Patent Publication Number: US-10780964-B1

Title: Method and apparatus for propulsion of kayaks and other watercraft

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     Priority of U.S. provisional Patent Application Ser. No. 62/752,440, filed Oct. 30, 2018, incorporated herein by reference, is hereby claimed 
    
    
     STATEMENTS AS TO THE RIGHTS TO THE INVENTION MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     None 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention pertains to a method and apparatus for propulsion of kayaks and other personal watercraft (such as, for example, catamarans). More particularly, the present invention pertains to a method and apparatus for propulsion of watercraft using human power. More particularly still, the present invention pertains to a method and apparatus for propulsion of a watercraft using power generated by the legs of a user and/or operator of said watercraft. 
     2. Brief Description of the Related Art 
     Typically, conventional kayaks and other non-motorized personal watercraft require a user to row with a paddle or oar in order to provide propulsion force through surrounding water. Such rowing frequently requires significant upper body strength and can be physically demanding. Further, rowing is generally inefficient; in many situations, the amount of propulsion force generated by the rowing is relatively low compared to the energy that must be expended by a rider/user. 
     Certain conventional kayaks and other non-motorized personal watercraft include propulsion systems that are powered by the legs of a rider or passenger. Although such leg-powered drive systems can often generate greater propulsion force than conventional rowing, they can also be inefficient; such existing leg-powered propulsion systems provide relatively small drive force compared to the power input expended by said user. Further, such conventional leg-powered propulsion systems often utilize relatively large flipper-like protrusions or appendages that extend below the hull of the vessel. Such systems typically require a predetermined minimum water depth and, as a result, are not functional and cannot be used in all water bodies (especially relatively shallow water depths). Additionally, such protrusions or appendages can inadvertently contact water bottoms or other underwater obstructions, thereby reducing the effectiveness of the propulsion system and/or damaging the vessel or such protrusions. 
     Thus, there is a need for an efficient user-powered propulsion system that provides significant propulsion or drive force to a kayak or other non-motorized personal watercraft or other vessel. The propulsion system should be more efficient than conventional leg-powered watercraft drive systems. Further, the propulsion system should not require the use of flipper-like appendages that extend or protrude a significant distance below a hull of a vessel. 
     SUMMARY OF THE INVENTION 
     In a preferred embodiment, the present invention comprises a propulsion assembly for non-motorized personal watercraft including, without limitation, boats, kayaks, catamarans and/or other floating vessels. It is to be understood that the terms “vessel” or “watercraft” as used herein generally refer to all of the foregoing, are illustrative only, and are not intended to be limiting or restrictive in any way. The propulsion assembly of the present invention can be incorporated into a new vessel as part of the manufacturing process, or it can be installed or “retrofit” to an existing vessel as an added component. 
     In a preferred embodiment, the propulsion assembly of the present invention comprises at least one fluid propulsion chamber operationally attached or mounted to a vessel. Said at least one fluid propulsion chamber generally comprises an outer housing and an inner sleeve; said inner sleeve and said outer housing are slidably disposed relative to one another. Each of said at least one fluid propulsion chambers further includes at least one water intake vent or aperture, and at least one outlet nozzle or jet. 
     Pedal assemblies are moveably disposed within elongated slots or apertures; said elongated slots or apertures are beneficially positioned on a vessel and extend through at least one surface of said vessel. In a preferred embodiment, said pedals (and related slots) are positioned in such a manner so that they can be conveniently and comfortably contacted by the feet (and, more specifically, the soles thereof) of a user, while also permitting space or clearance for said user to bend or extend his/her legs. 
     A linkage assembly operationally connects said pedals to said at least one fluid propulsion chamber. Force imparted on said pedals (such as by the legs/feet of a user) is transferred to said fluid propulsion chambers by said linkage assembly. In a preferred assembly, said linkage assembly comprises a cable and pulley system; however, it is to be observed that other known linkage means can be employed without departing from the scope of the present invention. 
