Abstract:
An improved planing watercraft hull having reduced surface area in contact with the water resulting in a minimization of drag said hull capable of being adapted for use with a small, easily transportable waterjet propelled watercraft.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates in general to an improved planing watercraft hull and more particularly to a hull adapted for use with a small, easily transportable waterjet propelled watercraft. 
     Personal watercraft currently enjoy widespread popularity due to their ease of use and affordability. These watercraft typically employ an internal combustion engine coupled with a waterjet propulsion system oriented below the level of a seat for accommodating a rider as generally described in U.S. Pat. No. 5,584,733 to Kobayashi, incorporated herein by reference. Other personal watercraft are intended for use by a standing or kneeling rider. All of these watercraft are heavy in weight and require a trailer or other means for transporting the watercraft to the water, where the trailer and watercraft descend a boat ramp to enable the watercraft to access the water. In addition, the large size and heavy weight of these watercraft necessitate large amounts of horsepower to enable the watercraft to achieve the speed required to attain an optimum planing orientation and performance. 
     Planing-type hulls are well-known and commonly incorporated in the design of watercraft. The primary advantage provided by a planing-type hull over hulls of other design, such as displacement-type hulls found in canoes and kayaks and the like, is that a planing-type hull rises out of the water vertically as the horizontal speed of the watercraft increases, reducing the volume of the hull that is submerged thereby reducing drag and permitting higher speeds. The primary drawback of planing-type hulls, particularly with respect to many of the narrower hulls of the type found in contemporary personal watercraft, is the lack of stability when travelling in a straight line. This problem is exacerbated in rough waters. When such planing-type hulls are powered by means of water-jet propulsion, the tendency of the transom to rise with increasing speed combined with rough waters inevitably results in a loss of power and control as the jet pump intake loses contact with the water. 
     Watercraft of the prior art have sought by various methods and designs to solve the control problem inherent in jet-powered watercraft having planing-type hulls. U.S. Pat. No. 4,004,542 to Holmes, incorporated herein by reference, is directed to a boat for use with a waterjet propulsion unit incorporating a planing hull having a generally V-shaped bottom with a depending flat-bottomed support pod and stabilizing strakes. U.S. Pat. No. 3,911,846 to England, incorporated herein by reference, is directed to a shallow draft boat hull for use with a waterjet propulsion unit, said hull comprising an elongate step extending longitudinally of the bottom along the keel forwardly from the transom. These prior art arrangements sought to improve straight ahead stability but at the cost of speed due to the increased resistance with the water surface of the structures depending from the hull. 
     In addition, waterjet powered personal watercraft currently almost uniformly employ a two-stroke engine because of the high horsepower output provided by the two-stroke engine. However, two-stroke engines contribute high levels of pollution to waterways, especially when used in tandem with an exhaust system which injects exhaust directly into the water. The use of a four stroke engine minimizes water pollution compared to two-stroke engines used in the majority of watercraft. In conventional watercraft employing a two-stroke marine engine, between 25 and 35 percent of all of the gasoline in the tank is discharged through the tailpipe unburned and directly into the waterway because water is drawn into the engine for cooling and then mixed with exhaust and expelled. The design of the two-stroke engine allows unburned fuel to enter the cylinder at the same time the burned residue from the previous stroke is expelled from the engine. In addition, in a two-stroke engine lubricating motor oil mixes with gasoline, and as a result the expelled unburned gasoline contains heavier, non-evaporating motor oils. A four-stroke engine, on the other hand, has a dedicated combustion and exhaust stroke, substantially eliminating the problem of escaping unburned fuel. The use in the present invention of a four-stroke engine in combination with an exhaust system which expels exhaust into the air therefore represents an improvement over personal watercraft of the prior art. 
     Accordingly, it is a principal object of the present invention to provide an improved hull for a watercraft having stability while stationary and at low speed as well as stability and minimal water resistance when travelling at high speed straight ahead. 
     It is yet another object of the present invention to provide an improved hull which reduces the structural stress concentration within the hull and provides an efficient means for removal of water that otherwise would create secondary drag. 
     It is another object of the present invention to provide an improved hull for a watercraft which facilitates boarding of the watercraft from the water; particularly deep water. 
     It is another object of the present invention to provide a lightweight waterjet powered watercraft having an improved hull. 
     It is still another object of the present invention to provide a waterjet powered water craft with a removable power source so that the watercraft may be carried by a single person and transported without the need of a trailer. 
