Abstract:
A multi-functional modular device includes: a shaft; electric motor(s); propeller(s); battery(s); and paddle blade(s) being removably attachable to the shaft for levering of a boat. With the blade(s) attached to the shaft and motor(s) de-energized, the device is usable for manual levering, and with the motor(s) energized, propeller thrust selectively assists in levering to propel the boat. Propeller thrust in a direction opposite to a propulsive direction from levering reduces work required per stroke, reducing the total levering power per stroke. Alternatively, using the thrust in the same direction as propulsive levering increases total propulsive power per stroke, but requires greater strength/work output by the rower/paddler. Removing the blade permits the propeller and motor to be statically submerged and clocked for directional propulsion. A hinged kayak paddle embodiment is adapted for pure levering, and is convertible to a propulsion device by releasably attaching an electric pod motor to the blade(s).

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. application Ser. No. 12/924,627, filed on Sep. 30, 2010, which claimed priority on U.S. Provisional Application Ser. No. 61/281,035, filed on Nov. 12, 2009 with the title, “Hand-Held Propulsion/Navigational Boating Device and Powered Oar/Paddle For Canoe, Kayak, Rowboat, Raft and the Like,” with the disclosures of each being incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to improvements in directional and propulsive control over small watercraft, and more particularly to an oar or paddle which is capable of providing powered assistance to the paddler or rower. 
       BACKGROUND OF THE INVENTION 
       [0003]    Recreational boating is a favorite American pastime, and such pleasure craft come in many different forms or categories: dinghies, paddlesports boats, runabouts, daysailers, cruisers, etc. The type of boat chosen by an individual will naturally suit the particular activities in which one seeks to engage, and it is not uncommon for many individuals to own two different kinds of boats. For some, the allure of boating comes with being powered solely by the wind filling the sails, and for others it may be the speed and maneuverability of a powerboat. But for many people, the appeal of being upon the water is heightened while in a basic watercraft that is propelled solely through the user&#39;s efforts, without the sounds of a motor or the flapping of sails. 
         [0004]    The so-called paddlesports boats may be divided into two sub-categories—those which involve paddling and those involving rowing. Rowing is characterized by the use of oars, which have a mechanical connection with the boat, in the form of a fixed fulcrum that is usable to transfer power from the handle to the blade. With the traditional rowboat, the oars are secured by pivoting oar locks mounted on gunwales, and with a similar arrangement used in competitive rowing craft, referred to in collegiate circles as crew. This competitive rowing has two forms-sweep-oar rowing, where each rower has one oar held by both hands; and sculling, where each rower has two oars, one in each hand. Rowing is normally accomplished in a rearward facing arrangement, where the seated rower pulls on either one or two oars, which act as a lever to propel the boat in the direction opposite to which the user faces. However, there is a number of forward facing rowing systems in which a two-piece oar in combination with a mechanical transmission reverses the direction of motion of the oar blade, relative to the pull of the rower. 
         [0005]    Paddling, on the other hand, involves the use of hand-held paddles that have no mechanical connection with the boat, and which similarly propel the watercraft by the reaction forces transmitted by the paddler to the boat from the oar blades, as they are pushed against the water. Without having use of a fulcrum to transfer power, the paddler instead use the athlete&#39;s shoulders or hands as the pivot-point. Watercrafts that typically utilize hand-held paddles are canoes, rowboats, rafts, and kayaks, which normally have a covered deck. The paddles utilized by the rower of such watercraft may be single bladed—with a transverse handle connected via a shaft to a flat or a curved “blade” that is either symmetrical or asymmetrical—or may be a double-bladed paddle, where there is no handle per se and a longer shaft connects to a blade at each end of the shaft. 
         [0006]    The recreational users of paddles and oars often debate in the relevant literature over the advantageous nature of these and other structural differences, in order to make paddling and rowing more easily sustainable for a long period of time. There have been several patents offering solutions to this end, such as U.S. Pat. No. 5,820,424 to Steinhour. The Steinhour patent offers an ergonomically improved kayak paddle, which claims to “improve the overall strength of the paddle, while substantially reducing hand and arm fatigue for a user.” The paddle achieves the improvement by incorporating non-concentric gripping regions, which also permit the user to determine the orientation of the paddle by touch . The Steinhour paddle, while providing a noticeable improvement that aids the paddler in the ergonomic aspect of rowing, does not take a significant step toward alleviating the arduous nature of sustained rowing. 
         [0007]    A more pronounced improvement is shown by U.S. Pat. No. 7,037,151 to Fan. The Fan oar comprises a supplemental blade that is pivotally connected to a primary blade, with its pivotal travel being limited by a chord so that it may occupy a position parallel and adjacent to the main blade, or alternatively occupy a position at an angle to the main blade. When the Fan oar blade is immersed in the water to initiate a stroke, the supplementary blade trails and will naturally extend to the maximum angle, and thereby serve to increase the area of the water expelling surface, and thus increase the efficiency for each stroke. However, where this added efficiency produces “a relatively greater force to move the row boat forward,” it is plain that it also requires correspondingly greater strength in the user to be able to move the combined paddle blades through the water to generate those forces. This added strength requirement may preclude its use by many recreational rowers. 
         [0008]    Another improved rowing device is shown by U.S. Pat. No. 7,144,284 to Horan. The Horan device uses two parallel shafts being pivotally linked on both ends to keep the “oar&#39;s blade and handle parallel to one another and perpendicular to the boat throughout the rowing cycle,” which “is critical to achieving a powerful, efficient stroke.” This would arguably increase the efficiency of each stroke without the corresponding increase in strength requirements necessitated by the Fan oar; however, it does not serve to dramatically ease the rower&#39;s burden for a sustained period of use. 
         [0009]    The invention disclosed herein has been developed to provide assistance for the rower who is not training to row competitively, and simply seeks to enjoy paddling leisurely about a lake or other waterway. However, it may also be utilized by those who are not merely recreational users and may intend to explore coastal and intra-coastal waterways in a canoe or kayak for extended periods of time, but wish to have some minimal assistance in paddling, while still enjoying the tranquility maintained by not running an outboard motor. 
       OBJECTS OF THE INVENTION 
       [0010]    It is an object of the invention to provide an enhanced means of rowing or paddling for users of canoes, kayaks, rowboats, rafts, and the like. 
         [0011]    It is another object of the invention to provide an oar or a paddle which decreases the physical exertion involved in propelling paddle sports watercraft. 
         [0012]    It is a further object of the invention to provide an oar or paddle that increases the range which may be attained when traveling in a paddle sports watercraft. 
