Flapping manual propulsion system for personal watercraft

Abstract

A manual propulsion system for a watercraft includes an axle horizontally mounted below a bottom surface of the watercraft in a direction perpendicular to a centerline of the watercraft, an elongated fin rotatable around the axle, the elongated fin being oriented along the centerline of the watercraft, a location of the axle dividing the elongated fin into a forward portion in front of the axle and an aft portion behind the axle in reference to a travel direction of the watercraft, the forward portion being shorter than the aft portion, a first foot pedal linked to the forward portion of the elongated fin, a forward motion by the first foot pedal lifting the forward portion of the elongated fin, and a second foot pedal linked to the aft portion of the elongated fin, a forward motion by the second foot pedal lifting the aft portion of the elongated fin.

Description

BACKGROUND

[0001] The present disclosure relates generally to propulsion systems for personal watercrafts, and, more particularly, to a flapping manual propulsion system for personal watercrafts.

[0002] Personal watercrafts, such as canoes, kayaks and standup paddle boards, are traditionally propelled using one or more paddles manipulated by the hands and arms of a user. One disadvantage of using paddles for propulsion is that the paddles provide propulsion only part of the time. After one stroke, the user recovers the paddle above the water. Further, the user's arms are generally weaker than legs, and therefore the user's power is not fully utilized. Furthermore, the user may need to use hands to steer the watercraft or operate a fishing apparatus while the watercraft still needs to be propelled. These make the hand-powered personal watercrafts less desirable.

[0003] In an alternative approach, U.S. Pat. No. 6,022,249 to Ketterman discloses an oscillating fin propulsion that is driven by feet and legs. However, Ketterman's fins extend vertically into the water thus prone to be damaged in shallow water. Further, Ketterman's oscillating fin propulsion system employs a complex thus less efficient mechanism to convert foot pumping motion to fin oscillating.

[0004] As such, what is desired is an efficient foot-powered propulsion system for a personal watercraft.BRIEF DESCRIPTION OF THE DRAWING

[0005] FIGS. 1A and 1B are port side views of a flapping manual propulsion system according to an embodiment of the present disclosure.

[0006] FIGS. 2A and 2B are port side and front view, respectively, of a flapping manual propulsion system according to another embodiment of the present disclosure.

[0007] FIG. 3 is a port side view of a flapping manual propulsion system according to yet another embodiment of the present disclosure.

[0008] FIG. 4 is a port side view of a flapping manual propulsion system according to yet another embodiment of the present disclosure.

[0009] FIG. 5 is a block diagram illustrating a flapping manual propulsion system according to yet another embodiment of the present disclosure.

[0010] FIGS. 6A and 6B are side and cross-sectional view, respectively, of an exemplary implementation of the shafts for the flapping manual propulsion system shown in FIG. 5.

[0011] FIG. 7 is a perspective view of an exemplary fin according to embodiments of the present disclosure.

[0012] FIG. 8 is a cross-sectional view of an exemplary structure for attaching a cable to the fin according to embodiments of the present disclosure.

[0013] FIG. 9 is a cross-sectional view of an exemplary structure for attaching a cable to a pulley wheel according to embodiments of the present disclosure.

[0014] The drawings accompanying and forming part of this specification are included to depict certain aspects of the disclosure. A clearer conception of the disclosure, and of the components and operation of systems provided with the disclosure, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings, wherein like reference numbers (if they occur in more than one view) designate the same elements. The disclosure may be better understood by reference to one or more of these drawings in combination with the description presented herein.DESCRIPTION

[0015] The present disclosure relates to a flapping manual propulsion system for a personal watercraft. A preferred embodiment of the present disclosure will be described hereinafter with reference to the attached drawings.

[0016] FIGS. 1A and 1B are port side views of a flapping manual propulsion system 100 according to an embodiment of the present disclosure. Referring to FIG. 1A, the flapping manual propulsion system 100 includes a pair of elongated fins 102L and 102R, both rotatable around a first axle 105. A distance from a forward end of the left fin 102L to the first axle 105 is shorter than a distance from an aft end of the left fin 102L. Similarly, a distance from a forward end of the right fin 102R to the first axle 105 is shorter than a distance from an aft end of the right fin 102R. When either the left fin 102L or the right fin 102R rotates around the first axle 105 in a small range near the horizonal plane, a propulsive force will be generated forward like a free-style swim kick.

[0017] To drive the left fin 102L to make such flapping motion, a forward end of the left fin 102L engages an aft end of a left crank 112L. A left extension 123L extrudes from a forward end the left crank 112L. A upper end of the left extension 123L is mounted with a left foot pedal 131L through a left foot pedal axle 135L. In embodiments, the left foot pedal axle 135L is crewed into the upper end of the left extension 123L, and the left foot pedal 131L can rotate freely around the left axle 135L.

[0018] As shown in FIG. 1A, the left crank 112L has an approximately right-angle bend and is rotatable around a second axle 115 located in a vicinity of the bend. When a left foot (not shown) pushes the left pedal 131L forward, the left crank 112L will rotate around the second axle 115 with the aft end of the left crank 112L swings upward causing a clockwise rotation of the left fin 102L.

[0019] As shown in FIG. 1A, the approximately right-angle bend converts a substantially horizontal movement of the left foot pedal 131L to a substantially vertical movement of the aft end of the left crank 112L and thus the flapping motion of the left fin 102L. As the user's foot may push-and-withdraw in a slanted direction, for example 10 to 15 degrees to the horizontal plane, while the left fin 102L preferably flaps up and down symmetrically around the horizontal plane, the angle of the bend in the left crank 112L is preferably 10 to 15 degrees leaning forward from a vertical plane.

[0020] In embodiments, the left extension 123L is removably inserted in a tube formed in the left crank 112L. During transportation of the personal watercraft, the user can remove the left extension 123L along with the left foot pedal 131L to reduce the weight and profile of the personal watercraft. Such removable structure can also be applied to other implementations of the flapping manual propulsion systems depicted in FIGS. 2-5.

[0021] As shown in FIGS. 1A and 1B, a starboard side of the flapping manual propulsion system 100 is symmetrical to its port side, i.e., the right fin 102R is symmetrical to the left fin 102L; a right crank 112R also rotatable around the first axle 105 is symmetrical to the left crank 112L; a right extension 123R is symmetrical to the left extension 123L; the right foot pedal 131R is symmetrical to the left foot pedal 131L and the angle of bend of the left crank 112L is approximately the same as that of the right crank 112R. FIG. 1A illustrates a state when the left pedal 131L is pushed forward causing the left fin 102L to flap downward. FIG. 1B illustrates a state when right pedal 131R is pushed forward causing the right fin 102R to flap downward.