     It is yet another object of the present invention to provide an improved hull which minimizes weight bias balance problems. 
     It is still another object of the present invention to provide an improved exhaust system for a watercraft comprising the improved hull. 
     It is still another object of the present invention to provide an improved waterjet pump system for a watercraft comprising the improved hull. 
     It is a still further object of the present invention to provide an environmentally friendly power supply for a watercraft comprising the improved hull. 
     These and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended Claims. 
     SUMMARY OF THE INVENTION 
     A novel planing boat hull has been developed which has an upper deck portion and a lower hull portion, a fore and an aft portion, a bow, a stern and a cockpit. The hull is configured having a bow tapering outwardly and increasing in width gradually to a point proximal to the rear of the cockpit at which point the width of the hull narrows and tapers inwardly. The inward taper of the hull flattens sternward so that opposing longitudinal sides of the aft portion of the hull are substantially parallel for a length, taper slightly and meet forming the stern. The lower hull portion comprises, in front elevational cross-section, a shallow V-shaped bottom face which extends substantially from the bow to the stern. The bottom face of the lower hull portion gradually curves upwardly toward the bow and further comprises a substantially T-shaped planing surface. The upper deck portion of the hull comprises a more gradual taper as the transition is made sternward from the fore portion of the hull to the aft portion than in the lower hull portion. The hull of the present invention provides optimum stability in the straight ahead direction while minimizing water resistance, thus enabling relatively high speeds with a minimum of horsepower. The hull further provides optimum stability when stationary in the water and when travelling at low speeds. The addition in a preferred embodiment of strakes to the fore portion of the hull provides increased stability with a minimum of drag at high speeds. The hull configuration also allows a rider to easily access the cockpit of the hull from the water because the narrower aft portion provides access to the cockpit closer to the center line of the hull than is possible in a hull having a traditional beam. 
     An opening is formed in the upper deck of the hull for receiving a power source into a compartment formed between the upper deck and lower hull. At least one watertight hatch covers said opening, said hatch further comprising at least one air intake port. The cockpit further comprises at least one seat for accommodating at least one rider. The hull further comprises at least one air exhaust port formed in the upper deck of the aft portion. In one embodiment the air exhaust port further comprises a cover which is movable between an open and closed position to prevent the entry of water into the engine compartment if the hull is capsized. In another embodiment the exhaust port is formed in said hatch. In another embodiment the hull further comprises a plurality of openings formed therein covered by watertight hatches for storage of valuables, safety gear and the like. In a preferred embodiment the invention further comprises a waterjet propulsion unit contained in said hull connected to the power source, steering means and a throttle means. The water jet propulsion unit further comprises a water intake duct, a pump assembly comprising a pump, a pump shaft and a shaft coupling device and a stern steering nozzle. In one embodiment the power source comprises a fuel source such as but not limited to a fuel tank or battery and an engine, an exhaust manifold, a drive shaft with or without a torque converter and a connector means for connecting the fuel source to the motor or engine. In the preferred embodiments, the engine is cooled by an air cooling system comprising an air intake duct coupled with an air intake port formed in the engine compartment hatch. Air is introduced to the engine compartment and circulated therein and expelled through a plurality of air exhaust ports. In yet another embodiment the fuel source is a battery and solar panels are disposed on or above the upper deck portion of the hull and the battery is connected to the solar panels to collect and store energy. In still another embodiment the power source is removably mountable in the engine compartment through said hatch. The waterjet propulsion unit may also be removably mounted to the hull. At least one handle means may be formed in the hull to facilitate transport of the hull. In still another preferred embodiment, the hull comprises two discrete, connectible units, the waterjet propulsion unit and at least one element of the power source being contained within the aft portion. 
     In a preferred embodiment the pump assembly comprises a specialized pump designed to operate at the limits of the power source. In another embodiment, the weight of the propulsion unit and power source is distributed to facilitate easy righting. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of the hull according to this invention. 
     FIG. 2 is a side elevational view of the hull of FIG.  1 . 
     FIG. 3 is a rear elevational view of the hull of FIG.  1 . 
     FIG. 4 is a front elevational view of the hull of FIG.  1 . 
     FIG. 5 is a bottom plan view of the hull of FIG.  1 . 
     FIG. 5 a  is a bottom plan view of a preferred embodiment of the hull of FIG.  1 . 
     FIG. 6 is a top plan view of a watercraft according to a preferred embodiment of the invention. 
