VESSEL CONFIGURED FOR PITCH REDUCTION

Abstract

A vessel (30) comprising a hull (15) having an apparent centre of pitch (23) located at a position between about 10% and 35% of the length of the vessel (10) measured from the aftermost point (17) of the vessel on the design waterline. The hull (15) may be bare, or alternatively may be fitted with a damping system (31) located forwardly to provide damping forces to reduce the vertical motion at the bow and hence the vertical accelerations. In one arrangement, the vessel (10) may comprise a single hull vessel. In another arrangement, the vessel (10) may comprise a multi-hulled vessel.

Claims

1.-2. (canceled)

3. A vessel comprising a hull with an apparent centre of pitch located at a position between about 10% and 35% of the length of the vessel measured from the aftermost point of the vessel on the design waterline, the hull being fitted with a damping system mounted on an underside of the hull proximate the bow to provide damping forces to reduce the vertical motion at the bow and hence the vertical accelerations.

4. The vessel according to claim 3 wherein the damping system comprises a hydrodynamic damping device such as a wing or foil mounted at or close to the bow.

5. The vessel according to claim 3 designed for speeds of between 20 and 70 knots.

6. The vessel according to claim 3 having a length on the waterline of between 24 metres and 250 metres.

7. The vessel according to claim 3 comprising a single hull vessel.

8. The vessel according to claim 3 comprising a multihulled vessel.

9. The vessel according to claim 8 comprising a trimaran having a centrally located main hull and two laterally spaced side hulls, wherein the hull constitutes the main hull.

10. The vessel according to claim 8 comprising a pentamaran having a centrally located main hull and four laterally spaced side hulls, wherein the hull constitutes the main hull.

11. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The invention will be better understood by reference to the following description of several specific embodiments thereof. The description will be made with reference to the accompanying drawings in which:

[0032] FIG. 1 is a schematic side view of a conventional hull configuration, illustrating the apparent centre of pitch;

[0033] FIG. 2 is a schematic side view of a conventional configuration, illustrating the apparent centre of pitch, the hull configuration incorporating a hydrodynamic damping device mounted at or adjacent to the bow;

[0034] FIG. 3 is a schematic side view of a conventional multi-hull configuration, illustrating the apparent centre of pitch, the multi-hull configuration incorporating a main hull having a hydrodynamic damping device mounted at or adjacent to the bow;

[0035] FIG. 4 is a graph of vertical acceleration (RMS) versus distance from the after end of the conventional hull configuration as depicted in FIG. 1 as a percentage of the length L of the vessel measured on the design waterline;

[0036] FIG. 5 is a schematic side view of the hull of a vessel according to a first embodiment, illustrating the apparent centre of pitch;

[0037] FIG. 6 is a graph of vertical acceleration (RMS) versus distance from the after end of the hull configuration according to the first embodiment as a percentage of the length L of the vessel measured on the design waterline;

[0038] FIG. 7 is a schematic side view of the hull of a vessel according to a second embodiment, illustrating the apparent centre of pitch;

[0039] FIG. 8 is a graph of vertical acceleration (RMS) versus distance from the after end of the hull configuration according to the second embodiments as a percentage of the length L of the vessel measured on the design waterline; and

[0040] FIG. 9 is a schematic side view of the hull of a vessel according to a third embodiment, illustrating the apparent centre of pitch.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

[0041] The first embodiment, which is shown FIG. 5, is directed to a vessel 10 comprising a high speed commercial or military vessel, such as a ferry, for passenger and cargo transport, including vehicle transport. In this embodiment, the vessel is designed for speeds between about 20 and 70 knots.

[0042] Typically, the vessel 10 has a waterline length between 24 metres and 250 metres, although it is of course not limited thereto.

[0043] The vessel 10 comprises an understructure 11 and a superstructure (not shown), both constructed primarily of aluminium. The actual waterline in relation to the understructure 11 is established by the water surface 13. The water surface rises and falls and under the influence of wave motion and is shown varying between three positions 13a, 13b and 13c. The pitching motion of the vessel 10 from the neutral position is depicted by broken lines 10a and 10b, with solid line 10c depicting the neutral position. The direction of pitching motion is depicted by the adjacent direction arrows 14.

[0044] The under structure 11 comprises a hull 15. In one arrangement, the vessel 10 may comprise a single hull vessel. In another arrangement, the vessel 10 may comprise a multi-hulled vessel. The vessel may, for example, comprise a trimaran having a centrally located main hull and two laterally spaced side hulls commonly known as amahs, in which case the hull 15 would be constituted by the main hull. Alternatively, the vessel 10 may, comprise a pentamaran having a centrally located main hull and four laterally spaced side hulls (two to each side of the main hull), in which case the hull 15 would be constituted by the main hull.

[0045] In the arrangement shown in FIG. 5, the vessel 10 is a single hull vessel. The hull 15 has a forward end terminating at a bow 17 and an aft end terminating at a stern 19. The bow 17 may incorporate a forwardly extending bulbous portion 21 below the waterline 13.

[0046] The design waterline of the hull 15 is denoted by reference numeral 20. The hull 15 has an apparent centre of pitch which is identified by reference numeral 23.

[0047] The hull 15 is configured to move the apparent centre of pitch 23 considerably further aft in comparison a conventional vessel design as discussed above and depicted in FIG. 1. This is generally not considered to be beneficial by those skilled in the art because such a hull shape is likely to increase the resistance of the vessel to forward motion and hence to reduce the speed of the vessel.

