Abstract:
There is provided a hybrid boat hull having a forward center vee-section extending from the bow and becoming shallower as the vee-shaped bow transitions aft to ensure the boat will not slam or pound in a seaway and additional lift generated by buffered air under the hull. The hull of the boat incorporates a centerline vee-hull which becomes shallower as it transitions aft to further enhance trapping air under the vessel to provide lift. The hull also includes a pair of spaced apart outboard sponsons extending from and below said central hull, beginning from above the center line of the vee-hull at the forward end to below the centerline vee-bow portion of the hull at the aft end. The outboard sponsons are connected to each other in such a manner as to provide a means to trap air, water, or a mixture of air and water between said sponsons.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The contents of Provisional Application U.S. Ser. No. 61/997,046 filed May 21, 2014, on which the present application is based and benefits claimed under 35 U.S. C. §119(e), is incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    (1) Field of Invention 
         [0003]    This invention relates to vee-hull planning, semi-planning, and displacement boats incorporating a vee-hull bow shape with aft sponsons, sponsons, or external appendages. 
         [0004]    (2) Description of Prior Art 
         [0005]    Conventional vee-hull boats and ships are designed to cut through waves without pounding or slamming but sacrifice speed and transverse stability. The design of the forward vee-section of a boat hull determines the smoothness of the ride. In practice vee-hull boats and ships tend to be long and narrow and as a result they heel significantly from side to side. The Damen Sea Axe hull utilizes this concept where the vee hull is narrow and has little to no flair. The Damen hull sacrifices reserve buoyancy in the bow as a result. The Damen hull is inherently unstable in a following sea and requires active control fins to keep from broaching. Broaching typically happens when a vessel is riding along with a wave or racing down one. 
         [0006]    Another vee-hull design is Austal&#39;s stabilized monohull used in Littoral Combat Ships (LCS-2). This hull has a long needle like bow that also provides little reserve stability and is shown to bury itself in large following seas. The LCS-2 hull also requires several sets of active control fins to remain stable in high seas. The LCS-2 hull also has amahs or outriggers to improve stability but the amahs contribute little to the vessel&#39;s overall displacement. 
         [0007]    Another factor affecting hull design is weight distribution and interior accommodation, which are challenges in any vessel. The center of gravity of the boat must be located directly over the center of buoyancy of the hull at its designed waterline. If the two centers are not located in the same plane the boat will trim and list until the centers are properly located. If there is more weight to one side then the boat will list to that side. If there is more weight aft the boat will trim aft, i.e., sit lower in the water by the stern. 
         [0008]    To achieve balance, conventional hulls have engines placed forward from the stern of the vessel. This encroaches on interior space and compromises the comfort of the vessel due to noise and heat from the engine. Also, lines must be run to the engine for cooling, intake air, and exhaust. Exhaust lines become quite hot requiring bulky insulation. An insulated housing is typically fashioned around the engine itself to deaden engine noise and contain heat. The insulated housing significantly reduces the available space for personal accommodation. This type of engine mounting also requires a propeller shaft to run from the engine normally under the boat or inside the hull to a stern drive propeller. If the shaft is under the boat, it is subject to damage should the boat run aground or hit debris in the water. Of course, any shaft configuration below the hull produces significant drag lowering the speed of the vessel and increasing operating cost. Both shaft configurations require bearing supports along the shaft length to ensure the shaft turns freely and does not vibrate. 
         [0009]    Traditional semi-displacement hulls and modern interpretations thereof produce hulls that have little reserve buoyancy in the bow and are transversely unstable with a tendency to broach in high seas, especially following seas requiring active control fins to be stable. These vessels also require engine placement forward of the transom to achieve static balance in the hull necessitating long shafts to the propellers. The engine placement encroaches on valuable living or shop space in areas of the vessel. An alternate to traditional propellers is a jet drive. Jet drives are directly attached to the vessel&#39;s transom. The engines are still forward of the jet drives requiring long shafts as in the LCS-2 vessel to maintain proper vessel trim. 