[0022] The starboard side and the port side of the flapping manual propulsion system 100 also operate in the same manner. As shown in FIG. 1A, a forward end of the right fin 102R engages an aft end of a right crank 112R. In an embodiment, the engagement between the right fin 102R and the right crank 112R is exemplarily achieved by inserting a pin 107R protruding from the right fin 102R into a slot 117R formed in the right crank 112R. The slot 117R is wider than the pin 107R, so that the pin 107R has room to move back and forth inside the slot 117R to accommodate swivels by both the right fin 102R and the right crank 112R while the first and second axles 105 and 115 are fixed to the personal watercraft (not shown).

[0023] As shown in FIG. 1A, a right extension 123R is extended from a forward end of the right crank 112R. An upper end of the right extension 123R is mounted with a right foot pedal 131R through a right foot pedal axle 135R. As shown in FIG. 1A, the right crank 112R has an approximately right-angle bend and is rotatable around the second axle 115 located in a vicinity of the bend. When a right foot (not shown) presses the right pedal 131R forward, the right crank 112R will rotate around the second axle 115 with the aft end of the right crank 112R swinging upward causing a clockwise rotation or flapping of the right fin 102R.

[0024] In embodiments, each of the left fin 102L and the right fin 102R are symmetrical and each has a wide horizonal surface toward the aft end, so that when flapping up and down around the first axle 105, the left fin 102L and the right fin 102R create a propulsive force forward.

[0025] As shown in FIGS. 1A and 1B, the forward end of the left crank 112L and the forward end of the right crank 112R are connected by a tension cable 142. The tension cable 142 wraps around a pulley wheel 146 which is rotatable around a pin 148. The pin 148 is mounted to the personal watercraft (not shown), thus in a fixed position in reference to the axles 105 and 115. When the forward end of the left crank 112L is pushed forward, the tension cable 142 will pull the forward end of the right crank 112R backwards, and vice versa. As a result, pushing the left foot pedal 131L will not only flap the left fin 102L downward, but also flap the right fin 102R upward. Similarly, pushing the right foot pedal 131R will not only flap the right fin 102R downward, but also flap the left fin 102L upward. Therefore, a continuous alternating foot pushing will create a continuous scissor motion by the left fin 102L and the right fin 102R.

[0026] FIGS. 2A and 2B are a port side and front view, respectively, of a flapping manual propulsion system 200 according to another embodiment of the present disclosure.

[0027] Referring to FIG. 2A, the flapping manual propulsion system 200 employs a left lifting cable 232L to connect a left pulley wheel 203L to the forward end of the left fin 102L, and a right lifting cable 232R to connect a right pulley wheel 203R to the forward end of the right fin 102R. The left pulley wheel 203L is attached to a left straight crank 241L with the left foot pedal 131L mounted to an upper end of the left straight crank 241L, so that when the user pushes the left foot pedal 131L forward with a left foot, the left pulley wheel 203L will rotate counterclockwise causing the left lifting cable 232L to lift the forward end of the left fin 102L. Similarly, the right pulley wheel 203R is attached to a right straight crank 241R with the right foot pedal 131R mounted to an upper end of the right straight crank 241R, so that when the user pushes the right foot pedal 131R forward with a right foot, the right pulley wheel 203R will rotate counterclockwise causing the right lifting cable 232R to lift the forward end of the right fin 102L.

[0028] As shown in FIG. 2A, the forward end of the left fin 102L and the forward end of the right fin 102R are connected by pulling cables 234L and 234R. The pulling cables 234L and 234R are one cable wrapped around a central pulley wheel 214. The central pulley wheel 214 is rotatable around a central axle 226 which in turn is rigidly connected, by a bracket 228, to an axle 205 for both the left pully wheel 203L and the right pully wheel 203R. When the forward end of the left fin 102L is lifted upward, the pulling cables 234L and 234R will pull the forward end of the right fin 102R downward, causing the fins 102L and 102R to perform a scissor-like flapping. Similarly, when the forward end of the right fin 102R is lifted upward, the pulling cables 234L and 234R will pull the forward end of the left fin 102R downward, causing the fins 102L and 102R to perform another scissor-like flapping.

[0029] Referring to FIG. 2B, a cross-sectional view of the bracket 228 shows that both the axle 205 and the central pulley wheel 214 are mounted to the bracket 228. As the foot pedals 131L and 131R travel in a limited range, only upper portions of the pulley wheels 203L and 203R are exemplarily circular as shown in FIGS. 2A and 2B. Lower portions of the pulley wheels 203L and 203R never come into contact with the lifting cables 234L and 234R, respectively, thus can be reduced to flat portion or entirely removed to save space and material. In case the lower portion of the pulley wheel 203L or 203R is hollow, the upper portion of the pulley wheel 203L or 203R can be exemplarily attached to a bearing (not shown) around the axle 205.

[0030] FIG. 3 is a port side view of a flapping manual propulsion system 300 according to yet another embodiment of the present disclosure. The flapping manual propulsion system 300 employs a left front lifting cable 312L and a left rear lifting cable 314L attached to the forward end and an aft point of the left fin 102L. The aft point is located on the left fin 102L aft to the first axle 105L. In embodiments, a distance from the aft point to the axle 105 is approximately equal to a distance from the forward end of the left fin 102L to the axle 105.

[0031] The term, “end” as in the “forward end” or “aft end”, as used herein, generally refers to a vicinity of an edge of an elongated member. For example, the left front lifting cable 312L is attached to a point 10 mm to the right of a forward edge of the left fin 102L. Such attachment is exemplarily considered to be at the forward end of the left fin 102L.

[0032] In embodiments, the left front lifting cable 312L and left rear lifting cable 314L are parts of one cable wrapped around the upper portion of the left pulley wheel 203L, so that a clockwise rotation of the left pully wheel 203L causes a downward flap of the aft portion of the fin 102L; and a counterclockwise rotation of the left pully wheel 203L causes an upward flap of the aft portion of the fin 102L. The term “aft portion” as used herein, generally refers to a portion of the left fin 102L to the right of the first axle 105 when view from a port side of the watercraft.

[0033] In embodiments, the port side and the starboard side of the flapping manual propulsion system 300 are symmetrical, i.e., the left fin 102L is symmetrical to the right fin 102R, the left pulley wheel 203L is symmetrical to the right pulley wheel 203R—same dimension as well as rotatable around the same axle 205; a right front lifting cable 312L is symmetrical to the right front lifting cable 312R; and a left rear lifting cable 314L is symmetrical to the right rear lifting cable 314R.

