Abstract:
Conversion of a stand up paddle (SUP) board or similar personal watercraft to enable it to be powered by a battery and an electric motor and propeller apparatus requires a practical and performance oriented configuration to be successful. This patent describes an optimal configuration that utilizes a vertical hollow protrusion through the stand up paddle board that supports the propulsion system and is comprised of two assemblies; a motor and propeller assembly, and a battery and control assembly. The location of the hollow protrusion on the board is a critical feature of this invention. Placing the hollow protrusion in a central location on the board mitigates, to the greatest extent possible, the negative aspects of propelling the board with a propeller and the extra weight of the motorized system on the board&#39;s balance and maneuverability characteristics. This is accomplished by locating the hollow protrusion and equipment associated with the motorized system relatively close to, and forward of the rider. This allows the rider to efficiently counterbalance the weight of the motorized system and effectively manage the forward thrust provided by propulsion. This invention allows battery powered, motorized stand up paddle boarding to be developed into an affordable, attractive and performance oriented recreational sport.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    There are a number of patents for powering surfboards in an effort overcome the difficulty associated with paddling through surf. This invention is not intended for surfboards because the propeller extending beneath the board will cause excessive drag when attempting to surf. 
         [0002]    There are a number of patents related to the use of internal combustion engines to power surfboards and similar personal watercrafts such as a stand up paddle board. There are also patents related to propelling surfboards and similar personal watercraft such as a stand up paddle board using water jet systems. This invention differs from both types of patents because it does not use an internal combustion engine to power the system, and it does not use water jets, impellors or enclosed propellers to propel the craft. 
         [0003]    This invention utilizes battery power and an electric motor with external propeller to propel a stand up paddle board, or similar watercraft. This configuration has the advantages being very efficient with regard to power consumption, it has relatively low noise and vibration characteristics, and does not emit air or water pollution during use. 
         [0004]    Patents and other information relevant to this invention are described below. 
         [0005]    An August 1968, Worthington Daily Globe article briefly describes a battery powered surfboard designed by a Fleischer Manufacturing Company of Salt Lake City. The article describes the use of an electric propulsion motor that uses “tiny motors and propellers”. The absence of subsequent information on the project implies that the idea was not successful. 
         [0006]    Namanny (Pat. App. Pub. No. US20030167991, now abandoned) discloses a small electric-powered propeller unit mounted on a surfboard fin. Ruan, et. al. (Pat. App. Pub. No. US20080168937, now abandoned, and previously issued U.S. Pat. No. 7,207,282) disclose a “propeller-driven surfing device” with an electric motor and power supply. Railey (Pat. App. Pub. No. US20080045096, and previously issued U.S. Pat. No. 7,226,329) discloses a surfboard with dual internal electric motors and impellers. Chang (U.S. Pat. No. 5,017,166) describes a DC-motor-powered board with a large rear propeller and foot-operated control. Jung (U.S. Pat. No. 6,702,634) describes a board powered with an electric motor controlled by switches on a steering column, driving a helical propeller and including a retractable “brake.” Efthymiou (U.S. Pat. No. 6,142,840) designed a board with a specialized shape and fin structure, dual water-jet pumps with angled intakes, and a wired handgrip control. Austin (U.S. Pat. No. 6,409,560) describes a motor housed in a box attached to the bottom of the board, with an external propeller and controls on a steering column. Rott, et. al. (Pat. App. No. US2011/024700) describes a battery powered, water jet system on a surfboard or similar personal watercraft. This invention was developed with the intent of make surfing more accessible. In 2013 products using this invention were marketed under the name WaveJet. In 2015 WaveJet products were discontinued due in part due to lack of sales. 
         [0007]    The patents related to water jets systems including impellers, or propellers located within internal chambers on a board (Railey, Ruan, et. al, Efthymiou, Rott et. al.) are not relevant to this invention because this invention it does not use water jets or impellers due their high power consumption requirements. Patents related to electric motors with propellers mounted on the fin on the aft section of the board (Namanny, Chang, Austin) are not relevant because this invention positions the electric motor and propeller assembly in the mid-forward section of the board and not on the aft section of the board where the fin is normally positioned. 
