Abstract:
A paddle for stand-up paddle boards includes a paddle blade at a lower end of the paddle shaft and a sail assembly slidingly stowed within the shaft, with the sail deployed by sliding the sail assembly distally out of the shaft upper end. The sail assembly may include a sail and support frame. A method and system for transporting a user across water or other surfaces has a board for the user to stand upon and a paddle with sail slidingly deployed from inside a paddle shaft via an opening in the upper end. To propel via paddling, the user leaves the sail stowed within the shaft. The propel via wind, the user deploys the sail out of the shaft, places the blade onto the board upper surface, and angles the paddle and sail to catch the wind and propel the user across the water.

Description:
RELATED APPLICATIONS 
     The current application claims priority from U.S. Provisional Patent Application No. 61/802,242, filed Mar. 15, 2013, and entitled “Sail Paddle for Stand Up Paddle Boards”, and also from U.S. Provisional Patent Application No. 61/688,837, filed May 22, 2012 and entitled “Sail Paddle for Stand Up Paddle Boards”, and also from U.S. Provisional Patent Application No. 61/687,279, filed Apr. 23, 2012 and entitled “Sail Paddle for Stand Up Paddle Boards”, the entire contents of each of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of standup paddle boards, where a person stands on a paddle board and propels himself/herself through the water using a relatively long paddle via a paddling motion and/or, with the current invention, via wind power. 
     BACKGROUND OF THE INVENTION 
     Paddle boarding is a sport where a relatively large and buoyant surfboard-like board is used, with a user standing on the board and paddling using a paddle having a relatively long shaft with a blade at one end, and often a handle at the other. The relatively long shaft permits the user to dip the blade into the water from a standing position in order to drive the board forward via the blade engaging the water. 
     A user can stand on the SUP board and paddle with the long-shafted paddle. The user can paddle the board over relatively flat water and, depending on the strength and skill of the user, in relatively rough water. Skilled SUP boarders can even use the paddle and board to surf waves. 
     Paddle boards permit the user to paddle across relatively long distances with relatively little resistance from the water due to the relatively small displacement of the SUP board. However, due to the relatively large cross-sectional area presented by a user&#39;s body when in the standing position, wind conditions can have a major impact on the user&#39;s ability to paddle the board through the water. Users may paddle to a desired destination, and then be relatively tired for the return journey back to their starting point. In windy conditions, the user may have great difficulty in advancing the board through the water, especially if the user is already tired from an outbound journey and is presented by a headwind on the return journey. 
     SUMMARY OF THE INVENTION 
     The invention comprises systems, methods, and devices for stand-up paddle boarding, and more particularly for using the wind to power a stand-up paddle board or other conveyance. The invention may also be applicable to other types of transport, including so-called land paddles for use with skateboards and other wheeled transport. 
     In an embodiment of the invention, a stand-up paddle is provided which has a shaft having a proximal end and a distal end. A paddle blade is provided at the proximal end. A sail assembly is slidingly disposed within an inner lumen of the shaft, and is configured to be slidingly deployed in telescoping relation out of an opening in the distal end of the shaft. The opening may be positioned in a handle, such as a substantially T-shaped handle, positioned at the distal end of the shaft. The opening may include a substantially funnel-shaped portion configured to guide the sail assembly into the shaft inner lumen when the user slidingly stows the sail assembly into the shaft. When the sail assembly is stowed within the paddle shaft, the paddle may have the same overall appearance and performance as a standard (i.e., non-sail-equipped) SUP paddle. 
     A sail assembly according to an embodiment of the invention may comprise a sail and a sail support structure. The sail and sail support structure may be of various shapes and configuration, depending on the particular embodiment. In one embodiment, the sail support structure comprises a mast and boom, with the mast in the deployed configuration extending distally from the distal end of the paddle shaft and in substantially longitudinal alignment therewith, while the boom extends laterally from the mast. The boom may extend from the mast at an angle between 60 and 12 degrees, or in a substantially perpendicular manner, such as at an angle of (or of about) 90 degrees from the mast. The boom may join the mast at a point at or adjacent the distal end of the paddle shaft when the sail assembly is in the deployed configuration. The sail may have an upper portion, which may be substantially triangular in shape, extending between the boom and mast. The sail may have a lower portion, which may be substantially triangular in shape, extending between the boom and paddle shaft. 
     When the SUP boarder has the sail assembly deployed and is sailing with the SUP board, the paddle blade may be set against the board top surface. The paddle blade may also be used for maneuvering/guiding the board by holding the blade in the water (e.g., on the downwind or upwind side of the board) to act as rudder and/or keel in guiding the board. 
     In one embodiment of the invention, a system for paddle boarding comprises a paddle board and a paddle. The paddle includes a paddle shaft having a paddle blade on a proximal end of the paddle shaft and a sail assembly configured to slidingly and telescopically extend from the distal end of the paddle shaft. The paddle board may include a multi-slotted paddle blade holder having slots configured to receive the lower edge of the paddle blade, with the slots sized to receive the paddle blade and to prevent rotational movement (about the longitudinal axis defined by the paddle shaft) of the paddle blade with respect to the SUP board. 
     In a further embodiment of the invention, a sail assembly and upper paddle shaft portion (including paddle handle) are sold or otherwise provided as a retrofitting kit to retrofit an existing adjustable-length SUP paddle, wherein the existing adjustable-length paddle has a previously-provided lower paddle shaft having a paddle blade at the proximal end thereof, and a previously-provided upper paddle shaft portion having a paddle handle at the distal end thereof, wherein the previously-provided upper paddle shaft is configured to slide within the previously-provided lower paddle shaft in order to adjust the overall length of the paddle. A user can slidingly remove the previously-provided upper paddle shaft from the previously-provided lower paddle shaft, and replace it with the new sail-equipped upper paddle shaft, which may be dimensioned (e.g., having the same diameter and/or similar length as the previously-provided upper paddle shaft) to mate with the previously-provided lower paddle shaft in the same manner as the previously-provided upper paddle shaft. The user can replace the upper paddle shaft portion multiple times, including swapping out an upper paddle shaft having no sail with an upper paddle shaft having a sail, or swapping out an upper paddle shaft having a first sail of a first size and shape with an upper paddle shaft having a second sail having a different size and/or shape from the first sail. 
     A paddle according to an embodiment of the invention is a specially designed paddle for the growing sport of stand-up paddle boarding. It is a standup paddle that can convert to a standup sailing rig for allowing ease of movement by enabling the user to sail or move without paddling in certain directions (i.e. with the wind). It may also be used to sail by tacking and jibing into the wind. Everything that is needed to sail may be self-contained within the paddle&#39;s shaft/tubular body (which may be 4 to 6½ in length) with no external accessories or hardware needed. 