       SUMMARY OF THE INVENTION 
       [0010]    Broadly speaking, this invention provides a hybrid boat hull designed wherein the planning, semi-planning, or displacement of a hull having a conventional vee-hull forward transitions into outboard sponsons. The sponsons originate in the bow, forward, at, or aft of the forward perpendicular, in a vee shape and transition as they go aft. The sponsons also become wider as they transition aft. In application, the sponsons generally perform best when the aft sections have a constant width. When planning or semi-planning the proposed hull rides on the sponsons providing lift to the hull. The vee forward remains in the water but is also lifted thereby reducing wetted surface and drag, while cutting through waves enhancing the vessel ride. Air is trapped between the two sponsons and the water creates an area of buffered air adding lifting forces on the hull and further reducing drag at semi-planning speeds. This lifting force on the hull is augmented by water, which impacts the curved/cupped after sections of the vee-bottom of the hull and is deflected down. A ram air effect is also induced by the changing width of the outboard sponsons as they transition aft. The distance between the sponsons is greater in the bow creating a funnel for air. A large volume of air is trapped under the boat or ship enhancing the ride of the vessel. The buffered layer of accelerated air acts to increase the lift on the boat reducing the hull drag in the water. 
         [0011]    The boat hull has a forward center vee-section to ensure the boat will not slam or pound in a seaway and additional lift generated by buffered air under the hull ensures a measurably smoother and faster ride. In the preferred embodiment of the proposed hybrid boat or ship the hull incorporates a centerline vee-hull which becomes shallower as it transitions aft to further enhance trapping air under the vessel to provide lift. 
         [0012]    The hull design provides outboard sponsons with sufficient width and depth for the engines and drive systems to be mounted inside the sponsons. Interior accommodation need not be encroached upon with the proposed design. The proposed design is ideal for placing water jets in the outboard sponsons since water jets require a flat surface for water intake and can be directly coupled to propulsion engines. Long propeller shafts are not required inside the hull or underwater. Since the vessel has no underwater propeller shafts there is no water drag on the shafting or supporting appendages. This enhances the efficiency of the proposed hull and consolidates the engine compartment to the extreme aft section of the vessel enhancing space utilization. 
         [0013]    The buoyant sponsons allow the engines to be placed next to jet drives, or other propulsion devices. The vessel&#39;s buoyancy is matched to the designed weight distribution by adjusting the width and depth of the sponsons. This allows the propulsion machinery to be in one consolidated location. Jet drives enhance the dynamic positioning of a vessel making this configuration ideal for work vessels that have to carefully maintain station. 
         [0014]    The hull is optimized for speed and comfort by changing the centerline vee and the outboard sponsons. The centerline vee section of the hull acts as a shock absorber deflecting waves. The wider the centerline vee section the more buoyancy that is provided, resulting in a stiffer, bumpier ride. Maximizing the depth of the centerline vee reduces speed but makes the ride smoother. A step can be added to the centerline vee to introduce turbulent flow in the water behind the step enhancing the water and air mixture trapped between the two outboard sponsons thereby reducing drag on the hull. 
         [0015]    The outboard sponsons can be made deeper providing a more cushioned but slower ride. Alternatively, the sponsons can be made shallower and wider providing more lift for a faster ride. The width of the outboard sponsons is also critical in producing a wake at speed. The wake produced by the outboard sponsons and the centerline vee can be optimized to cancel each other at speed ranges just as a bulbous bow does on a ship. It is possible to reduce the wake of the hull configuration by adjusting the after sections of the centerline vee along with the width and depth of the outboard sponsons. The wake produced by the outboard sponsons can adjusted to be canceled by the centerline vee or by each other. The result is to produce a faster more efficient hull over a given range of speeds. 
