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(11) | EP 0 613 816 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Hull of small craft |
| (57) A hull of a small craft such as a yacht which, if overturned, can return to its original
normal position making use of its own buoyant force. A partitioning wall is provided
at its longitudinally central portion to define a closed space in front thereof. A
cockpit provided in the rear of the partitioning wall is defined by the side boards
and a floor board. A shallow closed space is formed between the floor board and the
bottom of the yacht. |
[0001] This invention relates to the hull of a small craft such as a yacht, fishing boat or motorboat which can reliably turn back to its normal position if overturned by winds or side waves.
[0002] Today's yachts used in open-sea yacht races have various means for preventing them from being overturned even if inclined considerably due to winds or waves and means for allowing them to restore their original position if overturned.
[0003] Unexamined Japanese Patent Publication 60-42190 discloses a yacht of this type. It has a mast for hoisting sails at a longitudinal center of the hull. A center board as a weight protrudes from its bottom. A space called a cockpit is provided which extends for the entire length or at least for the rear half of the hull. A pilot sits in the cockpit to steer the yacht. Further, this yacht has closed spaces defined between the inner boards forming the cockpit and the side boards on both sides of the hull.
[0004] Fig. 8 shows a typical yacht used in open-sea yacht races. In order to provide stability against the rolling of the yacht, its side boards 1 have a streamlined configuration and the width of the hull is the largest at its longitudinal center. This yacht has a canopy 4, a deck 5, a cockpit 6, a mast 7 and a center board 8. The cockpit 6 is a recess in which a pilot can sit. Except the cockpit 6 and the canopy 4, the top of the yacht is completely covered with the deck 5.
[0005] Today, an increasing number of people are taking part in various international yacht races including such race events as Japan-Guam yacht race '92 "Marine-Marine" and America's Cup and some of them were involved in tragic accidents resulting from overturned yachts.
[0006] Concerning today's yachts, the following problem was pointed out in a report titled "Warning from the investigation of the Guam race accident" (written by Kensaku Nomoto; an article in the magazine "kaji" (steering), November, 1992 issue), which was summed up from the first interim report submitted by the accident investigation committee. Namely, when comparing an IOR racer A and a cruiser B, an older type than the IOR, type A is overturned if the heel angle exceeds 110°, while type B is not overturned until it approaches somewhere near 160°. Once type A is overturned, it stabilizes in the overturned state. Although type B is less likely to be overturned, it is difficult to return it to its original position once overturned.
[0007] The stability curve of the conventional yachts as described above depends upon their hull structure, especially the position of the center of gravity. Such conventional yachts have a tendency to stabilize in an overturned state and thus cannot return to their original normal position once overturned. People on board such yachts will thus be faced with a great danger of life if their yachts are overturned. The reason why the conventional yachts are difficult to recover once overturned is because they have longitudinally-extending closed spaces on both sides of the hull. In an overturned state, the closed spaces, which serve as floats, balance with the center of gravity of the hull, so that the hull stabilizes in this state just like a bucket afloat on the water with its bottom up.
[0008] This mechanism is described in detail with reference to Fig. 9, of which Figs. 9(a), 9(b) and 9(c) show the states in which the yacht has been turned by 90°, 135° and 180°(turned completely upside down), respectively.
[0009] In the state of Fig. 9(c), restoring moment which tends to turn the hull to its original position will be produced at the front portion of the hull as soon as the line of action of the buoyant force B gets out of alignment even slightly with the line of action of the center of gravity G. But at the rear portion of the hull, the buoyant forces produced by the closed spaces provided on both sides of the hull balance with each other and serve to counteract the restoring force produced at the front portion. Thus, as a whole, the hull stabilizes in the state shown in Fig. 9(c).
[0010] As described above, since conventional small crafts such as yachts have closed spaces as floats on both sides thereof so as to extend longitudinally, they are difficult to return to their original position once overturned. Some of such conventional boats are provided with a float on the top of the mast to prevent them from being completely turned over even if they are turned sideways. But such measures are not fundamental solutions to the above problems.
[0011] An object of this invention is to provide a hull of a small craft which can produce a turning moment if the hull is overturned so that it can recover its original normal position.