     A paddle of the invention may have an elongated paddle shaft having an internal lumen, a proximal end, a distal end, and distal opening at the distal end, with the distal opening leading to the internal lumen; a paddle blade secured to the proximal end of the paddle shaft; and a sail assembly comprising a sail and a collapsible support structure, wherein the sail assembly comprises a stored configuration and a deployed configuration, wherein in the stored configuration the support structure and sail assembly are slidingly stowed within the paddle shaft internal lumen, in the deployed configuration the support structure and sail extend outwardly from the paddle shaft distal end, and wherein the sail assembly transforms from the stored configuration to the deployed configuration by telescopically and slidingly extending from the distal opening of the elongated paddle shaft. The support structure may have a mast and a boom, with the mast comprises a mast proximal end and a mast distal end and the boom comprises a boom proximal end and a boom distal end, and wherein the boom proximal end is hingedly secured to the mast at a boom attachment point, and wherein the sail assembly has a deployed configuration and a stowed configuration, wherein in the stowed configuration the mast, boom, and sail are slidingly positioned within the paddle shaft internal lumen with the boom substantially parallel to the mast, wherein in the deployed configuration the sail, mast, and boom are positioned outside of the paddle shaft internal lumen with the boom substantially non-parallel to the mast, wherein the sail assembly transforms from the stowed configuration to the deployed configuration by hingedly rotating the boom to a substantially non-parallel orientation from the mast. The boom attachment point may be positioned at a proximal end of the mast and at a distal end of the paddle shaft when the sail assembly is in the deployed configuration. The mast may be positioned substantially in longitudinal alignment with the paddle shaft when the sail assembly is in the deployed configuration. The boom may be positioned substantially perpendicular to the mast when the sail assembly is in the deployed configuration. The paddle shaft may have a lower shaft portion to which the paddle blade is secured, an upper shaft portion, and a shaft locking mechanism, with the lower shaft portion and upper shaft portion telescopically and rotatably movable with respect to each other when the shaft locking mechanism is locked, and telescopically and/or rotatably locked with respect to each other when the shaft locking mechanism is locked. The sail may have a sail strap secured to the boom at a position closer to the distal end thereof than to the proximal end thereof (e.g., at or adjacent the distal end thereof) with the sail strap is sized and configured to permit a user to pass a hand therethrough to thereby grasp the sail strap. The strap may provide an opening from 3 to 8 inches in length for a user to pass his/her hand and/or fingers therethrough in order to grasp the strap/boom/sail. The paddle may include a sealing mechanism to prevent water form passing into the paddle shaft, which may be in the form of an O-ring at or adjacent a distal end of the mast, with the O-ring configured to seal the shaft distal opening when the mast, boom, and sail are slidingly positioned within the paddle shaft internal lumen in the stowed configuration. 
     An embodiment of the invention is a system for transport over water, with a stand up paddle board configured for a person to stand thereon; a paddle, wherein the paddle comprises a paddle shaft having a distal end and a proximal end, a paddle blade secured to the paddle shaft proximal end, and a sail assembly configured to slidingly and telescopically extend from and retract into the distal end of the paddle shaft. The system may have a pad positioned on an upper surface of the stand up paddle board, wherein the pad comprises one or more grooves on an upper surface thereof configured to receive a lower edge of the paddle blade. The pad may have at least 8 grooves, the grooves intersect at a single intersection point, and the grooves extend across the pad upper surface at different angles with respect to each other. The system may include a paddle blade engaging structure extending from a side of the paddle board, the structure configured to engage and secure the paddle blade to prevent rearward movement thereof with respect to the paddle board when the board is in water with the paddle blade positioned in the water against the structure. The paddle blade engaging structure may extend sideways from the side of the paddle board and forward with respect to the paddle board. 
     A method of traveling across the water surface on a paddle board according to an embodiment of the invention comprises: placing a paddle board in the water; holding a paddle in a hand of the user, wherein the paddle comprises a paddle shaft having a proximal and a distal end, wherein a paddle blade is secured to the proximal end and a sail assembly is slidingly disposed within the paddle shaft, wherein the user holds the paddle by the paddle shaft; the user standing on the upper surface of the paddle board; the user paddling the board by placing the paddle blade in the water and pushing against the water via the paddle blade; telescopically and slidingly extending the sail assembly out of the paddle shaft via the distal end of the shaft; unfolding the sail assembly to a deployed configuration; securing the sail assembly in the deployed configuration; sailing the paddle board by positioning the paddle and deployed sail assembly at a desired position with respect to the board to capture and/or redirect the wind to effectuate movement of the paddle board. After sailing the paddle board, the user can unsecure the sail assembly from the deployed configuration; fold the sail assembly from the deployed configuration; and slidingly and telescopically retract the sail assembly into the paddle shaft via the distal end of the shaft. 
     Sailing the paddle board may involve placing the paddle blade onto the top surface of the paddle board, and/or placing the paddle blade into the water along a side of the paddle board with the blade substantially parallel to, and/or angled from, the side of the paddle board. The paddle board may be steered by shifting the deployed sail to the right and/or left side of the paddle board. 