         [0016]    Additional advantages include variable fuel and water tanks that can be fitted below the deck centered over the vessel&#39;s design center of buoyancy. Tanks placed in this location do not affect the trim of the vessel regardless of how full or empty the tanks are. The added advantage is that nominal interior space is compromised to achieve this placement and safety is further enhanced over conventional vessels. A balance must be made between required buoyancy, outboard sponson draft, and outboard sponson width. Adjusting these variables allows for fuel and water tanks to be optimized around the vessel&#39;s center of buoyancy. 
         [0017]    At low speeds the hull of this invention has increased drag over conventional boats and ships but the hull also has much greater transverse stability and the hull&#39;s natural frequency can be adjusted to significantly reduce motions. This makes the hull a breakthrough hull design for offshore work boats where station keeping is critical. At higher speeds the increased transverse stability keeps the boat from healing and the buoyant vee bow ensures the vessel does not broach in following seas. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Having described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
           [0019]      FIG. 1A  illustrates the outboard sponsons transiting below the centerline vee-section of a hull according to the present invention; 
           [0020]      FIG. 1B  illustrates the body plan and transom of  FIG. 1A  according to this invention shown from behind a boat; 
           [0021]      FIG. 2  is a side view showing the vee bow and aft sponson of a hull of the present invention; 
           [0022]      FIG. 3  is the wake of a 200-ft patrol boat @ 35 knots speed; 
           [0023]      FIG. 4  is plain view of hull bottom designed according to this invention; 
           [0024]      FIG. 5  illustrates the opening between the outboard sponsons; 
           [0025]      FIG. 6A  shows the underwater volume distribution 
           [0026]      FIG. 7  is an isometric bow profile showing that the sponsons start forward FP; 
           [0027]      FIG. 8  is an isometric stern profile; 
           [0028]      FIG. 9  show the isometric bow profile sponson starting aft of FP; 
           [0029]      FIG. 10  is a profile of a patrol boat having a hull design according to the present invention with water jet propulsion; 
           [0030]      FIG. 11  is an aft view, similar to  FIG. 1B , of a patrol boat having sponsons according to the present invention and showing primary engine placement inside the sponsons; and 
           [0031]      FIG. 12  is a plan view of a patrol boat having sponsons according to the present invention showing primary engine placement. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0032]    The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather these embodiments are provided so that this disclosure will be through and complete and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to the elements throughout. 
         [0033]    The hybrid boat hull of this invention has a forward center vee-section of the hull to ensure the boat will not slam or pound in a seaway and additional lift generated by buffered air under the hull ensures a measurably smoother and faster ride. Existing vee-hulls have a higher wetted surface, while semi-planning, creating more drag and providing less lift at speed. Conventional vee-hulls are also notably less transversely stable. The hull of the boat or ship incorporates a centerline vee-hull which becomes shallower as it transitions aft to further enhance trapping air under the vessel to provide lift as shown in  FIG. 2  by the vee bow  1 . The lift generated improves vessel ride and stability as well as reducing drag. This configuration has extremely high form stability and is very transversely stable negating the requirement for active control fins. 
         [0034]    An example of a 200-ft high speed shallow water patrol boat is shown in  FIGS. 1A and 1B . The body plan shown in  FIG. 1A  illustrates the portside outboard sponson  3 A having inner portside sponson side  2 A transitioning below the centerline vee-bow  1  section of the hull.  FIG. 1B  illustrates the body plan from behind a boat including port sponson  3 A and starboard sponson  3 B each having inner sponsons sides  2 A and  2 B. The sponsons are joined by transom  5 . 