     In operation, a user can selectively impart force on said moveable pedals. Said force is transferred from said pedals to said at least one fluid propulsion chamber, thereby causing the outer housing and inner sleeve of each of said at least one fluid propulsion chambers to slidably move and interact relative to one another. As a fluid propulsion chamber extends (that is, as an inner sleeve moves outward relative to an outer housing), the inner volume of said fluid propulsion chamber increases, and water is drawn into a water intake vent or aperture of said fluid propulsion chamber. Conversely, as fluid propulsion chamber retracts or collapses (that is, as an inner sleeve moves inward relative to an outer housing), the inner volume of said fluid propulsion chamber decreases, and water is expelled or forced out of said at least one outlet nozzle or jet of said fluid propulsion chamber. 
     Water expelled from an outlet nozzle or jet of a fluid propulsion chamber creates positive thrust. Typically, said at least one fluid propulsion chamber is mounted or oriented so that each outlet nozzle or jet faces the rear of the vessel. As a result, the positive thrust created by functioning of the at least one fluid propulsion chamber will have the effect of propelling the vessel forward (that is, the opposite direction that the outlet nozzle(s) face). In a preferred embodiment, a diverter system can be selectively engaged to redirect flow from said outlet nozzle or jet in a different direction, thereby allowing positive thrust to move said vessel in a backward or “reverse” direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing summary, as well as any detailed description of the preferred embodiments, is better understood when read in conjunction with the drawings and figures contained herein. For the purpose of illustrating the invention, the drawings and figures show certain preferred embodiments. It is understood, however, that the invention is not limited to the specific methods and devices disclosed in such drawings or figures. 
         FIG. 1  depicts an overhead perspective view of the propulsion assembly of the present invention installed on a conventional watercraft. 
         FIG. 2  depicts a bottom perspective view of the propulsion assembly of the present invention installed on a conventional watercraft. 
         FIG. 3  depicts a rear view of the propulsion assembly of the present invention installed on a conventional watercraft. 
         FIG. 4  depicts a perspective view of first end of a fluid propulsion chamber of the present invention. 
         FIG. 5  depicts a perspective view of a second end of a fluid propulsion chamber of the present invention. 
         FIG. 6A  depicts a side sectional view of the propulsion assembly of the present invention along line  6 - 6  of  FIG. 3  in a first position. 
         FIG. 6B  depicts a side sectional view of the propulsion assembly of the present invention along line  6 - 6  of  FIG. 3  in a second position. 
         FIG. 7A  depicts a side sectional view of the propulsion assembly of the present invention along line  7 - 7  of  FIG. 3  in a first position. 
         FIG. 7B  depicts a side sectional view of the propulsion assembly of the present invention along line  7 - 7  of  FIG. 3  in a second position. 
         FIG. 8A  depicts an overhead view of the drive assembly of the propulsion assembly of the present invention in a first position. 
         FIG. 8B  depicts an overhead view of the drive assembly of the propulsion assembly of the present invention in a second position. 
         FIG. 9  depicts a detailed view of the highlighted area depicted in  FIG. 6A . 
         FIG. 10  depicts a detailed view of the highlighted area depicted in  FIG. 6B . 
         FIG. 11  depicts a detailed view of the highlighted area depicted in  FIG. 7A . 
         FIG. 12  depicts a detailed view of the highlighted area depicted in  FIG. 7B . 
         FIG. 13  depicts the view depicted in  FIG. 9 , with a fluid flow diverter engaged. 
         FIG. 14  depicts a rear perspective view of the propulsion assembly of the present invention installed on a conventional watercraft, with fluid flow diverters engaged. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     In a preferred embodiment, the present invention comprises a propulsion assembly for non-motorized personal watercraft including, without limitation, boats, kayaks, catamarans and/or other floating vessels. As used herein, the terms “watercraft” and “vessel” generally refer to virtually any personal watercraft and are not intended to be limiting or restrictive in any way. 
       FIG. 1  depicts an overhead perspective view of vessel propulsion assembly  100  of the present invention installed on a conventional watercraft  200 . Propulsion assembly  100  of the present invention is depicted, for illustration purposes, on catamaran watercraft  200  having dual, substantially parallel hulls  210 . Each of said hulls  210  has a bow (forward) end  211 , and a stern (rear) end  212 . Watercraft  200  is also equipped with deck  220 ; in the embodiment depicted in  FIG. 1 , said deck  220  generally comprises a planar member (having a substantially flat upper surface) positioned between said dual hulls  210 . Said watercraft  200  also has steering rudder  250  that is pivotally attached to said watercraft  200 . User seat  230  is disposed on the upper surface of deck  220  and generally faces bow ends  211  of hulls  210 . 