         [0008]    There are only two know companies that have advertised a battery powered system for propelling a stand up paddle board or similar water craft. In 2014, WaveJet began selling a battery powered, water jet driven system for stand up paddle boards. In 2015 WaveJet discontinued sales due to various reasons. In 2014, CurrentDrives began selling a battery powered, propeller driven system for stand up paddle boards. The CurrentDrives system is intended to be installed on stand up paddle boards as a conversion kit whereby, the standard fin is replaced by a motor and propeller assembly located on the aft section of the board. There are no battery powered, propeller driven systems for stand up paddle boards that locate the motor and propeller assembly in the mid-section of the board that are in known commercial or common use, aside from products designed by the inventor and sold by his company, Motorized SUP, LLC. 
       BACKGROUND OF THE INVENTION 
       [0009]    This invention provides a method for configuring a battery powered propulsion system for a stand up paddle board or similar stand up personal watercraft that involve standing on the craft during normal use. Critical performance factors for a personal watercraft of this type include being lightweight, balanced and hydrodynamic in shape. Installing a battery powered propulsion system on a stand up paddle board can have significant negative effects on these critical performance characteristics that consequently effect the rider&#39;s balance and control. Past configurations have not adequately addressed these negative effects resulting in major challenges to bringing a battery powered, motorized stand up paddle board system to commercial market. 
         [0010]    This invention provides a method to configure a battery powered, motorized stand up paddle board systems that mitigates, to the greatest extend possible, the negative effects of adding the system to the watercraft. This invention specifically addresses balance and control issues by providing a convenient method for locating the propulsion system at the center of the watercraft and slightly forward of the rider. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    Installing a battery powered, motorized propulsion system on a stand up paddle board, or similar watercraft, in a mid-forward position on the board using a hollow protrusion through the board provides a practical, convenient and commercially viable method for installing the motorized equipment on a balance-sensitive personal watercraft. This invention has become viable in recent years with the advent of commercially available small, yet powerful batteries. The invention is characterized by a motor and propeller assembly installed below the board in a position that is slightly forward of the rider&#39;s normal position on the board. The motor and propeller assembly including its support shaft ( FIGS. 1 through 4 : Item  2 ) is installed by placing the support shaft vertically through a hollow protrusion in the board ( FIGS. 1 through 6 , Item  3 ) with the top of the shaft terminating at or above the deck of the board. The interior of the shaft contains wires from the motor that allow the user to connect the motor to the battery and control assembly ( FIGS. 1 through 4 , Item  1 ) located on the deck of the board. 
         [0012]    There is also an apparatus to mechanically secure the shaft motor to the board. The securing device can be configured to secure the motor assembly in a fixed position to propel the watercraft forward. This fixed position is the preferred option for intermediate and advanced stand up paddle boarders because steering is performed by balancing and using the paddle as a rudder. Alternatively, the motor shaft may be secured in a manner that allows the motor and propeller assembly to rotate on a vertical axis, allowing the board to be steered by changing the direction of propulsion. This alternative configuration is a good option for novice paddle boarders because steering is relatively easy and a steering handle provides the rider with an additional balance point. 
         [0013]    The applicant is not aware of any prior art representing this shaft-through-board configuration on a stand up paddle board. The inventor has concluded through on water testing that this invention represents the optimal configuration for installing a battery powered propulsion system on a stand up paddle board. The key advantages of this configuration are a result of the hollow protrusion (Item  3 ) through the board supporting the installation of the battery/control assembly (Item  1 ) and the motor/propeller assembly (Item  2 ) in a location on the board that is in close proximity to, and in front of the rider. The advantages of centralizing the motorized propulsion system on the stand up paddle board are described herein. 
         [0014]    1. The extra weight of the propulsion system does not significantly change the rider&#39;s normal position on the board. This mitigates to the extend practical, the negative effects of the extra weight of the propulsion system on the maneuverability of this balance sensitive watercraft. This is a result of minimizing swing weight, with swing weight being any weight that is distal to the central balance point on the board. Excessive swing weight causes a board to react sluggishly during turns and other maneuverers. 
         [0015]    2. Positioning the motor and propeller assembly in the mid forward section of the board allows the watercraft to be easily rotated or turned around that position, This is an important performance characteristic for turning the board using a paddle as a rudder while the board is being propelled through the water, and when making tight turns where there is minimal clearance to obstacles such as in a narrow waterway. 