     The invention may also be used in connection with skate boards by replacing the paddle blade of the SUP paddle with a padded lower end, such as a rubber wheel-shaped end (which may be round or curved or of another shape), configured to engage a solid surface such as a road or sidewalk. Such a modified paddle becomes a so-called land paddle which an operator can use by pressing the lower end against the ground (e.g., sidewalks, roads, etc.) to push himself/herself along on a wheeled skateboard. In such an embodiment, the user can deploy the sail and place the padded lower end onto the skateboard upper surface, and let the wind drive the operator and skateboard along. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a perspective view of a system according to an embodiment of the invention; 
         FIGS. 2A-2C  depict perspective views, with sail assembly in stowed, being deployed, and fully deployed, respectively, of a paddle according to an embodiment of the invention; 
         FIG. 3  depicts a perspective (exploded) view of the paddle of  FIGS. 2A-2C ; 
         FIGS. 4A-4C  depict close-up (exploded) perspective views of portions of the paddle of  FIG. 3 ; 
         FIGS. 5A-5D  depict top, front, side (cross-sectional), and perspective views of a paddle blade according to an embodiment of the invention; 
         FIGS. 6A-6F  depict side, top (cross-sectional), side, side (close-up), perspective, and perspective (close-up) views of a lower portion of a paddle shaft according to an embodiment of the invention; 
         FIGS. 7A-7C  depict side, top (cross-sectional), and perspective views of an upper portion of a paddle shaft according to an embodiment of the invention; 
         FIGS. 8A-8F  depict perspective, top, back, front, side, and side (cross-sectional) views of a paddle handle according to an embodiment of the invention; 
         FIGS. 9A-9E  depict front perspective, rear perspective, side, front, and bottom views of a sail top cap according to an embodiment of the invention; 
         FIGS. 10A-10C  depict side, side (close-up), and side (close-up) views of a mast according to an embodiment of the invention; 
         FIG. 11  depicts a side view of a boom according to an embodiment of the invention; 
         FIG. 12  depicts a perspective view of a boom yoke according to an embodiment of the invention; 
         FIGS. 13A-13E  depict perspective, top, side, front, and back views of an inner slider portion according to an embodiment of the invention; 
         FIGS. 14A-14E  depict perspective, top, side, front, and back views of an outer slider portion according to an embodiment of the invention; 
         FIG. 15  depicts a perspective view of the inner and outer slider portions assembled with mast, yoke, and boom according to an embodiment of the invention; 
         FIGS. 16A-16C  depict side, side (cross-sectional), and side (cross-sectional) views of a distal portion of a paddle according to the invention, including the handle, slider, yoke, mast, and boom in the deployed configuration; 
         FIG. 17  depicts a perspective view, in cross-section, of a slider with the paddle in the deployed configuration according to an embodiment of the invention; 
         FIGS. 18A-18E  depict perspective, top, front, side, and side views, respectively, of a downhaul lock according to an embodiment of the invention; 
         FIGS. 19A and 19B  depict side views of the top portion and the lower portion, respectively, of a sail according to an embodiment of the invention; 
         FIG. 19C  depicts a side view of the top and side portions of  FIGS. 19A and 19B  assembled into a complete sail according to an embodiment of the invention; 
         FIGS. 20A-20D  depict top, perspective, front (cross-section), and front views of a paddle blade holder according to an embodiment of the invention; 
         FIGS. 20E-F  depict perspective views of the paddle blade holder of  FIGS. 20A-20D  secured to a paddle board and in use with a paddle according to an embodiment of the invention; 
         FIGS. 21A-21C  depict top, perspective, and side views of a paddle blade holder according to an embodiment of the invention; 
         FIGS. 22A-22C  depict perspective, front, and side (cross-sectional) views of a paddle blade holder according to an embodiment of the invention; 
         FIGS. 23A-23C  depict perspective views, in deployed, stowing, and stowed configurations, of a sail assembly according to an embodiment of the invention; 
         FIGS. 24A-24B  depict side (cross-sectional) views in deployed and stowed configuration, respectively, of a paddle according to a further embodiment of the invention; 
         FIGS. 25A-25B  depict perspective and rear views, respectively, of a system according to the invention having straps for holding the paddle blade adjacent the SUP paddle board; 
         FIGS. 26A-26B  depict perspective and front views, respectively, of a system according to the invention having a slot in the SUP paddle board for receiving a blade of the SUP paddle; and 
         FIG. 27  depicts a perspective view of a system for propelling an operator using a skateboard and a land paddle having a sail therein. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     A system  10  according to the invention is depicted in  FIG. 1 . The system comprises a stand-up paddle board  12  and a paddle  14 . The paddle  14  includes a paddle shaft  16  having a paddle blade  18  at a proximal end  20  thereof, and a handle  22  at a distal end  24  thereof. A sail assembly  26  extends from the paddle shaft  16 . The sail assembly  26  comprises a sail  28  and support structure  30 , with the support structure comprising a mast  32  and boom  34 . The paddle  14  can be used to paddle the SUP board  12  (preferably with the sail in a stowed configuration depicted in  FIG. 2A  below), or to sail the SUP board. To sail the SUP board  12 , the user can stand on the SUP board  12  and place a lower edge  36  of the paddle blade  18  against the top surface  38  of the SUP board  12 . The lower edge  36  of the paddle blade may be placed at a position toward the front end  40  of the SUP board  12 . A paddle blade holder  42  may be positioned on the SUP board top surface  38  at a desired position where the paddle blade lower edge  36  is intended to be positioned. The user can grasp the paddle  14  by the shaft  16  and/or by the sail assembly  26 , such as by grasping one or more of the sail straps  44 . Note that the sail straps may be secured to the sail (as via thread), to the boom, and/or both the sail and the boom. 
     The sail assembly can be stowed inside the paddle shaft  16  (as depicted in  FIG. 2A  below) for regular paddling, and can be extended (as depicted in FIGS.  1  and  2 B- 2 C) from inside the paddle shaft&#39;s tubular body  16  and unfolded to set the sail  28  into certain directions. The operator holds the paddle  14  by the shaft tubular body  16  and/or the sail assembly  26  (e.g., via the boom  34  and/or the sail  28 ) thus allowing the sail to be high enough to catch the wind and permit the operator to sail in a designated direction. To change the direction of sail, the operator rotates the sail assembly to a desired position (e.g., by rotating the entire paddle) to achieve the desired direction of travel. If the wind dies, or the wind direction is not conducive to the desired direction of travel, or the operator simply wants to paddle normally, the sail assembly  26  can be stowed by sliding the sail assembly  26  back into the paddle shaft  16 . 
     The paddle  14  has stowed and deployed configurations, as depicted in  FIGS. 2A-2C . In  FIG. 2A , the sail assembly is in the stowed configuration and thus not visible, and the paddle  14  looks and operates like a standard SUP paddle. In the particular embodiment depicted, the paddle shaft  16  is formed from two portions, a lower portion  50  and an upper portion  52 , with the upper portion  52  configured to slide within the lower portion  50  when a locking mechanism  54  is unlocked to permit the sliding action in order to adjust the shaft length  56  and thus the overall paddle length  58  from blade tip to handle. When the desired shaft length is achieved, the locking mechanism  54 , which may be a standard compressive locking fitting (e.g., operated by moving a lever or rotating the entire lock) such as those known in the art, may be returned to the locked position to prevent further sliding of the upper portion  52  with respect to the lower portion  50  and thus maintain the desired shaft length  56 . 
