Abstract:
A watercraft includes a stern flotation compartment. The hull is carved out underneath the gunwales to admit a vertical cylindrical sleeve extending through the flotation compartment from top to bottom, and sealed top and bottom. A studded vertical mounting tube carrying an electric motor fits within a slotted cylindrical steering tube; the latter is carried on rotatable bearings affixed to the vertical cylindrical sleeve. A steering assembly is affixed to the slotted cylindrical steering tube and a guide tube fits closely within the vertical mounting tube. An electrical power cable is connected to the electric motor and a retraction assembly is affixed to the electric motor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS   
       [0001]    This application is a continuation-in-part of International Application Serial No. PCT/US2013/061830, filed Sep. 26, 2013, entitled “Shallow-Draft Watercraft Propulsion and Steering Apparatus,” which claims priority to U.S. Provisional Applications Ser. Nos. 61/705,894, filed Sep. 26, 2012, entitled “Propulsion and Steering Apparatus for Shallow-Draft Watercraft,” and 61/793,925, filed Mar. 15, 2013, entitled “Improved Propulsion and Steering Apparatus for Shallow-Draft Watercraft;” and is a nonprovisional application of, and claims priority to, U.S. Provisional Application Ser. No. 61/882,949, filed Sep. 26, 2013, entitled “Shallow-Draft Watercraft Propulsion and Steering Apparatus,” the entirety of each of which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD  
       [0002]    This disclosure relates to propulsion and steering systems for watercraft, and more specifically to retractable electric-motor mountings and hull modifications providing for steering of light watercraft such as canoes. 
       BACKGROUND  
       [0003]    Canoes, pirogues, skiffs, dinghies, and similar shallow-draft boats are often used by fishermen or recreational boaters to paddle easily through reaches of shallow water that may be too narrow for rowing or that may be clogged to varying degrees by vegetation and debris. To reduce effort and speed their rate of travel, many boaters attach outboard electric trolling motors to their craft. Electric trolling motors are lightweight, efficient, and virtually silent, and derive their power from batteries or other sources of electric power carried in the boat. 
         [0004]    Efficiency of the motor&#39;s operation is a critical factor in the utility of such electric motors, since batteries are heavy, and since other sources of electricity such as solar panels are dependent on the intensity of the light they receive. The more efficient the motor, the greater the time the boat may be operated away from its sources of charging. The greater the time between charges, the greater is the range of the boat&#39;s possible travel. 
         [0005]    Most electric trolling motors are contained in a waterproof cylindrical housing, and drive a propeller at the aft end of the housing. The propeller is used to push the motor and thus the boat through the water. For the electric trolling motor to operate most efficiently, it must be immersed in the water so that its propeller blades are also fully immersed in the water where the flow of water is least disrupted by the boat hull or other parts of the boat that lie directly ahead of the motor and propeller. Although this problem is of less concern with canoe hulls, it is more important in other less-streamlined hull designs. Mounting the motor in the undisrupted water flow confronts a second problem: the presence of debris or vegetation in the path of the boat. Often the motor or propeller can become fouled in plants or lines, or can be damaged by striking hard objects that pass beneath the boat&#39;s hull as it moves. 
         [0006]    For those boats having a flat stern panel, such as square-stern rowboats or skiffs, the outboard trolling motor is customarily clamped or otherwise mounted to the flat stern piece at the longitudinal centerline or keel line of the boat. For those boats having a pointed stern, such as canoes or pirogues, the outboard trolling motor is customarily clamped or mounted to an external part of a stern crosspiece on one side or the other of the boat. Such mountings place the motor on the side of the pointed stern. 
         [0007]    The mounting of a motor on one side of the boat stern introduces a problem with steering. Since the motor is on one side, its thrust along the longitudinal axis of the boat will tend to turn the boat toward the other side. Consequently the tendency to turn the boat must be countered by adjusting the motor orientation, the boat&#39;s rudder, or any other steering device used. Such adjustments must vary according to the motor speed and thrust, the wind, and other factors affecting the course of the boat. 
         [0008]    From the above observations, there is an evident need for a propulsion system that retains the efficiency, quiet, speed, and other desirable characteristics of the conventional art, while protecting the motor, propeller and mountings from submerged obstacles and debris, and eliminating problems associated with mounting the motor on the side of the boat. 