     Elongated slots or apertures  221  and  222  beneficially extend through deck  220  of watercraft  200 . In a preferred embodiment, said elongated slots  221  and  222  are arranged in substantially parallel orientation relative to each other (and to substantially parallel hulls  210 ). Further, in a preferred embodiment, said elongated slots  221  and  222  are generally positioned between seat  230  and stern end  211  of said hulls  210 . 
     Pedal  11  is slidably disposed within elongated slot  221 , while pedal  12  is slidably disposed within elongated slot  222 ; said pedals  11  and  12  can move back-and-forth along a linear path within said elongated slots  211  and  222 , respectively. Pedals  11  and  12  (as well as slots  221  and  222 ) are also positioned so that they can be conveniently and comfortably contacted by the feet (and, more specifically, the soles thereof) of a person seated within seat  230 , while also permitting space or clearance for said person to bend, flex or extend his/her legs while positioned within seat  230 . 
     Propulsion assembly  100  of the present invention comprises at least one fluid propulsion chamber operationally attached or mounted to vessel  200 . As depicted in  FIG. 1 , in a preferred embodiment, said at least one propulsion assembly  100  comprises two tandem propulsion chambers  40  and  50  arranged in side-by-side orientation below deck  220 . Further, as depicted in  FIG. 1 , said propulsion chamber  40  has outlet jet nozzle  44 , while propulsion chamber  50  has outlet jet nozzle  54 ; said outlet jet nozzles  44  and  54  are also arranged in side-by-side orientation. As depicted in  FIG. 1 , said outlet jet nozzles  44  and  54  are generally oriented in the direction of the stern of vessel  200  (and generally away from the bow of said vessel  200 ). Notwithstanding the foregoing, it is to be observed that said outlet nozzles  44  and  54  can be arranged in other orientations without departing from the scope of the present invention. 
       FIG. 2  depicts a bottom perspective view of the propulsion assembly  100  of the present invention installed on a conventional watercraft  200 . Propulsion assembly  100  of the present invention is depicted, for illustration purposes, on catamaran watercraft  200  having dual, substantially parallel hulls  210 , each with a bow (forward) end  211 , and a stern (rear) end  212 . Substantially planar deck  220  is generally positioned between said dual hulls  210 , while rudder  250  is pivotally attached to deck  220  on the stern-side of said deck  220 . 
     As depicted in  FIG. 2 , in a preferred embodiment, propulsion assembly  100  comprises two tandem propulsion chambers  40  and  50  arranged in side-by-side orientation; said tandem propulsion chambers  40  and  50  are generally mounted within housing  30  disposed on the lower surface of deck  220 . Hinged door  55  of fluid propulsion chamber  50  is depicted in the closed position; a similar hinged door, discussed in more detail herein, is also mounted in propulsion chamber  40 , but is obscured from view in  FIG. 2 . 
     Still referring to  FIG. 2 , a plurality of fluid diverter panels  60  are disposed on the underside or lower surface of deck  220  of vessel  200 . Although the specific number and orientation can vary, as depicted in  FIG. 2 , said fluid diverter panels  60  are mounted in substantially perpendicular arrangement to deck  220 . Further, said fluid diverter panels  60  are positioned in spaced relationship, and are oriented at an acute angle relative to an imaginary bisecting line extending from the bow to the stern of vessel  200 . In a preferred embodiment, fluid diverter panels  60  aligned with propulsion chamber  50  are oriented parallel to each other, while fluid diverter panels aligned with propulsion chamber  40  are oriented parallel to each other. 
       FIG. 3  depicts a rear view of propulsion assembly  100  of the present invention installed on a conventional watercraft  200 . Propulsion assembly  100  of the present invention is installed on catamaran watercraft  200  having dual, substantially parallel hulls  210 , each hull  210  having a stern (rear) end  212 . Deck  220  is generally positioned between said dual hulls  210 , steering rudder  250  is hingedly attached to deck  220  using hinge assembly  251 ; the side-to-side orientation of said steering rudder  250  can be controlled using conventional steering linkage member  252 . User seat  230  is disposed on the upper surface of deck  220  and generally faces away from stern ends  212  of tandem hulls  210 . 