     As depicted in  FIG. 2B , with the sail assembly  26  can be slidingly deployed in a substantially telescoping manner from the paddle shaft  16  by pulling on the sail assembly cap  60 , which is secured to the mast distal end  62  and, when the sail assembly  26  is stowed, is positioned snuggly within the top of the paddle handle  22 . When initially slid out of the paddle shaft  16 , the mast  32  and boom  34  are substantially parallel to each other and also in longitudinal alignment with the paddle shaft  16 . When the sail assembly  26  is slid out to its maximum position from within the paddle shaft  16 , the mast  32  is still held in substantial alignment with the paddle shaft  16 , while the boom  34  can rotate with the boom distal end  64  rotating downward and away from the mast distal end  59 . The sail assembly comprises a lower sail loop  66  which acts as a downhaul for the sail  28 . As the sail assembly  26  is deployed and the boom  34  is lowered, the operator can secure the lower sail loop  66  to a lower portion of the paddle  14 , such as via the downhaul lock sleeve  68  which, in the embodiment depicted, includes a downwardly-directed hook  70  configured to receive and hold the lower sail loop  62 . Once the lower sail loop  66  is secured to the downhaul lock sleeve  68 , the downhaul lock sleeve  68  can be unlocked to permit it to slide. The user can slide the (unlocked) downhaul lock sleeve downward to tighten/stretch the sail  28  to a desired position (e.g., a fully open configuration with the sail fabric tightly drawn between the mast, boom, and paddle shaft) as depicted in  FIG. 2C , and then lock the downhaul lock sleeve  68  in the desired position to hold the sail in the desired position. Note that the user may wrap the sail lower portion partially around the paddle shaft  16 , such as by rotating the downhaul lock sleeve  68  (with the lower sail loop  66  secured thereto) by 360 degrees or more in order to further tighten the sail, and/or to reduce/eliminate airflow between the paddle shaft  16  and sail  28 . The sail  28  has a leading edge  46  and trailing edge  48 . In order to re-stow the sail assembly  26 , the operator disconnects the lower sail loop from the paddle (e.g., by unlocking the downhaul lock sleeve  68  and sliding it upward to reduce sail tension and then disconnect the lower sail loop  66  therefrom). The operator then gathers the sail  28  upward and pushes the boom  34  upward until the boom is substantially parallel with the mast  32 , as depicted in  FIG. 2B . The operator can then push down on the sail assembly cap  60  to slide the sail assembly  26  back into the paddle shaft  16 . 
     The individual components of the sail of  FIGS. 2A-2C  are depicted in exploded view in FIGS.  3  and  4 A- 4 C. As shown in  FIG. 3 , the sail  28  includes an upper portion  28   a  and a lower portion  28   b . The sail upper portion  28   a  may have a front sleeve  80  along the leading edge  82  thereof configured to slidingly receive the mast  32 , and possibly a leading edge cord  84 , therein. The lower edge  86  of the sail upper portion  28   a  and the upper edge  88  of the sail lower portion  28   b  may be sewn together in overlapping fashion to form a central sleeve  90  (with the lower edge  86  forming one side and the upper edge  88  forming the other side thereof) configured to receive the boom  34  therein. The central sleeve  90  may be sealed at the distal end  92  thereof to prevent the boom distal end  64  from extending out of the central sleeve distal end  92 . A cap  94  (possibly formed of a soft rubber-like material) may be provided on the boom distal end  64  to cushion the end thereof to prevent the boom distal end  64  from penetrating the sealed distal end  92  of the central sleeve  90 . 
     As depicted in  FIG. 4A , the top cap  60  includes an O-ring  100  which, when the sail assembly  26  is in the fully stowed configuration with the top cap  60  fully seated into the paddle handle  22 , seals around the top cap  60  to prevent water from flowing around the top cap  60  and into the paddle shaft  16 . The sail upper portion  28   a  is secured to the top cap  60  via an upper sail loop  102 . The upper sail loop  102  may be an upper end of a leading edge cord  84 , and/or may be secured directly to the uppermost corner  104  of the upper sail portion  28   a.    
       FIG. 4B  depicts the handle  22  and the lower portions of the sail assembly  26 , including the mast  32 , boom  34 , yoke  106 , and slider  108 . A center sail loop  110 , which may be a lower end of a leading edge cord  84 , is secured to the slider  108 , such as via a hook on the slider (not shown). The downhaul lock sleeve  68  is depicted in  FIG. 4C , with a lever  112  configured, when in the locked position, to compress the downhaul lock sleeve  68  onto the paddle shaft  16  to prevent the downhaul lock sleeve  68  from sliding thereon. The lower sail loop  66  is configured to be releasably secured to the hook  70  on the downhaul lock sleeve  68 . 
     A paddle blade  18  according to an embodiment of the invention is depicted in  FIGS. 5A-5D , the drawings of which are to scale. The blade has a width  114 , which may be between 7 and 10 inches, and a height  116  which may be between 12 and 24 inches. An upper connection  118  on the blade  18  is configured to be secured to the proximal end of the paddle shaft. In the particular embodiment depicted, the upper connection  118  comprises a cylindrical opening configured to slidingly receive the proximal end of the paddle shaft. As shown in the side view of  FIG. 5C , the paddle blade  18  is configured to be positioned at an angle  119  with respect to a paddle shaft secured within the upper connection  118 . In the particular embodiment depicted, the angle  119  is about 9 degrees, although other angles (including angles of between 5 and 15 degrees) are also within the scope of the invention. 
     In the embodiments depicted in  FIGS. 1-5 , the paddle blade is depicted as being at about 90 degrees with respect to the deployed sail boom and deployed sail (about the axis defined by the paddle shaft). However, for some sailing configurations, other blade-to-sail angles (i.e., angle of blade with respect to sail/sail boom) may be desired. The sail boom  34  and sail  28  can be rotated with respect to the paddle blade  18  by unlocking the locking mechanism  54 , thus permitting the upper shaft portion  52  (to which the sail boom  34  is attached) to rotate within the lower shaft portion  50  (to which the paddle blade  18  is attached). Once the upper shaft portion  52  and lower shaft portions  50  (and thus the sail boom  34  and paddle blade  18 ) have been rotated with respect to each other to a desired orientation, the locking mechanism  54  can be re-locked at the desired position. 
     A lower shaft portion  50  of a paddle shaft  16  according to an embodiment of the invention is depicted in  FIGS. 6A-6F . The lower shaft portion  50  has a proximal (lower) end  120  and a distal (upper) end  122  and an overall length  124 . The length  124  may be between 30 and 66 inches, or between 36 and 60 inches, or between 44 and 52 inches (although other lengths are also within the scope of the invention), and in the particular embodiment depicted the length  124  is about 48 inches (1220 mm). The lower shaft portion  50  has an outer diameter  126 , which may be from 1 to 2 inches (although other diameters are also within the scope of the invention), and which may be sized to fit tightly into an opening such as the blade upper end connection depicted in  FIGS. 5A-5F . In the particular embodiment depicted, the outer diameter  126  is about 1.15 inch (29 mm). The lower shaft portion includes an inner diameter  128 , which may be between ¾ and 1¾ inches and which may be sized to slidingly receive the upper shaft portion  52  therein in a relatively tight manner so that the upper shaft portion  52  can slide therein but wherein the two portions can be locked to prevent further sliding by applying a compressive force to the lower shaft portion  50 . In the particular embodiment depicted, the inner diameter  128  is about 1 inch (25.7 mm) (although other diameters are also within the scope of the invention). A compression slot  130  may be positioned adjacent the distal (upper) end and permits the distal (upper) end to be compressed, such as via a compressive shaft locking mechanism, to narrow the inner diameter at the distal end in order to lock the upper shaft portion  52  within the lower shaft portion  50  to prevent relative movement therebetween and thereby fix the overall length of the paddle. In a preferred embodiment, the difference between the lower shaft portion inner diameter  128  and the upper shaft portion outer diameter  136  is between 1 and 3 mm. In the particular embodiment, the difference is 2 mm. 