[0034] As shown in FIG. 3, the left pulley wheel 203L and the right pulley wheel 203R are connected by a cable 321 wrapped around a central horizontal pulley wheel 325. The pulley wheel 325 is situated in a horizontal plane so that the cable 321 is stretched horizontally between the left pulley wheel 203L, the central horizontal pulley wheel 325 and the right pulley wheel 203R. When the left pulley wheel 203L rotates counterclockwise in response to a push at the left foot pedal 131L, the cable 321 will pull the right pulley wheel 203R to rotate clockwise. Similarly, when the right pulley wheel 203L rotates counterclockwise in response to a push at the right foot pedal 131R, the cable 321 will pull the left pulley wheel 203L to rotate clockwise. Such reverse rotations by the left and right pulley wheels 203L and 203R causes scissor-like flapping by the fins 102L and 102R.

[0035] Although the horizontally rotatable central horizontal pully wheel 325 is depicted in FIG. 3, in other embodiments, the pully wheel 325 can be mounted at an acute angle to the horizontal plane, as long as the plane of the pully wheel 325 is approximately tangent to the circumference of the left pulley wheel 203L and the right pulley wheel 203R. The approximate tangency allows the cable 321 to stay inside a groove of the central pulley wheel 325 during the rotations of the left pulley wheel 203L and the right pulley wheel 203R.

[0036] FIG. 4 is a port side view of a flapping manual propulsion system 400 according to yet another embodiment of the present disclosure. The flapping manual propulsion system 400 employs an elongated fin 402 rotatable around the first axle 105. The elongated fin 402 is mounted below a bottom surface of the watercraft (not shown) thus submerged in the water in operation. The elongated fin 402 is oriented along a centerline of the watercraft, i.e., a long axis of the elongated fin 402 is parallel to the centerline of the watercraft.

[0037] In embodiments, a front lifting cable 412 connects a forward end of the fin 402 to the left pulley wheel 203L. When the left pulley wheel 203L rotates counterclockwise in response to a push at the left foot pedal 131L, the front lifting cable 412 will cause the fin 402 to rotate clockwise-making a downward flap. In embodiments, a rear lifting cable 417 connects an aft point of the fin 402 to the right pulley wheel 203R. The aft point of the fin 402 is exemplarily located at a point on the fin 402 to the right of the first axle 105. A distance from the aft point to the first axle 105 is proximately equal to a distance from the forward end of the fin 402 to the first axle 105. When the right pulley wheel 203R rotates counterclockwise in response to a push at the right foot pedal 131R, the rear lifting cable 417 will cause the fin 402 to rotate counterclockwise-making an upward flap. In operations, the user pushes one foot at a time while allowing the other foot to withdraw from an extended position in preparation for a next push.

[0038] As shown in FIG. 4, the left pulley wheel 203L is symmetrical to the right pulley wheel 203R; the left straight crank 123L along with the left foot pedal 131L are symmetrical to the right straight crank 123R along with the right foot pedal 131R. In embodiments, when the fin 204 is in a horizontal plane—a neutral position, a suspended portion of the front lifting cable 412 is of a same length as a suspended portion of the rear lifting cable 417, so that if the left foot pedal 131L and the right foot pedal 131R travel the same distance, the fin 402 flaps upward and downward by a same distance. In other embodiments, the neutral position slightly leans downward from the horizontal plane, so that the fin 402 flaps more distance downward than upward.

[0039] FIG. 5 is a block diagram illustrating a flapping manual propulsion system 500 according to yet another embodiment of the present disclosure. The propulsion system 500 employs two elongated fins 102L and 102R side by side and both rotatable around the first axle 105. Flapping motions of the elongated fins 102L and 102R are driven by 4 pulley wheels: 512L and 503R for the left elongated fin 102L and 514L and 505R for the right elongated fin 102R. The pulley wheels 512L and 514L are attached to and rotatable along with a first shaft 550. The pulley wheels 503R and 505R are attached to and rotatable along with a second shaft 560. The first shaft fits in a center hole and is coaxial with the second shaft.

[0040] In an embodiment, the left crank 123L is fastened to the pulley wheel 512L, thus when the left foot pedal 131L is pushed forward, both pulley wheels 512L and 514L rotate counterclockwise when viewed from a port side of the watercraft. In an embodiment, the pulley wheel 512L is linked by a cable 524L to a forward portion 541L of the left fin 102L; and the pulley wheel 514L is linked by a cable 526L to an aft portion 543R of the right fin 102R. Therefore, the push on the left foot pedal 131L forces the left fin 102L to flap downward while the right fin 102R to flap upward.

[0041] In an embodiment, the right crank 123R is fastened to the pulley wheel 505R, thus when the right foot pedal 131R is pushed forward, both pulley wheels 505R and 503R rotate counterclockwise when viewed from a port side of the watercraft. In an embodiment, the pulley wheel 503R is linked by a cable 535R to an aft portion 543L of the left fin 102L; and the pulley wheel 505R is linked by a cable 537R to a forward portion 541R of the right fin 102R. Therefore, the push on the right foot pedal 131R forces the left fin 102R to flap upward while the right fin 102R to flap downward.

[0042] In addition, a forward pushed on the left foot pedal 131L forces the left foot pedal 131R to swing backward, and vice versa, due the cables 524L, 526L, 535R and 537R being fastened between the pulley wheels 512L, 514L, 503R and 505R and the fins 102L and 102R as shown in FIG. 5.

[0043] FIGS. 6A and 6B are a side and cross-sectional view, respectively, of an exemplary implementation of the shafts 550 and 560 for the flapping manual propulsion system shown in FIG. 5. Referring to FIG. 6A, the first shaft 550 has two geared sections 612L and 612R for coupling to the pulley wheel 512L and 514L, respectively. The second shaft 560 is also geared for coupling to the pulley wheels 503R and 505R.

[0044] As shown in FIG. 6B, the second shaft 560 has a center hole for the first shaft 550 to fit in and rotate freely. An inner diameter D2 of the center hole of the second shaft 560 is larger than an outer diameter D1 of the first shaft 550, so that the first shaft 550 can be inserted in the second shaft 560.

[0045] FIG. 7 is a perspective view of an exemplary implementation of the elongated fin 402 according to embodiments of the present disclosure. The elongated fin 402 has an elongated body which becomes wider, thinner and more flexible toward an aft end. In an embodiment, a through hole 704 is formed in the elongated fin 402 in a direction perpendicular to the elongated direction and parallel to a surface of the elongated fin 402. The first axle 105 (not shown) fits in the through hole 704, so that the elongated fin 402 can rotate around the first axle 105. A location of the through hole 704 and thus the first axle 105 divides the elongated fin 402 into a forward portion 734 and an aft portion 737. In embodiments, the aft portion 737 is longer and more flexible than the forward portion 734. In operations, the elongated fin 402 is oriented along a centerline of the watercraft (not shown) with the aft portion 737 flapping up and down to propel the watercraft.