         [0013]    It is another object of the invention to provide an oar or paddle that enhances the duration of paddle sports activity that may be enjoyed by a given user. 
         [0014]    It is also an object of the invention to provide an oar or paddle that enables individuals who a not physically fit to nonetheless participate in and enjoy paddle sports activity. 
         [0015]    It is another object of the invention to provide an oar or paddle that incorporates a battery powered motor to assist in the rowing or paddling stroke of the user. 
         [0016]    It is also an object of the invention to provide a recharging means to enable individuals who are not physically fit to nonetheless participate in and enjoy paddle sports activity. 
         [0017]    It is another object of the invention to provide an oar or paddle that is convertible into a hand-held trolling device for use with small boats. 
         [0018]    It is also an object of the invention to provide a stand-, hand-held trolling device for small boats. 
         [0019]    It is another object of the invention to provide a battery-powered hand-held trolling device capable of maneuvering a small boat to navigate into slips, docks, and other tight areas. 
         [0020]    Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying figures. 
       SUMMARY OF THE INVENTION 
       [0021]    A multi-functional modular levering device may comprise: a hand-graspable shaft; one or more electric motors; one or more batteries being electrically coupled to the electric motors; one or more thrust producing fan assemblies being driven by the electric motors; and one or more paddle blades being removably attachable to the shaft for levering of a paddlesports boat. While it is possible to utilize the fan assembly to provide thrust by creating a current of air, which comports with the traditional usage of the term fan, the fan assembly herein will more preferably be adapted, in terms of the design of the shaft, hub, and blades, to be water submersible and to produce thrust in any body of water, in which case it may be more aptly referred to as a marine propeller assembly. Any use of the term fan or fan assembly throughout this patent specification is therefore intended to encompass both design types. The DC motors may have output shafts being transverse to the axis of rotation of the fan, and thus each fan may be driven through use of a pair of bevel gears. 
         [0022]    The modular combination device may be used in a first role to provide for manual and/or power-assisted levering of paddlesports boat, with said device being quickly transformable for use in a second role as a hand-held multi-directional propulsion device, as follows. 
         [0023]    With the blade(s) attached to the shaft and the motors) being either off or without power, the device is usable for manual levering. With the motor(s) on and being supplied with power, the fan blade thrust may selectively assist in levering, in order to propel the paddlesports boat. Fan thrust may be usable to produce a reaction force in one of two useful, but opposite, directions to aid the levering to achieve completely different effects. With the reaction force being opposite to a propulsive direction of levering (opposite to the forward motion of the boat), the power assistance serves to reduce the work required per stroke and eases the burden of rowing for the user, but which also reduces the amount of power per stroke. Alternatively, the reaction force may be oriented to be in the same direction as propulsive levering to increase total propulsive power per stroke, but may require greater strength/work output by the rower/paddler. Various sized blades may be interchangeable therein to adjust the total work output. Removing the blade(s) also permits the fan portion of the levering device to be statically submerged and clocked to propel the boat in a desired compass direction in a fashion similar to a trolling motor. 
         [0024]    The motors may be powered by one or more batteries, which may comprise a disposable battery, a rechargeable battery, or a marine battery. The motors may also actually be powered by a combination of those battery types. Where an ordinary battery, such as a “C” cell battery is used, it may be disposed within the shaft of the levering device. Where a marine battery is used, it may be stowed in the bottom of the boat, and be coupled to the device using an electrical cable and a quick connect plug, and may be a lead acid battery from the group of marine lead acid batteries consisting of: a flooded acid battery, a gelled acid battery, or an advanced absorbed glass mat battery. 
         [0025]    The fan may comprise a fan shaft and one or more fan blades, with the one or more fan blades being attached to the fan shaft, and where the fan shaft is rotatably attached to a fan housing, which may be attached to the hand-graspable shaft. The motor may also be disposed within the shaft; and may be a motor from the group consisting of: a single speed motor, a two-speed motor; or a variable speed motor. 
         [0026]    The combination device may preferably include at least one blade being attachable with a quick-release latch to permit easy removal of the blade(s) from the hand-graspable shaft. Interchangeability of the component parts allows the modular device to be easily converted between a double-bladed kayak paddle, an oar, a canoe paddle with a handle, and also a hand-held trolling/navigation device. Removability of the blades permits the various sized blades to be usable for adjustment to the work required per stroke. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a perspective view showing the levering device of the present invention converted into a double-bladed kayak paddle, which incorporates power assistance into the paddle. 
           [0028]      FIG. 1A  is a front view showing the double-bladed kayak paddle of  FIG. 1  after being converted into a single-bladed oar. 
           [0029]      FIG. 1B  is a front view showing the single-bladed oar of  FIG. 1A  converted into a paddle with a handle for canoeing, rafting, etc. 
           [0030]      FIG. 1C  is a front view showing the single-bladed paddle of  FIG. 1B  converted into the hand-held propulsion device. 
           [0031]      FIG. 1D  is a front view showing the hand-held propulsion device of  FIG. 1C , but with a blade being releasably attachable thereto, and being powered by four rechargeable lithium ion batteries. 
           [0032]      FIG. 1E  shows the embodiment of  FIG. 1D , but with the blade also being pivotally attachable thereto. 
           [0033]      FIG. 2  is a front view of the double-bladed kayak paddle of  FIG. 1 . 
           [0034]      FIG. 2A  is a partially exploded view of the kayak paddle of  FIG. 2 . 
           [0035]      FIG. 3  is a side view of the double-bladed kayak paddle of  FIG. 2 . 
           [0036]      FIG. 4  is section cut through the blade to show the tongue-and-groove connection with the fan and graspable handle. 
           [0037]      FIG. 5  is the view of  FIG. 3  enlarged to show a dual motor switch configuration. 
           [0038]      FIG. 6  is an exploded view of the component parts of the modular levering device of the present invention. 
           [0039]      FIG. 6A  is an assembled detail view of several of the components of the exploded view of  FIG. 6 . 
           [0040]      FIG. 7  is a front section view through the double-bladed kayak paddle of  FIG. 1 . 
           [0041]      FIG. 8  is the view of  FIG. 7  enlarged to disclose motor and battery details. 
           [0042]      FIG. 9A  is a first blade usable with the levering device of the current invention. 
           [0043]      FIG. 9B  is a second, larger blade being usable with the levering device of the current invention. 
           [0044]      FIG. 9C  is a third, even larger blade that may be usable with the levering device of the current invention. 