     An upper shaft portion  52  of a paddle shaft  16  according to an embodiment of the invention is depicted in  FIGS. 7A-7C . The upper shaft portion  52  has a proximal (lower) end  132  and a distal (upper) end  134  and an overall length  136 . The length  136  may be between 16 and 40 inches, or between 24 and 32 inches (although other lengths are also within the scope of the invention), and in the particular embodiment depicted the length  136  is about 27 inches (686 mm). The upper shaft portion  52  has an outer diameter  138 , which may be between ⅞ and 1½ inches (although other diameters are also within the scope of the invention), and which may be sized, at the upper shaft proximal (lower) end  132 , to be slidingly received within an upper opening in the lower shaft portion  50 , and also may be sized, at the upper shaft distal (upper) end  134 , to be tightly fit into a lower opening in the paddle handle. In the particular embodiment depicted, the outer diameter  138  is about 1 inch (25.5 mm). The upper shaft portion  52  has an inner diameter  140  which may be sized to slidingly receive the sail assembly, including the slider, yoke, mast, boom, and sail. The inner diameter  140  may be between 0.5 and 1¼ inches (13 mm-32 mm), although other diameters are also within the scope of the invention. In the particular embodiment depicted, the inner diameter  140  is about 0.92 inch (23.3 mm). 
     A paddle handle  22  according to an embodiment of the invention is depicted in  FIGS. 8A-8F . The particular handle  22  is substantially T-shaped, with small finger grooves  144  formed at the front and back toward the top 146 thereof for easier grasping of a sail cap positioned therein. A hole  148  passes through the handle  22 , with the hole  148  configured to permit a sail assembly to slide therethrough. The hole  148  has a smooth and tapered upper portion  150 , with the tapered shape configured to facilitate easier advancement of the sail assembly, including the sail, into the handle hole  148 . The tapered upper portion  150  thus acts as a funnel to facilitate stowing of the sail assembly. The hole  148  has a lower portion  152 , with a small step-like overhang  154  between the upper portion  150  and lower portion  152  where the inner diameter of the hole  148  is suddenly reduced between the upper portion  150  and the lower portion  152 . The small step-like overhang  154  may act as a block to prevent the slider (where the slider diameter is larger than the hole diameter at the step-like overhang) of the sail assembly from being pulled out of the paddle through the hole. 
     A sail top cap  60  according to an embodiment of the invention is depicted in  FIGS. 9A-9E . The sail top cap  60  may include an upper surface  160  that is contoured to match the contours of a handle (such as that depicted in  FIGS. 8A-8E ) when the top cap  60  is secured within a hole in the handle. The top cap  60  may include a notch  162  configured to receive and retain a sail loop (such as the upper sail loop) in a hook-like manner. A circular groove  164  encircles the sail top cap  60  just below the upper portion  166  thereof, with the circular groove  164  serving as a retention groove for an O-ring (not shown), such as the O-ring shown in  FIG. 4A . The O-ring provides a water-tight seal between the top cap  60  and paddle handle when the top cap  60  is secured within a hole in a paddle handle such as that depicted in  FIGS. 8A-8E . The top cap upper portion  166  includes overhangs  168  which, when the top cap  60  is secured within a handle such as that depicted in  FIGS. 8A-8E , extend over the finger grooves in the handle and permit a user to easily grasp and pull the top cap out of the handle. 
       FIGS. 10A-10C  depict a mast  32  according to an embodiment of the invention. The mast  32  has a proximal (lower) end  170  and a distal (upper) end  62  and a length  172  therebetween. Connection holes  171  may be provided, such as screw holes, to facilitate securing the mast  32  to a slider and/or top cap of the paddle. The mast may have a length  172  of between 30 and 60 inches, or between 40 and 50 inches, although other lengths are also within the scope of the invention. The mast may have a diameter of between 3/16 and ½ inches (4.75 mm to 13 mm), although other diameters are also within the scope of the invention. The mast  32  may be formed of various materials, such as fiberglass or carbon fiber or thermoplastic materials. The mast  32  may have sufficient flexibility to permit the mast  32  to deform slightly when subjected to the force from the tightening of the sail (e.g., when the downhaul it tightened) or from a sudden force, such as sudden gust of wind, but also to be able to return to its original shape once the force is removed. The mast  32  should also have sufficient resistance to tensile and compressive forces to withstand the force created when a user pulls the sail assembly out of the paddle shaft and when a user pushes the sail assembly back into the paddle shaft, during which times the pushing (compression) and pulling (tensile) forces will largely be carried by the mast  32 . Due to the somewhat large forces thus applied to the mast (as compared to the boom), the use of screws or other connectors applied to the connection holes  171  may be desirable to secure the mast to the slider and/or to the top cap. In one embodiment, the mast  32  is formed from carbon fiber and the mast length  172  is about 48 inches (1220 mm), with a diameter  173  of about ¼ inch (6.4 mm). The mast  32  may preferably have a diameter greater than (by perhaps 50% to 100% or more) that of the boom, so that the boom will have greater flexibility as compared to the mast. 
       FIG. 11  depicts a boom  34  according to an embodiment of the invention. The boom has a proximal (lower) end and a distal (upper) end, with a boom length  178  therebetween. The boom length may be between 28 and 58 inches (710 mm to 1475 mm) with a diameter between 0.1 and 0.4 inches (2.5 mm to 10 mm), although other lengths and diameters are also within the scope of the invention. The boom  34  may be formed of various materials, such as fiberglass or carbon fiber or thermoplastics. The boom  34  may have sufficient flexibility to permit the boom to deform when subjected to a sudden force, such as sudden gust of wind, and to return to its original shape one the force is removed. The boom  34  may preferably be configured to flex easily so that the sail assembly can flex sideways when subjected to a strong wind gust and thus spill most of the wind gust to prevent the operator from being tipped over by the wind gust. In one embodiment, the boom  34  is formed from carbon fiber and has a length of about 42 inches (1070 mm) and a diameter of about 0.19 inches (4.8 mm). The boom may preferably have a diameter less than that of the mast, so that the boom will have greater flexibility to spill wind gusts as compared to the mast. Note that in the embodiment depicted in  FIGS. 2A-2C , the boom  34  has an overall length which is slightly less than that of the mast to thus permit the boom to be closely placed against the mast but with the boom distal end position just below the top cap. 