     Propulsion assembly  100  of the present invention comprises two tandem propulsion chambers  40  and  50  installed within propulsion chamber housing  30 , and arranged in side-by-side orientation. Propulsion chamber housing  30  is disposed along the lower surface or underside of deck  220 . Said propulsion chamber housing  30  can be beneficially formed during manufacture of vessel  200 , or “retrofit” to attach to an existing vessel  200 . Propulsion chamber  40  has outlet jet nozzle  44 , while propulsion chamber  50  has outlet jet nozzle  54 ; said outlet jet nozzles  44  and  54  are beneficially arranged in side-by-side orientation, and generally face toward the stern of vessel  200 . 
     As depicted in  FIG. 3 , the lowest point of watercraft propulsion assembly  100  (including, without limitation, propulsion chamber housing  30 ) does not extend below the lowest surface of hulls  210 . As such, watercraft  200  can have an extremely shallow draft, thereby allowing vessel  200  equipped with propulsion assembly  100  to access relatively shallow water and, further, preventing undesired contact of said propulsion assembly  100  with a water bottom or other underwater obstruction(s). 
       FIG. 4  depicts a perspective view of first end of a fluid propulsion chamber  40  of the present invention, while  FIG. 5  depicts a perspective view of a second end of said fluid propulsion chamber  40 . Fluid propulsion chamber  40  generally comprises an outer sleeve  42 , and an inner sleeve  41 , that are moveable relative to each other. Said inner sleeve  41  is slidably disposed within said outer sleeve  42 , while said outer sleeve  42  is slidably disposed around at least a portion of the outer surface of said inner sleeve  41 . Referring to  FIG. 4 , outer sleeve  42  of fluid propulsion chamber  40  further comprises at least one water intake vent or aperture which can be selectively blocked or obstructed by hinged door  45  (shown in the closed position in  FIG. 4 ). Referring to  FIG. 5 , inner sleeve  41  further comprises outlet jet nozzle  44 . 
     In a preferred embodiment, fluid propulsion chamber  40  (including, without limitation, outer sleeve  42  and inner sleeve  41 ) can be constructed from many different materials having desirable strength and weight characteristics including, without limitation, aluminum, PVC plastic, ABS plastic, extruded plastic, or rotomolded or thermo-formed polyethylene. In a preferred embodiment, said inner sleeve  41  and outer sleeve  42  can each have an approximate length of approximately two feet (24 inches). Notwithstanding anything to the contrary contained herein, material selection and dimensions disclosed herein are illustrative only, and must not be construed as limiting in any way. 
     Further, in a preferred embodiment, outer dimensions of inner sleeve  41  are slightly smaller than the dimensions of the inner chamber formed by outer sleeve  42 ; as a result, inner sleeve  41  is capable of extending and retracting within the inner chamber of said outer sleeve  42  along the central longitudinal axes of said inner and outer sleeves. At least one O-ring or other dynamic elastomeric seal member can be disposed at the interface between inner sleeve  41  and outer sleeve  42  (that is, on the outer surface of inner sleeve  41  and/or the inner surface of outer sleeve  42 ) to create a fluid pressure seal, while also promoting smoother sliding motion between inner sleeve  41  and outer sleeve  42 . 
     Still referring to  FIG. 4 , a door or flap  45  is hingedly disposed at the distal end of outer sleeve  42  of fluid propulsion chamber  40 . (Similarly, a door or flap  55  is also hingedly disposed at the distal end of outer sleeve  52  of fluid propulsion chamber  50 , as shown in  FIG. 3 ). Said door  45  hinges or swings inwardly within outer sleeve  42  of fluid propulsion chamber  40 . 
     Similarly, although not depicted in  FIGS. 4 and 5 , it is to be observed that fluid propulsion chamber  50  is substantially identical to said fluid propulsion chamber  40 . Namely, a fluid propulsion chamber  50  generally comprises an outer sleeve  52 , and an inner sleeve  51  that are moveable relative to each other. Said inner sleeve  51  is slidably disposed within said outer sleeve  52 , while said outer sleeve  52  is slidably disposed around the outer surface of said inner sleeve  51 . Said outer sleeve  52  of fluid propulsion chamber  50  further comprises at least one water intake vent or aperture which can be selectively blocked or obstructed by hinged door  55 . Inner sleeve  51  further comprises an outlet jet nozzle  54 . 
