HK1014910B - Marine vessels - Google Patents

Description

BACKGROUND TO THE PRESENT INVENTION AND SUMMARY THEREOF

This invention relates to marine vessels.

EP-A-0495722 discloses a marine vessel comprising a central hull stabilised by first and second pairs of outboard sponsons and propelled by propulsion means carried by the sponsons or the hull, the first pair of sponsons being disposed forwardly of the second pair of sponsons, the sponsons of the first pair being disposed at a higher level than the sponsons of the second pair, so that, at zero heel angle, at the load water line of the vessel, the sponsons of the second pair are in contact with the water while the sponsons of the first pair are disposed above the water. The present invention relates to such a marine vessel, characterised however in that, at zero heel angle, the waterline breadth of each sponson of the second pair of sponsons is greater than the draft thereof, and that should the vessel heel to one side, the sponson of the second pair on the downgoing side of the vessel dips deeper into the water, while the other sponson of the second pair which is on the upgoing side of the vessel emerges from contact with the water, and the sponson of the first pair on the downgoing side of the vessel is simultaneously brought into contact with the water, so as to stabilise the vessel.

The hull may have a waterline length to beam ratio greater than 6, and preferably 10.

The vessel may be provided with first and second pairs of outboard sponsons, with the first pair disposed forwardly of the second pair, the sponsons of the first pair being disposed at a higher level than the sponsons of the second pair so that, at the load water line of the vessel, the sponsons of the second pair are in contact with the water while the sponsons of the first pair are disposed above the water whereby, should the vessel heel to one side, the sponson of the first pair on the heeling side of the vessel is brought into contact with the water, so as to create an upwardly acting restoring force which tends to stabilise the vessel.

The sponsons of each pair of first and second sponsons may be spaced from each other longitudinally of the vessel.

The sponsons of each pair of first and second sponsons may be combined so as to form a single integral structure of stepped form.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The various aspects of the invention will now be described by way of example only, with reference to the accompanying drawings, wherein:

• Figure 1 is a side view of a first form of marine vessel,
• Figure 2 is a plan view thereof,
• Figure 3 is a bow-end view which illustrates a modification,
• Figure 4 is a side view of another form of marine vessel,
• Figure 5 is a plan view thereof,
• Figures 6 to 11 are front views which illustrate the behaviour of the sponsons of the vessel at various heel angles, and
• Figures 15 and 16 are side views which illustrate modifications.

In the figures, like reference numerals refer to like structures and features.

DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

With reference to Figures 1 and 2, a marine vessel in the form of a freight ship 1 comprises a central hull 2 stabilised by a pair of outboard sponsons 3 flanking the stern end of the hull 2.

The hull 2 has a waterline length to beam ratio greater than 6. In this example, the ratio is 10. The waterline is shown at 8.

The sponsons 3 are pivotally attached to the stem end of the hull 2 by bridging structures 4 which are movable sternwards, relative to the hull, in a pantograph-like manner, so as to enable the hull to be manoeuvred close to a quay or like structure for hull loading/unloading operations.

The pivot points for the sponsons 3 are shown at 10 and 11, whereby the sponsons fold about substantially vertical axes.

The hull 2 carries a bridge accommodation superstructure 5 and has bulbous bow 6 and stern 7 structures.

The hull 2 defines four freight-carrying spaces in the form of cargo holds 9, with hatch covers 15, intended to accommodate cargo containers.

Alternatively, only a single freight carrying space may be provided if the marine vessel is to operate as a Roll-on Roll-off (RORO) ship.

The hull 2 is also formed with double-bottom tanks 16.

The sponsons 3 preferably have a waterline length of not more than 30% of the waterline length of the hull.

Details of the vessel 1 are as follows:

Overall length

: 250 metres

Waterline length

: 220 metres

Waterline width (of hull 2)

: 22 metres

Hull waterline length to beam ratio

: 10

Waterline length of each sponson 3

: 39 metres, i.e. 18 % of hull waterline length

Waterline beam of each sponson 3

: 6 metres

Containerised cargo

: 1000 cargo containers (each 6.096 x 2.438 x 2.438 metres)

Total length of cargo holds 9

: 150 metres.

