Paddle blade

Abstract

A blade 100 for a kayak paddle, comprising a throat region 104, a main region 110 defining a substantially concave front surface (122, Fig 3) on a first side of the blade, a substantially convex back surface (116, Fig 3) on a second side of the blade, and longitudinally extending upper and lower edge regions (118 and 120, Fig 5), and a tip region 112 defining a substantially curved tip edge 114 extending between the upper and lower edge regions. The upper edge region defines an aerofoil leading edge profile which extends along the blade from the throat region and terminates before the tip edge.

Description

The present invention relates to a paddle blade and more specifically, but not exclusively, to a wing blade for a high-performance kayak paddle. Conventional kayak paddle blades take many different forms including a variation / combination of profile and cross section. For example, the paddle blade may be substantially flat in cross section (laterally) and may be fully or partially curved along its length from throat to tip (longitudinally). The blade may be symmetric along its length, i.e. both sides of an imaginary centre line are an exact mirror image of each other, or asymmetric wherein one side of the centre line has a larger surface area than the other side. Asymmetric blades are typically used for a lower angle of stroke relative to the water, such as for kayaking as opposed to whitewater paddlers, to enable both halves of the power face of the blade when entering the water to have the same total area of contact with the water. Kayak blades may be substantially curved in lateral cross section and / or in longitudinal cross section, and are so-called curved or spooned blades. A variation of the spooned blade is called a wing blade which is typically used in flatwater racing and has a rounded side edge that acts like an aerofoil to provide lift across the back surface of the blade when moved sideways through the water. A wing blade requires torso twist strokes and the path of the blade through the water is rearwardly and outwardly from the kayak, preferably in a straight line at an angle of around 30 degrees relative to a longitudinal axis of the kayak, and is longer than a conventional high racing stroke used with other paddles, preferably ending around 50cm from the paddler’s hips. Wing-bladed paddles encourage the paddler to generate drive better from their torso rotation, so bringing larger muscle groups into play. They also allow for fewer power losses resulting from the formation of eddy currents around the blade associated with other designs and the older technique of only pulling backwards grabbing the same 'old’ water, i.e. ‘new’ water is pulled throughout the sideways stroke when using a wing-bladed paddle. In turn, wing-bladed paddles can improve a kayaker’s performance by at least 4%, but further improvements are desirable. It is an aim of certain embodiments of the present invention to provide a paddle for a kayak that further improves the paddler’s performance through the water. It is an aim of certain embodiments of the present invention to provide a wing-bladed paddle configured to improve the catch of the blade as it enters the water and to allow water to exit the power face of the blade more efficiently to thereby improve the paddler’s performance through the water. According to a first aspect of the present invention there is provided a blade for a kayak paddle, comprising: a throat region; a main region defining a substantially concave front surface on a first side of the blade, a substantially convex back surface on a second side of the blade, and longitudinally extending upper and lower edge regions; and a tip region defining a substantially curved tip edge extending between the upper and lower edge regions, wherein the upper edge region defines an aerofoil leading edge profile which extends along the blade from the throat region and terminates before the tip edge. Optionally, the aerofoil leading edge profile terminates between around 75-95% along the blade from the throat region. Optionally, the aerofoil leading edge profile terminates at around 85-90% along the blade. Optionally, an upper edge of the aerofoil leading edge profile terminates at a transition region between the main region and the tip region. Optionally, the transition region is substantially convex when viewed from above and defines an inflection point at its apex. Optionally, a lower edge of the blade opposed to the transition region of the upper edge is substantially concave. Optionally, the inflection point extends laterally beyond the lower edge region. Optionally, the inflection point is laterally spaced from a vertically oriented central plane of the blade by around 15-25 mm and optionally around 17 mm. Optionally, the curved tip edge proximal to the transition region is oriented with respect to a lateral axis of the blade by an angle 0 of around 95 to 130 degrees. Optionally, the angle 0 is around 100 degrees. Optionally, the tip region is substantially concave in both lateral and longitudinal directions. Optionally, tip region is angled with respect to a lateral axis of the blade by an angle Q of around 45 to 90 degrees. Optionally, the angle 0 is around 65 degrees. Optionally, the back surface of the main region of the blade is angled with respect to a longitudinal central axis of the blade by an angle [3 of around + / -10 degrees. Optionally, the angle P is around 3 degrees. Optionally, an upper edge of the main region of the blade extending from the throat region towards the tip region is substantially concave when viewed from above. Optionally, the throat region extends longitudinally from a tubular portion for receiving an end region of a paddle shaft to mount the blade thereto. According to a second aspect of the present invention there is provided a paddle comprising a blade according to the first aspect of the present invention. Optionally, the paddle is a kayak paddle. Description of the Drawings Certain embodiments of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 illustrates a front ‘power’ side of a blade according to certain embodiments of the present invention; Figure 2 illustrates a back side of the blade; Figure 3 illustrates a plan view of the blade; Figure 4a illustrates a bottom view of the blade; Figure 4b illustrates a longitudinal cross section through the blade; Figure 5 illustrates a tip end view of the blade; Figure 6 illustrates a root end view of the blade; Figures 7a and 7b illustrate a cross section through a main region of the blade; Figure 8 illustrates a cross section through a transition region of the blade; and Figures 9a and 9b illustrate a cross section through a tip region of the blade. Detailed Description As illustrated in Figures 1 and 2, a paddle blade 100 according to certain embodiments of the present invention includes a tubular portion 102 for receiving an end region of a paddle shaft to attach the blade to the shaft. A throat region 104 of the blade extends from the tubular portion 102 and the top and bottom edges 106,108 of the blade gradually widen to define a main region 110 before narrowing to define a tip region 112 of the blade. The top and bottom edges of the throat region 104 are substantially concave when viewing the blade from the side, whilst the top and bottom edges of the main region 110 are substantially convex. The end edge 114 of the tip region 112 extending between the top and bottom edges 106,108 is substantially curved and convex when viewing the blade