WO2008140332A1

WO2008140332A1 - Towable water craft and its method of steering

Info

Publication number: WO2008140332A1
Application number: PCT/NZ2008/000100
Authority: WO
Inventors: Phillip James Knowler
Original assignee: Phillip James Knowler
Priority date: 2007-05-09
Filing date: 2008-05-07
Publication date: 2008-11-20

Abstract

Towable water craft figure (7) which comprises of a seat (8) knee pads (7) and handle bars (9). The hull has a tow point (1) which facilitates the direct connection of a tow rop (4) from the craft to a suitable towing boat. The tow point (1) is located along the center line under the craft in a position which allows it to be rotated by the rider shifting their weight sideways. The airfoil shape on the edge of the hull (12) then harness's the angled flow of water under the craft to drag down the trailing edge of the craft. The force generated deflects the craft at an angle to the direction of tow. This type of craft would normally be associated with the sport of water skiing.

Description

TOWABLE WATER CRAFT AND ITS METHOD OF STEERING

I, Phillip James KNOWLER, a New Zealand citizen, of 137 Oteramika Road, Invercargill, New Zealand,

Hereby declare the invention, for which I pray that a patent may be granted to me and the method by which it is performed, to be particularly described in and by the following statement: -

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(The following page is numbered 1a) TOWABLE WATER CRAFT AND ITS METHOD OF STEERING

FIELD OF THE INVENTION

The present invention relates to the field of watersports, and more specifically to water craft of the type designed to be towed behind a boat or other vessel.

BACKGROUND TO THE INVENTION

The applicant's enquiries have indicated that in almost all the prior art the steering or maneuvering of a towed water craft is achieved by some form of rudder, keel, ski or hydrofoil. In the case of a wake board, knee board, or skier the rider must hold onto the ski rope. In the latter, the rider must have a significant degree of strength and skill to successfully ride the craft. This limits their use to only a small number of people. Alternatively, the down side of a basic ski biscuit or inflatable tube is that there is nil or limited control by the rider. The prior art has also shown the successful use of keels and rudders on the ski biscuit type craft. In most situations a keel or a rudder will turn a towed water craft but in practice and especially at increased speeds any type of protruding keel or rudder has the potential to dig in and even cause the towed water craft to flip unexpectedly.

There have been some attempts at making steer able towed water craft. Some examples are the inventions described in:

US Patent 6, 182,594

US Patent 5,819,680 and

US Patent 5,057,044.

1A In these examples the steering of the towed craft is achieved by pulling on ropes or levers attached to moving rudders. In US Patent 5,819,680 it is pulling on the tow line which rotates the towed crafts direction and more importantly in reference to this patent a fin is required and is attached to the underside of the towed craft. The fin assists in maintaining control and achieving a change in direction depending on the weight distribution of the rider.

These prior art inventions have gone some way toward developing a steerable towed water craft but there are still problems to eliminate and these include:

1. The physical effort required to steer the craft. One needs to appreciate the technique and skill of the rider as most of the rider's attention and strength is required just to hold onto the towed craft.

2. The complexity of the extra moving parts. Both in design and manufacture these crafts include intricate and costly to produce parts.

It is therefore an objective of the present invention to create many types of steerable towed water craft which are able to be controlled simply by the rider and have no moving parts. The present invention allows a towed water craft to be controlled by a rider while not limiting the direction or orientation of the towed water craft. The towed water craft can travel forward, sideways and even backwards for a short distance because it does not depend on normal keels or fins to affect its steering and carving.

A further object of the invention is to overcome the disadvantages inherent in known water craft of this type and to provide a useful alternative choice.

Further objects and advantages of the present invention will become apparent from the following description.

2 SUMMARY OF THE INVENTION

According to a broadest aspect of the present invention there is provided a towable water craft that uses a pivot tow point and the drag on the outside edges of the towed craft to steer.

The outside edges are shaped with a slight curve which generates the required drag. The bottom of the hull is preferably flat or has a slight V or round. A tow point is located along the center line of the towed water craft. This tow point is shifted back into or under the towed water craft to a point which allows the craft to freely rotate both left and right.

This tow point will vary with the width, length and/or hull shape and weight of the particular design of the towed water craft. It should be noted that it is feasible to shorten the bow on this invention to the extent where the tow point becomes the front of the craft.