[0046] As shown in FIG. 7, there are two pins 715 and 727 in the elongated fin 402 for securing the lifting cable 417 and 412 (shown in FIG. 4), respectively, to the elongated fin 402. The left pin 715 is recessed in a left opening 712 formed on the port side of the fin 402 when mounted on the watercraft. The right pin 727 is recessed in a right opening 724 formed on the starboard side of the fin 402 when mounted on the watercraft. In an embodiment, a distance (AL) from the left pin 715 to a center line of the elongated fin 402 is approximately equal to a distance (AR) from the right pin 727 to the center line. In an embodiment, a distance (BR) from the left pin 715 to the through hole 704 is approximately equal to a distance (BF) from the right pin 727 to the through hole 704.

[0047] FIG. 8 is a cross-sectional view of an exemplary structure for attaching the lifting cable 417 to the elongated fin 402 according to embodiments of the present disclosure. The exemplary structure is provided using the left pin 715 and the left opening 712 as an example. The exemplary structure can be applied to the right pin 727 and the right opening 724 as well. As shown in FIG. 8, the left lifting cable 417 is inserted in the opening 712 from above and wraps around the left pin 715 multiple times (the cross-sectional view shows only one round). A rigid cover plate 810 is attached to the fin 402 by screws 813 and 816 covering the bottom of the left opening 712. As a result, a surface of the cover plate 810 presses hard against the left lifting cable 417 to provide fiction thereto, so that the left lifting cable 417 is securely tied to the left pin 715.

[0048] FIG. 9 is a cross-sectional view of an exemplary structure for attaching a cable to a pulley wheel according to embodiments of the present disclosure. As an example, the right pulley wheel 203R pulling the front lifting cable 412 is illustrated in FIG. 9. In embodiments, only an upper portion of the right pulley wheel 203R is circular and the lower portion of the right pulley wheel 203R is removed as the right foot pedal 131R that drives the right pulley wheel 203R travels in a small range. In embodiments, the right pulley wheel 203R can be just a curved member with a circular section to maintain a suspended portion of the lifting cable 412 substantially stationary during a rotation of the right pulley wheel 203R.

[0049] As shown in FIG. 4, one end of the front lifting cable 412 is attached to the forward portion of the elongated fin 402, the other end of the front lifting cable 412 is attached to the right pulley wheel 203R. In embodiments, the end of the front lifting cable 412 is securely fixed with a threaded screw 915 which is inserted through a hole in a stopper 931 formed in the pulley wheel 203R. The threaded screw 915 is then secured to the right pulley wheel 203R by a washer 942 and a bolt 944.

[0050] In embodiments, the various implementations depicted in FIGS. 7-9 can be applied to each of the flapping manual propulsion systems 100-500 shown in FIGS. 1-5.

[0051] Although the disclosure is illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the disclosure and within the scope and range of equivalents of the claims. Accordingly. it is appropriate that the appended claims be construed broadly and, in a manner, consistent with the scope of the disclosure, as set forth in the following claims.

Examples

Embodiment Construction

[0015]The present disclosure relates to a flapping manual propulsion system for a personal watercraft. A preferred embodiment of the present disclosure will be described hereinafter with reference to the attached drawings.

[0016]FIGS. 1A and 1B are port side views of a flapping manual propulsion system 100 according to an embodiment of the present disclosure. Referring to FIG. 1A, the flapping manual propulsion system 100 includes a pair of elongated fins 102L and 102R, both rotatable around a first axle 105. A distance from a forward end of the left fin 102L to the first axle 105 is shorter than a distance from an aft end of the left fin 102L. Similarly, a distance from a forward end of the right fin 102R to the first axle 105 is shorter than a distance from an aft end of the right fin 102R. When either the left fin 102L or the right fin 102R rotates around the first axle 105 in a small range near the horizonal plane, a propulsive force will be generated forward like a free-style sw...

BACKGROUND

[0001] The present disclosure relates generally to propulsion systems for personal watercrafts, and, more particularly, to a flapping manual propulsion system for personal watercrafts.

[0002] Personal watercrafts, such as canoes, kayaks and standup paddle boards, are traditionally propelled using one or more paddles manipulated by the hands and arms of a user. One disadvantage of using paddles for propulsion is that the paddles provide propulsion only part of the time. After one stroke, the user recovers the paddle above the water. Further, the user's arms are generally weaker than legs, and therefore the user's power is not fully utilized. Furthermore, the user may need to use hands to steer the watercraft or operate a fishing apparatus while the watercraft still needs to be propelled. These make the hand-powered personal watercrafts less desirable.

[0003] In an alternative approach, U.S. Pat. No. 6,022,249 to Ketterman discloses an oscillating fin propulsion that is driven by feet and legs. However, Ketterman's fins extend vertically into the water thus prone to be damaged in shallow water. Further, Ketterman's oscillating fin propulsion system employs a complex thus less efficient mechanism to convert foot pumping motion to fin oscillating.

[0004] As such, what is desired is an efficient foot-powered propulsion system for a personal watercraft.BRIEF DESCRIPTION OF THE DRAWING

[0005] FIGS. 1A and 1B are port side views of a flapping manual propulsion system according to an embodiment of the present disclosure.

[0006] FIGS. 2A and 2B are port side and front view, respectively, of a flapping manual propulsion system according to another embodiment of the present disclosure.

[0007] FIG. 3 is a port side view of a flapping manual propulsion system according to yet another embodiment of the present disclosure.

[0008] FIG. 4 is a port side view of a flapping manual propulsion system according to yet another embodiment of the present disclosure.

[0009] FIG. 5 is a block diagram illustrating a flapping manual propulsion system according to yet another embodiment of the present disclosure.

[0010] FIGS. 6A and 6B are side and cross-sectional view, respectively, of an exemplary implementation of the shafts for the flapping manual propulsion system shown in FIG. 5.

[0011] FIG. 7 is a perspective view of an exemplary fin according to embodiments of the present disclosure.

[0012] FIG. 8 is a cross-sectional view of an exemplary structure for attaching a cable to the fin according to embodiments of the present disclosure.

[0013] FIG. 9 is a cross-sectional view of an exemplary structure for attaching a cable to a pulley wheel according to embodiments of the present disclosure.

[0014] The drawings accompanying and forming part of this specification are included to depict certain aspects of the disclosure. A clearer conception of the disclosure, and of the components and operation of systems provided with the disclosure, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings, wherein like reference numbers (if they occur in more than one view) designate the same elements. The disclosure may be better understood by reference to one or more of these drawings in combination with the description presented herein.DESCRIPTION

[0015] The present disclosure relates to a flapping manual propulsion system for a personal watercraft. A preferred embodiment of the present disclosure will be described hereinafter with reference to the attached drawings.