         [0016]    3. Positioning the motor and propeller assembly in the forward section of the board mitigates the risk of the rider striking the propeller in the event that the rider falls off the board while it is moving. This is different than most propeller-driven watercraft where the propeller is located on the aft section of the craft. In the aft position, a fallen rider is more likely to be struck by the propeller because of the forward momentum of the craft as it is propelled through the water. 
         [0017]    4. Positioning the motor and propeller assembly below the board and within the mid-section of the board increases the overall stability of the board. This is similar to how a keel stabilizes a sailboat. Longitudinal stability (port and starboard) is enhanced because the weight of the motor counterbalances the rider&#39;s weight during board handling and maneuvers. To a lesser extent there is also a counterbalancing effect on the board&#39;s lateral stability. 
         [0018]    5. Locating the battery and control assembly in close proximity and forward of the rider allows the rider easy access to equipment associated with the propulsion system. Access to this equipment provides the rider with a convenient means to monitor the system including checking the battery charge level, and ensuring that the electrical and mechanical connections are secure. In addition, this location provides the rider with convenient access to control of the propulsion system including; turning the system on and off, activating the emergency kill switch, and retracting the motor by lifting the motor shaft during beach landing or during times when the battery no longer has an adequate charge. 
         [0019]    6. Locating the battery and control assembly in close proximity and forward of the rider allows the rider full access to the mid and aft section of the board&#39;s deck. Unobstructed accesses to this portion of the deck is important for balancing on and maneuvering the board. Turns on a motorized stand up paddle board are performed by the rider moving their weight toward the back of the board and exerting pressure with the paddle in the water on either the port or starboard side of the board. Any obstructions on the aft deck of the board hinders the rider&#39;s ability to effectively control the board and poses a tripping hazard to the rider. A motorized stand up paddle board configuration that maintains a clear, unobstructed working deck for the rider is an important advantage of this invention. 
         [0020]    7. The hollow protrusion through the board is a simple and relatively easy modification to a typical stand up paddle board design that does not add weight to the board and does not impact the performance of the board when used without the motorized system. This allows board manufacturers to include this feature on their boards with little additional cost and with no adverse aesthetic, performance, or structural integrity effects to their product. Stand up paddle boards are commonly made using sandwich composite construction and a small, vertical hollow protrusion constructed properly through the board&#39;s centerline stringer will not undermine the structural integrity of the board. 
         [0021]    8. The hollow protrusion through the board may be used for accessories other than a motorized propulsion system. These include, but are not limited to; fittings for windsurfing comprised of a mast base and center fin, an underwater lighting system, or an underwater viewing apparatus. 
         [0022]    This invention and its identified advantages effectively mitigates problems with past inventions that compromise board performance by positioning the battery powered, propeller driven propulsion system on the aft section of the board. 
         [0023]    The inventor is currently fabricating and selling motorized stand up paddle board systems configured as described in this patent under Motorized SUP, LLC. Information including pictures and videos of the product are available on the company&#39;s website at: http://motorized-sup.com. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0024]      FIG. 1  is the preferred view for the patent cover page.  FIG. 1  shows the motorized system installed on a stand up paddle board as viewed from the side as a cross section through the board&#39;s centerline, commonly called the stringer. The motor and propeller assembly is marked as item  2 . This assembly is shaded grey including the motor support shaft that is part of the assembly. The support shaft extends vertically through the hollow protrusion in the board terminating at an elevation slightly above the deck of the board. The vertical hollow protrusion through the board is marked as item  3 . The upper section of the motor support shaft includes a fitting to connect wires to the battery and control assembly. The battery and control assembly marked as item  1 , is located on the deck of the board and just aft of the hollow protrusion and motor shaft. The battery and control assembly is comprised of a waterproof case holding a battery and control circuit and includes a watertight fitting to connect wires to the motor and propeller assembly. 
           [0025]      FIG. 2  shows the motorized system installed on a stand up paddle board as viewed from the top. The battery and control assembly is marked as item  1 . Only the top portion of the support shaft of the motor and propeller assembly is visible. The top of the motor shaft is marked as item  2  and shaded in grey to show that it is part of the motor and propeller assembly. The rest of the motor and propeller assembly is not shown because it is below the board. The hollow protrusion in the board is marked as item  3 . 