     A boom yoke  106  according to an embodiment of the invention is depicted in  FIG. 12 . The boom yoke  106  includes a boom-receiving opening  182  configured to receive and tightly secure the proximal end of the boom therein. The boom yoke  106  further includes hinge points  184  configured to connect to corresponding portions of a slider of the sail assembly. The boom yoke  106  may be formed from relatively rigid materials, including metals such as aluminum, stainless steel (possibly marine grade stainless steel), and/or titanium or from relatively rigid thermoplastics, to prevent the yoke from unwanted flexing. 
     A slider according to one embodiment of the invention is formed from an inner slider portion  188  depicted in  FIGS. 13A-13E  and an outer slider portion  190  depicted in  FIGS. 14A-14E , with the inner slider portion  188  and outer slider portion  190  configured to mate together to form a complete slider portion. The inner slider portion  188  includes a lower step portion  192  on the front and back thereof, with the lower step portion  192  configured to interact with the step-like overhang  154  of the handle hole  148  to prevent the slider portion from being accidentally pulled out of the paddle shaft. The inner slider portion includes an upper notch  194  that forms a hook-like structure configured to receive and secure the central sail loop. The inner slider may further include a locking tab  196  that, when the sail assembly is deployed, locks the slider in a desired position within the handle (as more clearly depicted in  FIG. 17  below). When it is desired to stow the sail assembly, the operator can release the locking tab by pressing inwardly against the tab. The locking tab may also unlock responsive to a sufficient downward forced being applied to the slider (e.g., via downward pressure on the top cab when an operator is stowing the sail assembly). The inner slider may be formed of various materials, such as thermoplastics, fiberglass, metal, etc. Materials may include ABS (acrylonitrile butadiene styrene) or PC/ABS (polycarbonate/acrylonitrile butadiene styrene) plastics or a glass-filled nylon. The materials may include so-called self-lubricating materials, such as polypropylene, to facilitate sliding of the slider within the paddle shaft inner lumen. 
     As depicted in  FIGS. 14A-14E , the outer slider portion  190  also includes lower step portions  198  configured to interact with the step-like overhang  154  of the handle hole  148  to prevent the slider portion from being accidentally pulled out of the paddle shaft. The outer slider portion  190  may be formed of various materials, such as the materials discussed above with respect to the inner slider portion. The materials may include so-called self-lubricating materials. 
       FIG. 15  depicts a perspective view of the inner and outer slider portions  188 ,  190  assembled to form the complete slider  108 , with mast  32 , yoke  106 , and boom  34  according to an embodiment of the invention. Note the locking tab  196 . 
       FIGS. 16A-16C  depict side, side (cross-sectional), and side (cross-sectional) views of a distal portion of a paddle according to the invention, including the handle  22 , slider  108 , yoke  106 , mast  32 , and boom  34  in the deployed configuration. Note that in the particular embodiment depicted, the boom is at an angle  200  of 90 degrees from the mast and paddle shaft, although other boom angles  200  are also within the scope of the invention (e.g., between 60 and 120 degrees, between 75 and 105 degrees, between 80 and 100 degrees, etc.). 
       FIG. 17  depicts a slider  108  with the paddle in the deployed configuration according to an embodiment of the invention. Secured to the slider  108  are the mast  32  as well as the yoke  106  (which is rotatably secured to the slider  108  and also has the boom  34  secured therein). The slider  108  also includes the notch  194  which receives the sail middle loop  110  therein to thereby secure the sail to the slider  108 . Note the locking tab  196 , which is engaging against an upper surface  202  of the handle  22  adjacent the handle hole  148  to prevent the slider  108  from unwanted downward movement into the handle hole  148 . An inward press (such as from an operator&#39;s finger) will cause the locking tab to move inward, thereby releasing the locking tab from engagement with the handle upper surface  202  and permitting the slider to be slid downward into the paddle shaft. 
       FIGS. 18A-18E  depict a downhaul lock  68  according to an embodiment of the invention, with the downhaul lock  68  comprising a substantially annular structure  210  having an opening  212  at one side. The downhaul lock  68  is configured to be slidingly advanced along the paddle shaft to a desired location, and then compressed onto the paddle shaft to a locked position via a screw-like mechanism passing through holes  214  on either side of the opening  212 . The downhaul lock  68  includes a hook-like appendage  216  configured to receive and secure the lower sail loop. 
       FIGS. 19A and 19B  depict a top sail portion  28   a  and a lower sail portion  28   b , respectively, of a sail according to an embodiment of the invention. The top sail portion  28   a  and/or lower sail portion  28   b  may be substantially triangular in shape as depicted. The top sail portion  28   a  may have a height  220  between 40 and 55 inches and a length  222  between 40 and 55 inches. The lower sail portion  28   b  may have a height  224  between 35 and 45 inches and a length  226  between 40 and 55 inches. Note that other heights and lengths are also within the scope of the invention. In one embodiment of the invention, the top sail portion has a height of 44 inches and a length of 43 inches, while the lower sail portion has a height of 39 inches and a length of 43 inches. Note that the upper and lower sail portions may be formed from a single piece of material, so that there is not separation in the material forming the upper and lower sail portions so that the sail is formed from a single continuous piece of material. The sail portions may include hemmed edges, which may include sleeves therein to receive a mast, boom, or other sail support structures therein. Materials used to form the sail include nylon, rayon, acetate, polyester, and polypropylene, including materials referred in the art as ripstop materials. The sail material may be 1.0 oz. to 2 oz. material, with a preferred range being 1.1 oz. to 1.3 oz. ripstop nylon material. 
       FIG. 19C  depicts a complete sail  28  comprising a top sail portion  28   a  and a lower sail bottom  28   b . The sail  28  includes so-called air pockets  228  at the upper corner thereof, with the air pockets  228  positioned on one or more sides of the sail  28 . In the particular embodiment depicted, the air pockets  228  are positioned on both sides of the sail  28 . The air pockets  228  are formed from pieces of material (which may be substantially triangular in shape, may be the same material of which the sail is formed, and/or may be substantially resistant to water and/or air passage therethrough) are from 12 to 32 inches (or 18 to 24 inches) in vertical length along the sail leading edge, and from 8 to 16 inches (or 11 to 15 inches) in trailing length along the sail trailing edge (although other dimensions are also within the scope of the invention). The air pockets  228  are secured to the sail at the leading edge thereof and also at the upper trailing edge thereof, but are open at the lower edge  228   c  of the air pocket material to thereby form an open pocket that captures a small amount of air when the sail  28  is stowed within the paddle shaft. The air captured within the air pockets  228  can prevent the paddle from sinking if the paddle is dropped in the water. 