In a preferred design the tow point is approximately one third from the front of the craft. To shift this tow point further forward is likely to reduce the rotational steering of the towed water craft. Shifting the tow point back causes the towed craft to rotate excessively fast making the rider feel unsafe. The basic principle of steering is achieved by the rider shifting their weight sideways to cause the towed water craft to rotate as facilitated by the pivot tow point. This rotation then exposes the trailing side or drag edge of the towed water craft, which in turn pulls the edge of the craft down into the water creating a carving force at an opposing angle to the towing boat. The drag edge is effectively a reverse aerofoil (down ward facing airplane wing). In addition and to further enhance the stability and handling of the towable water craft the applicant has added recessed tail fins. A view of the bottom of the hull showing the recessed tail fins resembles the shape of the tail of a flounder. In effect the fins are recessed V shapes which start near the center line of the underside of the towed water craft and open wider and deeper as they terminate at the sides and/or back of the craft.

The purpose of the two angled recessed tail fins is to enhance the steering (rotation) of the craft.

In the working invention the applicant has limited the rotation of the towed water craft by attaching a short length of rope from the bow of the craft across to the tow rope. This presets the optimum angle for maximum carving and control. This safety rope is a very simple and effective mechanical stop. It is envisaged that other forms of stop points near the front of the craft could be used without changing the basic principle of the pivot tow point and how it harnesses the effect of the drag edges. It may also be an option to delete the safety rope.

The purpose of the present invention is to have a towed water craft that floats like a boat and is stable enough to hold the rider out of the water. Using the pivot tow system and drag edges the applicant can transform what would normally be a dragged toboggan or ski biscuit type craft into a highly maneuverable towed water sport craft.

Further improvements on the invention are as follows.

The applicant has noted that the positive pressure created by the angled recessed tail fins was causing some unwanted lift at the rear of the craft. This was over come by the following improvements. Recessed hull and carving fin were formed by way of a stepped edge built into and parallel to the center line of the hull. These edges are located predominately parallel and close to both of the drag edges. The stepped edge now forms both a recessed carving fin and the leading edge to the airfoils (drag edges). The recessed carving fins supersede the use of the angled recessed tail fins but do not remove the applicants claim on their use.

The water flow trapped by the recessed carving fin can now freely exit the rear of the craft, there by reducing the extra lift previously caused by the angled recessed directional fins.

Further to this, there is pressure caused by the water hitting the face of the recessed fin when the craft is operated at an angle to the direction of tow. This pressure also creates a positive lift and reduces the carving effect of the recessed fin. This lift is over come by the suction created by both the adjacent recessed hull portion and drag edge.

The combination of a recessed hull and carving fin with a corresponding drag edge creates a very strong suction onto the water while exposing the recessed fins working surface for a clean carving line in the water. When combined with a pivot tow point the applicant has created a very effective means of steering a towed water craft with no moving parts.

Drag edges having a chine.

The drag edges work because water will be drawn up a gradual slope or curve due to the surface tension of the water on the wetted surface. The weight and velocity of this displaced water causes a downward drag on the corresponding surface. This downward drag can be very strong and could cause the towed craft to flip unexpectedly when ridden in a tilted, carving position. To control the downward pull on the drag edges the applicant has fitted a break away edge or chine. The water flowing up the drag edge is deflected by the chine thus adding stability to the edge of the craft.

5 Extra directional fins.

In one embodiment of the main invention the applicant has also fitted extra directional fins to the rear of the craft. Depending on the positioning of these extra tail fins they can enhance the steering, directional hold and stability of the craft. For this purpose the applicant has overcome the positive pressure and lift normally associated with normal fin or hull protrusion. The use of directional fins is now feasible because of the downward pull created by the shape of the recessed hull and the drag edges.

Further aspects of the invention will become apparent from the following descriptions which are given by way of example only.

Description of the Drawings

Examples of the invention will now be described with reference to the drawings in which:

Figure 1 show's a bottom view of a towed water craft with a tow rope 4 attached to a pivot tow point 1. There is also a short rope 3 which has one end attached to a safety anchor point 10 and the other end attached across to the tow rope 4. This same craft has drag edges 12 formed down both sides. Figure 1A is a rear view 6 showing the two drag edges 12

Figure 2 shows a bottom view of a towed water craft with recessed angled tail fins 16.