[0016] FIGS. 1A and 1B are port side views of a flapping manual propulsion system 100 according to an embodiment of the present disclosure. Referring to FIG. 1A, the flapping manual propulsion system 100 includes a pair of elongated fins 102L and 102R, both rotatable around a first axle 105. A distance from a forward end of the left fin 102L to the first axle 105 is shorter than a distance from an aft end of the left fin 102L. Similarly, a distance from a forward end of the right fin 102R to the first axle 105 is shorter than a distance from an aft end of the right fin 102R. When either the left fin 102L or the right fin 102R rotates around the first axle 105 in a small range near the horizonal plane, a propulsive force will be generated forward like a free-style swim kick.

[0017] To drive the left fin 102L to make such flapping motion, a forward end of the left fin 102L engages an aft end of a left crank 112L. A left extension 123L extrudes from a forward end the left crank 112L. A upper end of the left extension 123L is mounted with a left foot pedal 131L through a left foot pedal axle 135L. In embodiments, the left foot pedal axle 135L is crewed into the upper end of the left extension 123L, and the left foot pedal 131L can rotate freely around the left axle 135L.

[0018] As shown in FIG. 1A, the left crank 112L has an approximately right-angle bend and is rotatable around a second axle 115 located in a vicinity of the bend. When a left foot (not shown) pushes the left pedal 131L forward, the left crank 112L will rotate around the second axle 115 with the aft end of the left crank 112L swings upward causing a clockwise rotation of the left fin 102L.

[0019] As shown in FIG. 1A, the approximately right-angle bend converts a substantially horizontal movement of the left foot pedal 131L to a substantially vertical movement of the aft end of the left crank 112L and thus the flapping motion of the left fin 102L. As the user's foot may push-and-withdraw in a slanted direction, for example 10 to 15 degrees to the horizontal plane, while the left fin 102L preferably flaps up and down symmetrically around the horizontal plane, the angle of the bend in the left crank 112L is preferably 10 to 15 degrees leaning forward from a vertical plane.

[0020] In embodiments, the left extension 123L is removably inserted in a tube formed in the left crank 112L. During transportation of the personal watercraft, the user can remove the left extension 123L along with the left foot pedal 131L to reduce the weight and profile of the personal watercraft. Such removable structure can also be applied to other implementations of the flapping manual propulsion systems depicted in FIGS. 2-5.

[0021] As shown in FIGS. 1A and 1B, a starboard side of the flapping manual propulsion system 100 is symmetrical to its port side, i.e., the right fin 102R is symmetrical to the left fin 102L; a right crank 112R also rotatable around the first axle 105 is symmetrical to the left crank 112L; a right extension 123R is symmetrical to the left extension 123L; the right foot pedal 131R is symmetrical to the left foot pedal 131L and the angle of bend of the left crank 112L is approximately the same as that of the right crank 112R. FIG. 1A illustrates a state when the left pedal 131L is pushed forward causing the left fin 102L to flap downward. FIG. 1B illustrates a state when right pedal 131R is pushed forward causing the right fin 102R to flap downward.

[0022] The starboard side and the port side of the flapping manual propulsion system 100 also operate in the same manner. As shown in FIG. 1A, a forward end of the right fin 102R engages an aft end of a right crank 112R. In an embodiment, the engagement between the right fin 102R and the right crank 112R is exemplarily achieved by inserting a pin 107R protruding from the right fin 102R into a slot 117R formed in the right crank 112R. The slot 117R is wider than the pin 107R, so that the pin 107R has room to move back and forth inside the slot 117R to accommodate swivels by both the right fin 102R and the right crank 112R while the first and second axles 105 and 115 are fixed to the personal watercraft (not shown).

[0023] As shown in FIG. 1A, a right extension 123R is extended from a forward end of the right crank 112R. An upper end of the right extension 123R is mounted with a right foot pedal 131R through a right foot pedal axle 135R. As shown in FIG. 1A, the right crank 112R has an approximately right-angle bend and is rotatable around the second axle 115 located in a vicinity of the bend. When a right foot (not shown) presses the right pedal 131R forward, the right crank 112R will rotate around the second axle 115 with the aft end of the right crank 112R swinging upward causing a clockwise rotation or flapping of the right fin 102R.

[0024] In embodiments, each of the left fin 102L and the right fin 102R are symmetrical and each has a wide horizonal surface toward the aft end, so that when flapping up and down around the first axle 105, the left fin 102L and the right fin 102R create a propulsive force forward.

[0025] As shown in FIGS. 1A and 1B, the forward end of the left crank 112L and the forward end of the right crank 112R are connected by a tension cable 142. The tension cable 142 wraps around a pulley wheel 146 which is rotatable around a pin 148. The pin 148 is mounted to the personal watercraft (not shown), thus in a fixed position in reference to the axles 105 and 115. When the forward end of the left crank 112L is pushed forward, the tension cable 142 will pull the forward end of the right crank 112R backwards, and vice versa. As a result, pushing the left foot pedal 131L will not only flap the left fin 102L downward, but also flap the right fin 102R upward. Similarly, pushing the right foot pedal 131R will not only flap the right fin 102R downward, but also flap the left fin 102L upward. Therefore, a continuous alternating foot pushing will create a continuous scissor motion by the left fin 102L and the right fin 102R.

[0026] FIGS. 2A and 2B are a port side and front view, respectively, of a flapping manual propulsion system 200 according to another embodiment of the present disclosure.

[0027] Referring to FIG. 2A, the flapping manual propulsion system 200 employs a left lifting cable 232L to connect a left pulley wheel 203L to the forward end of the left fin 102L, and a right lifting cable 232R to connect a right pulley wheel 203R to the forward end of the right fin 102R. The left pulley wheel 203L is attached to a left straight crank 241L with the left foot pedal 131L mounted to an upper end of the left straight crank 241L, so that when the user pushes the left foot pedal 131L forward with a left foot, the left pulley wheel 203L will rotate counterclockwise causing the left lifting cable 232L to lift the forward end of the left fin 102L. Similarly, the right pulley wheel 203R is attached to a right straight crank 241R with the right foot pedal 131R mounted to an upper end of the right straight crank 241R, so that when the user pushes the right foot pedal 131R forward with a right foot, the right pulley wheel 203R will rotate counterclockwise causing the right lifting cable 232R to lift the forward end of the right fin 102L.

