GB2053805A

GB2053805A - Self propelled surf boards

Info

Publication number: GB2053805A
Application number: GB7924738A
Authority: GB
Original assignee: Dimmick R J C
Current assignee: Dimmick R J C
Priority date: 1979-07-16
Filing date: 1979-07-16
Publication date: 1981-02-11

Abstract

A shallow draft surface water craft comprising a hull (1) which in use is rudderless. The craft is self-propelled and may be driven by a screw-propeller (19) as shown, or, for example, by a jet, and is steered by a person on the deck (8) shifting his position to increase drag on one side of the hull relative to the other. The drive from the propulsion means, such as the screw-propeller, is preferably provided in a recess (21) or passage for protection when the craft is on a land surface. <IMAGE>

Description

SPECIFICATION A shallow draft surface water craft This invention relates to shallow draft surface water craft.

One-man surfboards which are steered by weightshift and propelled by maintaining them on a leading face of a large wave, are well known, as is the disadvantage that they cannot be used unless there are suitable waves.

Also well known are water-skis which are equally steered by weight-shift but which are propelled by a power-boat to which a person on the ski or skis is connected by a rope. At least two people are required to use water-skis, one on the skis and one in the power-boat, and a reasonably large engine is required to propel the weight of the boat, the people and the skis, particularly to draw the skier out of the water. Such engines are increasingly expensive to run.

It is in an effort to alleviate the above disadvantages of surfboards and water-skis that I have devised my invention and there is accordingly provided a shallow draft surface water craft comprising a rudderless, self-propelled hull with a rigid deck, the propulsion means being mounted on the hull to displace the craft through the water with the direction of drive being fixed relative to the hull, whereby a person on the deck directs the craft by shifting his position to increase drag at one side of the craft relative to the other as the craft is driven forwardly by the propulsion means.

My craft has the advantages of both surfboards and water-skis in that it will support at least one person, who may sit, stand or lie on the deck according to his preference and who requires skill to control the craft since it has no displaceable means capable of steering the craft, and additionally the craft is self-propelled so that neither large waves nor an additional power-boat is required. The term "self-propelled" does not include wind-propelled.

The bottom of the hull is preferably substantially smoothly contoured so as to obtain optimum efficiency through the water while at the same time being steerable by weight-shift. Further, the lateral cross-section of the bottom of the hull is preferably substantially planar, as may be the deck. The hull may include a fin or small keel to facilitate steering but it is preferred that, if provided, this is retractable so as to allow the craft to be used for jumping off a ramp in a similar manner to jumping on water-skis.

Clearly low friction materials may be required for the hull and ramp in such circumstances. A retractable fin may, for example, be pivoted or be in the form of a dagger-board. It is believed that the necessity for a keel may be minimised if the craft has flat sides, particularly if they are substantially perpendicular to the water surface and are parallel, but longitudinally and downwardly extending spaced fins may be provided, possibly extending from the hull sides.

Such twin fins may provide not only additional directional control but also support for the craft when used on a dry surface such as when jumping.

Under these circumstances, the twin fins may also protect the propulsion means, particularly where the propulsion means comprises a screw-propeller, since they define with the bottom of the hull a recess in which the screw-propeller may be totally located.

Where no twin fins are provided, a screw-propeller may be protected by locating it in a recess formed in the bottom of the hull, or in a passage in the hull, the passage having at least one inlet through which water is drawn and at least one outlet downstream of the inlet or inlets, from which the water is ejected by the screw-propeller. Inlets and outlets may be in the bottom of the hull, or one or both may be provided in each side of the craft. The screwpropeller may be driven by any means such as an internal combustion engine, a turbine or an electric motor, or it may be replaced by, for example, a jet nozzle. Such a jet nozzle may produce a water jet compressed by, for example, a turbine but more simply, the propulsion means may comprise a container of compressed gas, which gas is released through the jet nozzle to displace the craft.The jet will be rearwardly directed and preferably communicates with the exterior of the craft substantially flush with the bottom of the hull, and immediately aft of midships. Alternatively, the jet fluid inlets and/or outlets may be in the sides of the craft.

Two embodiments of a craft in accordance with the present invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal cross-section of a first embodiment of the craft; Figure 2 is a detailed sectional view of part of Figure 1; Figure 3 is a plan view, partly cut-away, to show the location of the propulsion means in the embodimenu of Figure 1, and Figure 4 is a view similar to Figure 1 but of a second embodiment of the craft.

The shallow draft surface water craft shown in the drawings is made of wood and I have found that approximately 0.07 m3 of air space is required in the hull to support a human being in use of the craft. My craft is approximately 2 m long by 61 cm wide and has a maximum depth of approximately 15.5 cm, although clearly the dimensions and volume of the craft may vary, particularly with different materials of manufacture. Other materials of manufacture may include polystyrene, polyurethane and polypropylene, in which case the hull may be injectionmoulded.