     FIG. 7 is a side elevational view of the watercraft of FIG.  6 . 
     FIG. 8 is a top plan view of a preferred embodiment of the invention. 
     FIG. 8 a  is a side elevational view of the preferred embodiment of FIG.  8 . 
     FIG. 9 is a top sectional view of one embodiment of the pump according to a preferred embodiment of the present invention. 
     FIG. 10 is a side sectional view of one embodiment of the pump according to FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1,  2  and  4  the invention comprises a planing hull  2  having essentially an upper deck portion  4  and a lower hull portion  6 , said upper deck and lower hull portions  4  and  6  secured together by any suitable means. Hull  2  may comprise a unitary construction wherein said upper deck portion  4  and lower hull portion  6  are formed together in one piece. The hull  2  may be formed of any suitable material including but not limited to molded plastic, fiberglass, reinforced fiberglass, epoxy resin, polycarbonate, and the like. In a preferred embodiment the hull  2  is a monocoque or one piece hull formed of a high density polyethylene resin such as but not limited to superlinear polyethylene by an environmentally friendly rotomolding process. 
     The hull  2  further comprises a fore portion  8 , an aft portion  10 , a stern  12  and a cockpit  14 . As best seen in FIG. 1, the fore portion  8  of the hull  2  comprises opposing longitudinal sides  18  and  20  meeting at a bow  22 , said bow  22  tapering outwardly, increasing in width gradually to a point  24  proximal to the rear of the cockpit  14 , at which point  24  the width of the hull  2  narrows and tapers inwardly. Fore portion  8  may comprise a bulkhead aft of cockpit  14  forming a closure of the fore portion  8  of the hull  2 . The point  24  at which the hull  2  begins to narrow substantially defines the start of the transition  23  between the end of the fore portion  8  and the beginning of the aft portion  10 . The inward taper of the hull  2  flattens sternward so that the opposing longitudinal sides  18  and  20  of the aft portion  10  of the hull  2  are substantially parallel for a length and meet forming the stern  12 . The maximum width of the aft portion  10  of the hull  2  is in the range of approximately ⅕ to approximately ⅘ of the width of the fore portion  8 . In a preferred embodiment the width of the aft portion  10  is approximately ½ the width of the fore portion  8  at the widest portion on the fore portion  8 . 
     Now referring to FIGS. 3 and 4, the lower hull portion  6  comprises in cross section a shallow V-shaped bottom face  26 , a centerline  32  forming the bottom of said V, said shallow V-shape extending substantially from the bow  22  to the stern  12 . The bottom face  26  of the lower hull portion  6  extends outwardly from either side of the centerline  32  forming a V-shaped bottom face  26 . Referring next to FIG. 2, the bottom face  26  of the lower hull portion  6  of the fore portion  8  gradually curves upwardly toward the bow  22 . Now referring to FIGS. 3,  4  and  5 , the bottom face  26  of the lower hull portion  6  further comprises a substantially T-shaped planing surface  15  comprising the bottom face of narrow aft portion  10  joined to the bottom face of wider fore portion  8  of the hull  2  and edges  25 ,  27 ,  28  and  29 . The upper deck portion  4  of the hull  2  comprises a more gradual taper as the transition  23  is made sternward from the fore portion  8  of the hull  2  to the aft portion  10  than in the lower hull portion  6 . This construction reduces the stress concentration of the transition  23  and provides an efficient means for water management, i.e., removal of water that otherwise would create secondary drag. 
     In a preferred embodiment the hull  2  is approximately twelve feet in length and approximately three feet in diameter at the widest portion of the fore portion  8 . The width of the aft portion  10  in the preferred embodiment is in the range of approximately seventeen to twenty four inches. 
     Now referring to FIG. 5 a , in another preferred embodiment the fore portion  8  of the hull  2  is equipped with at least one pair of strakes  35  along either side of the center line  32 . 
     It has been discovered that the hull configuration of the present invention provides surprisingly good stability in the straight ahead direction while minimizing the amount of water resistance encountered, providing an efficient means for travelling at relatively high speeds with a minimum of horsepower. As speed increases, the fore portion  8  of the hull  2  rises above the surface of the water, leaving substantially only the bottom face of the aft portion  10  and a minimal surface area of the fore portion  8  in contact with the water. The reduced surface area in contact with the water results in a minimization of drag and therefore an optimization of horsepower. The addition of strakes in the preferred embodiment add lateral stability without sacrificing efficiency at high speeds because the strakes are above the water line at elevated speeds. 
     The hull configuration also allows a rider to easily access the cockpit  14  of the hull  2  from the water because the narrower aft portion  10  provides access to the cockpit  14  closer to the center line  32  of the hull  2  than would be possible in a hull having a wider beam. Thus, the hull  2  is less apt to tip toward the boarding rider. 
     Tests were conducted using the hull  2  of the present invention to evaluate the efficiencies of the hull configuration. Tables 1 lists the results: 
     