           [0045]      FIG. 10  is a front view of the fan and fan housing of the current invention, with the mechanical connection to the motor. 
           [0046]      FIG. 10A  is the view of  FIG. 10  enlarged to disclose details of the mechanical connection to the motor. 
           [0047]      FIG. 11  is a side view of the details disclosed in  FIG. 10 . 
           [0048]      FIG. 12  is an alternate embodiment of one of the modular components of the present invention illustrating use of a single motor that has an output shaft connectable to first and second fans. 
           [0049]      FIG. 13  is a top view of the alternate embodiment of  FIG. 12 . 
           [0050]      FIG. 14  is a top view of the alternate embodiment of  FIG. 12 . 
           [0051]      FIG. 15  illustrates a typical oar lock usable on a rowboat for levering. 
           [0052]      FIG. 16  illustrates the basic mechanics of using the modular levering device of the current invention, without any power assistance. 
           [0053]      FIG. 17  illustrates the mechanics of using the modular levering device of the current invention in which fan thrust is in the same direction and approximately parallel to the paddle sport boat&#39;s forward motion to assist the rower, and reduce the amount of work required to overcome water resistance to the levering device&#39;s motion. 
           [0054]      FIG. 18  illustrates the mechanics of using the modular levering device of the current invention in which fan thrust is in an opposite direction to, though being approximately parallel to the paddlesport boat&#39;s forward motion, to assist the rower, and increase the total propulsive power per stroke of the levering device&#39;s motion. 
           [0055]      FIG. 19  illustrates use of the modular levering device of the current invention as a trolling motor, being capable of propelling the boat, which need not necessarily be a paddlesports boat, in a desired direction. 
           [0056]      FIG. 20  is a front view of another alternate embodiment of the modular levering device of the current invention, where a motor and propeller are positioned proximate to the tip of the paddle blade, and disposed within an opening therein. 
           [0057]      FIG. 21  is a perspective view of the levering device of  FIG. 20 , 
           [0058]      FIG. 22  is an enlarged front view of the blade portion of the levering device of  FIG. 20 . 
           [0059]      FIG. 23A  is an enlarged perspective view of the blade portion of the levering device of  FIG. 20 . 
           [0060]      FIG. 23B  is an enlarged reverse perspective view of the blade portion of the levering device of  FIG. 20 . 
           [0061]      FIG. 24  is a schematic for the wiring of the brushless DC motor (BLDC), with electronic speed controller (ESC) and variable pulse width modulator (PWM) signal generator. 
           [0062]      FIG. 25  is a perspective view of an outrunner motor. 
           [0063]      FIG. 26  is a perspective view of an inrunner motor. 
           [0064]      FIG. 27A  is a perspective view of an embodiment of the present invention directed to providing a kayak paddle with a hinged shaft, which permits the paddle to be partially folded or completely folded for storage. 
           [0065]      FIG. 27B  is the hinged kayak paddle of  FIG. 27A , shown in the folded position for storage of the paddle. 
           [0066]      FIG. 27C  is the hinged kayak paddle of  FIG. 27A , shown with a motor pod of the current invention releasably secured to the bottom of one of the blades of the paddle, for use as a propulsion device. 
           [0067]      FIG. 27D  is the hinged kayak paddle of  FIG. 27C , shown with the second blade having been removed, and with the hinge having been used to rotate the second shaft to be approximately 90 degrees to the first shaft, for use as a combination rudder and propulsion device. 
           [0068]      FIG. 27E  is the hinged kayak paddle of  FIG. 27A , shown with a motor pod of the current invention releasably secured to the bottom of each blade of the paddle. 
           [0069]      FIG. 27F  is the hinged kayak paddle of  FIG. 27E , shown partially folded to be converted for use as a propulsion device for a kayak. 
           [0070]      FIG. 28A  is a side view of the blade of the paddle of  FIG. 27A . 
           [0071]      FIG. 28B  is a cross-sectional view through the rotatable joint of the hinged kayak paddle of  FIG. 27A . 
           [0072]      FIG. 28C  is a side view of the blade of the paddle of  FIG. 27C . 
           [0073]      FIG. 29  is perspective view of the propeller end of the motor pod of  FIG. 27C . 
           [0074]      FIG. 30A  is a front view showing the motor pod of  FIG. 27C  just prior to being releasably secured onto the bottom of a blade of the hinged paddle of the current invention. 
           [0075]      FIG. 30B  is the front view of  FIG. 30A  showing the motor pod of  FIG. 27C  after being releasably secured onto the bottom of the blade of the hinged paddle. 
           [0076]      FIG. 31  is an enlarged cross-sectional view of the motor pod of  FIG. 27C . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0077]    There are many considerations which impact the design of a shaft and blade for levering a paddlesports boat, whether it be an oar for rowboats (sweep oar rowing or sculling), or a single-bladed paddle with a handle for canoeing, or a double-bladed paddle for kayaking. In each case, appropriate compromise and resolution between conflicting considerations are aimed at improving performance of the rower/paddler. But, the kind of performance being sought by one rower may be different than the kind of performance, or amount of performance, being sought by different occupants of the various paddlesports boats. 
         [0078]    The primary objective in designing a levering device is to help the user achieve the most efficient stroke in order to propel the paddlesports boat forward according to the user&#39;s expertise. In general, the greater the mass of water that the blade is able to “grip,” the greater the resistance against which the paddler can lever him/herself and propel the paddlesports boat forward. However, certain users may desire the ability to achieve greater speeds for shorter durations, while some users may wish to conserve energy and be able to paddle moderately, though efficiently, for a long sustained period of time. Any compromise between these considerations reduces efficiency of the device. Moreover, even when a device for levering a paddlesports boat is well designed for one user, it likely will be inappropriate for another user who may require a different device because of his or her size and/or strength and goals. 
         [0079]    The invention disclosed herein remedies many of the compromises forced upon the user by those conflicting considerations by providing a modular arrangement that can quickly be transformed to produce an oar, or a handled canoe paddle, or a double-bladed kayak paddle. The modular device also features four modes of operation, which will be discussed further hereinafter, but namely include: a purely manual mode in which the device is simply used to lever the paddlesports boat through the strength of the user alone; a first power assisted mode, in which a battery-powered fan provides thrust to help a user (who may be smaller and be less agile) to overcome the water resistance required in levering the device, but also thereby reduces the amount of propulsive thrust per stroke; a second power assisted mode, in which the fan thrust is combined with the manual lever action of the user to thereby increase the total propulsive power per stroke, but which requires greater strength on the part of the user; and a fourth mode in which the blade is removed or pivoted, and the fan is submerged in the water and clocked/oriented to propel the paddlesports boat (or any type of boat) in a desired direction, much like a trolling motor. 
