GB2261418A

GB2261418A - Oar or paddle blades

Info

Publication number: GB2261418A
Application number: GB9124396A
Authority: GB
Inventors: Geoffrey Fairbairn
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-11-16
Filing date: 1991-11-16
Publication date: 1993-05-19
Also published as: GB9124396D0

Abstract

A blade (10) for an oar or a canoe paddle, for example, is configured to encourage the formation of edge vortices (26) in the water and to direct the vortices close to the rear face of the blade (22) so that the associated low pressure produced at the rear face of the blade (22) increases the resistance to motion of the blade (10) through the water. In one embodiment, water meeting the front face of the blade (20) of a paddle is diverted to each side by a central spine (18) to form the vortices (26) as the water passes around the edges (28, 30) of the blade. The blade (10) is spear-shaped and has a forwardly inclined tip such that the vortices (26) tend to follow the rear face (22), from the tip towards the blade shaft. <IMAGE>

Description

IMPROVEMENTS IN PADDLES This invention relates to improvements in paddles and oars and, in particular but not exclusively, to an improved canoe paddle blade configuration.

Conventional canoe paddle blades are generally rectangular with a planar end or tip and a rounded upper edge where the paddle joins the paddle shaft. The front face of the paddle, that faces the paddler, is typically flat or concave and the rear face is flat or convex. When the paddle blade is pulled through the water towards the paddler, displacement and disturbance of the water results in resistance to motion and the reaction to this, acting through the paddler, drives the canoe forwards.

During a paddle stroke the paddle blade will slip through the water as it is pulled by the paddler, this slippage representing wasted energy, and which may be represented by the product of the paddle resistance (R) and the distance (X) the blade slips through the water.

For efficient paddling, the ratio of the resistance to the distance the blades slip through the water (R/X) should be as large as possible; conventionally, this is achieved by making the blade area as large as may conveniently be wielded, typically a blade of planform area of about 690 cm2. Larger blades are unwieldy and liable to unacceptable wind resistance on the return stroke through the air.

It is an object of the present invention to provide a blade configuration which provides for more efficient paddling than conventional paddle blades.

According to one aspect of the present invention there is provided a paddle blade configured to encourage the formation of edge vortices and to direct the vortices close to the rear face of the paddle so that the associated low pressure produced at the rear face of the blade increases the resistance to motion of the blade through water.

The present invention thus provides a means of increasing the ratio (R/X) between the paddle resistance and the distance the blade slips through the water without increasing the unwieldiness of the blade; a blade in accordance with the present invention and having a blade of planform area about 630 cm2 provides a higher ratio of resistance to paddle slippage than a conventional blade of planform area about 690 cm2. Thus, the present invention provides a blade which allows for more efficient paddling while providing a paddle which is less unwieldy and lighter.

Preferably, the front face is configured to direct water towards the edges of the blade and may define a central spine or have a convex surface across the width of the blade. The front face of the blade preferably flattens from the tip towards the paddle shaft.

Preferably also, the paddle blade is configured to retain edge vortices close to the rear face and has a relatively narrow tip and widens towards the connection with the paddle shaft, that is the blade is generally spear-shaped.

Further, it is preferred that the blade is symmetrical for use in sculling and thus the rear face of the blade also defines a central spine or has a convex surface across the width of the blade . Most preferably, the blade is substantially diamond shaped in cross-section at the tip, the front face progressively flattening and widening towards the shaft end to provide a substantially triangular cross-section. Further, it is preferred that the front face of the blade is generally concave along the length of the blade and the rear face of the blade is convex.

In use, as the blade is pulled through the water in an arc, water meeting the front face of the blade is diverted to each side and forms vortices as the water passes over the edges of the blade. With the forward inclination of the blade tip in the preferred blade configuration the vortices formed on each side of the blade tend to follow the rear face of the blade towards the shaft, thus creating low pressure on the rear face.

In a conventional paddle, vortices are formed as the paddle blade is pulled through the water though the vortices tend to diverge from the edges of the blades and thus provide no additional resistance to the passage of the blade through the water.