[0048] Specifically, the apparent centre of pitch 23 located at a position between 10% and 30% of the length L of the vessel measured from the aftermost point of the craft on the design waterline, when the underwater hull shape is bare and without any hydrodynamic force generators such as foils or fins, and without the assistance of any external force generators such as gyroscopic stabilisers. In this embodiment, the apparent centre of pitch 23 located at a position corresponding to about 20% of the length L. Aft of this location, the acceleration values rise, and forward of this location the acceleration values also rise at a reasonably consistent rate. The region of lowest vertical accelerations extends to each side of the centre of pitch 23 over a length identified schematically in FIG. 5 by line 24.

[0049] The vertical acceleration distribution for such a hull configuration is illustrated in FIG. 6. In particular, FIG. 6 a graph of vertical acceleration (RMS) versus distance from the after end 19 of the hull 15 as a percentage of the length L of the vessel measured on the design waterline 20.

[0050] In order to obtain the desired location of the centre of pitch 23, it is necessary that the buoyancy distribution of the hull shape (and therefore the associated weight distribution of the vessel) be considerably further aft than is generally desirable for a commercially viable layout of a conventional sea-going vessel. Accordingly, the superstructure (not shown) is configured such that the majority of the weight of the vessel 10 lies in the after part of the vessel.

[0051] Such an arrangement is conducive to the desired layout of the vessel 10. In particular, it allows the passenger area of the vessel 10 to be located further aft where there are lower vertical accelerations (as depicted in FIG. 6), thus potentially affording a higher degree of comfort to passengers.

[0052] With the vertical acceleration distribution as illustrated in FIG. 6, it is evident that the acceleration values in the forward part of the vessel 10 are noticeably greater than those of the conventional ship illustrated in FIG. 4. This is addressed in this embodiment by a superstructure layout in which personnel are not accommodated in the forward part of the vessel 10, and consequently the acceleration values would not be relevant to personnel comfort or safety.

[0053] Referring now to FIG. 7, there is shown a vessel 30 according to a second embodiment. The vessel 30 is similar to the vessel 10 according to the first embodiment and so corresponding reference numerals are used to identify corresponding parts. In this second embodiment, the vessel 30 is fitted with a damping system 31 located forwardly to provide damping forces to reduce the vertical motion at the bow 17 and hence the vertical accelerations. The damping system 31 comprises a hydrodynamic damping device 33 mounted at, or close to, the bow 17. In the arrangement shown, the hydrodynamic damping device 33 is configured as a hydrofoil 35 or similar hydrodynamic appendage.

[0054] FIG. 8 a graph of vertical acceleration (RMS) versus distance from the after end of the hull 15 as a percentage of the length L of the vessel measured on the design waterline 20. FIG. 8 also includes data from FIG. 6 for comparative purposes.

[0055] The effect of such a damping system 31 would be as illustrated in FIG. 8. The apparent centre of pitch 23 would remain substantially in the same location, although there may be some forward movement by up to about 10% L.

[0056] More particularly, the apparent centre of pitch 23 would be located at a position between 10% and 35% of the length L of the vessel measured from the aftermost point of the vessel on the design waterline.

[0057] Referring now to FIG. 9, there is shown a vessel 40 according to a third embodiment. The vessel 40 comprises a multi-hulled vessel. In the arrangement shown, the multi-hulled vessel 40 comprise a trimaran having a centrally located main hull 41 and two laterally spaced side hulls 43 commonly known as amahs. In another arrangement, the multi-hulled vessel 40 may comprise a pentamaran having a centrally located main hull and four laterally spaced side hulls (two to each side of the main hull).

[0058] The main hull 41 has a design waterline 44.

[0059] The pitching motion of the vessel 40 from the neutral position is depicted by broken lines 40a and 40b, with solid lines 40c depicting the neutral position.

[0060] The hull 41 has a forward end terminating at a bow 45 and an aft end terminating at a stern 46. The bow 45 may incorporate a forwardly extending bulbous portion 47 below the design waterline 44. Additionally, the vessel 40 may be fitted with a damping system 48 located forwardly to provide damping forces to reduce the vertical motion at the bow 45 and hence the vertical accelerations. The damping system 48 comprises a hydrodynamic damping device 49 mounted at, or close to, the bow 45. In the arrangement shown, the hydrodynamic damping device 48 is configured as a hydrofoil, as was the case with an earlier embodiment.

[0061] The hull 41 has an apparent centre of pitch which is identified by reference numeral 42.

[0062] The hull 41 is configured to move the apparent centre of pitch 42 considerably further aft in comparison a conventional multi-hull vessel design as discussed above and depicted in FIG. 3. As mentioned in relation to earlier embodiments, this is generally not considered to be beneficial by those skilled in the art because such a configuration is likely to increase the resistance of the vessel to forward motion and hence to reduce the speed of the vessel.

[0063] In particular, the apparent centre of pitch 42 is located at a position between 10% and 35% of the length L of the vessel 40 measured from the aftermost point of the vessel on the design waterline.

[0064] From the foregoing, it is evident that the present embodiments each provide a vessel with a hull configuration which delivers improved comfort and safety to personnel onboard the vessel through a reduction in vertical accelerations in the area where personnel are likely to be accommodated.

[0065] It should be appreciated that the scope of the invention is not limited to the scope of the embodiments described, and that various changes and modification may be made without departing from the scope of the invention.

[0066] Throughout the specification and claims, unless the context requires otherwise, the word comprise or variations such as comprises 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.