         [0080]      FIGS. 1 ,  1 A, and  1 B show different paddlesports boat levering devices that may be achieved through transformation of the present invention.  FIG. 1  shows a powered kayak paddle  10 , while  FIG. 1A  shows an oar,  FIG. 1B  shows a handled paddle for canoe, and the like, and  FIG. 1C  shows a first embodiment for a multi-directional propulsion device. The basic parts of the modular device may be constructed utilizing wood, aluminum, plastic, or some combination therein, or using any other materials or finishes commonly employed for such products, and it may be tailored for use in fresh water, or saltwater, or both. 
         [0081]    The double-bladed kayak paddle  10 , shown in front and side views in  FIGS. 2 and 3  and in the section views of  FIGS. 7 and 8 , may comprise the modular components illustrated in the exploded view of  FIG. 6 . In one embodiment the double-bladed kayak paddle  10  may be comprised of the following components: a pair of axially extending blades  20 ; a pair of fan assemblies  40 ; at least one water-resistant, electric motor  15 ; a first tube section  60 ; a second tube section  70 ; one or more batteries  31 ; and suitable electrical wiring/connection. Many different aspects of the individual components, the assembly thereof, and the performance capabilities of the invention require some discussion, as follows. 
         [0082]    The blade  20  may generally comprise the water gripping portion  21  ( FIG. 6 ), which may include curvature known as “scoop” (being in the widthwise direction) and “spoon” (being in the length-wise direction), to be bounded by an overall outer edge periphery  22 . The outer edge periphery  22  may be interrupted by an opening to form an interior edge periphery  23 , which is intended to mate with, and be removably attachable to, the fan assembly  40 . 
         [0083]    The fan assembly  40  may comprise a fan hub  41 , fan shaft  42  ( FIG. 10 ), a plurality of fan blades  43 , which extend outward from the hub  41 , and a fan housing  45 . The fan housing  45  may be an injection molded plastic part, or any other type of suitably formed part, such as, but not limited to, a casting, in which the housing may have a first cylindrical portion  46 , a second cylindrical portion  47  that is disposed transverse to the first cylindrical portion  46 , and a gusset plate  49  with an exterior groove. The blade  20  and fan housing  45  may be joined, in one embodiment, using a tongue and groove arrangement, as seen in  FIG. 4 , The interior periphery  23  of blade  20  may be inserted into groove  46 A, which may actually begin in the gusset  49  until reaching the first cylindrical portion  46 , in which the groove  46 A may become an annular groove. The “tongue” of the blade  20  may be secured to the “groove” of the fan housing  45  using many different quick release means. In one embodiment, a pin  80 , having a head  81 , may be inserted through aligned orifices in the blade and housing, and be therein retained by a pair of spring-loaded balls  82 , which may engage a groove in the housing to serve as a detent. Alternatively, any quick release pins, ball detent pins, plunger pins, or other suitable hardware available in the market from various manufacturers may be used, such as those offered by Innovative Components, Inc., which is located in Schaumberg, Ill. Innovative Components offers such hardware in its catalog, at http://www.knobsource.com/images/Catalog%202010.pdf, which is incorporated herein by reference. In another embodiment, instead of the pin  80 , a quick release catch may be used; being similar to the catch disclosed in expired U.S. Pat. No. 4,949,492 to Clifton, for “Quick Release Magazine Catch,” the disclosures of which are incorporated herein by reference. 
         [0084]    To provide for added structural strength, a cylindrical protrusion  24  on the interior periphery  23  of blade  20  may extend in the axial direction to be received in a corresponding orifice in the first cylindrical portion  46  of fan housing  45 . Alternatively, a cylindrical protrusion on the first cylindrical portion  46  of fan housing  45  may be received in a corresponding orifice in the blade  20 . This quick release approach for attachment of the blade permits interchangeability of different size blades  20 A,  20 B, and  20 C ( FIGS. 9A ,  9 B, and  9 C), whereby smaller or larger sized blades may be utilized to be more compatible with the particular user, or for the same user who may be on an earlier or later portion of a trip, and alternatively desires more or less blade area for correspondingly greater or lesser grip with the water, per stroke. 
         [0085]    The second cylindrical portion  47  of fan housing  45  may comprise a male extension  48  extending from one end thereof, which may be hollow, and in which may be disposed motor  15  ( FIGS. 7-8 ). The male extension  48  may be usable for coupling of the fan housing to an opening  61  in first tube section  60 , which may be a hollow tube. This coupling arrangement may similarly be used for coupling of the handle  38  thereto, as well as for coupling of the first tube section  60  to second tube section  70  (male extension  68  coupling within opening  71 ), which, when coupled together, may form a hand-graspable shaft to enable levering by the user. There are many possible means of coupling the tube-like sections. In one possible embodiment, male extension  48  of fan housing  45  may comprise external threads, while the opening  61  in first tube section  60  may comprise internal threading, and may be comparable to the method disclosed in U.S. Pat. No. 5,131,696 to Sykes for “Tube Joint for Annular Corrugated Tubing,” the disclosures of which are incorporated herein by reference. In another possible embodiment, a spring loaded detent may be used, similar to the method disclosed in expired U.S. Pat. No. 4,083,586 to Helm for “Tube Coupling,” the disclosures of which are incorporated herein by reference. In a third possible embodiment, resilient arms may be used, as in the method disclosed by expired U.S. Pat. No. 4,946,213 to Guest for “Tube Couplings,” the disclosures of which are also incorporated herein by reference. 
         [0086]    Coupling of the fan housing  45  to the first tube section  60  may also serve to retain one or more batteries within the first tube section  60 , so as to be in contact with, and electrically coupled to (direct contact and wiring from a far side end of the battery stack) the electric motor  15 . Battery power may be provided by any battery that serves to provide the proper amount of power to the motor  15 , and in one embodiment, each motor  15  may be powered using four “C” cell batteries, which may be disposable, or more preferably may be rechargeable lithium ion batteries. In another embodiment, the motor  15  may be powered by a marine battery  32  that can be connected, using an electrical cable  33 , to the kayak paddle  10  using a quick connect plug  34 , which may be received by a corresponding socket in the paddle. 