     The sail  28  may be formed from a single, continuous piece of material. In the embodiment depicted, the upper portion extends slightly forward (e.g., by about ½ to 1½ inch, or by about 1 inch) of the lower portion at the sail leading edge at a position adjacent the sail middle loop, thus providing room for the sail middle loop. 
     A sail for use with a SUP paddle according to an embodiment of the invention thus comprises an upper sail portion  28   a  comprising a substantially right triangular shape with an upper sail horizontal leg, an upper sail vertical leg, and an upper sail hypotenuse, wherein the upper sail horizontal leg is between 40 and 45 inches in length, the upper sail vertical leg is between 41 and 45 inches in length, and the upper sail hypotenuse is between 56 and 62 inches in length. The sail  28  also comprises a lower sail portion  28   b  comprising a substantially right triangular shape with a lower sail horizontal leg, a lower sail vertical leg, and an lower sail hypotenuse, wherein the lower sail horizontal leg is between 39 and 44 inches in length, the lower sail vertical leg is between 36 and 41 inches in length, and the lower sail hypotenuse is between 53 and 59 inches in length. 
     The particular sail  28  depicted is thus formed from combination of the upper sail portion  28   a  and the lower sail portion  28   b , and the upper sail portion and the lower sail portion are positioned with the upper sail horizontal leg and the lower sail horizontal leg adjacent to and parallel to each other and in contact in edge-to-edge fashion with each other, and the upper sail horizontal leg and the lower sail horizontal leg are positioned on a forward side of the sail in substantially parallel relationship to each other. The completed sail  28  thus has a leading edge  46  and a trailing edge  48 , with upper, center, and lower sail loops to secure the sail to the sail support structure and/or paddle shaft or other portions of the paddle. 
     A paddle blade holder  42  is depicted in  FIGS. 20A-20D . The paddle blade holder  42  is configured to be secured to the upper surface of a paddle board, such as depicted in  FIG. 1 . The paddle blade holder  42  includes a first set  230  of grooves and a second set  232  of grooves, with a dividing groove  234  therebetween. Each set of grooves comprises multiple grooves  236  centering on a central point  238 , with the grooves spaced apart at different angles. In the particular embodiment depicted, the grooves  236  are spaced around the central point  238  at angles of about 45 degrees between adjacent grooves  236 . Each groove is preferably sized to receive a paddle blade therein in order to prevent the paddle blade, and hence the paddle and deployed sail assembly, from being accidentally rotated to a non-desirable angle with respect to the SUP board. The holder  42  thus assists the operator in holding the paddle and sail assembly at a desired angle to the wind. The grooves may have a width of ¼ to 1 inch, and a depth of ¼ to 1 inch or more. The holder  42  may have a pressure-sensitive adhesive, which may be releasable responsive to upward (negative) pressure, on the lower surface thereof. The pressure sensitive adhesive may be covered by a peel-away covering that the operator can remove to expose the pressure sensitive adhesive and then press the holder on the desired surface of the SUP board. The holder  42  may have a length  240  between 6 and 16 inches (or between 8 and 12 inches), a width  242  between 5 and 8 inches, and a thickness  244  between ¼ and ¾ inches (although other lengths, widths, and thicknesses are also within the scope of the invention). The holder  42  may be formed from an easily compressible material such as a sealed foam rubber. Other materials include soft sponge/gel materials. 
       FIGS. 20E-F  depict a paddle blade holder  42  such as that depicted in  FIGS. 20A-20D  secured to an SUP paddle board  12  and in use with a paddle  14  according to an embodiment of the invention. As depicted in  FIG. 20F , the paddle blade  18  can be positioned within a desired groove of the holder  42  in order to assist the operator in holding the paddle at a steady angle when under sail. 
     In one example of usage a paddle according to the invention, which may be particularly useful for downwind (e.g., board reach and/or running) travel on the board, the paddle blade  18  could be oriented lengthwise with respect to the paddle board (i.e., 90 degrees from the sideways orientation depicted in  FIG. 20F ) with the boom and sail extending to one side or the other. The user can grasp the paddle shaft with one hand, grasp the boom and/or boom handle (element  44  in  FIG. 1 ) with the other, and keeping the body of sail substantially centered over the board in order to capture the wind. The sail could be angled forward or backward (e.g., by letting the boom/boom handle go forward or backward with respect to the paddle shaft) to improve the desired performance and adjust for wind direction. To steer the board to the right, the user could pivot the paddle shaft (and thus the entire sail) to the left of the board center position to thus position more sail area on the left side of the board, thus causing the board to turn to the right responsive to the added forward force on the left side of the board. Similarly, to steer the board to the left, the user could pivot the paddle shaft (and thus the entire sail) to the right of the board center position to thus position more sail area on the right side of the board, thus causing the board to turn to the left responsive to the added forward force on the right side of the board 
       FIGS. 21A-21C  depict a paddle blade holder  250  similar to that of  FIGS. 20A-20F , but having a substantially circular shape according to an embodiment of the invention. The paddle blade holder  250  comprises a single set  252  of grooves  254 , radiating from a single central point  256 . The paddle blade holder  250  may have a diameter  255  between 5 and 14 inches (or between 8 and 10 inches), and a thickness  257  between ¼ and ¾ inches (although other diameters and thicknesses are also within the scope of the invention). The grooves may have a width of ¼ to 1 inch, and a depth of ¼ to 1 inch or more. 
     Another embodiment of a paddle blade holder  260  is depicted in  FIGS. 22A-22C , and includes a fixed lower portion  262  (secured to an SUP paddle board  38  via such means as pressure-sensitive adhesive and/or screws  263 ) and an upper portion  264  that can rotate with respect to the lower portion  262 . The paddle blade holder  260  may be substantially circular, with a diameter of between 5 to 12 inches. The upper portion  264  includes a paddle blade slot  266  configured to receive the paddle blade. The paddle blade slot may have a length of 8 to 12 inches and a width of 0.25 to 2 inches, with a depth of ⅛ to ¾ inches (although lengths, widths, and depths are also within the scope of the invention). A locking mechanism  268 , such as a foot pedal, can be activated (via unlocking and locking) to permit the upper portion  264  to be selectively rotated to a desired angle and then locked into that position. 
     Additional sail assemblies are also within the scope of the invention. One such embodiment is the fan-shaped sail assembly  280  depicted in  FIGS. 23A-23C . As depicted in  FIG. 23A , a sail assembly  280  is deployed to create a fan-shaped sail  282  supported by a central mast  284  and outside masts  286 , with the central mast  284  extending distally and substantially in alignment with the paddle shaft  292 , and the outside masts  286  angled away from the central mast  284  at angles of about 45 degrees Other angles include angles between 90 degrees and 30 degrees. To stow the sail assembly  280 , the operator folds the outside masts  286  in against the central mast  284 , as depicted in  FIGS. 23B-23C , and then presses inwardly against the top cap  288  to slidingly the sail assembly  280  through the paddle handle  290  and into the paddle shaft  292 . 
