GB2161441A

GB2161441A - Hydrofoil steering mechanism

Info

Publication number: GB2161441A
Application number: GB08517517A
Authority: GB
Inventors: Miles Handley; Geoffrey Shine
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-07-13
Filing date: 1985-07-11
Publication date: 1986-01-15
Also published as: GB8517517D0; GB8417939D0; GB2161441B

Abstract

Hydrofoils 1 have stub axes 3 which rotate in hubs 4 fixed to the stern of a boat 2, in an inverted V arrangement with the axes of rotation at an angle which preferably lies between 101 DEG and 79 DEG . Each stub axle 3 is fitted with a crank arm 6 connected by a steering push rod 5 to a steering arm 7 pivoted at 9. The rods 5 are connected to the arm 7 by pivot joints 8 which are slightly offset to the rear of the pivot 9. Steering forces are applied to the arm 7 by cables or rods 10 controlled by a steering wheel, and movement of the steering arm 7 rotates the hydrofoils 1 in the same direction, so as to modify their angles of attack and creating an angle of attack differential between the two, thus inducing a steering force. The offset between the pivot points 8 and the pivot 9 renders the differential of the angle of attack non-linear so that each hydrofoil 1 describes the correct circle about a common centre of turn. <IMAGE>

Description

SPECIFICATION Hydrofoil steering mechanism This invention relates generally to hydrofoil boats and more particularly to steering mechanism for such boats. The terms "hydrofoil boat" or "hydrofoil assisted boat" are used to describe boats or similar vessels which use lifting forces produced by the flow of water over lifting surfaces to reduce the drag of the boat by raising the boat partially or completely out of the water.

Hydrofoil assisted boats are generally steered by either a "T" hydrofoil or a box hydrofoil. These systems of steering and other similar systems either require continual adjustment as speeds vary or produce excessively heavy load imbalance on the steering mechanism when wave action is encountered.

According to the present invention, hydrofoil steering mechanism comprises a pair of similar hydrofoils in inverted-V arrangement mounted for rotation about their respective axes so as to adjust the angle to attack and a common linkage connected to both hydrofoils for turning them in the samedirection under the control of a steering member.

The advantage of such an arrangement is that, as the boat rises with speed, all foils reduce in area and thereby retain lift stability, thus avoiding the need for the continual adjustment required with other systems.

Generally speaking, the hydrofoils will be straight, but this is not essential. In any case, whatever the shape of the hydrofoils, the V is defined between the two axes of rotation and its angle is preferably between 101" and 79O.

The linkage for turning the two hydrofoils prefer ably comprises a laterally extending pivoted steering arm turned by the steering member and connected on opposite lateral sides of its pivot by rods to crank arms extending from respective stub axles for the hydrofoils. As the steering arm is turned about its pivot by the steering member, one end moves forwardly to transmit a similar movement to the rod on that side, and the other end moves aft, also to transmit a similar movement to the rod on that side, the crank arms extending from the stub axles for the hydrofoil thus requiring to extend laterally in oppo site directions so that these two opposite move ments cause the two hydrofoils to turn in the same angular direction.This turning movement modifies -the angle of attack of each hydrofoil, thus creating an angle of attack differential between the two and thereby inducing a steering force.

As the boat turns as a result of the induced steering force, the two hydrofoils each move in a circular arc about a common centre of turn. The hydrofoil further from the centre of turn follows a somewhat greater radius than the other hydrofoil and should therefore be turned through a very slightly smaller angle than the other. For this purpose the connection points of the rods to the steering arm may be offset rearwardlyfrom the pivot of the arm, thereby introducing a small differential into the movement of the rods and hence a corresponding small differential in the turning movement of the two hydrofoils.

The steering arm will normally be controlled by a steering wheel, the motion being transmitted to the arm by cables or rods connected to it in the region of its outer ends. Alternatively, these cables or rods may be controlled by a tiller or similar form of steering member.

An example of steering mechanism in accordance with the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the mechanism attached to the stern of a boat; and Figure 2 is a plan view of the mechanism of Figure 1 adjusted to its central position.

The mechanism comprises a pair of hydrofoils 1 which, as best seen from Figure 1, are mounted in an inverted-V arrangement, the angle of the V (i.e. the angle between the axes of rotation) being shown as 0. The size of this angle will depend to a certain extent on the size and other characteristics of the boat to which the mechanism is fitted, but in general will lie between 112" and 68 , preferably between 101" and 79". In a particular example, this angle may be 90".

The hydrofoils 1 have stub axles 3 which rotate in bearing hubs 4 fixed to the stern of the boat 2. As shown in Figure 2, the steering mechanism is in its central position so that the horizontal components of the thrust exerted on the hydrofoils 1 cancel one another and produce no steering force, while the vertical components combine to produce a lifting force. When the hydrofoils 1 are turned in the same angular direction from the central position shown in Figure 2, the horizontal components no longer cancel one another and a side-ways steering force is produced while the vertical lift is maintained.

To produce the necessary turning movement, each stub axle 3 is fitted with a crank arm 6 having a pivotal connection to corresponding steering push rods 5 which, at their other ends, are connected by similar pivotal connections 8to a steering arm 7 which is pivoted about a spindle 9. Steering forces are applied to the ends of the arm 7 via cables or push rods 10 which, in their turn, may be controlled by a steering wheel ortiller arrangement (not shown). Turning movements of the arm 7 are transmitted via the rods 5 to the crank arms 6 and hence to the hydrofoils 1 which are thereby caused to turn in the same angular direction, their respective angles of attack thereby being modified to create a differential between the two, thus inducing a steering force as previously described.

