Field of the Invention

This invention relates to marine vessels particularly sea-going vessels for commercial or military use. More particularly, the invention is concerned with the hull configuration for a vessel having one or more hulls. In relation to multi-hulled vessels, the invention is particularly concerned with vessels having an odd number of hulls; for example, three or five hulls.

Background Art

The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

For this type of multi-hulled vessel, at least 80% of the buoyancy of the vessel is provided by one hull when the vessel is floating at any navigable wateriine and at rest. The hull with the majority of the buoyancy contribution is known as the main hull and has a length (L) measured on the design wateriine and has a buoyant volume of the main hull (V).

Where sea-going vessels are designed for high speeds, it is generally desirable for reasons of efficiency to have a hull which is long and thin. More particularly, long and thin hulls offer advantages in having a low drag and superior vessel motions, equating to improved passenger comfort. However, long and thin hulls are difficult to design such that they remain safely upright when subject to disturbing influences such as wind and waves. One technical description of a hull that is long and thin is known by those skilled in the art of naval architecture as the slenderness ratio, and is described as a non- dimensional coefficient L/V ^{1 3} .

A long and thin vessel may be of any size, and a desirable slenderness ratio may be applied to any size of vessel. However, the regulatory stability requirements for commercial vessels do not scale with size, being generally fixed for all vessel sizes of a particular type, such as a passenger craft.

Accordingly, there is a need to modify the relationship between the buoyant volume of the main hull (V) and the length (L) of the vessel in order to ascertain the optimum vessel size meeting the requirement for regulatory stability.

It is against this background and the problems and difficulties associated therewith, that the present invention has been developed

Disclosure of the Invention

The present invention stems from the realisation that Length to the power of 0.25 (L° ²⁵ ) provides a realistic modifier to the slenderness ratio to accurately account for the requirement for regulatory stability.

Accordingly, in one aspect of the present invention there is provided a vessel comprising a hull having a hull length (L) measured in metres on any navigable wateriine and an associated buoyant volume (V) measured in cubic metres, wherein the modified slenderness ratio of the hull, /V is greater than or equal to 2.5.

In other words, the parameter L is modified by L ^1/4 to yield the parameter L ³ ' ⁴ . The vessel may comprise a single hull vessel or a multi-hulled vessel.

The multi-hulled vessel may comprise a trimaran having a centrally located main hull and two laterally spaced side hulls commonly known as amahs, wherein the main hull is in accordance with the invention. The multi-hulled vessel may also comprise a pentamaran having a centrally located main hull and four laterally spaced side hulls (two to each side of the main hull), wherein the main hull is in accordance with the invention.

Typically, the modified slenderness ratio of the hull, L^ V ^{1 3} is in the range of 2.5 to 4.0. In one application, the modified slenderness ratio of the hull, L ^3/ /V ^{1 3} is in the range 3.5 to 3.6. In another application, it is in the range 2.7 to 3.2. In yet another application, it is in the range 3.0 to 3.5.

For one typical vessel of trimaran configuration with a main hull of waterline length of 97.8 metres and a navigable volume of the main hull of 1350 cubic metres, this will result in a modified slenderness ratio of 2.8. The volume of the main hull in this example is not the total volume of the vessel comprising all hulls but only that volume attributed to the main hull.

Brief Description of the Drawings

The invention will be better understood by reference to the following description of several specific embodiments thereof as shown in the accompanying drawings in which:

Figure 1 is a schematic perspective view of a hull of a vessel according to a first embodiment; and Figure 2 is a schematic underside perspective view of a hull of a vessel according to a second embodiment.

Best Mode(s) for Carrying Out the Invention

The embodiment shown in the drawing is directed to a vessel 10 configured as high speed commercial or military vessel, such as a ferry, for passenger and cargo transport, including vehicle transport.

The vessel 10 comprises an understructure and a superstructure (not shown). In this embodiment, the understructure and superstructure are both constructed primarily of aluminium, although of course other appropriate construction materials can be utilised.

The understructure comprises a hull 1 which can constitute the hull of a single hull vessel, or the main hull of a multi-hulled vessel.

In the first embodiment, which is shown in Figure 1 , the vessel 10 is a single-hull vessel and the hull 11 has a forward end terminating at a bow 15, and an aft end terminating at a stem 17. The bow 15 may incorporate a forwardly extending bulbous portion 19 below the waterline. The navigable waterline is depicted by the line denoted by reference numeral 21.

The hull 11 has a length L measured on any navigable waterline 21, as shown in Figure 1. Additionally, the hull 11 has a buoyant volume V. The hull 11 is configured to be long and thin, and is designed with a modified slendemess ratio, L^ ¹ ' ^3, ≥ 2.5 where L is in metres and V is in cubic metres. It has been found that L ¹ ' ⁴ provides a realistic modifier to the slendemess ratio to accurately account for the requirement for regulatory stability.

In the second embodiment, which is shown in Figure 2, the vessel 10 comprises a multi-hulled vessel configured as a trimaran. The hull 11 comprises the main hull of the trimaran and there are two side hulls 12 on opposed sides of the main hull 11. The hull 11 in this second embodiment is similar to the hull 11 of the first embodiment and corresponding reference numerals are used to denote corresponding parts. From the foregoing it is evident that the present embodiments each endeavour to describe the limit of the two principal characteristics of the vessel; namely the length and the weight (or displacement), in order to ascertain the optimum vessel size meeting the requirement for regulatory stability.

It should be appreciated that the scope of the invention is not limited to the scope of the embodiments described.

While the embodiments have been described in relation to a single hull vessel and a multi-hull vessel configured as a trimaran, the invention is also applicable to other multi-hull vessels such as, for example, catamarans and pentamarans..

Throughout the specification and claims, unless the context requires otherwise, the word "comprise" or variations such as ^u comprises ^D or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.