       FIGS. 24A-24B  depict a paddle  14  according to a further embodiment of the invention, wherein the paddle shaft  16  has a mast  32  slidingly received therein and having a signal or warning/safety flag  300  on the distal end thereof. The mast may have a length from 12 inches to 6 feet or more, and thus provides the user the ability to raise the signal/warning flag to a height where it can be easily seen. The signal or warning flag  300  may be brightly colored, and/or may include other information (e.g., dive flag markings, etc.) to signal a particular activity or danger or request for assistance. With the mast  32  and signal flag  300  in the stowed configuration, as depicted in  FIG. 24B , the SUP paddle may look like a regular SUP paddle. 
     Note that the signal flag of  FIGS. 24A-24B  may be used in addition to a sail as disclosed previously, with the signal flag being removably disposed and/or hidden from view until needed (so that a user can sail without displaying the signal flag, but when necessary can deploy the signal flag (e.g., by adding the signal/warning flag to the mast and/or unrolling or otherwise revealing the signal flag from a hidden position on the sail assembly). 
       FIGS. 25A-25B  depict a system  310  according to the invention where a SUP paddle board  12  has straps  312  on either side thereof which are sized to receive the paddle blade  18  therein in order to hold the paddle blade  18  against the side of the board  12 . The user can place the paddle blade  18  into the strap opening  313  for sailing, and then lift the paddle blade out of the strap opening as desired for paddling and/or changing sailing configuration. The strap opening  313  preferably has a length just greater than the width of the paddle blade  18 . For example, for paddles with blades between 7 and 10 inches in width, strap openings may have lengths between 8 and 12 inches. The strap  312  may be secured to the sides of the SUP paddle board via screws  314  or other conventional means, such as glue, etc. As depicted in  FIGS. 25A-25B , the operator can drop the blade  18  into the strap  312  and effectively use the paddle blade  18  as a type of dagger board/keel/rudder to improve pointing of the board  12  in the desired direction. Note that the strap may be formed from a flexible material such as canvas strapping, or formed from a more rigid material such as plastic. The strap  312  may be positioned at various positions along the length of the board, but may preferably be positioned just forward of the user. Because a user often stands at the middle position along the length of the board, the strap  312  may preferably be positioned just forward of the user, e.g., about 1-3 feet forward of the halfway point along the length of the board. 
     Note that instead of enclosed straps as depicted in  FIGS. 25A-25B , open-ended structures (such as a small peg or open-ended bracket) could be used to help hold the padded in place along the board. For example, an L- or U-shaped bracket could extend out from and parallel (lengthwise) with the board, with the open-end of the L- or U-shaped bracket facing forward with respect to the board. A user could thus position the blade at least partially within the bracket, with the bracket helping to hold the paddle against the board and preventing unwanted backward movement of the paddle blade with respect to the board. Similarly, a relatively small peg (e.g., ½ to 4 inches in length, or 1 to 3 inches in length) could extend substantially sideways (and/or angled outward but also forward with respect to the board) from the board. The user could position the paddle blade in contact with and on the forward side of the peg, with the bracket helping to hold the paddle against the board and preventing unwanted backward movement of the paddle blade with respect to the board. Note that all such structures (pegs, L- or U-shaped brackets, straps, etc.) could be configured to help hold the blade against the board while also permitting the user to rotate the blade angle with respect to the oncoming water flow (created by the forward movement of the board), with the change in blade angle used to enhance the trackability and/or to steer the board as desired by the user. For example, a user could angle the leading edge of the blade outward with respect to the board, or rotate the trailing edge of the blade outward with respect to the board, to effectuate desired tracking and steering. 
     The configuration depicted in  FIG. 25B  may be particularly useful for use in a beam reach and/or upwind sailing (e.g., close hauled). For example, the user could position the blade  18  in the water on the downwind/leeward side of the board (which may include positioning the shaft in a strap such as depicted in  FIG. 25B ) for tracking/steering, with the paddle shaft/sail mast extending backwards (with respect to the length of the board) and across to the windward side of the board (possibly with the boom pointing generally downward as opposed to upward) to capture/redirect the oncoming wind. Note that the sail  28  as depicted in  FIG. 25A  may be positioned with respect to the blade so that the sail presents a plane that is substantially parallel to the plane of the paddle blade. With the paddle shaft/sail mast (and thus the sail) thus positioned toward the rear and windward side of the board, the user could adjust the sail angle of attack with respect to the wind (e.g., by pulling on the boom handle  44  depicted in  FIG. 1  and/or adjusting the angle of the paddle shaft and/or adjusting the upper shaft portion with respect to the lower shaft portion, etc.) to effectuate forward movement of the paddle board  12 . 
       FIGS. 26A-26B  depict perspective and front views, respectively, of a system  320  where a SUP board  12  has a slot  322  passing therethrough, which may be generally centered on the board  12  and toward the front thereof. The slot  322  preferably has a length  324  greater than the width of the paddle blade (e.g., a length between 8 and 14 inches), and a width  326  sufficient to freely receive the paddle blade  18  and which may allow some movement of the blade  18  in side-to-side rotation fashion in order to permit the user to orient the mast/paddle shaft to a desired angle from the vertical with respect to the SUP board. For example, the width  326  may be between ½ inch to 2 inches. As depicted in  FIGS. 26A-26B , the operator can drop the blade  18  into the slot  322  and effectively use the paddle blade  18  as a type of dagger board/keel/rudder to improve pointing of the board in the desired direction. 
     Referring now to  FIG. 27 , a system  338  according to the invention comprises a skateboard  340  and a so-called land paddle  342 . The land paddle  342  comprises a shaft  344 , a handle  346 , and a padded lower end  348  for engaging the ground to pole the operator along the road or other ground surface. The device is thus similar to the water paddle disclosed above, but the paddle blade has been replaced with a padded lower end  348 . In such an embodiment, the user can deploy the sail assembly  350  by sliding it out of the handle  346 , and place the padded lower end  348  onto the skateboard upper surface as shown, and let the wind drive the operator and skateboard along. The sail for the land paddle may have dimensions and structure similar to, or identical to, that previously disclosed herein for the sail water paddle, and the land paddle  342  may include structures such as the upper shaft, lower shaft, shaft lock, and downhaul lock disclosed previously for the water paddle. 
     While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description and not of limitation. Therefore, changes may be made within the appended claims without departing from the true scope of the invention.