Abstract:
A keel pad is provided for a hull of a boat. The keel pad contains a main body and two fingers extending from the main body in a direction of a front of the hull. Due to curved shape of the fingers, drag is reduced allowing the boat better planing properties and greater fuel efficiencies.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation-in-part of copending U.S. patent application Ser. No. 29/434,671, filed Oct. 16, 2012. This application also claims the priority, under 35 U.S.C. §119, of U.S. provisional patent application No. 61/871,015, filed Aug. 28, 2013; the prior applications are herewith incorporated by reference in its entireties. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates, generally, to a keel pad, and more specifically, it relates to a retrofit kit for a boat hull and to a boat hull having an integrated keel pad. 
         [0003]    A boat hull is ideally configured to reduce drag, increase lift, maximize speed and maximize fuel economy. A key feature of the boat hull that influences these properties is the keel pad integrated on the bottom of the boat hull. Increased speed is generally obtained by minimizing the drag on the hull and by increasing the lift of the hull so that the hull planes over the water at high speeds. Drag is generally minimized by decreasing the wetted area of the hull. However, decreasing drag and increasing lift usually adversely affects comfort and handling. 
         [0004]    With regards to larger boats, being defined as boats larger than 35 plus feet, fuel economy is also a major concern and is influenced by the configuration of the keel pad. The purpose of a keel pad is to increase lift locally in an aft portion of a marine planing craft that has a dead rise angle greater than zero. The more increased lift, the less drag resulting in great speed and better fuel efficiency. 
       SUMMARY OF THE INVENTION 
       [0005]    It is accordingly an object of the invention to provide a keel pad, a boat hull with a keel pad and a retrofit kit that overcome the herein-mentioned disadvantages of the heretofore-known devices of this general type, which increases fuel economy, increases lift and does not decrease handling characteristics. 
         [0006]    With the foregoing and other objects in view there is provided, in accordance with the invention, a keel pad for a hull of a boat. The keel pad contains a main body and two fingers extending from the main body in a direction of a front of the hull. Because the keel pad ends in the shape of two fingers rather than a traditional triangular tip shape drag is surprisingly reduced and fuel economy improves. Ideally, these improvements occur because the two fingers define a V-shaped entry between the two fingers as viewed looking forward towards the front of the hull. This is further enhanced because the two fingers have inner sides tapering towards each other which reduces water flow turbulence. 
         [0007]    In a preferred embodiment of the invention, the main body has an elongated rectangular shape which results in greater surface area than prior art keel pads which provides greater lift thus reducing drag. 
         [0008]    In an added embodiment of the invention, the main body has a given length L 1 , the fingers each has a given length L 2 , and the following equation holds for L 2 : 
         [0000]      0.25L1&lt;L2&lt;2L1. 
         [0009]    In another embodiment of the invention, the main body has a given length L 1 , the fingers each has a given length L 2 , and the overall length of the keel pad is L 3  where L 3 =L 1 +L 2 , and the hull has a given length L OA . Therefore the following equation holds true for the overall length L 3 : 
         [0000]      0.05 L OA &lt;L3&lt;0.5 L OA . 
         [0010]    In a further embodiment of the invention, the keel pad is configured to be either integrated in the hull of a new boat or retrofitted on the hull over an existing keel pad of an existing boat. In order to be attached to an existing hull, the keel pad may have a flange extending along its side so that it may be attached to the hull by an adhesive, rivets, screws and other fastening methods. Instead of a flange extending from the sides, the surface area of the bottom of the keel pad can be adhesively attached to an existing hull. 
         [0011]    In an added feature of the invention, the two fingers each slope downward towards the hull in a frontal region of the keel pad. This further decreases drag and increases fuel efficiency. 
         [0012]    With the foregoing and other objects in view there is provided, in accordance with the invention, a boat. The boat contains a hull with a front and a transom, and a keel pad extending from the hull. The keel pad has a main body and two fingers extending from the main body in a direction of the front of the hull. 
         [0013]    In a preferred embodiment of the invention, the main body has a given width W KP , the hull has a given chine beam width W CB  and a given length L OA . The given width W KP  is defined by the following equation: 
         [0000]      0.05 W CB &lt;W KP &lt;0.5 L OA . 
         [0014]    Other characteristic features of the invention are set forth in the appended claims. 
         [0015]    Although the invention is illustrated and described herein as embodied in a keel pad, a boat hull with a key pad and a retrofit kit, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0016]    The construction of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0017]      FIG. 1  is a diagrammatic, perspective side view of a boat hull according to the invention; 
           [0018]      FIG. 2  is a diagrammatic, perspective bottom view of the boat hull according to the invention; 
           [0019]      FIG. 3  is a bottom perspective view of a recessed delta keel pad according to the prior art; 
           [0020]      FIG. 4  is a side view of the recessed delta keel pad according to the prior art; 
           [0021]      FIG. 5  is a bottom perspective view of a warp delta keel pad according to the prior art; 
           [0022]      FIG. 6  is a rear view of the warp delta keel pad according to the prior art; 
           [0023]      FIG. 7  is a bottom perspective view of a protruding delta keel pad according to th e prior art; 
           [0024]      FIG. 8  is a side view of the protruding delta keel pad according to the prior art; 
           [0025]      FIG. 9  is a plan view of one of the delta keel pads overlaid on the keel pad according to the invention; 
           [0026]      FIG. 10  is a diagrammatic, perspective view of the inventive keel pad according to the invention; and 
           [0027]      FIG. 11  is a rear view of the keel pad at the transom. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    In all the figures of the drawing, sub-features and integral parts that correspond to one another bear the same reference symbol in each case. Referring now to the figures of the drawings in detail and first, particularly, to  FIG. 1  thereof, there is shown a boat hull  1  with an inventive keel pad  2 , lift strakes  3  and a transom  7  (rear of the boat hull). The boat hull  1  is of a generalized V-hull shape. 
         [0029]      FIG. 2  shows a bottom view of the boat hull  1  with the inventive keel pad  2 . 
         [0030]    There are several factors to consider when trying to increase lift with a keel pad. These include:
   a). first, increasing an effective lifting surface area;   b). second, minimizing drag due to the keel pad;   c). third, maintaining a vessel&#39;s ability to linearly track; and   d). fourth, maintaining or increasing aft buoyancy.   
 