         [0035]    The side view of a 200-foot patrol boat is shown in  FIG. 2  wherein the sponsons originate in the bow above the waterline and blend into the vee bow  1  forward for the forward projection (FP). The centerline vee section at the bow is made shallower in the water as it transitions aft creating a void between the two outboard sponsons. (See  FIG. 5 ). As shown in  FIG. 2  a high speed interceptor boat is housed inside the stern of the patrol boat. The interceptor boat can be launched and recovered while the vessel is under way since the launch deck is near the load waterline. 
         [0036]    In reviewing the wave pattern shown in  FIG. 3  for the 200-ft patrol boat shown in  FIG. 2  traveling at 35 knots, note that there is no distinct bow wave and the wave pattern begins around the middle of the vessel. The stern wake is very slight immediately following the hull illustrating the capability to launch and recover the interceptor boat housed in the aft center of the patrol boat while it is underway. The transition of the sponsons from above the centerline vee-hull forward to below the centerline vee-bow portion of the hull aft is clearer in  FIG. 2  showing the profile of the vessel. Note that the centerline vee-hull is at its deepest point forward of midships, the middle of the boat, and transitions to a much shallower depth at the transom. This transition coupled with the added displacement of the sponsons ensures proper buoyancy distribution as well as enhancing the ground effect created by air trapped between the outboard sponsons. Alternately the centerline vee-hull may remain at a fixed depth with the outboard sponsons extending below the centerline vee-hull in the aft sections. 
         [0037]    The increase in width of the outboard sponsons  3 A and  3 B as they transition aft, shown in plan view of hull bottom ( FIG. 4  and in  FIG. 5 ), coupled with the increased depth in the water provide increased transverse stability over conventional vee-hull vessels. In another embodiment, the outboard sponsons themselves become wider as they transition aft. The sponsons can have a flat bottom or an angled bottom, either inboard or outboard. The example shown is angled deeper as the sponson moves inboard. The inboard angle of the sponson increases the wing in ground effect during semi-planning or planning without impairing the vessel during turns. The opposite angle, an outboard angle, will provide a similar effect but in higher performance vessels this can create some difficulty in turning at high speeds. In high performance hulls, turning can be improved by adding to the deeper portion of the sponson a small second upward angle or an arc. This will allow water to flow under or around the sponson more easily and prevent “hobby horsing” of the hull when turning. 
         [0038]      FIG. 5  shows the flow of water and air trapped between the outboard sponsons  3 A and  3 B. Because the outboard sponsons increase in width as they transition aft, the open volume between the outboard sponsons decreases. Air and water passing between the sponsons is compressed or accelerated as a result of the reduced open volume. The result is to increase lift on the hull, which reduces drag. 
         [0039]    The combined advantages of increased stability lift on the hull, and accelerated fluid flow between the outboard sponsons dramatically increase the attainable speed of the hull and comfort for the passengers. The hull design of this invention represents a significant advance in the technology. 
         [0040]    The distribution of underwater volume shown in these figures is accommodated by machinery weight and the weight of the hull itself. A profile view with general arrangements of the 200-ft patrol boat is shown in  FIG. 6 . The graph represents the distribution of underwater volume of a hull having the design shown in  FIG. 2 . The large amount of underwater volume aft offsets the weight of the engines, fuel, and outfitted hull resulting in an inherently balanced hull. 
         [0041]      FIG. 7  shows an isometric bow profile sponson starting forward FP; while  FIG. 8  show an isometric stern profile. These profiles show a 200-ft patrol boat hull representing a preferred embodiment of the hull design. The hull is made of components which are mirrored about the hull centerline, noted as “A” for port and “B” for starboard (Stbd). The hull has centerline vee bow starboard  1 B and a counterpart  1 A on the port side (not shown). As shown in  FIG. 2  sponson bottom port  3 A and sponson bottom starboard  3 B, each having inner sides  2 A and  2 B, respectively. There is also shown starboard freeboard  4 B and transom  5 . 
         [0000]    Note in  FIG. 7  how the forward part of the sponson is blended in with the bow and is effectively a part of the vee-bow above the waterline. This design diverts the bow wave and spray trapping it around amidships where the sponsons are developing below the waterline. This phenomena is illustrated in  FIG. 3  which shows the wave pattern for a 200-ft vessel travelling at 35-knots. 