Referring to the drawings, the hull 1 illustrated is made of plywood, preferably marine ply, with wooden lateral strengthening members 2 and 3 at the bow 4 and stern 5 respectively, and centrally spaced longitudinal strengthening members 6 and 7 (shown schematically).

The hull 1 has a planar deck 8 and planar sides 9 and 10 which extend parallel to each other and perpendicular to the deck 8 and, in the usual floating condition of the hull, to the surface 11 of the water.

The bottom edges 12 of the sides 9 and 10 are generally arcuate and the bottom 13 of the hull comprises a rectangular piece of plyboard curved around the bottom edges 12 to give a smooth contour to the bottom 13. A lateral cross-section of the bottom 13 of the hull is substantially planar and the bottom 13 forms an acute angle with the deck 8 at the bow 4 and stern 5, preferably in the order of 15 -20 . The overall shape of the hull is substantially symmetrical fore and aft of midships.

Referring to Figures 1 to 3, aft of midships there is provided a housing 14 in the hull between the longitudinal strengthening members 6 and 7. The housing 14 contains an electric motor 15 and is made watertight with a removable cover 16 on the deck 8. The cover 16 may be retained in place by, for example, clips or an elastic member connecting the cover to the housing 14. Also provided in the housing 14 is an accumulator 17 or other electrical energy supply means which is connected to the motor 15. Extending from the electric motor 15, and driven thereby, is a propeller shaft 18 carrying a screw-propeller19which is in contactwiththe water.It is believed that an accumulator supplying 5.4 kJ will power an electric motor giving 1/20 HP to drive the craft at 2 knots when carrying a human being and it is anticipated that the craft will eventually be used at speeds in the order of 20 knots. Other means (not shown) may be used to drive the screw-propeller, such as for example an internal combustion engine or turbine. Other means not using a screw-propeller are also envisaged, such as a water or compressed gas jet, the latter being described hereinafter with reference to Figure 4. The craft is intended to plane at speeds and it may be preferable to ensure that the drive from the propulsion means is provided substantially amidships of the hull so that it is continuously in the water at whatever speed.

The propeller shaft 18 and electric motor output are shown aligned in a horizontal plane in Figures 1 to 3, but it may often be convenient to misalign the two and a universal coupling 20 is provided to facilitate this. The shaft 18 will extend from the housing 14 to the water by way of sealed bearings (not shown).

To maintain the smooth contour of the bottom 13 of the hull the screw-propeller 19 is located above the contour in a recess 21 and to ensure optimum conditions for the screw-propeller a cross-piece 22 is provided beneath the propeller which is contoured to direct water into the recess 21. The recess 21 and cross-piece 22 thus define a longitudinally extending passage through which the water is drawn and ejected by the screw-propeller. The direction and shape of the passage will be important to the efficiency of the propeller, although it is not yet clear what the optimum design is for use of the craft at high speed. In case air becomes trapped in the recess 21, a one-way valve 23 may be provided to enable its release.

Clearly more than one screw-propeller may be provided and other arrangements may be provided for directing water to the or each screw-propeller.

Thus, for example, a screw-propeller may be located in a passage having one or more water inlets in the bottom or sides of the hull and, for instance, an opening in each side of the hull, beneath the waterline to act as water outlets.

In the embodiment shown in Figure 4, the hull 1 is essentially identical to that of the first embodiment.

However, a housing 14' is located substantially amidships and supports a container 24 of compressed gas. The container 24 has a conduit 25 connected thereto, via a tap 26, which leads to an outlet 27 defining a jet nozzle. The outlet 27 directs the stream of gas from the container 24 rearwardly and substantially tangentially to the contour of the bottom of the hull immediately aft of midships, although its position may be varied if desired. The outlet 27 is thus located in the vertical wall 28 of a narrow recess 29 formed centrally in the bottom of the hull. The tap 26 is shown located within the housing 14', but as described in the next following paragraphs it may be convenient to provide controls for the flow of gas, on the deck.In an alternative arrangement (not shown) the outlet 27 may be located in a passage in the hull having a water inlet and a water outlet downstream of the inlet.

Access to controls of the propulsion means will be required as the craft moves across the water, and such controls (not shown except in Figure 4) are conveniently provided on or above the deck. Since the person on the craft may be standing, the controls may be foot-controls such as switches, levers, pedals or pressure points on the deck, or they may be hand-held as, for example, twist grips with cables, and as there is a reasonable likelihood of the person falling off the craft such cable controls may be retractable under spring-biasing, and the controls generally may automatically switch off under such circumstances.

In order for the person to maintain his balance on the craft he may have to more fore and aft on the deck and foot-controls may therefore be in the form of longitudinally extending rods. The drive motor (if provided) may have a gearbox (not shown) in which case the rods may be operated to change gear in a similar fashion to a motor-cycle gear change.