         [0087]    The plug and socket are available for purchase at many retailers, including Minn Kota Accessories, at www.minnkotamotors.com/products/accessories/marine/quick_connect.aspx, the disclosures of which are incorporated herein by reference. The socket may preferably be located near the center of the hand graspable shaft, so as to reduce any interference of the cable with the paddling motion of the user. It should also be noted, that the batteries stored within the paddle may serve as a primary source of power for motor  15 , while the marine battery  32 , which may be disposed upon a boat bottom, may serve as a back-up power source for when the rechargeable cells are exhausted during an outing. Since weight is a major consideration in the design of a paddle for long trips, use of the marine battery  32  as the primary power source may be preferable. The battery may be a true marine battery or a deep cycle battery, or a hybrid. Marine batteries tend to be among one of three different types of lead acid batteries, any of which may be suitable for use herein, and may include: a flooded acid battery, a gelled acid battery, and an advanced absorbed glass mat battery. 
         [0088]    In a preferred embodiment, the socket may also be able to receive a power cable, which may be plugged in to an AC power source, to permit recharging of the batteries while disposed within the levering device. This embodiment would permit a user to take a longer excursion and stop en route at a convenient dock location to eat a meal, or buy provisions, or simply enjoy the scenery, but to also utilize the time to recharge the batteries. Such an embodiment would also provide a means for the recharging of those batteries when the user had returned home, so that the paddle would always be ready for immediate later use. 
         [0089]    The total power needed may depend upon the motor  15  that is selected, which may in turn depend upon the total amount of thrust that the user desires to have available. The motor utilized may be a single speed motor, a two-speed motor, or a variable speed motor. A suitable motor  15  may be obtained from Faulhaber Miniature Drive Systems, and in particular, the series 1724 DC motor may be suitable for use within the levering device shaft, having its specification and envelope available at www.faulhaber.com/uploadpk/EN — 1724_SR_DFF.pdf, the disclosures of which are incorporated herein by reference. Although the motor may be sealed between the fan assembly  40  and corresponding tube sections  60  and  70 , the motor  15  may nonetheless be advantageously selected to be a water resistant motor. The other electrical components and wiring may also similarly be sealed and protected in a water-tight environment, which may involve the use of rubber O-ring seals, or other commonly used sealing shapes and materials that are known in the art. 
         [0090]    The torque generated by the motor  15  may be delivered mechanically to the fan blades, and be coupled thereto, through use of a transmission shaft  16  ( FIG. 10 ) being connected to the output shaft of the motor. The end of the transmission shaft  16  may comprise a first bevel gear  17 , having teeth engaged with corresponding teeth of a second bevel gear  18 . The second bevel gear  18  may have connectivity with the hub  41  to thereby drive fan blades  43  to produce propulsive thrust. 
         [0091]    As seen in  FIG. 7 , the double bladed kayak paddle  10  may preferably have two motors with connectivity to two fan assemblies  40 , each of which may be independently activated using a dedicated switch  30  ( FIG. 5 ). As a result, the two halves of the double bladed kayak paddle  10  ( FIG. 2A ) may be separable to permit independent operation by a single user, possibly being used as oars for rowing, or instead the two halves may be used by two different individuals as paddles. To be usable as a paddle—a paddle that is commonly used for canoeing—a handle  38  may be connected to the non-bladed end of each of the halves, which may require one handle with a male extension to be inserted into second tube section  60 , and one handle comprising a female opening to receive the male extension  48  of the first tube section  60 . 
         [0092]    In an alternate embodiment, seen in  FIGS. 12-14 , a single motor  15 A may be utilized to power dual fans, whereby the motor has output shafts protruding from opposing ends of the motor that connect to a first transmission shaft  16 A and also to a second transmission shaft  16 B, to drive the fans. In another alternate embodiment, the fan assembly  40  and the blade  20  may be made as a unitary member  90  ( FIG. 6A ), which may provide greater strength for the paddle, but would preclude interchangeability of the blades. 
         [0093]    In yet another alternate embodiment, shown in  FIG. 1D , a propulsion/navigation device  12 B may comprise a motor and fan, whereby the motor is aligned axially with the axis of the fan shaft, which may thereby eliminate the need for gears and serve to reduce weight. The motor may be a water-proof brushless motor or a brushed motor. In this arrangement, the rechargeable C-size batteries may be disposed farther down the shaft to be in close proximity to the motor, to reduce the necessary electrical wiring. One example of such an in-line fan and motor arrangement may be the ROV/UAV thrusters that may be purchased from Crust Crawler Robotics (available at http://www.crustcrawler.com/products/urov/index.php?prod=300, the disclosures of which are incorporated herein by reference). 
         [0094]    A variation on this  12 B embodiment of the powered oar/paddle may leverage the advantages offered by brushless motors, and is seen in the propulsion/navigation device  12 BR of  FIGS. 21-23B . Brushless motors offer many advantages over brushed motors, including better wear because there are no brushes and commutator to wear out, reduced maintenance because there are no brushes and commutator that need to be cleaned periodically, longer battery life because the friction from the brushes contacting the commutator plates is eliminated, and a higher power to weight ratio because of the elimination of those parts. In addition to the  12 BR device using a brushless motor, it also leverages, for this particular application, the advantages of the “Outrunner” type of brushless motors, which have permanent magnets on the outside of the electromagnets, as opposed to the “Inrunner” type motor, which have them on the inside, Inrunner motors are commonly utilized on remote controlled aircraft, and tend to be more efficient because they operate at higher RPMs, with lower torque capability, but with a gearbox being required to permit adjustment in the output speed and torque to the propeller to achieve different flying characteristics, which tends to result in more noisy operation. Where a transmission shaft and gearing are utilized in the propulsion/navigation device ( FIG. 10 ), a suitable inrunner motor may also be used, which is seen illustrated in  FIG. 26 , and in which only the shaft rotates. 
         [0095]    The outrunner motor serves quite effectively in the propulsion/navigation device  12 BR because, while it may typically operate at lower RPMs, it produces higher torque, and is quieter while not requiring any associated gearing to furthermore reduce the weight of the device. This outrunner type of motor may be much smaller than the previously mentioned ROV/UAV thrusters. A suitable outrunner brushless motor may have a diameter of 28 mm, length of 30 mm, and may only weigh approximately 70 grams. It may be obtained from Model Motors S.R.O. (see specs at www.modelmotors.cz/index.php?page=61&amp;product=2808&amp;serie=24&amp;line=GOLD, the disclosures of which are incorporated herein by reference). An exemplary outrunner motor  100  is illustrated in  FIG. 25 , and in which the shaft  100 S and the outer portion  100 T both rotate relative to the inner portion  100 I. Wire stator coils in the fixed inner portion  100 I, which may be fixed to a housing using holes  100 H, drives the outrunner. 