       
         
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                   
                 Estimated 
                 Shaft 
               
               
                   
                 Speed 
                 Trim 
                 Draft 
                 Drag 
                 HP 
                 HP 
               
               
                 Run 
                 (mph) 
                 (deg) 
                 (ft) 
                 (lb) 
                 (EHP) 
                 (SHP) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Configuration B3: 2 passengers, driver aft, with strakes 
               
             
          
           
               
                 134 
                 0.00 
                 −1.88 
                 0.488 
                 0.00 
                 0.00 
                 0.00 
               
               
                 135 
                 15.05 
                 3.90 
                 0.190 
                 73.79 
                 2.96 
                 4.47 
               
               
                 136 
                 24.98 
                 1.93 
                 0.083 
                 79.88 
                 5.32 
                 8.04 
               
             
          
           
               
                 Configuration B1, driver only, aft, with strakes 
               
             
          
           
               
                 137 
                 0.00 
                 −0.63 
                 0.393 
                 0.00 
                 0.00 
                 0.00 
               
               
                 138 
                 15.04 
                 3.67 
                 0.078 
                 50.35 
                 2.02 
                 3.05 
               
               
                 139 
                 24.95 
                 2.79 
                 0.028 
                 62.27 
                 4.14 
                 6.26 
               
             
          
           
               
                 Configuration C3, 2 passengers, driver aft, no strakes 
               
             
          
           
               
                 140 
                 0.00 
                 −1.95 
                 0.475 
                 0.00 
                 0.00 
                 0.00 
               
               
                 141 
                 15.04 
                 3.55 
                 0.200 
                 68.94 
                 2.77 
                 4.18 
               
               
                 142 
                 24.95 
                 1.91 
                 0.088 
                 79.63 
                 5.31 
                 8.01 
               
             
          
           
               
                 Configuration C1, driver only, aft, no strakes 
               
             
          
           
               