The craft is totally rudderless, and in use, the person on the deck 8 may change the direction of the craft by shifting his weight sideways to increase drag on one side of the craft relative to the other. As the craft changes speed or vertical angle because, for example, of waves, he may also need to change his balance fore and aft, so some skill will be required, as in surfboarding.

Afin (not shown) may be fitted on the hull but it is believed the flat sides 9 and 10 of the hull may alleviate this requirement. If a fin is provided it is preferred that it is retractable to facilitate launching of the craft from the shore as well as to allow the craft to be used forjumping. The fin may thus be in the form of a dagger-board or it may be pivoted to retract lengthwise of the hull. The pivoted fin may be biased downwardly. Alternatively, spaced twin fins or keels may be provided, the bottom of which can provide a surface on which the craft can be displaced on land. A screw-propeller or other drive from the propulsion means may then be protected by the twin fins when the craft is on a rigid surface.

The provision of the propulsion means at or above the level of the bottom 13 of the hull also facilitates jumping, which is carried out by driving the craft at speed up a short ramp. Low-friction surfaces, such as of PTFE, may be required on the hull and ramp, and foot supports, such as on water-skis, may be necessary for the person on the craft. Hand supports (not shown) may also be provided, usually extending from the bow, and these may be rigid or flexible and incorporate any hand controls.

Claims

1. A shallow draft surface water craft comprising a rudderless, self-propelled hull with a rigid deck, the propulsion means being mounted on the hull to displace the craft through the water with the direction of drive being fixed relative to the hull, whereby a person on the deck directs the craft by shifting his position to increase drag at one side of the craft relative to the other as the craft is driven forwardly by the propulsion means.

2. A shallow draft surface water craft as claimed in claim 1 in which the propulsion means comprises a screw-propeller and means for rotating the screwpropeller.

3. A shallow draft surface water craft as claimed in claim 2 in which the screw-propeller is totally located in a recess in the underwater section of the hull.

4. Shallow draft surface water craft as claimed in claim 3 in which the recess is formed in the bottom of the hull.

5. A shallow draft surface water craft as claimed in claim 3 in which the recess is defined by the bottom of the hull and two laterally spaced fins which extend longitudinally and downwardly of the hull.

6. A shallow draft surface water craft as claimed in claim 2 in which the screw-propeller is located in a passage in the hull, the passage having at least one inlet through which water is drawn and at least one outlet downstream of the inlet or inlets, from which the water is ejected by the screw propeller.

7. A shallow draft surface water craft as claimed in claim 6 in which there is an inlet to and/or an outlet from the passage in each side of the craft.

8. A shallow draft surface water craft as claimed in any one of claims 3 to 7 in which a one-way valve is provided in the hull to release air trapped adjacent the screw-propeller.

9. A shallow draft surface water craft as claimed in any one of claims 2 to 8 in which the screwpropeller is driven by an electric motor.

10. A shallow draft surface water craft as claimed in claim 1 in which the propulsion means comprises a jet nozzle and means capable of directing fluid through the jet nozzle.

11. A shallow draft surface water craft as claimed in claim 10 in which the jet produced by the jet nozzle is rearwardly directed and communicates with the exterior of the craft substantially flush with the bottom of the hull.

12. A shallow draft surface water craft as claimed in claim 11 in which such communication occurs immediately aft of midships.

13. A shallow draft surface water craft as claimed in claim 10 in which there is an inlet and/or an outlet for the fluid in each side of the craft.

14. A shallow draft surface water craft as claimed in any one of claims 9 to 13 in which the propulsion means further comprises a container of compressed gas, which gas is released through the jet nozzle to displace the craft.

15. A shallow draft surface water craft as claimed in any one of the preceding claims in which the propulsion means is located below the level of the deck.

16. A shallow draft surface water craft as claimed in any one of the preceding claims in which controls for the propulsion means are provided above the deck.

17. A shallow draft surface water craft as claimed in any one of the preceding claims in which the deck is substantially planar.

18. A shallow draft surface water craft as claimed in any one of the preceding claims in which the hull has substantially planar sides.

19. A shallow draft surface water craft as claimed in claim 18 when dependent from claim 17 in which the hull sides lie in respective planes at right angles to the deck.

20. A shallow draft surface water craft as claimed in claim 18 or claim 19 in which the sides of the hull are parallel for the full length of the craft.

21. A shallow draft surface water craft as claimed in any one of the preceding claims in which the underwater section of the bottom of the hull has a substantially smooth contour.

22. A shallow draft surface water craft as claimed in any one of the preceding claims in which the lateral cross-section of the bottom of the hull is substantially planar.

23. A shallow draft surface water craft as claimed in any one of the preceding claims in which a retractable underwater fin is provided.

24. A shallow draft surface water craft as claimed in claim 23 in which the fin is pivoted to retract lengthwise of the craft.

25. A shallow draft surface water craft substantially as herein described with reference to Figures 1 to 3 of the accompanying drawings.

26. A shallow draft surface water craft substantially as herein described with reference to Figure 4 of the accompanying drawings.