Boat Having a Variable Hull Configuration

This invention relates to boats or vessels designed for operation under different conditions.

The criteria for an acceptable sailing boat and for an acceptable fast planing hull differ widely, so that the design of a "motor sailer" usually involves the use of a relatively small engine so that, when under power, the boat is used as a displacement vessel. Even so, there is a degree of compromise towards one use or the other. Where the requirement is for a power boat, or sailing boat that can also be used as a fast planing boat under power, there is a basic incompatibility of hull shape, and the present invention aims to remove this, or at least reduce it to negligible or acceptable proportions.

According to the invention, a vessel, such as a power boat or a sailing boat, comprises a displacement hull designed for low resistance at relatively low speeds, such as sailing speeds, and includes an aft section having a pair of surfaces displaceable to a position and attitude such that at higher speeds, such as speeds under power, the hull gives lift to the stern to facilitate a planing action.

Preferably, the hull shape is such that it includes an amidships area where the bottom of the hull is nearly flat so that at planing speeds it provides a principal planing supporting surface.

According to a feature of the invention, the surfaces are symmetrically arranged about the vessel center line and are hinged along a line which extends in approximately the same plane as the amidships area. The hinge line may thus conveniently extend from a point near the center line adjacent the stern, outwards and forwards to a point near the outside of a principal planing supporting surface. The displaceable surfaces may thus be approximately triangular in plan.

In the case of some hull shapes, it may be desirable for the displaceable surface to be sub-divided and separately operated in order to create the necessary area extending from the principal supporting surface. Moreover, the displaceable surfaces may, if desired, be operated so as to introduce a transverse step in the underwater sections of the hull.

The propulsion gear for use under power may be quite conventional, with a shaft log and a propeller bracket mounted below the hull. In a preferred arrangement, a transom drive unit is fitted to a transverse bulkhead located forward of the stern and is arranged, when not in use, to fold into a flooded compartment. The bottom of the compartment may be closed by one or more doors which follow the hull shape. The bulkhead conveniently may be part of a main bulkhead forward of the cockpit so that the engine is located in a housing accessible from the accommodation space.

The displaceable portions of the hull may be in the form of plates which follow the hull shape or are flexed to adapt to it. Alternatively, the displaceable portions may be solid bodies which fit into recesses in the hull so that, when extended, they have sides that reduce turbulence when planing. Such solid bodies are stronger and can be arranged to prevent the ingress of foreign bodies.

The use of a transom drive in the position outlined above has the advantages of accessibility and zero drag when sailing or operating at low speeds. Such design also places the weight of the engine and drive in the most beneficial position, both from the point of view of ballast and of minimising the area of the displaceable surfaces that is necessary to provide adequate lift for the stern.

One form of the invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a typical aft and fore section of a displacement type sailing hull,

FIG. 2 is a typical aft and fore section of a power planing hull,

FIG. 3 is an elevational sketch of a boat to which the invention has been applied, when in the sailing mode,

FIG. 4 is a view similar to FIG. 3 but in the power mode,

FIG. 5 is a perspective sketch of the after underside of the hull corresponding to the condition shown in FIG. 3, and

FIG. 6 is a perspective sketch similar to FIG. 5, but corresponding to the condition shown in FIG. 4.

In the following description, an embodiment of the invention will be described in which the inventive planing surface will be used with a motor sailer. It should be readily apparent that the invention is usable with power boats that are not equipped with sails.

Referring first to FIGS. 1 and 2, there is shown typical after and forward hull sections of conventional shapes for respectively a displacement sailing hull and a power planing hull. It will be seen that these shapes are totally different. In FIGS. 3 and 4 however, which show one application of the invention, the hull 1 has a center plate 2 and a sailing rudder 3. The bottom sections are rounded and faired in the manner illustrated in FIG. 1. An engine 4 is located just ahead of the cockpit area and is mounted in conjunction with a bulkhead 5 through which it can drive a propeller 6 by means of a folding transom drive 7. A pair of approximately triangular hull sections 8 are completely retracted into the hull in FIG. 3 so as to present an uninterrupted outer surface, so the hull can be designed as an ideal sailing shape.

In FIG. 4, necessary changes have been made to convert the hull to a shape suitable for planing under power. The centre plate 2 has been raised into its casing, the rudder 3 has been retracted to have a smaller effective area, the transom drive leg 7 has been lowered to place the propeller 6 in its operative position, and the hull sections 8 have been moved downwards about hinge lines 8a. The effect of this is shown more clearly in FIGS. 5 and 6 which are perspective sketches showing the after underside of the hull in the conditions illustrated respectively in FIGS. 4 and 5. It will be seen that the hinge line 8a extends from a point adjacent the stern near the centre line, outwards and forwards to a point near the water line on the outside of the hull. Although this appears as a curve in this view it can in fact be a straight line. The outside of the wedge section 8 can be arranged to coincide with a strake or chine so that the slight discontinuity introduced by having a separate section is kept to a minimum in its effect.

It will also be seen from FIGS. 5 and 6 that when the leg of the transom drive unit 7 is retracted the continuity of the hull for sailing is maintained ny a pair of doors 9 conforming to the hull contour. These doors and the displaceable hull sections 8 are controlled from inside the boat and may be moved by means (not shown) which may consist of hand levers or mechanical, electrical or hydraulic actuators.

As an indication of the radical departure from existing craft offered by the invention, it has been determined by tank tests that a vessel of 36 feet L.O.A. can be powered, if sufficient attention is paid to weight saving in the structure and fittings, by a motor of 135 H.P., to give a planing speed of some 16 knots. Such a sailing vessel would ordinarily be fitted with an engine of not more than about 40 H.P., which would, without the improvements of the invention, give a speed under power of only 6 or 7 knots. Even if a 135 H.P. engine were fitted to such a conventional sailing vessel, the result would only be that it would trim up by the bow by about 13.degree. and create much wash with a maximum speed of no more than 10 knots and a very high fuel consumption.

In summary, the present invention provides a hull configuration usable under varying operating conditions. The hull can have a smooth contour or be a multi-chine or double-chine hull.

According to the invention, such a boat comprises a hull designed to operate at low speeds as a "displacement" hull, for example a round bilge or multi-chine or double-chine hull, in which there are portions approximately amidships that are comparatively flat and comparatively horizontal aft from which the hull narrows and steepens and sweeps upwards to the waterline, the aft portion being characterised by a pair of surfaces displaceable out of the hull section about a line extending from a point towards the center line forwards to a point further outwards of the center line; the arrangement being such that the said amidships portion and the said surfaces combined are adequate to enable the boat to plane.

The boat may be a sailing boat or a motor craft the basic hull shape of which is a displacement hull such as a fishing boat. The application of the invention would thus permit the boat to be used as a planing boat, e.g., when lightly loaded and in reasonably fair weather, but could revert to normal operation in other conditions.

While the invention has been described herein in terms of preferred embodiments, numerous variations may be made in the arrangement illustrated in the drawings and herein described without departing from the invention as set forth in the appended claims.