HYDROFOIL BOAT

Abstract

A hydrofoil boat (100), having a T foil comprising an underwater mast (41) and an elongated horizontal hydrofoil (47) The draft and underwater beam of the boat can be reduced by sliding the mast upwards and rotating the hydrofoil from the normal transverse orientation to a fore-and-aft direction.

Claims

1. Watercraft (100), having an underwater appendage comprising an underwater mast (41) and an elongated hydrofoil (47) centrally connected to the lower end of the mast (41), wherein the hydrofoil is oriented transversally in a first configuration to generate lift, characterized in that the hydrofoil (47) is rotatable about a vertical axis such that the hydrofoil (47) can be turned towards a longitudinal plane (L) of the watercraft (100) in a second configuration.

2. The watercraft of claim 1, wherein the underwater mast (41) can be caused to slide upwards such that, in the first configuration, the hydrofoil (47) is separated from a hull (10) of the watercraft, and, in the second configuration, the hydrofoil (47) is closer to the hull (10) than in the first configuration.

3. The watercraft of claim 1 or 2 wherein a width (w) of the hydrofoil (47) exceeds a maximum beam (b) of the hull (10).

4. The watercraft of any one of the preceding claims, wherein the hydrofoil (47) and the underwater mast (41) are connected rigidly.

5. The watercraft of any one of the claims 2 to 4, wherein the underwater mast (41) is slidable inside a hollow post (49) above the waterline.

6. The watercraft of any one of the preceding claims, wherein the hydrofoil (47) has control surfaces (48) whose inclination can be set by a control system.

7. The watercraft of any one of the preceding claims, further comprising, abaft the underwater appendage, a rudder (51) having an underwater horizontal stabilizer (57), wherein the rudder is slidable vertically to reduce a draft of the watercraft.

8. The watercraft of any one of the preceding claims, wherein the underwater appendage and/or the rudder have a propulsion pod (43, 53) comprising an electric motor and a propeller (45, 55).

9. The watercraft of claims 4 and 5, wherein the horizontal stabilizer (57) has additional control surfaces (58) whose inclination can be set by the control system.

10. The watercraft of any one of the preceding claims, wherein the hydrofoil (47) is aligned with the longitudinal plane (L) of the watercraft in the second configuration, and a total angle of rotation of the hydrofoil (47) between the first configuration and the second configuration is essentially 90.

11. The watercraft of any one of the preceding claims, wherein the hull has a longitudinal tunnel (11) and the hydrofoil (47) enters in the tunnel (11) in the second configuration.

Description

SHORT DESCRIPTION OF THE DRAWINGS

[0009] Exemplar embodiments of the invention are disclosed in the description and illustrated by the drawings in which:

[0010] FIGS. 1a and 1b show schematically a boat according to the invention, seen from the side, in a deep-water configuration and flying, respectively in a shallow-water configuration at slow speed.

[0011] FIGS. 2a to 2c illustrate the transition from the deep-water configuration to the shallow-water configuration, from below and in three steps

[0012] FIGS. 3a and 3b show the boat in the deep-water configuration, respectively in the shallow-water configuration, as seen from the bow.

EXAMPLES OF EMBODIMENTS OF THE PRESENT INVENTION

[0013] FIG. 1a shows a watercraft 100 in motion, sustained by the vertical lift of its underwater appendages, which are, in this embodiment, a horizontal elongated hydrofoil 47 and a rudder-mounted horizontal stabilizer 57. The hydrofoil 47 is at the lower end of an underwater mast 41, while the horizontal stabilizer 57 is at the lower end of a rudder 51 abaft the underwater mast 41. Preferably, these appendages are configured to provide a high lift/drag ratio at moderate speed and, to this end, are slender elongated hydrodynamic bodies with a high aspect ratio, as it can be seen in FIG. 2a where the watercraft 100 is represented as seen from below.

[0014] Returning to FIG. 1a, the hydrofoil 47 is at the lower end of an underwater mast 41 that extends from the centreline below the hull 10 in an essentially vertical direction. The mast inserts a distance between the hull and the hydrofoil such that the boat can fly above the waterline 31 with the desired clearance.

[0015] Either or both the underwater mast 41 and the rudder 51 may have propulsion pods 43, 53 with an electric motor and a propeller 45, 55. This is not essential for the invention, however, and the watercraft 100 may have any suitable means of propulsion including propellers connected to the hull or to other appendages, sails or kites, bow propellers for manoeuvring, water jets, and so on.