As the present invention permits efficient paddle blades to be provided with a relatively small area, the blade on the return stroke will meet less air resistance than a conventional paddle and may therefore be used in an unfeathered form; conyentional paddles have the blades at opposite ends of the shaft feathered, normally at 900. An unfeathered blade is generally safer to use in strong winds and is less tiring to use as an unfeathered paddle does not have to be turned through 900 at each stroke.

The preferred section of a blade made in accordance with the present invention results in a higher volume blade than in a conventional paddle and thus provides a more buoyant paddle. This is advantageous when the paddle is used for support strokes or on righting a capsized canoe.

A further advantage of the preferred paddle configuration is that the blade may be constructed in the form of a shell, providing a blade which is more rugged than the traditional construction of a thin plate stiffened by a spine.

A preferred embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a canoe paddle blade in accordance with a preferred embodiment of the present invention; Figure 2 is a plan view of the blade of Figure 1; Figure 3 is a side view of the paddle blade of Figure 1; and Figures 4 and 5 are sectional views on lines 4-4 and 5-5 of Figure 3.

The drawings illustrate a canoe paddle blade 10 in accordance with a preferred embodiment of the present invention. For use in paddling a kayak type canoe, two blades 10 will normally be provided at either end of a paddle shaft 12, though the blade 10 may equally well be utilised on a single blade paddle or a conventional oar.

The blades 10 is generally spear shaped and widens from a relatively narrow, blunt tip 14 to a wider central portion 16 before necking to an area of reduced cross-section at the connection to the shaft 12.

As can be seen most clearly in Figures 4 and 5, the cross-section of the blade 10 is substantially diamond shape at the tip (Figure 4), the spine 18 on the front face 20 of the blade gradually reducing until the blade is substantially triangular in cross-section at the shaft end (Figure 5). As will also be noted from Figure 3, the front face 20 is concave along the length of the blade, while the rear face 22 is convex.

In use, the blade 10 is pulled through the water in the direction of arrow 24 (Figure 1). Water meeting the front face 20 is diverted to each side by the central spine 18 and forms vortices 26 as the water passes around the edges 28, 39 of the blade. Due to the spear-like shape of the blade and the forward inclination of the tip the vortices so formed tend to follow the rear face 22, from the tip towards the shaft, and create an area of low pressure on the rear face 22, thus increasing the water resistance acting on the blade 10.

As may be seen from Figures 4 and 5, the blade 10 is formed of a hollow shell 32. To increase the rigidity of the blade, the shell 32 may be filled with foam. The shell itself may be formed of any suitable material, such as moulded plastic or fibreglass.

It will be clear to those of skill in the art that the above described embodiment is merely exemplary of the present invention, and various modifications and improvements may be made to the blade without departing from the scope of the invention.

Claims

1. A blade for movement through a body of fluid or for location in a fluid stream, the blade being configured to encourage the formation of edge vortices in the fluid and to direct the vortices to the rear face of the blade so that the associated low pressure produced at the rear face of the blade increases the resistance to motion of the blade through the fluid or increases the force applied to blade by the fluid stream.

2. The blade of claim 1 in which the front face of the blade is configured to direct fluid towards the edges of the blade.

3. The blade of claim 2 in which the front face of the blade defines a spine.

4. The blade of claim 2 or 3 in which the front face of the blade has a convex surface across the width of the blade.

5. The blade of claim 2, 3 or 4 in which the front face of the blade flattens from the blade tip towards a blade mounting.

6. The blade of any one of the preceding claims in which the blade is configured to retain edge vortices close to the rear face of the blade and has a relatively narrow tip and widens towards a connection with a blade mounting.

7. The blade of any one of the preceding claims in which the blade is substantially diamond shaped in cross-section at the tip, the front face progressively flattening and widening towards the mounting end to provide a substantially triangular cross-section.

8. The blade of any one of the preceding claims in which the front face of the blade is generally concave along the length of the blade and rear face of the blade is convex.

9 The blade of any one of the preceding claims in which the blade is in the form of a hollow shell.

10. A paddle or oar including at least one paddle blade in accordance with any one of the preceding claims.

11. A blade for movement through a body of fluid or for location in a fluid stream substantially as described herein and as illustrated in their accompanying drawings.