Figure 2A is a rear view 6 of a towed water craft with recessed angled tail fins.

Figures 3 and 3A shows a larger bottom and rear views of an example of one recessed tail fin 16.

6 Figure 4 shows a sectional view of an airplane wing creating lift. This is an example of how the drag edges generate its down ward pull.

Figures 5 and 5A shows a sectional view near the rear of a towed craft showing how accelerated water flow 17 creates a downward drag on one edge of the craft 12. Figure 5A also shows the position of the chine 11 in relationship to the corresponding drag edge 12.

Figure 6 shows the bottom of a towed water craft utilizing curved drag edges 12.

Figure 7 shows an abstract isometric view of a working towed water craft which embodies the basic principles of a pivot tow point 1 with drag edges12, tow rope 4 with safety rope 3, knee pads 7, seat 8 and handle bars 9. The bow 5 is the front of the craft and the rear is 6. The venting of the recessed angled tail fins 16 is visible at both rear 14 corners.

Figure 8 and 8A show the bottom of a towed water craft which shows the Relationship between the pivot tow point 1 and the safety anchor point 10. It also shows the positioning of the drag edges 12 with an attached chine 2 and how the carving fin 11 is formed by recessing part of the hull 13.

Figure 9 shows a rear directional fin 15 attached to the chine 2 for added directional and stability performance.

The best mode for carrying out the invention

The embodiments of the invention will now be described as it is incorporated into one type of towed water craft. It should be appreciated that these basic principles should not be limited to the specific working model shown in these drawings.

7 Figure 7 is an abstract drawing showing a working concept of a towed water craft which is able to float with the rider sitting on top. To facilitate this, the craft in figure 7 has a seat 8 and knee pads 7 which supports the rider in a ^ΛA seated ^ΛA kneeling position. The handle bars 9 allow the rider to operate the craft in a predominately up right position. Figure 7 also shows the tow rope 4 and the attached safety rope 3. The safety rope 3 is attached to the front of the bow 5 and is used to limit the rotational movement of the craft. Viewed from the rear 6 of the craft there are two recesses which show the venting 14 of the original angled recessed tail fins 16.

Figure 1 and 1a show a bottom and a rear view of a towed water craft showing the original angled recessed tail fins 16. Figure 1 shows a pivot tow point 1 which is located along the center line of the craft. Attached to tow point 1 is a tow rope 4 which is normally 20-25m long and able to be attached to a suitable tow boat. The pivot tow point 1 is located far enough back into or under the craft to allow it to rotate freely when the craft is being towed at planning speed. To limit the rotation of the craft there is fitted a safety rope 3 between the safety anchor point 10 and the tow rope 4. The triangle formed by the safety rope 3 and tow rope 4 is to be referred to as a tow harness. It is feasible that this invention could operate with out the safety rope 3.

With the correct location of pivot tow point 1 the towed water craft can now be freely rotated just by the rider shifting their weight to one side. With the rider in an upright central position the craft can be towed straight with the water passing freely under the craft from bow 5 to stern 6. As the rider leans or shifts their weight to the left the craft will rotate anticlockwise as facilitated by the pivot tow point 1. The water flow is now passing at an angle from right to left under the craft; the trailing left side drag edge 12 shown in Figure 5A is beginning to lift the water which causes this edge of the craft to be pulled down into the water. This exposes the under side of the hull to the water flow 16 which deflects the towed water craft at an angle to the direction of tow. This deflection or carving has been achieved by the hull design and required very little effort from the rider.

8 In Figure 2 the applicant has placed towards the rear 6 of the craft two angled recessed tail fins 16. For this application the trailing fin edges have been shortened. This allows the deflected water flow to freely exit the back corner and rear 14 of the recessed fin 16 and the suction of this water pulls the working fin and craft slightly deeper into the body of water on which the craft is being towed. In effect it simulates a shorter, more maneuverable craft and creates a keeling point in the water. Figure 3 and 3A shows a larger view of the venting or opening 14 at the rear 6 of the craft. In this example the main hull shape is predominantly flat with a slight overall V or round. This gives a floating sensation when ridden in a level orientation. The hull shape gives good stability, rotates easily and can travel in any direction, even backwards for a short distance. A clear example of how the drag edge 12 works is shown in figure 4.The drag edge is like an upside down airplane wing Figure 4. Where the airplane wing creates lift, the drag edge 12 creates suction which pulls part of the craft down into the water, refer to Figure 5.