       BRIEF DESCRIPTION  
       [0009]    One embodiment herein provides a redesigned hull stern, propulsion system, and steering system for a canoe or other light watercraft. The craft&#39;s hull contour shows a stern carved out underneath the gunwales to admit a vertical motor shaft mount while streamlining water flow during travel. The vertical motor shaft extends through the craft&#39;s stern flotation compartment from above the compartment&#39;s top down to an electric motor below the waterline. The vertical motor shaft retracts in shallow water and provides for lateral steering of the motor. 
         [0010]    According to various aspects, there is provided a watercraft, comprising: 
         [0011]    a) gunwales; 
         [0012]    b) a stern flotation compartment; 
         [0013]    c) a hull having a modified stern hull contour carved out underneath the gunwales to admit a vertical cylindrical sleeve; 
         [0014]    d) the vertical cylindrical sleeve extending through the stern flotation compartment from the compartment&#39;s top down to the bottom of the modified stern hull contour and sealed to the compartment&#39;s top and sealed to the bottom of the modified stern hull contour; 
         [0015]    e) a slotted cylindrical steering tube having one or more vertical slots open through its sides; 
         [0016]    f) a steering assembly affixed to the slotted cylindrical steering tube; 
         [0017]    g) a vertical mounting tube fitting closely within the slotted cylindrical steering tube; 
         [0018]    h) one or more studs anchored to an exterior of the vertical mounting tube, each protruding through one of the one or more vertical slots in the slotted cylindrical steering tube; 
         [0019]    i) a guide tube fitting closely within the vertical mounting tube; 
         [0020]    j) an electric motor attached to a bottom end of the vertical mounting tube; 
         [0021]    k) an electrical power cable connected to the electric motor; 
         [0022]    l) a retraction assembly affixed to the electric motor; and 
         [0023]    m) an upper bearing and a lower bearing both affixed to the vertical cylindrical sleeve and the slotted cylindrical steering tube so as to allow free rotation of the cylindrical steering tube around its longitudinal axis. 
         [0024]    According to various aspects, there is provided a watercraft, comprising: 
         [0025]    a) a stern flotation compartment; 
         [0026]    b) a hull having a modified stern hull contour carved out underneath the gunwales; 
         [0027]    c) a vertical cylindrical sleeve extending through the stern flotation compartment from the compartment&#39;s top down to the bottom of the modified stern hull contour and sealed to the compartment&#39;s top and sealed to the bottom of the modified stern hull contour; 
         [0028]    d) a retractable shaft and a steering tube adapted to permit the retractable shaft to rotate, the retractable shaft and the steering tube arranged within the vertical cylindrical sleeve; 
         [0029]    e) an electric motor attached to the bottom end of the retractable shaft; and 
         [0030]    f) an upper bearing and a lower bearing both affixed to the vertical cylindrical sleeve so as to allow free rotation of the cylindrical steering tube around its longitudinal axis. 
         [0031]    This brief description is intended only to provide a brief overview of subject matter disclosed herein according to one or more illustrative embodiments, and does not serve as a guide to interpreting the claims or to define or limit the scope of the invention. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]      FIG. 1  shows a canoe incorporating hull and motor-related modifications. 
           [0033]      FIG. 2  provides a closer view of a craft&#39;s hull and motor-related modifications, showing greater detail. 
           [0034]      FIG. 3  is a cutaway view of mountings for a motor. 
           [0035]      FIG. 4  shows a craft&#39;s retraction and steering structures in partial cutaway. 
           [0036]      FIG. 5  illustrates a craft&#39;s helical retraction-screw embodiment for retraction and extension of the motor, in partial cutaway. 
           [0037]      FIG. 6  shows a horizontal cross-section of the vertical tubes, sleeves, and shafts of the propulsion and steering system. 
           [0038]      FIG. 7  shows a horizontal cross-section of the vertical tubes, sleeves, and shafts of the propulsion and steering system in a helical retraction-screw embodiment. 
           [0039]      FIG. 8  shows relationships and connections between the sleeve, the upper bearing, the slotted steering tube and steering gears, and the guide tube of the propulsion and steering system, in an exemplary embodiment. 
           [0040]      FIG. 9  shows a propulsion and steering system mounted on a lateral pivot. 
