AU5344400A - A surf craft - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant: DREW BLATCHFORD Invention Title: A SURF CRAFT The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 A SURF CRAFT Field of the Invention The present invention relates generally to a surf craft. In one form the invention relates particularly to a paddle board for an individual rider in oceans, lakes and rivers, and will primarily be described with reference to this context. It should be remembered, however, that the invention has broader use in water based applications and can be used as an improvement to skiing devices (such as surfskis or surfboards) to enhance the speed, performance and flexibility of use.

Background Art Paddle board surf craft are well known devices.

Typically such boards are manufactured from a polystyrene 15 core covered with a fibreglass skin. Often these articles are heavy and cumbersome to manoeuvre in the surf because their length and weight whether they are used in a kneel-up or a lay-down riding technique. Poor speed and handleability characteristics can result from the use of such boards. To improve these characteristics, it is known to add cavities to the underside of such boards to streamline the movement action of the boards over a body of water, as shown in German patent no. 3102650, and United States patent No.'s 4314384 and 3827096. These prior art specifications do not form part of the common general knowledge in the relevant art.

Summary of the Invention The present invention provides a surf craft including at least one longitudinal recess extending at least part way thereunder in a manner that defines a pair of opposing hulls which rest and move upon the water in use, the recess fitted with a fin which is fixed against movement and in use does not protrude from that recess.

There are several advantages of locating the fin in the recess. In such a position the fin is shielded by the 3 opposing hulls enhancing the safety of the board by reducing the incidence of the fin accidentally striking the rider in conditions where the rider is no longer atop the board. Prominent fins also are prone to maintenance problems, and can be bent, damaged or torn completely out of the board, especially when struck against an object or when dragged on sand. The location of the fin within the recess also enhances the hydrodynamic lift, because of the extra water being channelled through the recess/es in normal use. Thus, the turning action of the board is greatly assisted. In terms of stability on rough water, the fin also reduces the incidence of the board rocking from side to side, which is good for the purposes of attaining maximum speed. Longer protruding fixed fins do not allow the same finesse of directional control of the board in surf conditions of any type.

Preferably the or each longitudinal recess is concave in cross section.

Preferably the or each longitudinal recess extends: from the front end and part way along the craft underside; (ii) from the rear end and part way along the craft underside; or (iii) for the whole length of the craft.

Preferably the surfcraft includes a single recess.

Alternatively the surf.craft includes two recesses and a central hull located therebetween. Preferably the two recesses are symmetrically located about a longitudinal axis of the surf craft.

Preferably the surf craft is a paddle board.

Brief Description of the Drawings Notwithstanding any other forms which may fall within the scope of the present invention, a preferred form of theinvention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows an underside plan schematic view of one 4 embodiment of a paddle board apparatus in accordance with the invention; Figure 2 shows a further underside plan schematic view of another embodiment of a paddle board apparatus in accordance with the invention; Figure 3 shows a still further underside plan schematic view of an embodiment of a paddle board apparatus in accordance with the invention; Figure 4 shows a side schematic view of the embodiment shown in Figure 1; Figure 5 shows a top schematic view of the embodiment shown in Figure 1.

Figure 6 shows an end schematic view of the embodiment shown in Figure 3.

15 Figure 7 shows a rear end schematic view of the embodiment shown in Figure 1.

Figure 8 shows a further embodiment of a rear end schematic view of the embodiment shown in Figure 1.

Modes for Carrying out the Invention Referring to the drawings, in Figure 1 a surf craft in the form of a paddle board 10 is shown which includes at least one longitudinal recess 12 extending typically fully along the underside of the paddle board 10 so as to define a pair of opposing hulls 14 and 16 which normally rest upon the body of water and support the movement of the paddle board 10 upon the water. The longitudinal recess is concave in its cross sectional shape although alternative shaped concave recesses other than smoothly curved ones are within the scope of the invention, for example square or inverted V-shaped cross section recesses.

In use the longitudinal recess 12 streamlines the movement action of the paddle board 10 over the body of water and provides a significant speed and handleability advantage over smooth-hulled paddle boards. The longitudinal recess 12 channels water past the moving board and reduces the surface area interface presented to the 5 water, thereby reducing drag and making the board more manoeuvrable.

As shown in Figure 2 typically the longitudinal recess 13 may also extend from the rear end of the board 10 and part way along the craft underside. The longitudinal recess can also extend from the front end of the board and part way along the craft underside also.

Figure 3 shows an alternative preferred embodiment of a paddle board 10 which includes two recesses 18 and extending part way along the underside of the paddle board from its rear end with a central hull 22 located therebetween. The two recesses 18 and 20 are symmetrically located about a longitudinal axis of the paddle board Any number of recesses extending at least part way along 15 the underside of the paddle board are within the scope of oo. the invention. All such embodiments offer similar o o advantages in terms of improvements to the speed and manoeuvrability of the board.

An upper view of the deck 23 of board 10 is shown in Figure 5, which schematically depicts kneepads 24 and handgrips 26 used by a rider in normal use when atop the board. Typically boards can be anywhere from 2.0 to 3.2m in length. Typically the underside 25 of the paddle board is rounded in shape, known in the art as the 'rocker' of the board. Typically the longitudinal recess 12 does not recess too deeply into the underside of the board 10 at the nose region 29. In the underside region immediately below the deck 23 and kneepad 24 area of the board the recess 12 is relatively less shallow and can represent as much as 40% of the thickness of the paddle board 10 itself. In the underside of the board 10 at the end region 30, the recess 12 is relatively deeper again and can represent as much as 40-50% of the thickness of the paddle board 10. Typically the recess 12 is not shallower than 10mm at any point along the length of the board. Typically the recess 12 is not less than 80mm in width.