The purpose of this invention is to create a direct towed water sports craft which has the handling and performance of a water ski. The carving affect which is generated by the drag edge 12 figure 5A would previously be generated by the rider leaning aggressively while holding the tow rope for balance, as in water skiing, wakeboarding or kneeboarding. The drag edge 12 in Figure 5A creates the force necessary to tilt the towed water craft while the rider remains in a predominantly upright balanced position. To limit excessive tilting of the towed water craft by the drag edge 12 there is incorporated a breakaway point or chine 2. This is done by sharply increasing the radius or by changing the direction of the water flow. Other kinks or obstructions may have the same effect as water will only suction up a smooth undisturbed slope especially at high velocity. Effectively the drag edges 12 form straight lines parallel to each other which mirror each other across the center line of the towed water craft refer Figure 1 A. Slightly curved drag edges 12, refer Figure 6 could be utilised without distracting from the embodiment of this invention.

9 A low tow point 1, Figure 1 has been used in this embodiment of the invention. By towing from the underside of this craft the applicant gave the bow 5 the lift necessary when penetrating larger waves. A slightly higher tow point could also be used.

Figure 8 shows improvements the applicant has made to the fore mentioned towed water craft refer figure 7. More specifically he has removed the recessed angled tail fins 16 figure 2 as it was found that the recessed angled tail fins had the potential to create lift at the rear 6 of the craft when being towed at speed. The preferred method of steering and carving is now achieved by a straight carving fin 11 figure 8A which has been formed by the recessing of the adjacent hull 13. The use of a straight carving fin 11 should not affect the claim made on the use of an angled recessed tail fin 16 figure 2.

With reference to figure 8 the applicant has incorporated a recessed portion of the hull 13 to form the working face of two recessed carving fins 11 figure 8A. The recessed portion of the hull 13 works with the adjacent out side drag edge 12 to pull down and hold the recessed carving fin 11 into the water.

The rider is able to rotate the craft left or right by shifting their weight sideways. The rotation of the craft is facilitated by the pivot tow point 1 figure 8. Once the craft has rotated the angled flow of water under the craft hits the opposing carving fin surface 11. This water pressure then deflects the craft away from the direction of tow. When working the carving fin surface 11 creates a strong lift on the hull. This is corrected by the suction on both the recesses hull 13 and the adjacent outside drag edge 12.

In figure 9 the applicant has fitted directional fins 15 near the rear 6 of this craft. Water escaping up the outside drag edge is first deflected by the break away edge or chine 2. This deflection of water limits the suction on the drag edge and helps stabilise the craft when being operated in a carving position.

10 To further enhance the stability & steering of this craft the applicant has fitted rear directional fins 15. When the craft is operated in an angled carving position one of the rear directional fins 15 will penetrate the water giving the craft enhanced directional performance. Directional fins 15 could also be fitted to the rear of the recessed hull surface 13 without limiting the extent of the claim. The fitting of these directional fins 15 is made possible by the constant suction on the hull.

Thus by the invention there is provided a direct towed water craft that uses a pivot tow point and the drag on the outside edges to achieve the performance of a ski or knee board.

Particular embodiments of the invention have been described and it is envisaged that improvements and modifications can take place without departing from the scope thereof.

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Claims

What I claim is

1. A towable water craft comprising of a water skimming hull surface having a pivot tow point in conjunction with drag edges.

2. A towable water craft as in claim 1 , wherein the drag edges also incorporate a chine or break away edge.

3. A towable water craft as in claim 1 , wherein the drag edges have a relatively straight configuration.

4. A towable water craft as in claim 1 , wherein the drag edges have a distinct curvature to their configuration.

5. A towable water craft as in claim 1 , which also has recessed tail fins fitted.

6. A towable water craft as in claim 1 , in conjunction with tail fins which are either attached at the rear of the drag edge or the recessed hull.

7. A towable water craft that uses a tow rope with an attached safety rope for the purpose of limiting the rotation of the attached tow water craft.

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