           [0041]      FIGS. 10 and 11  show a flexible-jet jet drive system. 
           [0042]      FIG. 12  shows a fixed-jet jet drive system. 
           [0043]      FIG. 13  shows a diagram of a jet drive. 
           [0044]      FIG. 14  shows various embodiments of compact jet drives. 
       
    
    
     DETAILED DESCRIPTION 
       [0045]    Referring to  FIGS. 1 and 2 , a depicted watercraft, e.g., a canoe, has hull  10  pointed at both ends, with a flotation compartment  12 ,  52  at bow and stern respectively, and two or three flat seats  14  on which a canoeist can face forward. Flotation compartment  12  and flat seats  14  are features of conventional canoes. 
         [0046]      FIGS. 1 and 2  show the exemplary craft&#39;s hull modifications  50 . Each flotation compartment  12 ,  52  is sealed off from the rest of the canoe by a bulkhead  54 , and may be fashioned from flotation foams made from urethane or PVC. Such flotation foam inserts are required for fiberglass hulls to prevent the craft from sinking if the hull is breached. Other options include sealed flotation compartments filled with air, lightweight plastic foam such as foamed polystyrene, air-containing objects such as table-tennis balls, or other substances and structures providing buoyancy. A canoe may or may not have a full-length keel. 
         [0047]    In embodiments using conventional electric power, batteries  16  are mounted in the watercraft for connection to cable  18  to supply power to the motor. 
         [0048]    The embodiment of craft has a hull modified to accept an electric motor. The craft may be fabricated initially to accept the electric motor or an existing craft may have its hull modified to accept an electric motor. The exemplary craft&#39;s hull modifications are most clearly shown in  FIG. 2 . In a custom-built embodiment, the hull is cut along two contours  62  extending from at or near the topmost stern point  64  in a rough ‘S’ path as shown, down to where the cuts meet a the keel or centerline  66 . The hull&#39;s integrity is restored by installing panels  72 ,  74 , and  76 , restoring any buoyancy materials, and sealing the seams of panels  72 ,  74 , and  76  to the cut hull. 
         [0049]    Panels  72 ,  74 , and  76  are shaped so as to smooth the flow of water past the hull during normal forward travel, narrowing from the conventional hull contour at  66  to a point  78  at the bottom flaring to full hull width at their top. The reshaped keel or centerline at the stern helps straighten and stabilize the course of the watercraft. 
         [0050]    Various embodiments described herein may be installed in hulls of watercraft other than canoes, with hull modification appropriate to each hull type. 
         [0051]    Two round openings  102  and  104  are drilled one above the other to admit the vertical motor shaft  202  of the craft&#39;s propulsion and steering systems, and a sleeve  106  is inserted vertically into the resulting openings and sealed to the hull at both openings  102  and  104  to restore hull integrity again. 
         [0052]    In a hull-fabrication embodiment, the craft&#39;s hull modifications are subsumed in the design of the hull, after which the hull is vacuum-formed in a single step according to the craft&#39;s designed structure. The vacuum-formed hull may or may not incorporate sleeve  106 . Buoyancy compartment  52  is formed separately, incorporating opening  102 , and sealed to the hull and sleeve  106  as is done in the custom-built embodiment. 
         [0053]    In both hull embodiments, the craft&#39;s propulsion and steering system  200  is installed and secured in sleeve  106  using any of a range of conventional fittings, longitudinal serrations, adhesives, sealants, and attachment hardware. The installed propulsion and steering system  200  is then connected to motor controls, steering controls, and retraction controls as described hereinbelow. 
         [0054]      FIGS. 3 and 4  show construction and design of an exemplary craft&#39;s propulsion and steering system. As shown in  FIG. 3  in a cutaway view, motor  202  with propeller  204  is attached to a vertical retraction arm or cable  206 . In a mounting-tube enclosed embodiment, vertical retraction arm or cable  206  and electrical power line  18  are then threaded through vertical mounting tube  208 . The result is that the control of power and retraction of motor  202  and propeller  204  may then be accomplished remotely. 