[0028] As shown in FIG. 2A, the forward end of the left fin 102L and the forward end of the right fin 102R are connected by pulling cables 234L and 234R. The pulling cables 234L and 234R are one cable wrapped around a central pulley wheel 214. The central pulley wheel 214 is rotatable around a central axle 226 which in turn is rigidly connected, by a bracket 228, to an axle 205 for both the left pully wheel 203L and the right pully wheel 203R. When the forward end of the left fin 102L is lifted upward, the pulling cables 234L and 234R will pull the forward end of the right fin 102R downward, causing the fins 102L and 102R to perform a scissor-like flapping. Similarly, when the forward end of the right fin 102R is lifted upward, the pulling cables 234L and 234R will pull the forward end of the left fin 102R downward, causing the fins 102L and 102R to perform another scissor-like flapping.

[0029] Referring to FIG. 2B, a cross-sectional view of the bracket 228 shows that both the axle 205 and the central pulley wheel 214 are mounted to the bracket 228. As the foot pedals 131L and 131R travel in a limited range, only upper portions of the pulley wheels 203L and 203R are exemplarily circular as shown in FIGS. 2A and 2B. Lower portions of the pulley wheels 203L and 203R never come into contact with the lifting cables 234L and 234R, respectively, thus can be reduced to flat portion or entirely removed to save space and material. In case the lower portion of the pulley wheel 203L or 203R is hollow, the upper portion of the pulley wheel 203L or 203R can be exemplarily attached to a bearing (not shown) around the axle 205.

[0030] FIG. 3 is a port side view of a flapping manual propulsion system 300 according to yet another embodiment of the present disclosure. The flapping manual propulsion system 300 employs a left front lifting cable 312L and a left rear lifting cable 314L attached to the forward end and an aft point of the left fin 102L. The aft point is located on the left fin 102L aft to the first axle 105L. In embodiments, a distance from the aft point to the axle 105 is approximately equal to a distance from the forward end of the left fin 102L to the axle 105.

[0031] The term, “end” as in the “forward end” or “aft end”, as used herein, generally refers to a vicinity of an edge of an elongated member. For example, the left front lifting cable 312L is attached to a point 10 mm to the right of a forward edge of the left fin 102L. Such attachment is exemplarily considered to be at the forward end of the left fin 102L.

[0032] In embodiments, the left front lifting cable 312L and left rear lifting cable 314L are parts of one cable wrapped around the upper portion of the left pulley wheel 203L, so that a clockwise rotation of the left pully wheel 203L causes a downward flap of the aft portion of the fin 102L; and a counterclockwise rotation of the left pully wheel 203L causes an upward flap of the aft portion of the fin 102L. The term “aft portion” as used herein, generally refers to a portion of the left fin 102L to the right of the first axle 105 when view from a port side of the watercraft.

[0033] In embodiments, the port side and the starboard side of the flapping manual propulsion system 300 are symmetrical, i.e., the left fin 102L is symmetrical to the right fin 102R, the left pulley wheel 203L is symmetrical to the right pulley wheel 203R—same dimension as well as rotatable around the same axle 205; a right front lifting cable 312L is symmetrical to the right front lifting cable 312R; and a left rear lifting cable 314L is symmetrical to the right rear lifting cable 314R.

[0034] As shown in FIG. 3, the left pulley wheel 203L and the right pulley wheel 203R are connected by a cable 321 wrapped around a central horizontal pulley wheel 325. The pulley wheel 325 is situated in a horizontal plane so that the cable 321 is stretched horizontally between the left pulley wheel 203L, the central horizontal pulley wheel 325 and the right pulley wheel 203R. When the left pulley wheel 203L rotates counterclockwise in response to a push at the left foot pedal 131L, the cable 321 will pull the right pulley wheel 203R to rotate clockwise. Similarly, when the right pulley wheel 203L rotates counterclockwise in response to a push at the right foot pedal 131R, the cable 321 will pull the left pulley wheel 203L to rotate clockwise. Such reverse rotations by the left and right pulley wheels 203L and 203R causes scissor-like flapping by the fins 102L and 102R.

[0035] Although the horizontally rotatable central horizontal pully wheel 325 is depicted in FIG. 3, in other embodiments, the pully wheel 325 can be mounted at an acute angle to the horizontal plane, as long as the plane of the pully wheel 325 is approximately tangent to the circumference of the left pulley wheel 203L and the right pulley wheel 203R. The approximate tangency allows the cable 321 to stay inside a groove of the central pulley wheel 325 during the rotations of the left pulley wheel 203L and the right pulley wheel 203R.

[0036] FIG. 4 is a port side view of a flapping manual propulsion system 400 according to yet another embodiment of the present disclosure. The flapping manual propulsion system 400 employs an elongated fin 402 rotatable around the first axle 105. The elongated fin 402 is mounted below a bottom surface of the watercraft (not shown) thus submerged in the water in operation. The elongated fin 402 is oriented along a centerline of the watercraft, i.e., a long axis of the elongated fin 402 is parallel to the centerline of the watercraft.

[0037] In embodiments, a front lifting cable 412 connects a forward end of the fin 402 to the left pulley wheel 203L. When the left pulley wheel 203L rotates counterclockwise in response to a push at the left foot pedal 131L, the front lifting cable 412 will cause the fin 402 to rotate clockwise-making a downward flap. In embodiments, a rear lifting cable 417 connects an aft point of the fin 402 to the right pulley wheel 203R. The aft point of the fin 402 is exemplarily located at a point on the fin 402 to the right of the first axle 105. A distance from the aft point to the first axle 105 is proximately equal to a distance from the forward end of the fin 402 to the first axle 105. When the right pulley wheel 203R rotates counterclockwise in response to a push at the right foot pedal 131R, the rear lifting cable 417 will cause the fin 402 to rotate counterclockwise-making an upward flap. In operations, the user pushes one foot at a time while allowing the other foot to withdraw from an extended position in preparation for a next push.

[0038] As shown in FIG. 4, the left pulley wheel 203L is symmetrical to the right pulley wheel 203R; the left straight crank 123L along with the left foot pedal 131L are symmetrical to the right straight crank 123R along with the right foot pedal 131R. In embodiments, when the fin 204 is in a horizontal plane—a neutral position, a suspended portion of the front lifting cable 412 is of a same length as a suspended portion of the rear lifting cable 417, so that if the left foot pedal 131L and the right foot pedal 131R travel the same distance, the fin 402 flaps upward and downward by a same distance. In other embodiments, the neutral position slightly leans downward from the horizontal plane, so that the fin 402 flaps more distance downward than upward.

[0039] FIG. 5 is a block diagram illustrating a flapping manual propulsion system 500 according to yet another embodiment of the present disclosure. The propulsion system 500 employs two elongated fins 102L and 102R side by side and both rotatable around the first axle 105. Flapping motions of the elongated fins 102L and 102R are driven by 4 pulley wheels: 512L and 503R for the left elongated fin 102L and 514L and 505R for the right elongated fin 102R. The pulley wheels 512L and 514L are attached to and rotatable along with a first shaft 550. The pulley wheels 503R and 505R are attached to and rotatable along with a second shaft 560. The first shaft fits in a center hole and is coaxial with the second shaft.