         [0035]    In addition, the ability to retro fit a vessel with an appropriate keel pad is also a factor in the design of the keel pad. 
         [0036]    We first turn our attention to increasing the lifting surface area of the boat hull. It is known that the surface for a given area that provides the most lift is a flat surface. Unfortunately flat surfaces do not have good sea keeping and hinder fast accelerations, therefore most planing sea going vessels have some sort of “V” shaped hull. Sea keeping ability is a measure of how well-suited a watercraft is to conditions when underway (ability to turn and maintain a straight linear path in view of wave forces). A ship or boat which has good sea keeping ability is said to be very seaworthy and is able to operate effectively even in high sea states. The angle of the V is called the deadrise. The V-shape of the hull is typically sharp at the bow and reduces gradually towards a stern, but still maintains a deadrise angle at the transom  7 . In some vessels it is desirable to gain lift at the aft end of the vessel for various reasons such as reducing the running trim angle, and to vertically translate the vessel higher out of the water while running, etc. in order to increase performance. There is a mathematical relationship to represent the increase in lift given a fixed pressure on a given inclined area of the deadrise: 
         [0000]      Percent Increase Lift Force=Pressure×Area/(Pressure×Area×Cos(deadrise angle)).
 
         [0037]    It can be observed that as the deadrise angle approaches zero (or a flat surface) the equation goes to unity. 
         [0038]    Second, we turn our attention to minimizing drag due to the addition of the keel pad. By the nature of the addition of the keel pad there will be an inherent drag component. This is due to the added surface area of the keel pad obstructing the flow of bypassing water. The frontal area of the keel pad creates the most drag and disturbs the water flow resulting in a creation of negative pressures relative to the rest of the hull. To minimize the surface area of the keel pad is therefore thought to be obvious. The frontal drag component is most influenced and reduced by the shaping of the frontal area. Lastly, the water flow when made to change direction frequently or abruptly can cause increased drag, so it is best to make the flow as uniform as possible when flowing over sections. 
         [0039]    Third, we turn our attention to maintaining the vessel&#39;s ability to linearly track. A flat bottom boat has difficulty to linearly track and slides outs in turns. The addition of a keel pad can cause the same characteristic to a lesser degree due to the flat section if not properly addressed. Some shapes can provide some linear tracking, but have a tendency to be unstable in either turns and/or with wave incident angles other than head on. 
         [0040]    Fourth, we turn to the ability to maintain or increase buoyancy. Often it is desirable to at least maintain current hydrostatic characteristics (e.g. pressure) or increase the buoyancy as this helps with static trim and as well as the running trim of the vessel if combating a stern down condition. 
         [0041]    A further consideration in the configuration of the keel pad relates to the ability to retro-fit the keel pad onto existing boat hulls. In other words, the need for the keel pad to be added after the vessel has been built. In this case it is important to have a shape that can be easily retro-fitted without compromising the hulls integrity, preferably a piece that can be added in lieu of cutting an existing hull. 
         [0042]    Turning now to  FIGS. 3-8 , there are shown designs of three prior art keel pads. 
         [0043]    The keel pad shown in  FIGS. 3 and 4  is known as a recessed (delta) keel pad  20 . The recessed keel pad  20  is triangular in shape and extends from the transom forward to a tip of the recessed keel pad  20 . The recess keel pad  20  is integrated in the hull of the boat. More specifically, the stern and bottom area of the V-shaped hull is flattened (molded) in a flat triangular shape to form the recessed keel pad  20 . 
         [0044]    The recessed keel pad  20  results in a decrease in buoyancy and generates negative pressure unless the vessel is trimmed to the same angle as the recessed keel pad  20 . Unfortunately the recessed keel pad  20  provides no or poor linear tracking and causes the stern to slide out in turns. 
         [0045]    The keel pad shown in  FIGS. 5 and 6  is known as a warped (delta) keel pad  30 . Like the recessed keel pad  20 , the warped key pad  30  is also triangular shaped and extends from the transom  7  to the tip of the warped key pad  30 . The warped key pad  30  is also integrated into the hull as the sides of the V-shaped hull are warped or widened out and the warp keel pad  30  extends between the widened out portions. 