The pivotal connections 8 between the rods 5 and the steering arm 7 are offset rearwardly from the pivot line of the arm 7 buy a distance shown as 12, thus rendering the differential of the angles of attack non-linear and causing each hydrofoil 1 to described the correct circle about a common centre of turn, as previously described.

1. Hydrofoil steering mechanism comprising a pair of similar hydrofoils in inverted-V arrangement

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Hydrofoil steering mechanism This invention relates generally to hydrofoil boats and more particularly to steering mechanism for such boats. The terms "hydrofoil boat" or "hydrofoil assisted boat" are used to describe boats or similar vessels which use lifting forces produced by the flow of water over lifting surfaces to reduce the drag of the boat by raising the boat partially or completely out of the water. Hydrofoil assisted boats are generally steered by either a "T" hydrofoil or a box hydrofoil. These systems of steering and other similar systems either require continual adjustment as speeds vary or produce excessively heavy load imbalance on the steering mechanism when wave action is encountered. According to the present invention, hydrofoil steering mechanism comprises a pair of similar hydrofoils in inverted-V arrangement mounted for rotation about their respective axes so as to adjust the angle to attack and a common linkage connected to both hydrofoils for turning them in the samedirection under the control of a steering member. The advantage of such an arrangement is that, as the boat rises with speed, all foils reduce in area and thereby retain lift stability, thus avoiding the need for the continual adjustment required with other systems. Generally speaking, the hydrofoils will be straight, but this is not essential. In any case, whatever the shape of the hydrofoils, the V is defined between the two axes of rotation and its angle is preferably between 101" and 79O. The linkage for turning the two hydrofoils prefer ably comprises a laterally extending pivoted steering arm turned by the steering member and connected on opposite lateral sides of its pivot by rods to crank arms extending from respective stub axles for the hydrofoils. As the steering arm is turned about its pivot by the steering member, one end moves forwardly to transmit a similar movement to the rod on that side, and the other end moves aft, also to transmit a similar movement to the rod on that side, the crank arms extending from the stub axles for the hydrofoil thus requiring to extend laterally in oppo site directions so that these two opposite move ments cause the two hydrofoils to turn in the same angular direction.This turning movement modifies -the angle of attack of each hydrofoil, thus creating an angle of attack differential between the two and thereby inducing a steering force. As the boat turns as a result of the induced steering force, the two hydrofoils each move in a circular arc about a common centre of turn. The hydrofoil further from the centre of turn follows a somewhat greater radius than the other hydrofoil and should therefore be turned through a very slightly smaller angle than the other. For this purpose the connection points of the rods to the steering arm may be offset rearwardlyfrom the pivot of the arm, thereby introducing a small differential into the movement of the rods and hence a corresponding small differential in the turning movement of the two hydrofoils. The steering arm will normally be controlled by a steering wheel, the motion being transmitted to the arm by cables or rods connected to it in the region of its outer ends. Alternatively, these cables or rods may be controlled by a tiller or similar form of steering member. An example of steering mechanism in accordance with the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the mechanism attached to the stern of a boat; and Figure 2 is a plan view of the mechanism of Figure 1 adjusted to its central position. The mechanism comprises a pair of hydrofoils 1 which, as best seen from Figure 1, are mounted in an inverted-V arrangement, the angle of the V (i.e. the angle between the axes of rotation) being shown as 0. The size of this angle will depend to a certain extent on the size and other characteristics of the boat to which the mechanism is fitted, but in general will lie between 112" and 68 , preferably between 101" and 79". In a particular example, this angle may be 90". The hydrofoils 1 have stub axles 3 which rotate in bearing hubs 4 fixed to the stern of the boat 2. As shown in Figure 2, the steering mechanism is in its central position so that the horizontal components of the thrust exerted on the hydrofoils 1 cancel one another and produce no steering force, while the vertical components combine to produce a lifting force. When the hydrofoils 1 are turned in the same angular direction from the central position shown in Figure 2, the horizontal components no longer cancel one another and a side-ways steering force is produced while the vertical lift is maintained. To produce the necessary turning movement, each stub axle 3 is fitted with a crank arm 6 having a pivotal connection to corresponding steering push rods 5 which, at their other ends, are connected by similar pivotal connections 8to a steering arm 7 which is pivoted about a spindle 9. Steering forces are applied to the ends of the arm 7 via cables or push rods 10 which, in their turn, may be controlled by a steering wheel ortiller arrangement (not shown). Turning movements of the arm 7 are transmitted via the rods 5 to the crank arms 6 and hence to the hydrofoils 1 which are thereby caused to turn in the same angular direction, their respective angles of attack thereby being modified to create a differential between the two, thus inducing a steering force as previously described. The pivotal connections 8 between the rods 5 and the steering arm 7 are offset rearwardly from the pivot line of the arm 7 buy a distance shown as 12, thus rendering the differential of the angles of attack non-linear and causing each hydrofoil 1 to described the correct circle about a common centre of turn, as previously described. CLAIMS

1. Hydrofoil steering mechanism comprising a pair of similar hydrofoils in inverted-V arrangement mounted for rotation about their respective axes so as to adjust the angle of attack and a common linkage connected to both hydrofoilsforturning them in the same direction under the control of a steering member.

2. Mechanism according to claim 1 in which the linkage comprises a laterally extending pivoted steering arm turned by the steering member and connected on opposite lateral sides of its pivot by rods to crank arms extending from respective stub axles for the hydrofoils.

3. Mechanism according to claim 2, in which the connection points of the rods of the steering arm are offset rearwrdly from the pivot of the arm.

4. Mechanism according to claim 2 or claim 3, in which the steering arm is turned by cables or rods connected to it in the region of its outer ends.