[0040] In an embodiment, the left crank 123L is fastened to the pulley wheel 512L, thus when the left foot pedal 131L is pushed forward, both pulley wheels 512L and 514L rotate counterclockwise when viewed from a port side of the watercraft. In an embodiment, the pulley wheel 512L is linked by a cable 524L to a forward portion 541L of the left fin 102L; and the pulley wheel 514L is linked by a cable 526L to an aft portion 543R of the right fin 102R. Therefore, the push on the left foot pedal 131L forces the left fin 102L to flap downward while the right fin 102R to flap upward.

[0041] In an embodiment, the right crank 123R is fastened to the pulley wheel 505R, thus when the right foot pedal 131R is pushed forward, both pulley wheels 505R and 503R rotate counterclockwise when viewed from a port side of the watercraft. In an embodiment, the pulley wheel 503R is linked by a cable 535R to an aft portion 543L of the left fin 102L; and the pulley wheel 505R is linked by a cable 537R to a forward portion 541R of the right fin 102R. Therefore, the push on the right foot pedal 131R forces the left fin 102R to flap upward while the right fin 102R to flap downward.

[0042] In addition, a forward pushed on the left foot pedal 131L forces the left foot pedal 131R to swing backward, and vice versa, due the cables 524L, 526L, 535R and 537R being fastened between the pulley wheels 512L, 514L, 503R and 505R and the fins 102L and 102R as shown in FIG. 5.

[0043] FIGS. 6A and 6B are a side and cross-sectional view, respectively, of an exemplary implementation of the shafts 550 and 560 for the flapping manual propulsion system shown in FIG. 5. Referring to FIG. 6A, the first shaft 550 has two geared sections 612L and 612R for coupling to the pulley wheel 512L and 514L, respectively. The second shaft 560 is also geared for coupling to the pulley wheels 503R and 505R.

[0044] As shown in FIG. 6B, the second shaft 560 has a center hole for the first shaft 550 to fit in and rotate freely. An inner diameter D2 of the center hole of the second shaft 560 is larger than an outer diameter D1 of the first shaft 550, so that the first shaft 550 can be inserted in the second shaft 560.

[0045] FIG. 7 is a perspective view of an exemplary implementation of the elongated fin 402 according to embodiments of the present disclosure. The elongated fin 402 has an elongated body which becomes wider, thinner and more flexible toward an aft end. In an embodiment, a through hole 704 is formed in the elongated fin 402 in a direction perpendicular to the elongated direction and parallel to a surface of the elongated fin 402. The first axle 105 (not shown) fits in the through hole 704, so that the elongated fin 402 can rotate around the first axle 105. A location of the through hole 704 and thus the first axle 105 divides the elongated fin 402 into a forward portion 734 and an aft portion 737. In embodiments, the aft portion 737 is longer and more flexible than the forward portion 734. In operations, the elongated fin 402 is oriented along a centerline of the watercraft (not shown) with the aft portion 737 flapping up and down to propel the watercraft.

[0046] As shown in FIG. 7, there are two pins 715 and 727 in the elongated fin 402 for securing the lifting cable 417 and 412 (shown in FIG. 4), respectively, to the elongated fin 402. The left pin 715 is recessed in a left opening 712 formed on the port side of the fin 402 when mounted on the watercraft. The right pin 727 is recessed in a right opening 724 formed on the starboard side of the fin 402 when mounted on the watercraft. In an embodiment, a distance (AL) from the left pin 715 to a center line of the elongated fin 402 is approximately equal to a distance (AR) from the right pin 727 to the center line. In an embodiment, a distance (BR) from the left pin 715 to the through hole 704 is approximately equal to a distance (BF) from the right pin 727 to the through hole 704.

[0047] FIG. 8 is a cross-sectional view of an exemplary structure for attaching the lifting cable 417 to the elongated fin 402 according to embodiments of the present disclosure. The exemplary structure is provided using the left pin 715 and the left opening 712 as an example. The exemplary structure can be applied to the right pin 727 and the right opening 724 as well. As shown in FIG. 8, the left lifting cable 417 is inserted in the opening 712 from above and wraps around the left pin 715 multiple times (the cross-sectional view shows only one round). A rigid cover plate 810 is attached to the fin 402 by screws 813 and 816 covering the bottom of the left opening 712. As a result, a surface of the cover plate 810 presses hard against the left lifting cable 417 to provide fiction thereto, so that the left lifting cable 417 is securely tied to the left pin 715.

[0048] FIG. 9 is a cross-sectional view of an exemplary structure for attaching a cable to a pulley wheel according to embodiments of the present disclosure. As an example, the right pulley wheel 203R pulling the front lifting cable 412 is illustrated in FIG. 9. In embodiments, only an upper portion of the right pulley wheel 203R is circular and the lower portion of the right pulley wheel 203R is removed as the right foot pedal 131R that drives the right pulley wheel 203R travels in a small range. In embodiments, the right pulley wheel 203R can be just a curved member with a circular section to maintain a suspended portion of the lifting cable 412 substantially stationary during a rotation of the right pulley wheel 203R.

[0049] As shown in FIG. 4, one end of the front lifting cable 412 is attached to the forward portion of the elongated fin 402, the other end of the front lifting cable 412 is attached to the right pulley wheel 203R. In embodiments, the end of the front lifting cable 412 is securely fixed with a threaded screw 915 which is inserted through a hole in a stopper 931 formed in the pulley wheel 203R. The threaded screw 915 is then secured to the right pulley wheel 203R by a washer 942 and a bolt 944.

[0050] In embodiments, the various implementations depicted in FIGS. 7-9 can be applied to each of the flapping manual propulsion systems 100-500 shown in FIGS. 1-5.

[0051] Although the disclosure is illustrated and described herein as embodied in one or more specific examples, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the disclosure and within the scope and range of equivalents of the claims. Accordingly. it is appropriate that the appended claims be construed broadly and, in a manner, consistent with the scope of the disclosure, as set forth in the following claims.

Examples

Embodiment Construction

[0015]The present disclosure relates to a flapping manual propulsion system for a personal watercraft. A preferred embodiment of the present disclosure will be described hereinafter with reference to the attached drawings.

[0016]FIGS. 1A and 1B are port side views of a flapping manual propulsion system 100 according to an embodiment of the present disclosure. Referring to FIG. 1A, the flapping manual propulsion system 100 includes a pair of elongated fins 102L and 102R, both rotatable around a first axle 105. A distance from a forward end of the left fin 102L to the first axle 105 is shorter than a distance from an aft end of the left fin 102L. Similarly, a distance from a forward end of the right fin 102R to the first axle 105 is shorter than a distance from an aft end of the right fin 102R. When either the left fin 102L or the right fin 102R rotates around the first axle 105 in a small range near the horizonal plane, a propulsive force will be generated forward like a free-style sw...

