surface  20 . A preferred embodiment of position control and shock absorber system  30  is shown schematically in FIG.  3 . System  30  includes a cylinder  32  housing a piston  34  that is coupled (e.g., via piston rod  35 ) to adjunct hull surface  20 . Piston  34  defines a first chamber  32 A and a second chamber  32 B in cylinder  32 . A supply  36  of pressurized compressible fluid (e.g., hydraulic fluid, air, etc.) is selectively introduced into chambers  32 A and  32 B as controlled by a supply control  38  through respective valves  38 A and  38 B. Supply control  38  is representative of user controls or an adaptive control system. To positively maintain adjunct hull surface  20  in its retracted or nested position (for low speeds or trailer handling) with respect to hull  12  (FIG.  1 A), the pressure in chamber  32 A is kept less than the combination of the pressure in chamber  32 B and the water pressure impressed upon bottom surface  20 B of surface  20 . To position adjunct hull surface  20  away from hull  12  (FIG.  1 B), supply control  38  causes supply  38  to increase the pressure in chamber  32 A. More specifically, the pressure increase must overcome the pressure in chamber  32 B and any upward forces impinging on bottom surface  20 B of surface  20 . Once pressurized in this fashion, cylinder  32 , piston  34  and compressible fluids in chambers  32 A and  32 B cooperate to work as a spring. 
     In operation, as hull  12  is propelled by a motor (not shown) to the point of planing, a user operates supply control  38  to permit the introduction of pressurized compressible fluid from supply  36  into chamber  32 A of cylinder  32 . As chamber  32 A is pressurized to overcome both the pressure in chamber  32 B and the water pressure on adjunct hull surface  20 , piston  34  moves downward to rotate surface  20  (about hinge point  24 ) downward and away from hull  12  as shown in FIG.  1 B. In general, adjunct hull surface  20  is lowered for planing and raised to nest with hull  12  for slow speed operation or when hull  12  is placed on a trailer. Thus, the force provided by position control and shock absorber system  30  can be varied to adjust the position of surface  20  relative to hull  12  and to adjust reactive movement of surface  20  in response to various impact loads and sea states. 
     At planing speeds, chamber  32 A is pressurized such that piston  34  is moved downward to extend adjunct hull surface  20  to approximately half of its maximum range thereby forming a step in the hull shape. When the forward part of hull  12  becomes airborne, adjunct hull surface  20  extends to its maximum position due to the pressure in chamber  32 A and the elimination of water pressure on bottom surface  20 B. Then, when adjunct hull surface  20  descends and again makes contact with the water, surface  20  moves upward slowly as the pressure in chamber  32 A slows the descent of hull  12  towards the water. A bleed valve  33  can be provided in chamber  32 A to let excess pressure escape from chamber  32 A during water impact. In addition, whenever adjunct hull surface  20  is spaced from hull  12  while in the water, a stepped hull configuration is produced by the present invention. In this way, the main planing surface of planing boat  10  is forward and raised. 
     The advantages of the present invention are numerous. Adjunct hull surface  20  is more than a simple planing surface. First, it should be understood that it is a three-dimensional rigid body. Thus, when it is forcibly immersed in the slip-stream of water moving past hull  12 , it is producing a hull response beyond simple planing. In particular, the action of the immersed surface  20  combined with the positioning and shock damping effects provided by position control and shock absorber system  30  produces a hull response satisfying all the objectives recited herein, including improving hull efficiency and performance. Adjunct hull surface  20  and position control and shock absorber system  30  work together to increase the time for hull  12  to decelerate when impacting a wave. As surface  20  moves upwards from its extended or immersed position against the forces supplied by the pressurized compressible fluid in chamber  32 A, some of the impact energy is absorbed before hull  12  makes contact with the water. Tests have shown that time for hull impact is increased to approximately 100 milliseconds from approximately 50 milliseconds for a typical deep vee high-speed boat. In addition to mitigating hull impact shock, the movable surface  20  provides a step in a planing surface that, at higher speeds, i.e., above 20 knots, increases performance efficiency. The present invention will work with any hull shape propelled at planing speeds, i.e., when the hull is supported by dynamic lift rather than buoyancy. 
     Although the present invention has been described relative to a particular embodiment thereof, it is not so limited. For example, additional planing surfaces (not shown) can be mounted on the port and starboard sides of stern  16  equidistant from the longitudinal centerline of hull  12 . Each such stern-mounted planing surface can be hinge connected to hull  12  aft of adjunct hull surface  20 . Control of each stern planing surface can be accomplished by a similar system to position control and shock absorber system  30  described above. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described.