Propulsion and steering means for the vessel 1 are preferably carried by the sponsons 3. The propulsion means so carried may comprise:

• a) water-screw propellers, driving machinery therefor, and rudders,
• b) steerable water jet units, driving machinery therefor,
• c) water screw propellers, electric drive motors therefor, supplied with electrical current by generators either disposed in the sponsons, or alternatively, in the hull 2, plus rudders.

Whatever form of vessel propulsion and steering means may be chosen, the object should be to keep the stern of the hull 2 free of water-screw propellers and rudders, and to avoid the employment of propulsion machinery in the hull itself. Electrical generating equipment for diesel electric propulsion may be carried by the hull 2, but this can be disposed on the hull deck, leaving the hull free to accommodate freight.

The stern end of the hull 2 is also free to be shaped so as to have a form whereby resistance is substantially reduced, compared with a conventional vessel provided with a water-screw and a rudder.

Use of both bow and stem bulbous sections also reduces wave-making resistance by creating wave-cancelling pressure fields at the bow and stern of the hull 2.

In the example illustrated, the bulbous bow 6 is larger and projects further forward than on most conventional vessels, and is faired upwardly and sternwards, back into the hull 2, as shown at 17. This creates a forebody which tends to run through waves rather than responding to them and causing the vessel to pitch.

The design also enables use of a stern bulbous section larger than employed conventionally.

Folding back of the sponsons 3 may cause the vessel 1 to become unstable. To avoid instability, water may be introduced into the double bottom tanks 16, to serve as ballast, The water is subsequently discharged when the sponsons 3 are restored to their normal, ie extended positions.

With reference to Figure 3, the vessel 1 may be provided with sponsons 3a movable about substantially horizontal axes 20 between inoperative (raised) and operative (lowered) positions.

The shape of the bulbous bow 6 may vary according to requirements

With reference now to Figures 4 to 11, a marine vessel in the form of a freight ship 201 comprises a single, central hull 202 (of waterline length to beam ratio grater than 6 and, as illustrated, about 10) stabilised by first and second pairs of outboard-disposed buoyant sponsons 230, 231.

The sponsons 230 of the first pair are disposed at a higher level than the sponsons 231 of the second pair so that, at the load water line 208 of the vessel hull 202, the sponsons 231 of the second pair are in immersed contact with the water level 252 (Figures 9 to 14) at water line 208, while the sponsons 230 of the first pair are (normally) disposed above the water 252 at waterline 208. As explained hereinafter with reference to Figures 6 to 11, should the vessel heel to one side, the sponson 230 of the first pair on the heeling or downgoing side of the vessel is brought into contact with the water 252 so as to create an upwardly-acting restoring force 250 which tends to stabilise the vessel 201.

The vessel 201 is provided with fore and aft ballast tanks 260, 261 whereby the vessel is trimmed so as to ensure that the sponsons 230, 231 are disposed where required, relative to the water line 208.

The sponsons 230, 231, which have a waterline length of not more than 30% of the waterline length of the central hull 202, are spaced from each other longitudinally of the marine vessel 201 as indicated at S. The sponsons 230, 231 are also spaced outboard of the centrally-disposed hull 202, being connected thereto by bridging structure 204, which in this example is non-foldable, but may be replaced by foldable structure.

The sponsons 230, 231 and non-foldable bridging structure 204, may be covered with decking 251 (Figure 5) which may be extended in area beyond that illustrated.

The sponsons 230 of the first pair of sponsons are aligned with the sponsons 231 of the second pair thereof (Figure 5 refers).

The first and second pairs of sponsons 230, 231 of this example are disposed one behind the other, as best seen in Figure 8. The sponsons of each pair are disposed laterally of each other. The sponsons 231 of the second pair are aligned with the sponsons 230 of the first pair, and spaced longitudinally therefrom, whereby the wave trains of the first pair of sponsons 230 beneficially interfere with the wave trains of the second pair of sponsons 231 so as to reduced wave resistance.