     In a preferred embodiment, fluid propulsion chamber  50  (including, without limitation, outer sleeve  52  and inner sleeve  51 ) can be constructed from many different materials having desirable strength and weight characteristics including, without limitation, aluminum, PVC plastic, ABS plastic, extruded plastic, or rotomolded or thermo-formed polyethylene. In a preferred embodiment, said inner sleeve  51  and outer sleeve  52  can each have an approximate length of approximately two feet (24 inches). Notwithstanding anything to the contrary contained herein, material selection and dimensions disclosed herein are illustrative only, and must not be construed as limiting in any way. 
     Further, as with fluid propulsion chamber  40 , outer dimensions of inner sleeve  51  are slightly smaller than the dimensions of the inner chamber formed by outer sleeve  52 ; inner sleeve  51  is capable of extending and retracting within the inner chamber of said outer sleeve  52  along the central longitudinal axes of said inner and outer sleeves  51  and  52 . At least one O-ring or other dynamic elastomeric seal member can be disposed at the interface between inner sleeve  51  and outer sleeve  52  (that is, on the outer surface of inner sleeve  51  and/or the inner surface of outer sleeve  52 ) to create a fluid pressure seal, while also promoting smoother sliding motion between said inner sleeve  51  and outer sleeve  52 . 
       FIG. 6A  depicts a side sectional view of propulsion assembly of the present invention along line  6 - 6  of  FIG. 3  in a first position, while  FIG. 6B  depicts a side sectional view of said propulsion assembly along line  6 - 6  of  FIG. 3  in a second position. Catamaran watercraft  200  has hull  210  and deck  220 . User seat  230  is disposed on the upper surface of deck  220  and generally faces forward (toward bow end  211  of hulls  210 , depicted in  FIG. 3 ). Elongated slot  221  extends through deck  220  in substantially parallel orientation to the longitudinal axis of hull  210 . Pedal  11  is slidably disposed within elongated slot  221 ; said pedal  11  can move linearly within said elongated slot  221 . Pedal  11  (and slot  221 ) are positioned so that pedal  11  can be conveniently and comfortably contacted by a left foot of a person positioned within seat  230 , while also permitting space or clearance for said person to bend, flex and/or extend his/her legs while remaining in said seat  230 . 
     Propulsion assembly  100  of the present invention further comprises at least one fluid propulsion chamber  40  operationally attached or mounted to said vessel  200 . Propulsion chamber  40  is mounted within housing  30  disposed on the lower surface of deck  220 . Hinged door  45  of fluid propulsion chamber is depicted in the closed position in  FIG. 6A , while said hinged door  45  is depicted in the open position in  FIG. 6B . Fluid diverter panel  60  is disposed on the underside or lower surface of deck  220  of vessel  200 , and is generally aligned with the intake or inlet of said fluid propulsion chamber  200 . 
     A linkage assembly operationally connects pedal  11  to fluid propulsion chamber  40  (and, more specifically, outer sleeve  42  of said fluid propulsion chamber  40 ). Force imparted on said pedal  11  (such as by the legs/feet of a user) is transferred to said fluid propulsion chamber  40  (and, more specifically, outer sleeve  42  of said fluid propulsion chamber  40 ) by said linkage assembly. In a preferred embodiment, said linkage assembly comprises cable  71  having first end  71   a  and second end  71   b ; first end  71   a  is operationally attached to pedal  11 , while second end  71   b  is attached to outer sleeve  42  of fluid propulsion chamber  40 . 
     As depicted in  FIGS. 6A and 6B , cable  71  extends around pulleys  72  and  73  disposed in a chamber or space  225  formed within deck member  221  of watercraft  200 . However, it is to be observed that other known linkage means can be employed without departing from the scope of the present invention. In the first position depicted in  FIG. 6A , pedal  11  is positioned at or near the end of elongated slot  221  nearest to seat  230 . In the second position depicted in  FIG. 6B , pedal  11  is positioned at or near the opposite end of elongated slot  221 , farthest away from seat  230 . 