         [0046]    The warped keel pad  30  adds extra buoyancy and a warped surface frontal area. Due to the nature of the orientation of the warped surface, the warped keel pad  30  produces instability in linear tracking and creates significant bow down and possible hooking. Hooking is the occurrence of an unexpected sharp turn (e.g. 90 degree turn) of the boat while underway. In addition, due to the shape of the warped keel pad  30 , the water flow is forced to change direction continually and therefore causes additional drag. 
         [0047]    The keel pad shown in  FIGS. 7 and 8  is a protruding (delta) keel pad  40 . Like the other keel pads  20 ,  30 , the protruding keel pad  40  is also triangular shaped but extends below the natural boundaries of the V-shaped hull. The protruding keel pad  40  provides added buoyancy and added frontal area. However, the frontal area does not generate any additional lift, rather it generates drag. The angled vertical surface of the protruding keel pad  40  does provide increased linear tracking but also creates instability in certain conditions where the wave incident angle is unfavorable. 
         [0048]      FIG. 9  is a plan view of one of the prior art keel pads having the delta or triangular shape overlaid on the keel pad  2  according to the invention. First, as you can see from the overlay, the keel pad  2  according to the invention has a greater surface area and therefore a more effective lifting surface than the prior art delta shaped keel pads  20 . Of course in the case of a retrofit, the keel pad  2  would have to be elongated to completely cover the prior art keel pad  20 ,  30 ,  40  so that the tip is disposed in the main body. 
         [0049]    Second, drag is reduced by creating a shape for the frontal area that also provides lift and minimizes the drag component. The water flow is also kept as uniform as possible with minimal directional changes. This occurs because the keel pad  2  ends not in a tip shape but rather has two fingers  4 ,  5 . 
         [0050]    Third, the front of the inventive keel pad  2  ends in an inverted V shape in combination with the sides of the keel pad  2  which provides stable linear tracking. 
         [0051]    Fourth, due to the nature of the shape, the inventive keel pad  2  can easily be retro-fitted to hulls without jeopardizing hull integrity. The keel pad  2  can be adhered to an existing hull by adding side flanges to the keel pad  2  and then riveted, glued, screwed, and/or fastened to the hull over the existing keel pad. 
         [0052]    Fifth, the buoyancy of the boat is increased because it does not experience additional drag found from the prior art keel pads. 
         [0053]      FIG. 10  shows the inventive keel pad  2  and its associated fingers  4 ,  5  extending from the main body  6  having a generally rectangular shape S 1  until the fingers  4 ,  5 . The main body  6  has sides S 2 , S 3  and a given length L 1 . The fingers  4 ,  5  are curved, scoped or tapered fingers S 4 , S 5  defining an entry surface for the keel pad  2  and each of the fingers  4 ,  5  has a given length L 2 . The inner sides of the fingers  4 ,  5  taper toward each other and have a curved frontal area. The fingers  4 ,  5  also can be described as a tapering blade shape. The main body  6  has a width W KP . The hull  1  has a chine beam width W CB , a deadrise angle  11  and an overall length L OA . The keel pad  2  has an overall length L 3  where L 3 =L 1 +L 2 . 
         [0054]    The sides S 2 , S 3  each have a given height h and the following relationship: h is approximately=0.5 W KP  tan (β). 
         [0055]    The following proportions hold true: 
         [0000]      0.05 L OA &lt;L3&lt;0.5 L OA ;   a)
 
         [0000]      0.05 W CB &lt;W KP &lt;0.5 L OA ;   b)
 
         [0000]      0.25L1&lt;L2&lt;2L1;   c)
 
         [0000]      3°&lt;β&lt;60°;   d)
 
         [0000]      1/5 &lt;h/L 2&lt;1/30; and   e)
 
         [0000]        H  is approximately=0.5  W   KP  tan(β).   f)
 
         [0056]      FIGS. 1 ,  2  and  10  show the keel pad  2  integrated in the hull  1  of the boat. However, the keel pad  2  can easily be retrofitted onto existing boats where the prior art keel pads are. More specifically, the keel pad  2  is laid over the existing keel pad and attached to the boat. 
         [0057]      FIG. 11  is a rear view of the keel pad  2  attached to the hull and extending from the transom  7 . As can be seen, an angle alpha a describes the angle from a center line  8  to the side S 3  of the keel pad. The angle beta  11  describes the dead rise or angle of the transom. The following relationship holds: 
         [0000]      Alpha=2/3 (90°−Beta).