           [0026]      FIG. 3  shows the motorized system installed on a stand up paddle board as viewed from the front of the board at a cross sectional location centered on the hollow protrusion. In this view all three critical components of this invention are visible. The battery and control assembly marked as item  1  is located on the deck of the board. Item  2  is the motor and propeller assembly that is located below the board with its support shaft extending vertically through the board using item  3 , the hollow protrusion. 
           [0027]      FIG. 4  shows the motorized system as individual components and the stand up paddle board viewed from the side without the motorized system installed. The battery and control assembly is marked as item  1 . The motor and propeller assembly is marked as item  2 . And the vertical hollow protrusion through the board is marked as item  3 . 
           [0028]      FIGS. 5 and 6  show the stand up paddle board from a side view without the motorized system installed. Each figure illustrates a method that can be used to determine the proper location of the hollow protrusion in the stand up paddle board to facilitate installation of a battery powered, propulsion system described in this patent. 
           [0029]      FIG. 5  illustrates a method to determine the location of the hollow protrusion on any type of stand up paddle board or similar stand up personal watercraft based on the board&#39;s buoyancy characteristics defined by the waterline and the rider&#39;s operating position on the board without the motorized system installed. The proper location for the hollow protrusion ( 3 ) is 13% of the length of the waterline (a×0.13=b) forward of the rider&#39;s position without the motorized system installed ( 4 ). And, where the rider&#39;s position without the motorized system installed ( 4 ) is determined by the location where the section of the board below the waterline is divided into two equal volumes that result in the waterline being relatively parallel with the bottom and top surfaces of the board. 
           [0030]      FIG. 6  illustrates a method to determine the location of the hollow protrusion on a surf style stand up paddle board that is determined by applying the Golden Ratio method where; the length from the tail to the hollow protrusion (c) divided by the length from the nose to the hollow protrusion (d) is equal to the entire length of the board (c+d) divided by the length from the tail to the hollow protrusion (c). 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    This patent describes an optimal configuration of a motorized system on a stand up paddle board, or similar personal watercraft that is intended to be used while the rider is in a standing position that utilizes a vertical hollow protrusion through the board or craft. In this configuration the hollow protrusion supports the installation of a battery powered, motorized propulsion system comprised of two assemblies; a motor and propeller assembly, and a battery and control assembly. The location of the hollow protrusion on the board is a critical characteristic of this invention because the location serves to effectively mitigate, to the greatest extent possible, the negative aspects of adding extra weight to the board and propelling the board with an underwater motor and propeller assembly. 
         [0032]    The extra weight of equipment associated with a motorized system can negatively affect a board&#39;s handling and maneuverability characteristics. This occurs because a board sits lower in the water incurring more drag. This cannot be mitigated except by minimizing the weight of the motorized system. The extra weight of the system also increases swing weight, where swing weight in this application refers to any weight that is distal to the rider&#39;s operating position on the board without the motorized system installed. Any additional weight that is added by the motorized system (i. e., swing weight) forces the rider to relocate their balance point on the board, compromising performance because the rider is no longer at the board&#39;s intended design location for its operator. If there is excessive swing weight in the aft section of the board, the rider may be required to move forward on the board to a position where the rider experiences difficultly using the paddle as a rudder to steer the board. This is a particular challenge for motorized configurations where the motor and propeller assembly are located at, or in close proximity to the fin at the far aft section of the board. 
         [0033]    Another negative aspect of swing weight occurs when the rider turns or maneuvers the board by changing its direction. Excessive swing weight during maneuvers slows the responsiveness of the board when conducting maneuvers making the board feel sluggish and more difficult to control. This sluggish characteristic increases in effect as the swing weight is more distal to the rider. When a maneuver is initiated, the momentum of the board&#39;s mass is redirected. This redirected momentum requires work in the form of energy expended by the rider. If the rider turns the board with a paddle, the effort to make the turn increases in direct relation to the excess weight on the board and its relative distance from the rider, i. e., swing weight. 