       FIG. 7A  depicts a side sectional view of the propulsion assembly of the present invention along line  7 - 7  of  FIG. 3  in a first position, while  FIG. 7B  depicts a side sectional view of said propulsion assembly along line  7 - 7  of  FIG. 3  in a second position. As in  FIGS. 6A and 6B , catamaran watercraft  200  has hull  210  and deck  220 . User seat  230  is disposed on the upper surface of deck  220  and generally faces forward (toward bow end  211  of hulls  210 , depicted in  FIG. 3 ). 
     Elongated slot  222  extends through deck  220  in substantially parallel orientation to hull  210 . Pedal  12  is slidably disposed within elongated slot  222 ; said pedal  12  can move within said elongated slot  222  along the longitudinal axis of said slot  222 . Pedal  12  (and slot  222 ) are positioned so that pedal  12  can be conveniently and comfortably contacted by a foot of a person seated within seat  230 , while also permitting space or clearance for said person to bend, flex and/or extend his/her legs. 
     The propulsion assembly of the present invention comprises at least one fluid propulsion chamber operationally attached or mounted to a vessel. Propulsion chamber  50  is mounted within housing  30  disposed on the lower surface of deck  220 . Hinged door  55  of fluid propulsion chamber  50  is depicted in the open position in  FIG. 7A , and the closed position in  FIG. 7B . Fluid diverter panel  60  is disposed on the below lower surface of deck  220  of vessel  200 , and is generally aligned with fluid propulsion chamber  50 . 
     A linkage assembly operationally connects pedal  12  to fluid propulsion chamber  50  (and, more specifically, outer sleeve  52  thereof). Force imparted on said pedal  12  (such as by the legs/feet of a user) is transferred to said outer sleeve  53  of fluid propulsion chamber  50  by said linkage assembly. In a preferred embodiment, said linkage assembly comprises cable  81  having first end  81   a  and second end  81   b ; first end  81   a  is operationally attached to pedal  12 , while second end  81   b  is attached to outer sleeve  52  of fluid propulsion chamber  50 . 
     As depicted in  FIGS. 7A and 7B , cable  81  extends around pulleys  82  and  83  disposed in an internal chamber or space  225  formed within deck member  221  of watercraft  200 . However, it is to be observed that other known linkage means can be employed without departing from the scope of the present invention. In the first position depicted in  FIG. 7A , pedal  12  is positioned at or near the end of elongated slot  222  nearest to seat  230 . In the second position depicted in  FIG. 7B , pedal  12  is positioned at or near the opposite end of elongated slot  222 ; that is, farthest away from seat  230 . 
       FIG. 8A  depicts an overhead view of the drive assembly of the propulsion assembly of the present invention in a first position—that is, the same position depicted in  FIGS. 6A and 7A .  FIG. 8B  depicts an overhead view of the drive assembly of the propulsion assembly of the present invention in a second position—that is, the same position depicted in  FIGS. 6B and 7B . Cables  71  and  81 , and associated pulleys, provide the direction of the motion; for example, pushing of a (right) pedal  12  causes retraction or collapsing of a left fluid propulsion chamber  40 , while pushing of a (left) pedal  11  causes retraction or collapsing of a right fluid propulsion chamber  50 . In a preferred embodiment, said pedals  11  and  12  each have a pedal stroke ranging from six to fourteen inches depending on the operator; however, said pedal strokes can be adjusted depending on user preferences. 
     As noted above, a linkage assembly operationally connects pedal  11  to fluid propulsion chamber  40 . Force imparted on said pedal  11  (such as pushing by the legs/feet of a user) is transferred to said fluid propulsion chamber  40  by said linkage assembly. In a preferred embodiment, said linkage assembly comprises cable  71  having first end  71   a  and second end  71   b ; first end  71   a  is operationally attached to pedal  11 , while second end  71   b  is attached to fluid propulsion chamber  40 . 
     Similarly, said linkage assembly operationally connects pedal  12  to fluid propulsion chamber  50 . Force imparted on said pedal  12  (such as pushing by the legs/feet of a user) is transferred to said fluid propulsion chamber  50  by said linkage assembly. In a preferred embodiment, said linkage assembly comprises cable  81  having first end  81   a  and second end  81   b ; first end  81   a  is operationally attached to pedal  12 , while second end  81   b  is attached to fluid propulsion chamber  50 . 