The longitudinal spacing S of the sponson pairs 230, 231 is such that the wave trains generated by the leading sponsons 230 are substantially 180° out of phase with the wave trains generated by the trailing sponsons 231. Thus the peaks of the leading wave trains interfere with the troughs of the trailing wave trains whereby wave-making resistance is substantially reduced.

As a general rule, faster marine vessels would employ larger longitudinal spacings of sponson pairs than slower ships.

Each fore and aft pair of longitudinally aligned sponsons 230, 231 are positioned relative to the central hull 202 so as to allow beneficial interference between the nett wave-making generated by the sponson and the wave-making generated by the hull 202.

The sponsons 230, 231 need not be disposed in alignment in order to achieve wave train interference.

The hull 202 carries a bridge accommodation superstructure 205 and has bulbous bow 206 and bulbous stern 207 structures.

The hull 202 defines freight-carrying spaces (not shown) in the form of cargo holds intended to accommodate cargo containers.

Alternatively, only a single freight carrying space may be provided if the marine vessel is to operate as a Roll-on Roll-off (RORO) ship.

The hull 202 is also formed with the usual double-bottom tanks.

The sponsons 230, 231 preferably have a waterline length of not more than 30% of the waterline length of the central hull 202.

Propulsion and steering means for the vessel 201 carried by the sponsons 230, 231 may comprise propulsion and steering means as described above, with reference to the marine vessel 1 of Figures 1 and 2. However, propulsion engines are preferably located in the central hull 202 and drive a contra-rotatable propeller 280.

Figures 6 to 11 illustrate what happens during progressive heeling of the marine vessel 201. Figures 6, 8 and 10 show the action of the aft-disposed sponsons 231 and Figures 7, 9 and 11 show the action of the forward-disposed sponsons 230.

It will be seen from these figures that at zero heel angle, the waterline breadth of each rearward sponson 231 is greater than the draft thereof (Figure 6 refers).

With reference first to Figures 6 and 7, these figures show the positions of the forward and aft-disposed sponsons 230, 231 respectively, at zero heel angle, that is with the hull 202 upright, In these positions, the bottoms of the relatively low sponsons 231 are immersed in the water 252, thus providing the vessel 201 with initial stability, while the bottoms of the relatively high sponsons 230 are clear of the water 252.

Figures 8 and 9 show the marine vessel 201 disposed at a small angle of heel. The aft-disposed sponson 231 (Figure 8) on the heeling or downgoing side of the hull 202 now dips deeper into the water 252 while the aft-disposed sponson 231 on the upgoing side of the hull emerges from contact with the water. The forwardly-disposed sponson 230 (Figure 9) on that downgoing side is simultaneously brought into contact with the water. This creates an upwardly-acting restoring force 250 on the downgoing sponson 230, which tends to stabilise the vessel 201.

The restoring force 250 is assisted by a similar force 255 created as the downgoing sponson 231 dips deeper into the water 252.

At a larger angle of heel, illustrated by Figures 10 and 11, the downgoing aft-disposed sponson 231 is immersed further into the water 252 while the upgoing sponson 231 of the pair is pulled clear of the water.

At the same time, the downgoing and upgoing forwardly-disposed sponsons 230 are immersed deeper into the water 252 and drawn further away from the water 252 respectively.

Figure 12 illustrates a modification wherein the first and second pairs of sponsons 230, 231 are combined into a single integral or unitary structure 256 of stepped form.

The step 257 is abrupt, in Figure 12, but with reference to the modification illustrated by Figure 13, a structure 256 may be profiled so as to have a rearwardly-sloping step 257a, whereby wave-impact forces are reduced.

The forwardly-disposed sponsons 230 will also come into play should the marine vessel 201 be subjected to pitching forces.

Where possible, and where desirable, any of the above-described features may be substituted for, or added to, each other.