[0012] According to this invention, there is provided a hull of a small craft comprising a bottom, a pair of side boards extending upwards from both edges of the bottom, the side boards being contiguous to each other at front portion thereof, a partitioning wall provided at a substantially longitudinally central portion of the hull so as to extend across the side boards, a deck provided in front of the partitioning wall so as to extend between the top edges of the side boards, and a floor board provided behind the partitioning wall and located over and spaced apart from the bottom, whereby forming a first closed space by the deck, the bottom, the side boards and the partitioning plate, forming a cockpit by the partitioning plate, the side boards and the floor board, and forming a second closed space by the floor board, the bottom, the side boards and the partitioning plate.
[0013] If the yacht is overturned, the first closed space as a float exhibits a large buoyant force, thus preventing the yacht from sinking soon if overturned.
[0014] Since the cockpit at the rear is not covered with a deck, it may be partially submerged in the water if the yacht is overturned.
[0015] But in this state, at the front portion of the hull, a turning moment is produced as soon as the line of action of the center of buoyant force gets out of line even slightly with the center of gravity, so that the yacht can turn back to its original normal position. At the rear portion of the hull, no closed spaces are provided on both sides of the hull unlike the prior art hull. Thus, the turning moment produced at the front portion of the hull will never be interfered.
[0016] As the hull turns back toward its original position, its rear portion will rise by the buoyant force of the second closed space defined under the cockpit at the rear of the hull. As the water in the cockpit is emptied, the hull can regain its original horizontal position.
[0017] The front portion of the hull in front of the partitioning wall provided at a longitudinal center of the hull serves as a float. The rear ends of the side boards are spaced apart from each other to provide an opening in the rear of the cockpit. Thus, if the yacht is overturned, it can return to its original position easily by the turning moment due to the buoyant force produced at the front portion of the hull. Once the yacht returns to its original position, a person can get on board. Thus, this arrangement makes it possible to save many people's lives, which might otherwise be lost.
[0018] Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which:
Fig. 1 is a side view of the yacht of the first embodiment;
Fig. 2 is a plan view of the same;
Figs. 3(a) - 3(e) are sectional views of the same taken along lines A-A, B-B, C-C, D-D and E-E of Fig. 1, respectively;
Figs. 4(a) - 4(c) are views of the same showing its operation;
Figs. 5(a) and 5(b) are views of the same showing its operation;
Fig. 6 is a schematic side view of a fishing boat of the second embodiment;
Fig. 7 is a schematic side view of a motorboat of the third embodiment;
Figs. 8(a) and 8(b) are schematic views of the prior art; and
Figs. 9(a) - 9(c) are views of the same showing its operation.
[0020] Figs. 1 and 2 are a side view and a plan view, respectively, showing schematically the structure of the yacht of this embodiment. The yacht illustrated is for use in open-sea yacht races.
[0021] Thus, it has a pointed tip and is wide at its longitudinal central portion so that it can maintain stability even if it is subjected to strong winds or side waves. If the yacht is an ordinary one for leisure, it may be configured in a different way.
[0022] In the embodiment, the hull is formed of FRP which is lightweight and strong, but may be of any other light metal such as aluminum alloy or wood.
[0023] A partitioning wall 2 is provided in the hull at its longitudinal central portion so as to extend across side boards 1 on both sides of the hull. It is contiguous at its bottom end to a horizontal floor board 3. In front of the partitioning wall 2 is provided a canopy 4 of a suitable size. A deck 5 is provided in front of the partitioning wall 2 so as to bridge the side boards 1 and define a closed space with the side boards 1 and a bottom board and the partitioning wall 2.
[0024] Though not shown, under the deck 5 is provided a kitchen and a closet. Crew members can enter these rooms by opening the canopy 4 to take a rest. When it is necessary to steer the yacht, they can get out of these rooms and move into a cockpit 6. The yacht also has a mast 7, a center board 8 as a ballast and a check valve 9. If the rear end of the cockpit 6 is open, such a check valve 9 is not needed. But if the cockpit has a rear wall of a certain height, it is preferable to provide a plurality of check valves. Their function is described later.
[0025] As shown in the figure, the cockpit 6 is defined by the side boards 1, partitioning wall 2 and floor board 3. The hull of the present invention does not have closed spaces on both sides thereof so as to extend longitudinally as in the prior art. The side boards 1 may be cut so that the cockpit 6 will be open at rear end thereof. A shallow closed space 3' is defined between the floor board 3 and the bottom of the yacht to provide buoyancy. It is an important feature of the present invention that the cockpit is formed in such a manner.