       FIG. 9  depicts a detailed view of the highlighted area depicted in  FIG. 6A , while  FIG. 10  depicts a detailed view of the highlighted area depicted in  FIG. 6B . Cable  71  extends around pulleys  72  and  73  disposed in a chamber or space  225  formed within deck member  221  of watercraft  200 . In the first position depicted in  FIG. 9 , it is to be understood that pedal  11  (not visible in  FIG. 9 ) is positioned at or near the end of elongated slot  221  nearest to seat  230 . In the second position depicted in  FIG. 10 , it is to be understood that said pedal  11  (not visible in  FIG. 10 ) is positioned at or near the opposite end of elongated slot  221 , farthest away from seat  230 . 
       FIG. 11  depicts a detailed view of the highlighted area depicted in  FIG. 7A , while  FIG. 12  depicts a detailed view of the highlighted area depicted in  FIG. 7B . Cable  81  extends around pulleys  82  and  83  disposed in an internal chamber or space  225  formed within deck member  221  of watercraft  200 . In the first position depicted in  FIG. 11 , it is to be understood that pedal  12  (not visible in  FIG. 11 ) is positioned at or near the end of elongated slot  222  nearest to seat  230 . In the second position depicted in  FIG. 12 , it is to be understood that pedal  12  (not visible in  FIG. 12 ) is positioned at or near the opposite end of elongated slot  222 ; that is, farthest away from seat  230 . 
     The forward or stern end of outer sleeve  42  has a hinged door or flap  45  to allow for water intake on a forward stroke; said flapper door  45  is hinged at the top and can swing inwardly as fluid enters said outer sleeve  42 . Similarly, the forward or stern end of outer sleeve  52  also has a hinged door or flap  55  to allow for water intake on a forward stroke; said flapper door  55  is hinged at the top and can swing inwardly as fluid enters said outer sleeve  52 . Each flapper door  45  and  55  opens on a forward stroke to allow the respective propulsion assembly to fill with water. 
     However, on a backstroke, said flapper door  45  drops down and closes to form a fluid pressure seal against outer sleeve  42  within fluid propulsion chamber  40 . Similarly, on a backstroke, flapper door  55  drops down and closes to form a fluid pressure seal against outer sleeve  52  within fluid propulsion chamber  50 . In a preferred embodiment, each of said outer sleeves  42  and  52  further comprises a lip to engage against and prevent said hinged door flaps  45  and  55 , respectively, from over-swinging and extending outside of the respective outer sleeves when in the closed (lowered) position. Further, in a preferred embodiment, flapper door  45  is open when flapper door  55  is closed; conversely, flapper door  55  is open when flapper door  45  is closed. Put another way, said flapper doors  45  and  55  beneficially alternate between open (upper) and closed (lower) positions relative to each other. 
     Referring to  FIG. 10 , as fluid propulsion chamber  40  extends (that is, as outer sleeve  42  moves axially forward relative to substantially stationary inner sleeve  41 ), the inner volumetric capacity of said fluid propulsion chamber  40  (that is, the combined inner volumes of cooperating outer sleeve  42  and inner sleeve  41 ) increases, and water is drawn into said fluid propulsion chamber  40  through aperture  31  of housing  30  and open flap  45 . Similarly, referring to  FIG. 11 , as fluid propulsion chamber  50  extends (that is, as outer sleeve  52  moves axially forward relative to substantially stationary inner sleeve  51 ), the inner volumetric capacity of said fluid propulsion chamber  50  (that is, the combined inner volumes of cooperating outer sleeve  52  and inner sleeve  51 ) increases, and water is drawn into said fluid propulsion chamber  50  through aperture  31  of housing  30  and open flap  55 . 
     Referring to  FIG. 9 , as fluid propulsion chamber  40  retracts (that is, as outer sleeve  42  moves axially inward relative to substantially stationary inner sleeve  41 ), the inner volumetric capacity of said fluid propulsion chamber  40  (that is, the combined inner volumes of cooperating outer sleeve  42  and inner sleeve  41 ) decreases; with flap  45  closed, incompressible liquid is forced or expelled out jet nozzle  44 . Similarly, referring to  FIG. 12 , as fluid propulsion chamber  50  retracts (that is, as outer sleeve  52  moves axially inward relative to substantially stationary inner sleeve  51 ), the inner volumetric capacity of said fluid propulsion chamber  50  (that is, the combined inner volumes of cooperating outer sleeve  52  and inner sleeve  51 ) decreases; with flap  55  closed, incompressible liquid is forced or expelled out jet nozzle  54 . Water expelled from outlet nozzles  44  and  54  creates positive thrust which is used to propel vessel  200 ; because said outlet nozzles  44  and  54  are oriented toward the stern of vessel  200 , said thrust propels vessel  200  in a substantially forward direction. 