         [0096]    As seen in  FIG. 23B , an outrunner motor  100  may be secured to a housing  101  that may be secured to a blade  27 . Blade  27  may have a suitable opening  270  located proximate to the tip of the blade periphery, with the motor  100  preferably being centered upon the opening. The opening  270  may be internal to the periphery of the blade, or may, as seen in  FIG. 20 , be a part of the periphery. The motor housing  101  may comprise a plurality of integral mounting flanges  102  extending radially outward from the motor housing, each of which may comprise a tapered I-beam. The flanges  102  may generally be disposed to be parallel with the fluid flow generated, so as to produce less drag. The ends of each flange  102  may comprise a boss  103 , which may include an internally threaded hole. In one embodiment, a mechanical fastener, including, but not limited to, a bolt, may be used to fasten each boss  27 B of each flange  27 F to the blade  27 . Being mechanically coupled to the shaft of the motor  100 , may be a propeller assembly  104  ( FIG. 23A ), which may be comprised of a hub  105 , and a series of propeller blades  106  being attached thereto. Activating the switch for the motor  100  may turn on the motor and cause its spinning shaft to rotate the propeller assembly  104 , and produce thrust through the displacement of fluid through and about the opening  270  of blade  27 . 
         [0097]    Locating the motor  100  and propeller assembly  104  at the tip of the blade  27  provides additional mechanical benefits for the propulsion device  12 BR. The motor/propeller location serves to increase the leverage (longer lever arm for the motor&#39;s thrust) for increased propulsion, and it serves to increase the time the motor is in the water per stroke to thereby increase the powered assistance to the paddler. Another advantage derived from the location and the increased time that the motor spends submerged, is better cooling of the motor, and its associated electronic speed controller. 
         [0098]    Advantageously being utilized in conjunction with the outrunner motor, may be a battery manufactured by A123 Systems of Watertown, Massachusetts, which dramatically improves upon other lithium ion batteries, particularly the lithium cobalt oxide (LiCoO 2 ) battery, which tends to be highly combustible. The Lithium Ferrous Phosphate (LiFePO4) battery by A123 Systems has superior thermal and chemical stability and offers a longer life cycle over other lithium ion batteries, and furthermore maintains a higher percentage of its power over a more prolonged shelf life. In addition, the LiFePO4 battery packs may have a separate power receptacle usable for outputting power and for receiving a recharging cable. Power from the batteries  35  may be supplied to the motor  100  using electrical cable  36 . A preferred embodiment of the propulsion device may use three cylindrical ANR 26650 batteries made by A123 Systems (see http://www.a123systems.com/products-cells-26650-cylindrical-cell.htm, the disclosures of which are incorporated herein by reference) for a total of 9.9 volts and 2.3 Ah). These batteries may be located inside the shaft for reserve or short-distance powered paddle assistance, while an external stack of cells may also be utilized to supply multiple hours of power. 
         [0099]    The  12 BR device may also include, as seen in  FIG. 22 , a blade being fixed to a portion of the shaft being proximate to the end of the shaft, and may have one or more removable blade portions  27 R. The removable portions  27 R may be insertable into the blade portion that is fixed to the shaft, by using a tongue and groove interface and quick release pins  80  similar to the arrangement shown in  FIG. 4 . 
         [0100]    In yet another embodiment of the aforementioned devices, shown in  FIG. 1E , a propulsion/navigation device  12 C may configured to be similar to the  12 B device, but instead of, or in addition to, the blade being removable, the blade may be pivotally attached to be rotatable 90 degrees using pivot means  12 Cp, so as to eliminate the need to remove the quick release fasteners. This arrangement would allow the user to be able to more quickly convert the combination device being used as an oar/paddle, into the propulsion/navigation device, as seen in  FIG. 19 . Such means of 90 degree pivotal attachment means may be found, for example, in expired U.S. Pat. Nos. 4,586,763 to Paulsen, and 5,037,088 to Bernstein, the disclosures of each being incorporated herein by reference. 
         [0101]      FIG. 16  illustrates use of the modular levering device in the oar  6  configuration, and of it being utilized without any power assistance (i.e., the motor is off, or the battery power has been completely expended). As seen in the figure, the force exerted by the user, F user , overcomes the water resistance, F water resistance , encountered by the grip of the paddle in the water to propel the paddlesports boat forward. The propulsion of the boat is purely due to the mechanical levering provided from the strength of the user. 
         [0102]      FIG. 17  illustrates use of the modular levering device in the oar  6  configuration, and with it being utilized in a first power assisted mode. As can be seen in the Figure, the rower imparts a force, In addition, the motor  15  is supplied with battery power and switched on, with the paddle being oriented to have the fan blades directing the flow forward, which results in the generally aftward reaction force, F fan , being imparted to the oar  6 . The aftward reaction force, F fan , therein serves to counter the water resistance force, F water resistance , which makes it easier for the user to paddle, which may be desirable where the paddle blade and graspable shaft may be large for the user, as it will therefore require less strength per stroke to lever; however, this also results in less of a levering force being accomplished to propel the boat forward. The arrangement may permit a smaller user to paddle for a significantly longer period of time. 
         [0103]    It should be noted that power assistance according to this approach requires the user to maintain a consistent stroke frequency when the paddles are “wet” and to quickly remove the paddles at the end of the stroke, without dipping the paddle into the water and then holding it statically submerged for any period of time, as this would no longer serve to simply counter water resistance, but would instead act to counter the forward motion. It would be the equivalent of having a trolling motor operating in a direction opposite to the desired course, which would be further exaggerated by the drag resulting from the gripping area  21  of the blade  20  lingering in the water flowing relative to the boat. 
         [0104]      FIG. 18  illustrates use of the modular levering device in the oar  6  configuration, and with it being utilized in a second power assisted mode. For other rowers, and even for that same rower described above for the first power assisted mode, but being at a different stage of the trip, conserving energy while paddling may not be the goal, because those users may be seeking to produce the maximum amount of propulsion possible to achieve a greater speed for a short duration. In this mode, the rower imparts a force, F row 2 , and in addition, the paddle is oriented to have the fan blades directing the flow aftward, which results in the generally forward reaction force, F fan , being imparted to the oar  6 . This is the equivalent of increasing the gripping capability of the gripping area  21  of the blade  20 . The generally forward force, F fan , is additive with the water resistance force, F water resistance , which permits the paddler, having sufficient strength, to apply a larger rowing force, F row 2 , to produce greater forward speed. Here, the effects of an oar/paddle lingering statically in the water are not as deleterious as in the first power assisted mode, as the drag resulting from the gripping area  21  of the blade  20  lingering in the water flowing relative to the boat may be partially or completely countered by the propulsion being provided. 