Although mono-hull marine vessels have been described herein, the various aspects of the invention are not to be restricted thereto, as they are also applicable to multi-hull marine vessels.

Similarly, although freight vessels have been described herein, the various aspects of the invention are also applicable to car ferries, with the following advantages compared with presently-known car ferries:

• a) lower propulsive power
• b) better vessel motion control
• c) lower construction costs
• d) wide deck area (decking 251 and extensions thereof)
• e) possible use of heavier, more efficient engine machinery, due to lower weight sensitivity.

With reference to Figures 2 to 13 it will be noted that, in the case of a two pair sponson arrangement, at least part of each forward sponson 130, 230 is beneficially disposed in the stern half of the associated hull 102, 202.

Claims (16)

1. A marine vessel (1, 101, 201) comprising a central hull (2, 102, 202) stabilised by first and second pairs of outboard sponsons (3; 130, 131; 230, 231), and propelled by propulsion means (eg 180, 280) carried by the sponsons or the hull, the first pair of sponsons (230) being disposed forwardly of the second pair (231) of sponsons, the sponsons (230) of the first pair being disposed at a higher level than the sponsons (231) of the second pair so that, at zero heel angle, at the load water line (208) of the vessel (201), the sponsons (231) of the second pair are in contact with the water while the sponsons (230) of the first pair are disposed above the water, characterised in that, at zero heel angle, the waterline breadth of each sponson (231) of the second pair of sponsons is greater than the draft thereof, and that should the vessel heel to one side, the sponson (231) of the second pair on the downgoing side of the vessel dips deeper into the water, while the other sponson (231) of the second pair which is on the upgoing side of the vessel emerges from contact with the water, and the sponson (230) of the first pair on the downgoing side of the vessel is simultaneously brought into contact with the water, so as to stabilise the vessel.
2. A marine vessel (1, 201) as claimed in claim 1 wherein the hull (202) is for carrying payload.
3. A marine vessel as claimed in claim 2, wherein the hull (2, 202) has a waterline length to beam ratio greater than 6.
4. A marine vessel as claimed in claim 1 wherein the sponsons of each pair of first (230) and second (231) sponsons are spaced from each other longitudinally (by distance S) of the vessel (201).
5. A marine vessel as claimed in claim 1, wherein the sponsons of each pair of first (230) and second (231) sponsons are combined so as to form a single integral structure (256) of stepped form.
6. A marine vessel as claimed in claim 5, wherein the step (257a) slopes rearwardly.
7. A marine vessel as claimed in claim 1, wherein the pairs of sponsons (230, 231) are covered by deck structure (251).
8. A marine vessel as claimed in claim 1, wherein the waterline length of each sponson (eg 3) is not more than 30% of the waterline length of the vessel hull.
9. A marine vessel as claimed in claim 3, wherein the hull waterline length to beam ratio is 10 or more.
10. A marine vessel as claimed in claim 1, wherein the sponsons (eg 3, 3a) are movable relative to the vessel hull (2).
11. A marine vessel as claimed in claim 3, wherein the hull defines at least one freight carrying space (9).
12. A marine vessel as claimed in claim 1, wherein the sponsons of each pair are spaced laterally from each other, the sponsons of the second pair being spaced longitudinally (by distance S) from the sponsons of the first pair, whereby the wave trains of the first pair of sponsons interfere with the wave trains of the second pair of sponsons, so as to reduce wave resistance.
13. A marine vessel as claimed in claim 12, wherein the peaks of the wave trains of the first pair of sponsons (230) interfere with the troughs of the wave trains of the second pair of sponsons (231).
14. A marine vessel as claimed in claim 1, wherein the sponsons of the second pair are aligned with the sponsons of the first pair.
15. A marine vessel as claimed in claim 1, wherein one pair of sponsons (3) is disposed at the stern end of the hull (2).
16. A marine vessel as claimed in claim 1, wherein at least part of each forward sponson (230) is disposed in the stern half of the hull.