         [0034]    This invention mitigates the negative effects of swing weight by reducing, to the greatest extent possible, the distance between the rider and the equipment associated with the motorized system. This allows the rider to remain in the optimal position on the board as intended by the board&#39;s designer. It also keeps the board responsive and lively during turns and other maneuvers. A motorized stand up paddle board configured with minimal swing weight assures that the fundamental performance characteristics of the board are preserved. Once preserved, a motorized propulsion system may serve to enhance these performance characteristics without significantly compromising balance and maneuverability. 
         [0035]    A critical element of this invention is related to the location of the hollow protrusion in the stand up paddle board and the equipment associated with the motorized system being located in close proximity to this hollow protrusion. For a system to be configured that has all the advantages described in this patent, the position of the hollow protrusion must meet the following criteria. For the purposes of this discussion, the location of the hollow protrusion means the cross sectional center of the hollow area that runs vertically through the board and assumes the hollow protrusion is located on the centerline with respect to port and starboard. 
         [0036]    1. The hollow protrusion is oriented vertically. This means that the axis of the hollow protrusion is in line with the zenith when the board is in normal use. This orientation is relative and the vertical orientation may not be exact. However, the general concept of relatively vertical is necessary to ensure that the weight of the motor and propeller assembly below the board is in dose proximity to the hollow protrusion. 
         [0037]    2. The hollow protrusion has a round, oval or other geometric cross sectional shape. Round is considered the best shape for the hollow protrusion because a round shaft common to small electric trolling motors will properly fit into the protrusion, and the motor and propeller assembly will be able to rotate allowing the motor to be directionally steered. Other geometric shape can be utilized as well, including those intended to be used to support a non-rotating shaft. 
         [0038]    3. The hollow protrusion is located forward of the rider&#39;s operational position on the board. A rider&#39;s normal operating position on a stand up paddle board is close to the board&#39;s center of buoyancy. More specifically, a rider&#39;s optimal operating position is at a point on the board relative to forward and aft that results in the waterline of the board being relatively parallel with the bottom and top surfaces of the board. This is illustrated in  FIG. 5  where the hollow protrusion ( 3 ) is forward of the rider&#39;s operating position ( 4 ). 
         [0039]    4. The distance from the rider&#39;s position without the motorized system installed, to the hollow protrusion can be determined using the following method. 
         [0040]    The optimal position of the hollow protrusion relative to the rider&#39;s position can be estimated as thirteen percent (13%) of the waterline. This location may range from 5% to 25% depending on specific design preferences. However, for most applications 13% serves as a good design criteria. This method is derived from empirical testing using motorized systems on a variety of personal watercraft that are intended to be operated in the standing position. 
         [0041]    The method is illustrated in  FIG. 5  where the hollow protrusion ( 3 ) is located a distance that is 13% of the board&#39;s waterline forward of the rider without the motorized system installed ( 4 ). 
         [0042]    An example of this methodology is presented as follows on a common sized stand up paddle board. A twelve foot (12′) long stand up paddle board has a waterline that is eleven feet (132 inches) with an average 160 pound adult standing on the board. Using the 13% rule, the hollow protrusion is to be located seventeen inches (132″×0.13=17″) forward of the rider&#39;s position without the motorized system installed. Therefore, installing the hollow protrusion 17 inches forward of the rider&#39;s normal operating position on the stand up paddle board without the motorized system is considered the proper location for the hollow protrusion. 
         [0043]    This distance could be shorter than 17 inches for various reasons including the need to accommodate a battery and control case that is located forward of the hollow protrusion instead of aft of it. The distance could also be longer than 17 inches to provide more open space on the deck for the rider to operate. The 13% of the waterline method serves as a sound basis for making an initial determination of the location of the hollow protrusion on a particular stand up paddle board or similar personal watercraft. 
         [0044]    The 13% rule can also be used to determine the rider&#39;s new operating position on the stand up paddle board when the battery powered motorized system is installed. Using the example above, the new position is calculated as follows. 
         [0045]    (132 in×0.13)+(20 lb×(132 in×0.13)/160 lb)=19.3 inches
       Where, the weight of the motorized system is 20 pounds (20 lb) with its mass centered at the location of the hollow protrusion, and   Where, the rider&#39;s weight is 160 pounds (160 lb), and   Where, the length of the waterline is 132 inches.       