         [0105]    The fourth mode of operation is seen in  FIG. 19 , with the advantageous nature of having the blade  20  being removable through use of a quick-release catch, which enables easy conversion of the levering device into a hand-held multi-directional propulsion device, with it being more convenient to use than the more cumbersome, transom-mounted trolling motor. The arrangement may be directed towards the boat&#39;s stern, which propels the boat forward, just like a standard trolling motor. Alternatively, as seen in  FIG. 19 , the device may be held on the port or starboard sides to provide a lateral propulsive force in order to navigate the boat so as to come abeam another boat, or to a dock, or to generally navigate into tight places like a berth, slip, etc. Alternatively, the device may be more broadly utilized by being so located on the side of the boat, and simply be oriented or clocked at the appropriate position so as to cause thrust in any one of the possible compass directions (zero to 360 degrees), for navigation in the opposite direction. 
         [0106]    Also, while the invention is herein described as a modular levering device that may quickly be transformed for alternative uses in any one of the four operating modes, the fourth mode—the propulsion/navigation portion of the invention—may also advantageously be separately adapted, manufactured, and marketed solely to serve as an emergency battery-operated propulsion device  12 A for small boats. As such, the device may be particularly useful when mechanical problems are encountered with sails or masts, as well as to serve as a back-up when day-sailing on a sunfish, etc., and the winds inconveniently dissipate. The back-up propulsion/navigation device  12 A may thus be integrally mounted within such small boats, as an accessory. The specially adapted propulsion/navigation device (which may or may not have an attachable blade) may further include a tethering cable  85  ( FIG. 19 ) extending from the manually graspable shaft or the handle, and being attached to the boat, to prevent a run-away paddle in case the paddle/oar slips from the user&#39;s grasp. For users who may prefer to not operate the propulsion/navigation device  12 A in a strictly hand-held manner, the device may include an L-shaped or U-shaped bracket  86  which may be used so the device can slidably rest atop the gunwale  2 —the top edge of the side of the boat  1 . The bracket may be connected to the shaft via a hinge arrangement which would permit pivotal movement of the device to thus allow direction changes, while the propulsion/navigation device  12 A remains generally fixed to the gunwale. 
         [0107]    A further embodiment of the present invention is shown by the kayak paddle  14  of  FIG. 27A . The kayak paddle  14  may comprise a dual shaft arrangement with a hinge therebetween, which permits the shafts to be extended away from each other for use in levering of a kayak, or to be partially folded for conversion of the paddle into a propulsion device through the addition of one or more motor pods, or to be folded even further for convenient storage of the paddle. 
         [0108]    The kayak paddle  14  may include a first shaft  141  and a second shaft  151 , with the first end of the first shaft being pivotally connected to the first end of the second shaft. The second ends of first shaft  141  and second shaft  151  may have paddle blades  161  and  171 , respectively, extending therefrom, each of which may be integrally formed with the shafts or be secured thereto. To be releasably secured to the shaft, each of the blades  161  and  171  may have an axially extending cylindrical protrusion that may be releasably received in a hollow tube portion of the respective first and second shafts, and may be secured therein using internal and external threading, or may be secured therein using the spring loaded detent and tube coupling approach disclosed above, which may also be used to permit rotation of the shafts relative to the respective hub portions using additional holes in the tube sections of each shaft. To be fixedly secured to the shaft, a portion of each blade may be secured using any suitable means known in the art, including, but not limited to, mechanical fasteners, adhesive, etc. 
         [0109]    Pivotal attachment of the first shaft  141  to the second shaft  142  may be suitably accomplished in one or more different ways. In a first approach, illustrated within  FIGS. 27A and 28 , one of the shafts—shaft  151  in FIG.  28 —may have a cylindrical axle  153  protruding from a hub portion  152 . The axle  153  may be received in a corresponding cylindrical recess  143  in the hub  142  of the shaft  141 . The axle  153  may be retained in the corresponding recess by having an annular protrusion  153 P on the end of the axle be received within an annular recess at the bottom of the circular recess  143 . Instead of using the annular protrusion  153 P, axle  153  may instead be constructed to have a sufficient length so as to extend through the entire hub portion  142  of shaft  141 , and may have a cylindrical plate member (not shown) be fastened to it to pivotally nest the hub portion  142  of shaft  141  upon the axle  153 , so as to be nested between the hub portion  152  of shaft  151  and the cylindrical plate member. Pivotal attachment of the first shaft  141  to the second shaft  151  may alternatively be accomplished using oblique annular flanges and an intermediate shaft section analogous to that structure described in U.S. Pat. No. 2,557,507 to Lang for “Adjustable Joint Structure for Electric Lap Supports.” Use of the oblique flanges and intermediate shaft section would allow the first and second shafts to be parallel to each other in the stowed position (similar to  FIG. 5  in the Lang patent), instead of as seen within  FIG. 27B  herein. 
         [0110]    With the first shaft  141  pivotally mounted to the second shaft  151  as disclosed above, the angular relationship between the axial direction of the first shaft, which may be the axis of a cylindrical shaft member, and the axial direction of the second shaft, may be controlled in one of several ways. A tensioning knob may be used (not shown, but see U.S. Design Pat. No. D416,060 and U.S. Pat. No. 4,521,010 to Hahn for “Exercise Tension Device Assembly,” the disclosures of each being incorporated herein by reference). The tensioning knob may have a shaft slidably disposed in a hole in the hub portion  142  of shaft  141 , and be threadably received in the axle  153  of the hub portion  152  of shaft  151 . Torquing of the tension knob may thus cause a sufficient friction force between the two hub portions to deter relative motion therebetween. In addition, the faying surface between the hub portion  142  and hub portion  152  may each have a plurality of teeth at each of the hubs&#39; periphery that may interlock, to reduce the amount of torque and friction that would be needed by the tension knob to prevent relative motion between the two hubs. Thus, unscrewing the tension knob would permit the hub portions to be backed away from each other to disengage those teeth, to thereafter allow relative pivotal motion between the hubs using the axle  153 , so that the axis  141 X of the first shaft  141  may be set to be at a desired angle with respect to the axis  151 X of the second shaft  151 . 