Claims

1. A manual propulsion system for a watercraft, the system comprising:a first axle horizontally mounted below a bottom surface of the watercraft in a direction perpendicular to a centerline of the watercraft;a first elongated fin rotatable around the first axle, the first elongated fin being oriented along the centerline of the watercraft, a location of the first axle dividing the first elongated fin into a first forward portion in front of the first axle and a first aft portion behind the first axle in reference to a travel direction of the watercraft, the first forward portion being shorter than the first aft portion;a first foot pedal linked to the first forward portion of the first elongated fin, a forward motion by the first foot pedal lifting the first forward portion of the first elongated fin; anda second foot pedal linked to the first aft portion of the first elongated fin, a forward motion by the second foot pedal lifting the first aft portion of the first elongated fin.

2. The system of claim 1, wherein the first aft portion of the first elongated fin is wider than the first forward portion of the first elongated fin.

3. The system of claim 1, wherein at least a portion of the first aft portion of the first elongated fin is flexible.

4. The system of claim 1, wherein at least a portion of the first aft portion of the first elongated fin is detachable.

5. The system of claim 1, wherein the first and second foot pedal are attached to a first and second crank, respectively, both the first and second crank being rotatable around a second axle horizontally mounted to the watercraft in a direction perpendicular to the centerline of the watercraft.

6. The system of claim 5, wherein the first crank is attached to a first curved member linked to the first forward portion of the first elongated fin; and the second crank is attached to a second curved member linked to the apt portion of the first elongated fin.

7. The system of claim 6, further comprising a first cable linking the first curved member to the first forward portion of the first elongated fin and a second cable linking the second curved member to the apt portion of the first elongated fin, wherein the first cable wraps around at least a portion of the first curved member and has a first end attached to the first curved member and a second end attached to the first forward portion of the first elongated fin, and the second cable wraps around at least a portion of the second curved member and has a third end attached to the second curved member and a fourth end attached to the apt portion of the first elongated fin.

8. The system of claim 7, wherein a distance from the first cable on the first forward portion of the first elongated fin to the first axle is equal to a distance from the second cable on the apt portion of the first elongated fin to the first axle.

9. The system of claim 7, wherein a suspended portion of the first cable is of a same length as a suspended portion of the second cable.

10. The system of claim 6, wherein the first curved member has a first circumference in contact with the first cable, the first circumference being a part of a first circle centered in the second axle; and the second curved member has a second circumference in contact with the second cable, the second circumference being a part of a second circle centered in the second axle.

11. The system of claim 10, wherein the first and second circle have a same diameter.

12. The system of claim 10, wherein the first and second circle have a different diameter.

13. The system of claim 1, further comprising a second elongated fin rotatable around the first axle, a location of the first axle dividing the second elongated fin into a second forward portion in front of the first axle and a second aft portion behind the first axle in reference to the travel direction of the watercraft, the second forward portion being shorter than the second aft portion, wherein the first foot pedal is linked to the second aft portion of the second elongated fin and the second foot pedal is linked to the second forward portion of the second elongated fin.

14. The system of claim 13, wherein the first and second foot pedal are attached to a first and second crank, respectively, the first crank being attached to and rotatable along with a first shaft, the first shaft being rotatably mounted to the watercraft in a direction perpendicular to the centerline of the watercraft, the second crank being attached to and rotatable along with a second shaft, wherein the first shaft fits coaxially in a center hole of the second shaft.

15. The system of claim 14, wherein the first crank is attached to a first curved member, the first curved member and a second curved member being attached to and rotatable along with the first shaft, the first curved member being linked to the forward portion of the first elongated fin by a first cable, the second curved member being linked to the aft portion of the second elongated fin by a second cable; and the second crank is attached to a third curved member, the third curved member and a fourth curved member being attached to and rotatable along with the second shaft, the third curved member being linked to the aft portion of the first elongated fin by a third cable, the fourth curved member being linked to the forward portion of the second elongated fin by a fourth cable.

16. A method for manually propelling a watercraft, the method comprising:mounting a first axle horizontally below a bottom surface of the watercraft in a direction perpendicular to a centerline of the watercraft;engaging a first elongated fin rotatable around the first axle, the first elongated fin being oriented along the centerline of the watercraft, a location of the first axle dividing the first elongated fin into a first forward portion in front of the first axle and a first aft portion behind the first axle in reference to a travel direction of the watercraft, the first forward portion being shorter than the first aft portion;linking a first foot pedal to the first forward portion of the first elongated fin, a forward motion by the first foot pedal lifting the first forward portion of the first elongated fin; andlinking a second foot pedal to the first aft portion of the first elongated fin, a forward motion by the second foot pedal lifting the first aft portion of the first elongated fin.

17. The method of claim 16, wherein the first and second foot pedal are attached to a first and second crank, respectively, both the first and second crank being rotatable around a second axle mounted horizontally to the watercraft in a direction perpendicular to the centerline of the watercraft.

18. The method of claim 17, wherein the first crank is attached to a first curved member linked to the first forward portion of the first elongated fin by a first cable; and the second crank is attached to a second curved member linked to the apt portion of the first elongated fin by a second cable.

19. The method of claim 16, further comprising engaging a second elongated fin rotatable around the first axle, a location of the first axle dividing the second elongated fin into a second forward portion in front of the first axle and a second aft portion behind the first axle in reference to the travel direction of the watercraft, the second forward portion being shorter than the second aft portion, wherein the first foot pedal is linked to the second aft portion of the second elongated fin and the second foot pedal is linked to the second forward portion of the second elongated fin.

20. The method of claim 19, wherein the first and second foot pedal are attached to a first and second crank, respectively, the first crank being attached to and rotatable along with a first shaft, the first shaft being rotatably mounted to the watercraft in a direction perpendicular to the centerline of the watercraft, and the first crank being also attached to a first curved member, the first curved member and a second curved member being attached to and rotatable along with the first shaft, the first curved member being linked to the forward portion of the first elongated fin by a first cable, the second curved member being linked to the aft portion of the second elongated fin by a second cable, the second crank being attached to and rotatable along with a second shaft, the first shaft being fitted coaxially in a center hole of the second shaft, and the second crank being also attached to a third curved member, the third curved member and a fourth curved member being attached to and rotatable along with the second shaft, the third curved member being linked to the aft portion of the first elongated fin by a third cable, the fourth curved member being linked to the forward portion of the second elongated fin by a fourth cable.

Images