         [0055]    Vertical mounting tube  208  is then fitted around guide tube  210 , and tubes  208  and  210  are in turn fitted into slotted steering tube  212  as shown in  FIG. 4 . Vertical mounting tube  208  is then secured to slotted steering tube  212  by a stud  214  that protrudes outward from vertical mounting tube  208  through slot  216  in slotted steering tube  212  as shown in  FIG. 4 , thereby preventing vertical mounting tube  208  from rotating independently of slotted steering tube  212  while allowing said tube  212  to move vertically throughout the length of slot  216  to retract or extend the motor&#39;s position with respect to the watercraft. 
         [0056]    Slotted steering tube  212 , vertical mounting tube  208 , and guide tube  210  comprise vertical motor shaft  202 . 
         [0057]    The present embodiment separates its steering and retraction functions as follows. Steering is done by turning the propulsion and steering system  200  of motor  202 , vertical mounting tube  208 , guide tube  210 , and slotted steering tube  212 , using gears  226  or (as shown in  FIG. 2 ) a pulley  228 . Gears  226  or pulley  228  serve to rotate said entire assembly around its vertical axis within sleeve  106 . Bearings  222  and  224  provide both stabilization and ease of rotation of said propulsion and steering system  200 . More details of bearing  222  and gears  226  are described hereinbelow. 
         [0058]    Retraction is done by applying upward retracting force to motor  202  via vertical retraction arm or cable  206 . In a retraction-arm embodiment, extension is performed by applying downward pressure at the top of arm  206  or by allowing gravity to lower motor  202 . In a retraction-cable embodiment, extension is performed by releasing tension at the top end of cable  206 , letting gravity lower motor  202 . 
         [0059]    In a retraction-screw embodiment, retraction and extension of motor  202  are performed using an additional rotating sleeve  218  as shown in  FIG. 5 . Rotating sleeve  218  is fabricated with one or more helical grooves  220  on its inner surface. To incorporate sleeve  218 , slotted steering tube  212  in the retraction-screw embodiment is fabricated to provide added space between its outer surface and the inner surface of vertical motor shaft  106 , each stud  214  is lengthened so as to protrude into a corresponding helical groove of rotating sleeve  218 . 
         [0060]    Rotating sleeve  218  is installed concentrically between vertical motor shaft  106  and slotted steering tube  212  so that rotation of sleeve  218  around its vertical axis causes stud  214  to move up or down depending on the direction of rotation. Stud  214  cannot move horizontally due to the restriction imposed by slot  216  of slotted steering tube  212 , and therefore the effect is that the entire assembly of motor  202  is retracted or extended as in above-described retraction embodiments. 
         [0061]    In said retraction-screw embodiment, retraction and extension are driven by gear system  232 , separate from gear system  226  or pulley system  228  used to steer the watercraft. 
         [0062]    For horizontal cross-sections of the vertical tubes, sleeves, and shafts of propulsion and steering system  200  at the level of stud  214 , see  FIGS. 6 and 7 . In order from outermost to innermost for the retraction-cable and retraction-arm embodiments,  FIG. 6  shows sleeve  106 , slotted steering tube  212 ,vertical mounting tube  208 , and guide tube  210 . Stud  214  is also shown protruding from mounting tube  208  into slot  216  in slotted steering tube  212 . 
         [0063]    Likewise for the retraction-screw embodiment,  FIG. 7  shows sleeve  106 , rotating sleeve  218 , slotted steering tube  212 , vertical mounting tube  208 , and guide tube  210 . Stud  214  is also shown protruding from mounting tube  208  through slot  216  in slotted steering tube  212  into groove  220  in rotating sleeve  218 . 
         [0064]    For the relationships and connections between sleeve  106 , bearing  222 , slotted steering tube  212 , gears  226 , and guide tube  210 , see  FIG. 8  showing two views of said components. The fixed portion  222   a  of bearing  222  is anchored to sleeve  106  which is stationary with respect to the boat hull. In a molded hull embodiment, the fixed portion  222   a  of bearing  222  is anchored directly to the hull. 
         [0065]    The rotating portion  222   b  of bearing  222  is anchored on its inner surface to the outer surface of slotted steering tube  212 . 
         [0066]    Direct rotation gear  226   a  of gears  226  is anchored to the top surface of slotted steering tube  212 . Driving gear  226   b  of gears  226  meshes with direct rotation gear  226   a , which provides steering force to propulsion and steering system  200 . 