 
         [0049]    Using the 13% rule, the hollow protrusion will be located nineteen inches (19″) forward of the rider&#39;s position with a motorized system installed weighting 20 pounds. The first part of the equation equals 17.2 inches (132 in×0.13) and represents the distance between the rider&#39;s position without the motorized equipment and the location of the hollow protrusion. 
         [0050]    The second part of the equation equals 2.1 inches and represents the distance that the rider is displaced aft from their original position to counterbalance the 20 pounds of motorized equipment installed on the board. In this case the rider must relocate 2.1 inches aft their original position on the board to keep the board balanced in the water so that the waterline remains relatively parallel with the top and bottom surfaces of the board. 
         [0051]    As presented in the example, the 13% rule can be used to calculate both the proper location of the hollow protrusion and the new location of the rider when the motorized system is installed on the board. 
         [0052]    In this example, the rider is relocated two inches aft of their normal operating position on board without the motorized system. This relatively small relocation distance is an advantage of this invention because it ensures that the performance of the board including paddling and maneuvering characteristics remain relatively constant with and without the motorized system installed. A distance of 19 inches between the rider and the hollow protrusion provides an adequate area to locate a battery and control assembly and to mechanically secure the motor shaft to the board. The battery and control assembly is comprised of a battery and electrical control circuit contained in a waterproof case. A typical waterproof case will occupy about nine inches (9″) of space between the rider and the hollow protrusion. The mechanism securing the motor shaft will occupy another two inches (2″). The remaining eight inches (8″) is required for the rider to have ample space to move forward while maneuvering the board without touching the battery and control assembly. 
         [0053]    This methodology can be simplified as a practical matter due to the limited range in the lengths of stand up paddle boards that are in common use today. For an adult rider, stand up paddle boards range nominally from 10 feet to 15 feet, nose to tail. Subtracting one foot from the length to account for the length of the board that does not touch the water and is not part of the waterline, results in a waterline range of 9 to 14 feet. Thirteen percent of this waterline length is 14 to 22 inches. For practical purposes the optimal location for the hollow protrusion on any stand up paddle board be from 14 to 22 inches forward of the rider&#39;s optimal operating position on the board without the motorized system installed. Empirical data suggests that using this range on a variety of boards instead of 13% of the waterline on a particular board will not result in a significant negative effect on performance. Other considerations may broaden this range further, but for general applications, this range is considered within the normal range for a motorized system with the battery and control assembly located aft of the hollow protrusion. 
         [0054]    5. The Golden Rule can be used as an alternative, or as a supplementary, to the 13% rule described above for determining the proper location of the hollow protrusion on a surf style, stand up paddle board. Surf style boards are characterized as having more rocker, i.e., convex curve across the bottom length of the board, compared to non-surf style boards. In addition, surf style boards have more rounded noses and tails, and more width across on the forward section of the board compared to non-surf style boards. 
         [0055]    For a surf style board, the hollow protrusion can be determined using the Golden Ratio method. The Golden Ratio as applied in this invention, is c/d=(c+d)/c, where “c” is the length from the tail (furthest aft) of the board to the hollow protrusion, and “d” is the length from the nose of the board (furthest forward) to the hollow protrusion.  FIG. 6  illustrates the application of the Golden Ratio method to determine the proper location of the hollow protrusion on a surf style, stand up paddle board. 
         [0056]    The following example shows how the Golden Ratio method is applied in determining the proper location of the hollow protrusion on a twelve foot long (144 inches), surf style, stand up paddle board. In accordance with the standard Golden Ratio equation below, the hollow protrusion is to be placed 89 inches forward of the tail (c=89) and 55 inches aft of the nose (d=55).
       (c+d)/c=c/d=1.618=Phi   (89+55)/89=89/55=1.618=Phi       
 
         [0059]    Once the location of the hollow protrusion is identified using the Gold Ratio, the distance to the rider&#39;s optimal operating position without the motorized system install is determined. If that distance is a nominal 17 inches plus or minus 3 inches, the Golden Rule method is considered valid. Similar to the 13% Rule method described above, the location of the hollow protrusion may be adjusted forward or aft depending on the designer&#39;s interest.