from the side. The blade defines an asymmetric wing blade. As illustrated in Figures 3, 4a and 4b, the bottom edge 108 of the blade starting at the throat region 104 is slightly convex along its length before curving concavely into the tip region 112. The top edge 106 of the blade is substantially convex along the throat region 104 and substantially concave along the main region 110 before curving convexly at a transition region 115 when transitioning from the main region into the tip region 112. The tip region 112 is convex in both lateral and longitudinal directions to form a spooned tip region. The transition region 115 defines an inflection point wherein the upper edge changes direction to smoothly extend into the tip region. The inflection point extends laterally beyond the lower edge region of the blade as shown in Figure 4a. Aptly, the inflection point is located around 380-400 mm from the start of the throat region 104 and around 100 mm from the end / extremity of the tip edge. Aptly, the inflection point is laterally spaced from a vertically oriented central plane of the blade by around 15-25 mm, and preferably around 17 mm, when viewing the blade from above or below, e.g. when looking down on the top edge of the blade (as in Figure 3), and aptly by around 70-90 mm, preferably around 82 mm, from a horizontally oriented central plane. As illustrated best in Figure 4a, when viewing the blade from below, the back surface 116 of the blade in the throat region 104 is substantially concave in a longitudinal direction but then transitions to being substantially convex along the main region 110 and the tip region 112. A radius of curvature of the main region in the longitudinal direction is substantially greater than a radius of curvature of the tip region. Figure 4b shows a cross section through the blade along its longitudinal axis which shows the longitudinal curvature of the tip region relative to the main region of the blade. Aptly, the tip region is angled with respect to a lateral axis by an angle Q which is around 45 to 90 degrees and preferably around 65 degrees. The tip region of the blade defines an arc and the resultant force vector at the point of contact with the water is angled forwards providing improved catch and traction. Aptly, the back surface 116 of the main region 110 of the blade is angled with respect to a longitudinal axis of the blade by an angle P which is around + / -10 degrees and preferably around 3 degrees. As illustrated in Figures 5 and 6, the back surface 116 is also substantially convex in the lateral direction, i.e. across the blade, wherein a radius of curvature at the upper edge region 118 of the blade is smaller than a radius of curvature at the lower edge region 120 of the blade. Aptly, the radius of curvature gradually increases across the blade, particularly across the main region of the blade. Likewise, in view of the thickness of the blade being substantially uniform along its length and across its width, the front ‘power’ surface 122, i.e. the leading surface of the blade when being pulled through the water, is substantially concave in the lateral direction and defines the same radii of curvature as the back surface, particularly across the main region of the blade. Aptly, the radius of curvature of the main region of the blade increases along the blade in a direction towards the tip. For example, the radius of curvature of the blade at around 280 mm from the open end of the tubular portion 102 is around 26 mm and the radius of curvature of the blade at around 455 mm from the open end of the tubular portion 102 is around 560 mm. The radii of curvature of the aerofoil profile upper edge region at these two points along the blade is around 26 mm and 28 mm respectively. Figures 7a and 7b illustrate the cross section at around lateral plane B-B referenced in Figure 4a. As illustrated by the cross-sectional views in Figures 7a and 7b, the top edge 106 of the upper edge region 118 of the blade, specifically along the throat and main regions of the blade, is located forwardly, relative to the front ‘power’ side of the blade, and below an apex 124 of the upper edge region along the blade from the throat region towards the tip region. This substantially curled-over upper edge region defines the leading edge of an aerofoil to create lift when the blade is moved through the water in a direction away from the kayak and in turn to create an additional force to urge the kayak forwardly through the water. As the blade is urged through the water by the kayaker in a backwards and outwards hybrid direction, preferably in a substantially straight line at an angle of around 30 degrees with respect to a longitudinal axis of the kayak, water is forced along the power surface of the blade towards the tip region 112. Aptly, according to one example, dimension A in Figure 7b is around 148 mm and dimension B is around 17 mm. Figure 8 illustrates a cross section through the blade at the apex / inflection point defined by the transition region 115. Figures 9a and 9b illustrate the cross section at around lateral plane C-C referenced in Figure 4a. As illustrated by the cross-sectional views in Figures 9a and 9b, the curled aerofoil upper edge region 118 defining the top edge of the blade terminates at the start of the tip region 112, i.e. shortly after the inflection point defined by the transition region 115, and smoothly transitions into the curved tip edge 114 shown in Figures 3 and 4a. Aptly, the aerofoil leading edge profile terminates between around 75-95% along the blade from the throat region, and preferably around 85-90% along the blade. Aptly, the aerofoil leading edge terminates into the tip edge at around 445 mm from the throat region. Aptly, according to one example, dimension A in Figure 9b is around 152 mm and dimension B is around 26 mm. As illustrated in Figure 4a, the curved edge 114 of the tip region 112 in the upper half of the blade is oriented, when viewing from below and with respect to a lateral axis, by an angle 6 which is around 95 to 130 degrees and preferably around 100 degrees. In use, water is guided along the front power face of the blade and contained thereon during the power stroke by the curled upper edge region of the aerofoil profile for optimum traction and displacement of water, before being desirably allowed to exit the blade at the tip edge 114, i.e. the water being urged down the blade during a stroke is not trapped at the tip which can otherwise undesirably compromise performance. Aptly, the blade 100 is a plastics material, such as nylon, fibreglass, or carbon fibre, and formed by injection moulding or the like. According to one example, the blade is around 500 mm long from the end of the tubular portion 102 along a longitudinal axis 5 of the blade and the tubular portion is around 120 mm long. The blade is around 175 mm wide across its widest point. The size of the blade can be smaller or larger than these example dimensions, whilst the proportions remain the same, to accommodate different sizes and / or strengths of paddler. Aptly, the paddle including the blade according to certain embodiments of the present invention is a kayak paddle but it io may be suitable or configured for other water sports, such as stand-up paddle boarding or the like. Certain embodiments of the present invention therefore provide a kayak paddle configured to improve the paddling performance and efficiency of a kayaker, and 15 specifically when entering the paddle tip into the water and when pulling through the stroke.