         [0067]    The inner opening of gear  226   a  is sized so as to fit snugly to the outer surface of guide tube  210 , thereby adding stability to the rotating components of propulsion and steering system  200 . 
         [0068]    Refer to  FIG. 1  to see connection of electrical cable  18  to speed controls  20 , and to  FIG. 2  to see a pulley connection of slotted steering tube  212  to external pulley  228  for steering. 
         [0069]    For embodiments providing improved distribution of steering forces, slotted steering tube  212  has two or more vertical slots  216 , each corresponding to a separate stud  214 . 
         [0070]    For embodiments providing improved range of retraction and extension, vertical mounting tube  208  incorporates telescoping sections, of which the largest at the top serves as vertical mounting tube  208  with stud  214 . The sections below telescope inside the largest section. 
         [0071]    In  FIGS. 3 ,  4 , and  5 , recess  56  in the craft&#39;s hull allows propeller  204  to be more closely and safely retracted upward. 
         [0072]    In  FIGS. 2 and 4 , fin or vane  205  is attached to the bottom of motor  202  in an embodiment. Vane  205  reduces the probability of damage to propeller  204  in the event of unintentional contact with hard objects or bottom of a body of water. In case of such contacts, vane  205  translates impacts into retraction force to retract the motor and propeller. In order to simplify presentation, vane  205  is not shown in  FIGS. 1 ,  3  and  5 . 
         [0073]    Fin or vane  205  also contributes to the stabilization of the course of the watercraft, and may be turned when the watercraft is being paddled to offset lateral forces resulting from paddling on one side. 
         [0074]      FIG. 9  shows a propulsion and steering system mounted on a lateral pivot. On watercraft having a geared or integrated steering system mounted atop or around and in a fixed position relative to the propulsion and steering system  200 , said steering system and the entire propulsion and steering system  200  described herein can be mounted on a lateral pivot  105  to allow system  200  to rotate in a suitable hull opening  107  either sternward or toward the bow upon encountering obstacles or debris, thereby altering the bodily pitch of motor  202  and propeller  204  as is conventionally provided for outboard motor mounts. Suitable hull opening  107  expands upon and replaces sleeve  106 , opening through buoyancy compartment  52  and sealed to the hull at both ends, as shown in  FIG. 2 . 
         [0075]      FIG. 9  shows only sternward rotation, but lengthening of suitable hull opening  107  sternward and providing adequate hull clearance forward of motor  202 . The present embodiment provides a low-cost, quiet, lightweight, easy-to-use, long-range propulsion system for users of light watercraft such as canoes, at speeds normally requiring either great manual effort or conventional propulsion systems lacking the craft&#39;s advantages. 
         [0076]      FIG. 10  shows a flexible-jet jet drive embodiment having a jet drive  301 , a flexible section  311  for redirecting the output jet, and an output jet  321 . 
         [0077]      FIG. 11  shows a detailed diagram view of jet drive embodiment  301 , with water intake opening  303 , electric jet pump drive unit  305 , flexible steering and lift passage  311 , and movable jet discharge tube  321 .  FIG. 11  further shows steering shaft and mechanism  412  for lateral redirection of the output jet, and raising and lowering shaft and mechanism  408  for vertical redirection of the output jet. 
         [0078]      FIG. 12  shows a fixed-jet jet drive embodiment having a jet drive  351  ( FIG. 13 ) similar to the jet pump drive unit  305  and flexible section  311  shown in  FIG. 10 . The flexible section  311  redirects the output jet, and an output jet  321 .  FIG. 12  further shows rudder  451  for lateral redirection of the output jet. 
         [0079]      FIG. 13  shows a detailed diagram view of jet drive embodiment  351 , with water intake opening  303 , electric jet pump drive unit  305 , and movable jet discharge tube  321 . In an additional feature of embodiment  351 , horizontal vanes may be incorporated on rudder  451 , and in combination with the tilting feature shown in  FIG. 9 , may serve to redirect the output jet upward or downward. 
         [0080]      FIG. 14  shows a compact jet drive embodiment developed through four stages of design change from jet drive  301  producing a more compact jet drive  391 . Compact jet drive  391  may be substituted in all embodiments having electric motor  202  and propeller  204  for said electric motor and propeller, thereby combining the advantages of the jet drive with the steering and raising and lowering features of said embodiments.