         [0042]    The bow can also have a single chine forward of the forward perpendicular (FP). This allows the deep vee in the bow to be fuller having move volume and buoyancy. A fuller deep vee increases reserve buoyancy making the boat dryer. In this configuration there is a single chine forward of the FP and the sponsons are blended into the deep vee for a longer length in the bow. The sponsons don&#39;t develop until aft of the FP as shown in  FIG. 9 . This is a subtle but important option to tune the hull so it will not slam in seas or pitch excessively. 
         [0043]    The 150-ft patrol boat example in  FIG. 10  illustrates an installation with the primary engines fitted into the outboard sponsons. Water jet propulsion is directly coupled to the primary engines. The outboard sponsons extend below the centerline in the after portion of the vessel. The sponsons are adjusted in width and depth to match the weight of the engines and jet drives and projected cargo aft thereby tuning the hull with respect to underwater volume and buoyancy. The space between the sponsons, noted here as the centerline hollow aft, coupled with this can also be adjusted to effect motions in waves and the resonant frequency at which the vessel moves. 
         [0044]    The ability to adjust the resonant frequency of the hull is critical to ensure reduced motions. Even a small wave with the proper size and height can excite a hull to roll and pitch if it falls in the resonant frequency of the vessel. The induced roll and pitch can be so large as to make operations unsafe or impossible. The ability to move the natural frequency of the vessel away the excitation period of waves gives the hull of this invention a unique advantage over other hull forms. 
         [0045]    The aft view shown in  FIG. 11  illustrates a typical width of the outboard sponsons aft and shows properly sized primary engines fitted inside each sponson. Note the centerline hollow aft well above the bottom of the sponsons. Lift generated from waves and air passing between the sponsons elevates the vessel in the water and cushions the ride. Since air is less dense than water it is easier to drive the hull the more it is elevated and the boat can go faster more economically. The outboard sponsons account for the greatest portion of underwater volume aft providing increased transverse stability as a result. As one side is driven down the buoyant force is applied to the center of underwater volume which is mainly made up of the sponsons. Since the sponsons are well outboard of the vessel centerline the restoring moment is significantly greater than that of a conventional vee hull whose lowest point is at the vessel centerline. Adding to this effect is the weight of the machinery in the sponson opposite the side that is being immersed. The machinery weight is pushing down to create a restoring force on one side of the vessel and the buoyant force of the opposite side creates additional restoring force to bring the vessel back to an even level heel. 
         [0046]    The plan view shown in  FIG. 12  further illustrates the importance of the width of the outboard sponsons and the primary engine placement. The aft portion of the vessel houses the engines without encroaching on interior space. The design allows the vessel to have a greater beam, width, than would normally be practical from a sea-keeping perspective. The added beam actually enhances sea-keeping ability unlike a typical monohull which would suffer from it. The added width increases available interior space and provides more living space while improving the vessel&#39;s stability and ability to smoothly cut through offshore seas. Weight of the engines is kept low in the hull adding to overall vessel stability and the centerline vee-hull ensures slamming or pounding in waves is kept to a minimum. Compared to a similar sized vessel the proposed hull has improved performance, shallower draft, increased interior space, improved comfort both in ride, and insulation from the engines with respect to sound and heat as well as sea-keeping enhancements and improved speed. Direct comparison with a typical existing vessel shows the embodied the hybrid vee-hull of the present invention notably reduced draft and increased beam while maintaining similar displacement: 
         [0047]    Comparison of an Existing Vessel with the Hybrid Vee-Hull 
         [0000]    
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 EXISTING HULL* 
                 HYBRID VEE-HULL 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Length 
                 42.8-meters 
                   45-meters 
               