[0016] The combined lift of the hydrofoil 47 and of the stabilizer 57 is such that the boat 100 flies at the desired height above the waterline and remains level. Preferably, this is achieved automatically, by a computer control that receives information about the instantaneous height and attitude of the boat, and acts on suitable control surfaces of the underwater appendages, as it will be shown later.

[0017] Preferably, the boat has means to detect the height of flight above the water, for example height sensors 71 and its position with respect to other vessels and obstacles, for example by a LIDAR 75, and this information is provided to the computer control as input.

[0018] FIG. 1b shows the boat 100 at low speed, when the lift generated by the appendages is not enough to overcome the weight, and the boat is sustained essentially by its buoyancy. The appendages are lifted closer to the hull to reduce the water draft. The underwater mast 41 is raised inside the hollow post 49, while the rudder is lifted vertically. In this case, the aft propeller 55 is underwater and provides propulsion and direction at low speed, but other solutions are possible. Preferably, the boat allows a third configuration, not shown, where the rudder can be raised even higher, lifting the pod 53 above the waterline.

[0019] FIGS. 2a to 2c show the transition between the deep-water configuration of FIG. 1a to the shallow-water configuration of FIG. 1b in three steps. While the hydrofoil 47 is lifted close to the hull, at the same time it rotates along a vertical axis towards the longitudinal plane L. In the example shown the rotation is quite complete and, in the final configuration of FIG. 2c, the hydrofoil 47 is aligned with the longitudinal plane L, but this is not an essential requirement.

[0020] Advantageously, turning the hydrofoil fore-and-aft reduces its side encumberment. In the example, the width w, or wingspan of the foil exceeds the beam b of the hull, and the boat could not safely dock to a wall in the deep-water configuration. By rotating the hydrofoil towards the midplane L, the hydrofoil is no longer an encumberment. In this configuration the risk of snagging with the foil to weeds or loose lines is also greatly reduced.

[0021] Preferably, the hydrofoil 47 is connected rigidly to the underwater mast 41, which has a flattened section to minimize the drag and, in the shallow-water configuration, the hydrofoil 47 and the mast 41 rotate together as a body. This is not the only option, however.

[0022] The combined movement of the mast 41 and of the hydrofoil 47 can be obtained in several ways, all comprised in the invention. In a preferred solution, the underwater mast is guided helically inside the post 49 along at least a part of its travel such that, as it rises, it necessarily turns of the desired angle. The total angle a of rotation of the foil 47 may be 90, as shown in FIG. 2c, but even a lesser rotation would procure a useful reduction of the underwater beam.

[0023] FIGS. 2a-2c show also the control surfaces 48, 58 of the hydrofoil 47, respectively the stabilizer 57. This is just an example, however, and the control surfaces could be configured otherwise, without leaving the invention. Possibly, the lift of the hydrofoil and of the stabilizer could be controlled by pitching the whole wing, rather than a smaller surface. In can be said, in this case that each of the wings of the hydrofoil is a control surface.

[0024] Left-right differential control of the surfaces 48, 58 causes a change in the roll angle of the boat 100, while a differential setting of the hydrofoil surfaces 48 with respect to the additional surfaces 58 influences the pitch of the boat. These actions are interlinked in a complex manner that depends on the dynamic state of the boat, and can be controlled by a skillful skipper, or by an automatic control unit using a dynamic model, as it is known in the art.

[0025] FIGS. 3a and 3b show the boat in the two configurations of FIGS. 1a and 1b, as seen from the bow. Advantageously, the hydrofoil 47 tucks inside a tunnel 11 of the hull when it is raised in the shallow-water configuration. This minimizes the chances of a snag and, if the tunnel is deep enough, the pod 43 can be lifted above the waterline to reduce fouling, as represented in FIG. 3b.

REFERENCE SYMBOLS IN THE FIGURES

[0026] 9 superstructure [0027] 10 hull [0028] 11 tunnel [0029] 31 waterline [0030] 41 mast [0031] 43 centre pod [0032] 45 centre propeller [0033] 47 hydrofoil [0034] 48 control surfaces [0035] 49 hollow post [0036] 51 rudder [0037] 53 aft pod [0038] 55 aft propeller [0039] 57 horizontal stabilizer [0040] 58 additional control surfaces [0041] 71 height sensor [0042] 75 lidar [0043] 100 boat, watercraft