         [0111]    Instead of using the tension knob to inhibit relative pivotal motion between the hubs, a quick release pin  180  may be slidable disposed in a hole in the hub  152 . The quick release pin  180  may be of sufficient length so as to extend past the side of the hub  152  of shaft  151  that contacts hub  142  of shaft  141 , to be received in a corresponding hole  142 H i  within hub  142  in a clearance fit, which may be a tight clearance fit. The quick release pin  180  may have a flange  181  that may be biased relative to the hub  152  of shaft  151  by a helical spring  182  to have the pin be normally engaged within the hole  142 H i  of the hub  142 . The quick release pin  180  may protrude out from the other side of the hub  152 , and have a ring  183  be pivotally secured thereon. The pivotal mounting of the ring  183  may permit it to extend outwardly from hub  152 , as seen in  FIG. 28 , or to be pivoted to be flush against the hub, as seen in  FIG. 27A . 
         [0112]    The ring  183  may be engaged by a finger of the paddler to exert a force on the pin to overcome the biasing and withdraw the pin from its position within the hole  142 H i  in the hub  142  of shaft  141 , to allow relative pivotal motion between the hubs using the axle  153 , so that the axis  141 X of the first shaft  141  may be set to be at a desired angle with respect to the axis  151 X of the second shaft  151 . With this approach, if only one hole is used in the hub portion  142 —hole  142 H i , the clocking of that hole would define the only relative orientation between axes of the shafts at which the two hub portions could be locked. As seen in  FIGS. 27A and 28 , a first such hole, being hole  142 H i , may permit locking of the two shafts with the axis of the first shaft being parallel to the axis of the second shaft, and with the blade at the second end of the first shaft being distal from the blade at the second end of the second shaft, to be configured for paddling. Use of another such hole (not shown), which may be clocked at approximately 90 degrees away from hole  142 H i  may permit securing of the axis of the first shaft to be perpendicular to the axis of the second shaft, to be configured for propulsion of the kayak or other paddlesports boat, as discussed hereinafter. 
         [0113]      FIG. 27C  illustrates the hinged kayak paddle of  FIG. 27A , but having a motor pod  200  of the current invention having been releasably secured to the bottom of one of the blades of the paddle for use as a propulsion device. The motor pod  200  is shown in detail in  FIG. 31 . Motor pod  200  may include a motor housing  201  that may receive a motor  202  therein, which may be secured therein using a wall  203  and brackets, to have the shaft  204  protruding outward therefrom. The motor  202  may be protected against water damage by sealing the motor housing  201  to prevent the intrusion of water therein, through the use of gaskets or O-rings  205 . A multi-bladed propeller  206  may be fixedly secured to the shaft  204 . The propeller  206  may be protected by a shroud  207  that may be integral with the motor housing  201 , but has openings therein to allow for the passage of water displaced by the propeller to provide the propulsive force, or the shroud  207  may be secured to the motor housing  201  through the attachment of flanges  207 F ( FIG. 29 ). 
         [0114]    Also extending away from the motor housing  201  may be the motor pod mounting flanges  208 A and  208 B, which are also seen in  FIGS. 29 and 31 . The motor pod mounting flanges  208 A and  208 B may each have a rectangular slot therein to slidably receive an elongated rectangular protrusion  161 Pi and  161 Pii on each side of the blade  161 . The motor pod mounting flanges  208 A and  208 B may be releasably secured to the rectangular protrusions using an integral retaining clip  209  that may have a spring loaded pin that is received within a hole in one or both of the rectangular protrusions. The interior side of one or both of the mounting flanges  208 A and  208 B may include as many electrical contacts as are necessary to accommodate the motor. In  FIG. 31 , three electrical contacts  210 A,  210 B, and  210 C are shown on the flange(s) which may be electrically coupled to supply control over, and power to, the motor  202 . These electrical contacts  210 A,  210 B, and  210 C may become electrically coupled to the source of power used for the invention, through wiring in the paddle&#39;s shaft, by engaging corresponding contacts  161 A,  161 B, and  161 C on the paddle blade  161 , as the flanges of the motor pod  200  are slidably received upon the rectangular protrusions of the blade (see  FIGS. 30A and 30B ). 
         [0115]      FIG. 27C  illustrates one possible configuration of the modular paddle  14 , being shown after the removal of blade  161 . (Note that the blade  161  could be removed and be replaced by the handle  38  in  FIG. 6  for the device to be used as a long canoe paddle, instead of a kayak paddle, or the shaft  151  and hubs  142 / 152  could also be removed and the handle  36  could be received within the shaft  151  to fix n a shorter length canoe paddle).  FIGS. 27C and 27D  also illustrate the use of holes at 90 degree increments at the shaft ends to further permit rotation of the second shaft  141  to be clocked at 90 degrees from its 90 degree folded position. This is illustrated in  FIG. 27D . So, folding of the shaft  141  in  FIG. 27C  roughly 90 degrees using the axle arrangement of the hubs  142 / 152  as previously described and being locked thereat using a hole  142 H ii , would result in the shaft being oriented to protrude outward relative to the plane of blade  171  as seen in  FIG. 28C , and by depressing the pin  151 P of shaft  151 , the shaft  141  and the hubs may be rotated to appear as seen in  FIG. 27D . 
         [0116]    Note that the blades used herein may be curved; however, where the blades that are used are not curved, although they will have a discrete thickness forming a three-dimensional part, the flat face of either side of the blade may generally be planar, and any reference herein to a shaft or an axis of a shaft being at a 90 degree angle to the plane of the blade, refers to the shaft being generally orthogonal to either side of the flat paddle blade, or the theoretical mid-plane between those two planar surfaces. Furthermore, any reference to a shaft or axis of a shaft being co-planar with the “plane” of the paddle blade refers to the shaft or its axis being generally parallel to either side of the flat paddle blade and generally falling within the theoretical mid-plane between those two planar surfaces. 
         [0117]    The arrangement of  FIG. 27D  is advantageous for use in the propulsion of other boats, such as a row boat. The arrangement of  FIG. 27D  may be placed upon the gunwale at the stern of the boat, and may be releasably mounted there using a bracket as described previously, or may be handheld to propel the boat, with the blade  171  also being capable of serving as a rudder. 
         [0118]    The examples and descriptions provided merely illustrate a preferred embodiment of the present invention. Those skilled in the art and having the benefit of the present disclosure will appreciate that further embodiments may be implemented with various changes within the scope of the present invention. Other modifications, substitutions, omissions and changes may be made in the design, size, materials used or proportions, operating conditions, assembly sequence, or arrangement or positioning of elements and members of the preferred embodiment without departing from the spirit of this invention.