               
                 Beam 
                 7.11-meters 
                   10-meters 
               
               
                 Draft 
                 2.52-meters 
                  1.8-meters 
               
               
                 Displacement 
                  238-Mtons 
                  243-Mtons 
               
               
                 Metacentric Height 
                 1.52-meters 
                 7.65-meters 
               
               
                   
               
               
                 *The existing hull was a Damen 42-M hull. 
               
             
          
         
       
     
         [0048]    The difference in draft and beam are notable and the ramifications of the differences are significant. The draft of the Damen vessel does not include the propeller below the hull. Equipped with jet drives the hybrid vee hull is capable of traveling in significantly less water and has increased interior space with greater stability. The shallower draft greatly increases the range of the vessel especially in regions like the Caribbean. 
         [0049]    The hybrid vee-hull has significant improvements over conventional vee-hulls in stability, performance, accommodation, sea-keeping and station keeping. The hybrid vee-hull SEV has greatly improved transverse stability inherit in the added width of the outboard sponsons and increased possible width of the hull. The metacentric height of a vessel represents the initial stability of the vessel. It is the height about which the vessel heels like a pendulum on a clock. The higher the metacentric height the more stable a vessel is. Note the extreme difference between the Damen vessel with a metacentric height of 1.52 meters compared to 7.65-meters for the hybrid vee-hull of a similar size and displacement. The hybrid vee-hull has over five times the initial stability of the Damen Stan 4207. This illustrates the Damen vessels tendency to broach in following seas and the inherent stability of the hybrid vee-hull. 
         [0050]    Increased lift on the hull provides a smoother ride and greater obtainable speed as a result of the wing-in-ground effect, which is augmented by the shape of the outboard sponsons. The centerline vee-hull ensures good motions in a seaway. Maintaining proper fore and aft balance, regardless of fuel level, is designed into the hull by adjusting the width and depth of the sponsons coupled with the centerline vee-hull, taking into account engine weight and placement. Additional items such as active control fins which are an absolute requirement on long slender vessels to keep them from broaching in following seas are not required to achieve proper balance which represents a savings in cost and complexity of the vessel. It is also a significant safety imperative no competing vessel can claim such inherent stability. Inboard engines can be fit into the hybrid vee-hull outboard sponsons and can be adjacent to stern drives, long propeller shafts and the complexity they entail are not required, thereby consolidating machinery space while preserving interior and accommodation space. Also, interior space can be increased while maintaining improved performance. 
         [0051]    In addition to the advantages of the hybrid vee-hull invention already mention and in summary, there is provided:
       a) A centerline vee-section forward to cut through seas reducing hull slamming loads and providing directional stability coupled with outboard sponsons.   b) Outboard sponsons extending below the centerline vee-section aft are fully buoyant and wide enough to provide lift at speed.   c) The outboard sponsons may be narrower forward increasing in width as the sponsons transition aft creating a funnel shape to trap air and provide lift.   d) Water bouncing off the cupped after sections of the centerline vee-hull is pushed back down which creates additional lift on the hull.   e) The outboard sponsons provide notably improved transverse stability over conventional hulls.   f) Air trapped between the outboard sponsons and the water creates a buffered layer which raises the boat out of the water thereby reducing drag.   g) Design improves weight distribution by adding buoyancy aft where machinery weights are ideally concentrated.   h) Design significantly improves the safety of the vessel as a result of improved stability.   i) Design can house water jets and primary engines in the sponsons. Both reduce the intrusion of propulsion systems into the personal accommodation spaces and increase the versatility of interior design space.   j) Utilizing jet drive propulsion negates underwater shafting which produces drag on the vessel and can be damaged during grounding or by debris in the water. Jet drives also significantly improve station keeping capabilities.   k) Design results in an extremely shallow hull draft. This hull can travel over shallow shoals conventional vessels would not manage.   l) Design helps protects propellers during grounding if they are used.   m) Design can have increased beam for the same displacement when compared to a typical vee-hull. The added beam allows for increased interior and aft deck space. It also enhances the ground effect by providing a larger surface providing   n) Design provides enhanced tracking during turns and reduces healing and the possibility of broaching as the outboard sponsons and high form stability.   o) Design can be optimized to produce less wake at speed through “wake canceling” reducing drag over conventional hulls.   p) The natural frequency of the hull can be tuned to assist in reducing vessel motions   q) The design inherently reduces stern wake while providing lift to the hull   r) The sponsons can be designed to enhance stern wake cancelling reducing drag on the hull   s) The hull design facilitates launching a small patrol or interceptor boat housed in the stern of the patented hull between the sponsons. This small boat can be launched with the patented hull underway because of the minimal wake in the stern between the sponsons.   t) The sponsons can start forward of the FP typically in a double chine configuration or aft of the FP typically with a single chine configuration forward of the FP. This allows forward buoyancy and wave generation to be controlled.       
 
         [0072]    Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions. Therefore, it is to be understood that the inventions are not be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included with the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.