[0026] Figs. 3(a)- 3(e) show sectional views taken along lines A-A, B-B, ... E-E of Fig. 1. These figures show the detailed hull structure. In the normal state shown in Fig. 3(c), the center of gravity G of the hull is located below the center B of the buoyant force, so that the hull is afloat stably on the water.
[0027] Referring to Figs. 4 and 5, we will describe the behavior of the hull how the hull returns to its original position when it is turned sideways or overturned upside down.
[0028] First, let us consider the situation where the yacht is turned sideways, i.e. by 90° as shown in Fig. 4(a). In this state, the rear portion of the hull where there is the cockpit 6 shows a tendency to sink into the water. At its front portion, represented by the C-C cross-section, the center of gravity G of the hull is located above the center B of the buoyant force. Thus, restoring moment is produced which tends to turn the hull to its normal position about an unillustrated point (which is located somewhere between the points B and G). If there exists no force tending to turn the hull completely upside down in this state, the hull will be turned back to its original normal position by the restoring moment.
[0029] If winds are so strong or side waves so high that the yacht is turned by about 135°, the center of gravity G overpasses the center B of buoyant force (The heel angle at which the point G overpasses the point B varies with the hull structure and may be larger or smaller than 135°). In this state, the hull will not turn back to its original position any more and will incline still further.
[0030] When it is turned completely upside down, i.e. by 180°, the front portion of the hull is still afloat and the center of gravity G is located above the center of buoyant force B as shown in Fig. 4(c). In the state shown, the point G is located right over the point B.
[0031] In this sate, the rear portion of the hull will begin to sink into the water. Namely, only the front portion of the hull is afloat. This state is shown in Fig. 5(a).
[0032] Even in this overturned state, the yacht of this invention will show a tendency to turn back to its original normal position because of its unique hull structure. Namely, in the overturned state shown in Fig. 4(c), the center of gravity G is located above the center of buoyant force B at the front portion of the hull with its rear portion in the water. Although the points G and B balance with each other in the state of Fig. 4(c), it is impossible that the hull keeps this balanced state in actual situations because it is rolling. As soon as the downwardly-directed line of action of point G gets slightly out of alignment with the upwardly-directed line of action of the center of buoyant force B, the hull will show a tendency to turn back about a point between points G and B.
[0033] Due to the restoring moment produced at the front portion of the hull, the hull will begin to turn back to the position of Fig. 4(b), then to the position of Fig. 4(a), and finally to the original normal position. When the heel angle decreases to less than 90° and approaches 0°, the space 3' will sink into the water and serve as a float, lifting the rear portion of the hull as shown in Fig. 5(b). The hull thus begins to regain its horizontal position. Since the side boards are open at their rear ends, any water in the cockpit 6 will be discharged quickly through the rear opening.
[0034] When the cockpit 6 is emptied, the hull returns completely to its original position in which the hull is inclined neither longitudinally nor transversely.
[0035] Fig. 6 shows a fishing boat to which is applied the basic structure of the yacht of the first embodiment. It has side boards 11, a partitioning wall 12, a floor board 13, a steering room 14, a deck 15, a fish storage space 16, an engine 17, a propeller 18 and a rudder 19. The rear end of the fish storage space 16 is closed by the side boards in this embodiment but may be open. If closed, it is necessary to provide a plurality of check valves 20.
[0036] Fig. 7 shows a small motorboat which employs the structure of the first embodiment. It has side boards 21, a partitioning wall 22, a floor board 23, a steering room 24, a deck 25, a cargo compartment 26, an engine 27, a propeller 28 and a rudder 29. Its basic structure is substantially the same as the second embodiment.
1. A hull of a small craft comprising a bottom, a pair of side boards extending upwards
from both edges of said bottom, said side boards being contiguous to each other at
front portion thereof, a partitioning wall provided at a substantially longitudinally
central portion of the hull so as to extend across said side boards, a deck provided
in front of said partitioning wall so as to extend between the top edges of said side
boards, and a floor board provided behind said partitioning wall and located over
and spaced apart from said bottom, whereby forming a first closed space by said deck,
said bottom, said side boards and said partitioning plate, forming a cockpit by said
partitioning plate, said side boards and said floor board, and forming a second closed
space by said floor board, said bottom, said side boards and said partitioning plate.