                 143 
                 0.00 
                 −0.71 
                 0.387 
                 0.00 
                 0.00 
                 0.00 
               
               
                 144 
                 15.09 
                 3.49 
                 0.087 
                 48.12 
                 1.94 
                 2.93 
               
               
                 145 
                 25.08 
                 2.78 
                 0.035 
                 60.79 
                 4.07 
                 6.14 
               
               
                   
               
             
          
         
       
     
     Now referring to FIGS. 6 and 7, in another preferred embodiment a watercraft constructed in accordance with the hull  2  of the present invention comprises hull  2 , a cockpit  14  formed in the upper deck  4  of hull  2 , an opening  40  formed in the upper deck  4  of the aft portion  10  for receiving a power source such as but not limited to an engine and a fuel tank into a compartment  42  formed between the upper deck  4  and lower hull  6  and at least one watertight hatch  44  for covering said opening  42 . Said hatch further comprises an air intake port  46 . The cockpit  14  further comprises at least one seat (not shown) for accommodating at least one rider  80 . The hull  2  further comprises at least one air exhaust port  48  formed in the upper deck  4  of the aft portion  10 . In one embodiment the air exhaust port  48  further comprises a cover  49  which is movable between an open and closed position to prevent the entry of water into the compartment  42  if the hull  2  is capsized. In another embodiment the exhaust port  48  comprises an opening in the hatch  44 . The hull  2  may further comprise a plurality of openings formed therein covered by watertight hatches for storage of valuables, safety gear and the like. The hull may further comprise a bulkhead  41  forming a barrier between the cockpit  14  and compartment  42 . Bulkhead  41  is preferably fireproof. 
     The watercraft according to the preferred embodiment of FIGS. 6 and 7 further comprises a waterjet propulsion unit  50 , a power source  70 , steering means (not shown) and a throttle means (not shown). 
     As best seen in FIG. 7, water jet propulsion unit  50  further comprises a water intake duct  52 , a pump assembly comprising a pump  54 , a pump shaft  56  and a shaft coupling device  58 , and a stern steering nozzle  59  of known design such as that described in U.S. Pat. No. 4,047,494, incorporated herein by reference. 
     As best seen in FIGS. 6 and 7, power source  70  further comprises a fuel source  72 , such as but not limited to a fuel tank or battery, an engine  74  such as but not limited to a Honda four stroke engine or a combustion engine of any number of cycles or an electric-motor, an ignition means (not shown), an exhaust manifold  76 , a drive shaft  78  with or without a torque converter, and a connector means  79  for connecting the fuel source to the motor or engine, such as a fuel line where the engine is a combustion engine or an electrical cable wherein the motor is electric. The engine  74  may be water-cooled; however, in the preferred embodiments, the engine  74  is cooled by an air cooling system comprising air intake duct  47  coupled with air intake port  46  formed in the hatch  44 . Air is introduced to the engine  74  for cooling and expelled through at least one air exhaust port  48  to facilitate air exchange. In this preferred embodiment the exhaust manifold  76  communicates with at least one of air exhaust ports  48  so that exhaust is expelled into the air rather than into the water as is customary with most watercraft. In this manner the environmental impact on aquatic and marine systems is minimized. 
     The combination of the design of hull  2  and the weight and location of the propulsion unit  50  and power source  70  results in a highly balanced watercraft which resists tipping and if the watercraft of the present invention rolls, the watercraft is easily righted. 
     In yet another embodiment the fuel source is a battery (not shown) located in the compartment  42  and solar panels (not shown) are disposed on or above the upper deck portion  4  of the hull  2  of the watercraft and the battery is connected to the solar panels to collect and store energy. 
     A cable  57  connects steering nozzle  59  to a steering means (not shown) such as but not limited to a wheel or stick to enable an operator to steer the watercraft. 