     In operation, a user positioned within seat  230  can selectively impart force on said moveable pedals  11  and  12 , typically in an alternating manner, using force generated by said user&#39;s legs. Said force is transferred from said pedals  11  and  12  to said fluid propulsion chambers  40  and  50 . More specifically, force acting on said pedals  11  and  12  is conveyed via linkage assemblies and transferred to outer housings  42  and  52 , thereby causing said outer housings  42  and  52  to move relative to substantially stationary inner sleeves  41  and  51 , respectively, to slidably move and interact relative to one another. In a preferred embodiment, inner bores of inner sleeves  41  and  51  can each have a tapered profile, wherein each of said inner bores is wider at one longitudinal end that at an opposite longitudinal end. 
     The bow (intake) ends of said fluid propulsion chambers  40  and  50  beneficially have debris filters/deflectors  60  separated by several inches or more and angled downward to prevent debris from building up on said deflectors. In a preferred embodiment, a first debris deflector  60  can be larger and is positioned to block or obstruct the bow end of said fluid propulsion chambers  40  and  50  and prevent solids from entering the intake openings thereof (via opening  31 ). At least one deflector  60  can be curved to encompass the sides of a secondary line of deflectors  60 ; said second line of filters can be smaller and is designed to function with respect to each fluid propulsion chamber  40  and  50 . 
     In a preferred embodiment, said fluid propulsion chambers  40  and  50  operate in alternating forward (intake) and backward (compression) strokes. Typically, said fluid propulsion chambers are mounted or oriented so that each outlet nozzle or jet faces the rear or stern of vessel  200 . As a result, positive thrust created by liquid expelled from said fluid propulsion chambers has the effect of propelling a vessel  200  forward (that is, the opposite direction that the outlet nozzle(s) face). 
       FIG. 13  depicts the view depicted in  FIG. 9 ; a fluid flow diverter  20  is engaged against an outlet nozzle of a fluid propulsion chamber.  FIG. 14  depicts a rear perspective view of the propulsion assembly of the present invention installed on a conventional watercraft, with fluid flow diverters  20  engaged. In a preferred embodiment, said fluid flow diverters  20  are pivotally attached to vessel  200 , and can be selectively engaged using a linkage system controlled by a user in seat  230  to redirect fluid flow from said outlet nozzle or jet in a different direction. In the embodiments depicted in  FIG. 13  and  FIG. 14 , fluid flow that is normally directed toward the stern of vessel  200  is redirected toward the bow of said vessel  200 , thereby allowing positive thrust to move said vessel  200  in a backward or “reverse” direction. 
     The present invention comprises a propulsion system for virtually any type of non-motorized personal watercraft including, without limitation, kayaks and/or catamarans. Said propulsion system uses water pressure that is generated by fluid propulsion chambers positioned under the vessel and powered by the legs/feet of an operator. However, because said fluid propulsion chambers do not extend below or beyond the hull(s) of a vessel or watercraft, the present invention can be used in relatively shallow water depths without said propulsion assembly inadvertently contacting a water bottom or underwater obstruction (like conventional flaps or flippers). 
     The watercraft propulsion assembly of the present assembly can be mounted on and used in connection with “homemade” or kit-constructed kayaks that are commonly made from foam board or the like. Further, the watercraft propulsion assembly of the present invention can be incorporated into a new vessel as part of the manufacturing process, or can be installed or “retrofit” to an existing vessel as an added or aftermarket component. 
     The above-described invention has a number of particular features that should preferably be employed in combination, although each is useful separately without departure from the scope of the invention. While the preferred embodiment of the present invention is shown and described herein, it will be understood that the invention may be embodied otherwise than herein specifically illustrated or described, and that certain changes in form and arrangement of parts and the specific manner of practicing the invention may be made within the underlying idea or principles of the invention.