Claims

1. A blade for a kayak paddle, comprising:a throat region;a main region defining a substantially concave front surface on a first side of the blade, a substantially convex back surface on a second side of the blade, and longitudinally extending upper and lower edge regions; anda tip region defining a substantially curved tip edge extending between the upper and lower edge regions,wherein the upper edge region defines an aerofoil leading edge profile which extends along the blade from the throat region and terminates before the tip edge.

2. The blade according to claim 1, wherein the aerofoil leading edge profile terminates between around 75-95% along the blade from the throat region.

3. The blade according to claim 2, wherein the aerofoil leading edge profile terminates at around 85-90% along the blade.

4. The blade according to claim 2 or 3, wherein an upper edge of the aerofoil leading edge profile defines a transition region between the main region and the tip region.

5. The blade according to claim 4, wherein the upper edge of the transition region is substantially convex when viewed from above and defines an inflection point at its apex.

6. The blade according to claim 5, wherein a lower edge of the blade opposed to the transition region of the upper edge is substantially concave.

7. The blade according to claim 5 or 6, wherein the inflection point extends laterally beyond the lower edge region.

8. The blade according to any of claims 5 to 7, wherein the inflection point is laterally spaced from a vertically oriented central plane of the blade by around 15-25 mm and optionally around 17 mm.

9. The blade according to any of claims 4 to 8, wherein the curved tip edge proximal to the transition region is oriented with respect to a lateral axis of the blade by an angle 0 of around 95 to 130 degrees.

10. The blade according to claim 9, wherein the angle 0 is around 100 degrees.

11. The blade according to any preceding claim, wherein the tip region is substantially concave in both lateral and longitudinal directions.

12. The blade according to claim 11, wherein tip region is angled with respect to a lateral axis of the blade by an angle a of around 45 to 90 degrees.

13. The blade according to claim 12, wherein the angle a is around 65 degrees.

14. The blade according to any preceding claim, wherein the back surface of the main region of the blade is angled with respect to a longitudinal central axis of the blade by an angle [3 of around + / -10 degrees.

15. The blade according to claim 14, wherein the angle P is around 3 degrees.

16. The blade according to any preceding claim, wherein an upper edge of the main region of the blade extending from the throat region towards the tip region is substantially concave when viewed from above.

17. The blade according to any preceding claim, wherein the throat region extends longitudinally from a tubular portion for receiving an end region of a paddle shaft to mount the blade thereto.

18. A paddle comprising a blade according to any preceding claim.

19. The paddle according to claim 18, wherein the paddle is a kayak paddle.12

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