     Throttle means (not shown) may comprise any throttle means commonly found in pleasure craft such as but not limited to a throttle cable connecting the power source  70  to a stick, handlebar throttle or pedal means. 
     A flexibility closure such as a spray skirt for keeping the cockpit  14  watertight is not shown. At least one handle means (not shown) may be formed in the hull  2  to facilitate transport of the hull  2 . Furthermore, it is contemplated that cockpit  14  may be modified to accommodate more than one person. The driver  80  of the watercraft of the preferred embodiment may be seated fore or aft in the cockpit, either behind or in front of a passenger. 
     Now referring to FIGS. 6 and 7, power source  70  turns drive shaft  78  through coupling  58  which in turn transfers rotational power to the waterjet propulsion unit  50  via the pump shaft  56 . The coupling  58  can be direct drive or can incorporate a torque converter. The pump assembly receives water via water intake duct  52  and accelerates the water and communicates it through pump  54 . Water is ejected to the stern steering nozzle  59 . 
     In another embodiment the power source  70  and/or the waterjet propulsion unit  50  are removably mountable in the compartment  42 . Access to said removably mounted power source  70  and/or waterjet propulsion unit is through hatch  44 . Power source mounting means (not shown) may be of any type such as but not limited to clamping means whereby the power source and/or fuel source are clamped to load dispersing rails, slidable engagement means such as tongue and groove-type assemblies, mounting means disclosed in U.S. patent application Ser. No. 08/861,845, incorporated herein by reference, and the like. Waterjet propulsion unit  50  comprising pump  54 , a pump shaft  56  and shaft coupling device  58  may be removably mounted to the hull  2  by similar means to sealingly engage said water intake duct  52 . Coupling  58  may be disengaged to disconnect power source  70  from waterjet propulsion unit  50 . 
     Now turning to FIGS. 8 and 8 a , in still another preferred embodiment, hull  2  comprises two discrete, connectible units substantially comprising the fore portion  8  and the aft portion  10  to facilitate transport of the watercraft out of the water. In a most preferred embodiment, the waterjet propulsion unit  50  and engine  74  are contained within the aft portion  10 . The fore portion  8  contains fuel source  72 . Alternatively, the entire power source may be contained in either the fore portion  8  or the aft portion  10 . The fore portion  8  and aft portion  10  further comprise complementary connectible mating means of known design for connecting said fore and aft portions  8  and  10 . In the most preferred embodiment the mating means comprises at least one male register  90  and at least one female register  92 . Male register  90  is received in female register  92  to ensure secure alignment of said fore and aft portions  8  and  10  and at least one over-center clamp  94  or other suitable clamping means secures said fore and aft portions  8  and  10 . A handle means (not shown) for facilitating carrying of the discrete fore and aft portions  8  and  10  of the hull  2  are formed in each of the respective portions  8  and  10 . 
     In a preferred embodiment the pump assembly comprises a specialized pump designed to operate at the limits of the power source. In a most preferred embodiment the power source  70  is a Honda air-cooled four-stroke overhead cam single cylinder engine such as the GC 160 (horizontal shaft) engine comprising a displacement of 160 cc and a compression ratio of 8.5:1, having a maximum power output of 5.0 horsepower/3,600 rpm and 7.6 ft.-lbs of torque and is coupled with said specialized pump. Now referring to FIGS. 9 and 10, the pump  54  employs an axial flow pump system comprising a plurality of rotor vanes  51 , a venturi/stator vane  53 , and at least one rotor  55  having a diameter in the range of about 3 inches and about 5 inches and preferably approximately 3.91 inches and a jet diameter in the range of about 1.5 inches and about 3.5 inches and preferably approximately 2.43 inches. Pump  54  further comprises a hub cone  60 , a plurality of seals  61 , venturi/stator  62 , a plurality of bearings  63  and housing  64 . This most preferred embodiment resulted in a flow of 749 gallons per minute, 49.3 pounds of thrust, a jet velocity of 52.0 feet/second and a pump efficiency 80 percent. In this embodiment the water inlet  52  comprises a scoop formed in the bottom of hull  2 . 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.