6 An important feature of the invention is the underside fixed fin 28 which is located in and does not protrude from recess/es 12, 13, 18, 20 on the underside 25 of the board.

Such an arrangement of fixed fin/s within recess/es 12, 13, 18, 20 provides improved steering control of the board in surf conditions of all types. One advantage of locating the fin 28 in the recess is that it is shielded by the opposing hulls and this enhances the safety of the board.

A major cause of injuries resulting from the use of surfcraft which feature protruding fins is the accidental cutting of the skin or breakage of the limbs or torso of a rider by the action of a fin accidentally striking the rider in conditions where the rider is no longer atop the board. Additionally, the fin contained in the hull recess helps to reduce the chance of the curved hull of the board from rolling over while the support deck is being held upright during an initial sprint segment of a race from oooo beach to surf.

Typically the fixed fin 28 is thin in shape and contoured to allow superior cutting action through the water for easy directional control. Typically the fin 28 is of a depth equal to the depth of the recess, although any depth of fin less than that maximum can provide some directional control. Various cross sectional views of the concave recess/es, fin/s and board are shown in Figures 6 to 8.

Typically the fin is considerably thinner than the width of opposing hulls 14, 16 of the board 10, having a typical radial thickness of 3mm on its leading edge to minimise drag. The location of the fin within the recess also enhances the hydrodynamic lift, because of the extra water being channelled through the recess/es in normal use.

Thus, the turning action of the board, for example -in a race around a buoy, is greatly assisted. In terms of stability on rough water, the fin also reduces the incidence of the board rocking from side to side, which is -7good for the purposes of attaining maximum speed. Longer protruding fixed fins, apart from being dangerous, do not allow the same finesse of directional control of the board in surf conditions of any type. Prominent fins also are prone to maintenance problems, and can be bent, damaged or torn completely out of the board, especially when struck against an object or when dragged on sand.

Such an improvement to a surf craft design can substantially increase the racing performance as shown by the experimental test results given in Tables 1 and 2 below. This has implications in both competition racing and surf life saving applications.

Experimental test results Racing course design Course A was set at a distance 15 of 450m across a lake. The course was set in a straight oo. line between two jetties. The course was used because it was protected from the elements such as the wind and the •go• tide, which could otherwise bias the results. Course B was set at a distance of 20 Experiment Three paddlers of high fitness were oooo selected to twice complete both Courses A and B consecutively, with 30 minutes of recovery time after ompleting Course A and 15 minutes recovery time after completing Course B. A standard racing board was used by each paddler the first time they completed the course. The invention board was then used to complete the course a second time. Each paddler was asked to provide their best effort to race over each distance as they were timed. The results are recorded in Table 1 and Table 2.

From the results it may therefore be concluded that a significant speed advantage of typically 6-9% was gained by use of the invention board on either course.

Course B was specifically selected to measure the speed of the invention board 'off the mark', ie. the initial acceleration. This is of particular importance for both surf rescue and competition paddlers.

8

S

S.

S

be..

S*

C

TABLE 1 Course A 450m Standard Board Invention %Reduction in racing time Board racing time to (seconds) time (seconds) complete course Paddler 1 237 168 29% Paddler 2 176 166 6% Paddler 3 186 175 6% TABLE 2 Course B Standard Board Invention %Reduction in racing time Board racing time to (seconds) time (seconds) complete course Paddler 1 19.32 17.87 Paddler 2 18.91 17.17 9.2% Paddler 3 20.18 19.02 5.7% Ocean testing trials, although subject to much variability, revealed that the invention board performed faster, especially in downwind paddling, with less drag on 10 the board in upwind paddling, as well as having improved maneoeuvring ability compared with the selected standard paddle board. The board performed particularly well passing over broken waves, with the nose lifting the board upward over the foam.

Whilst the invention has been described with reference to several preferred embodiments it should be appreciated that the invention can be embodied in many other forms.

Claims (7)

1. A surf craft including at least one longitudinal recess extending at least part way thereunder in a manner that defines a pair of opposing hulls which rest and move upon the water in use, the recess fitted with a fin which is fixed against movement and in use does not protrude from that recess.

2. A surf craft as claimed in claim 1 wherein the or each longitudinal recess is concave in cross section.

3. A surf craft as claimed in claim 1 or claim 2 wherein the or each longitudinal recess extends: from the front end and part way along the craft underside; (ii) from the rear end and part way along the craft underside; or 0906 (iii) for the whole length of the craft.

4. A surf craft as claimed in any one of the preceding 0e €o claims including two recesses and a central hull located f therebetween.

5. A surf craft as claimed in claim 4 wherein the two recesses are symmetrically located about a longitudinal axis of the surf craft.

6. A surf craft as claimed in any one of the preceding claims that is a paddle board.

7. A surf craft as herein described with reference to the accompanying drawinfgs. S Dated this 1 6 th day of August 2000 DREW BLATCHFORD By his Patent Attorneys GRIFFITH HACK