Ships – Displacement-type hull – Having specific forebody
Patent
1998-11-12
2000-05-09
Avila, Stephen
Ships
Displacement-type hull
Having specific forebody
114 613, 114 6131, 114 72, B63B 100
Patent
active
060588640
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a ship hull in the shape of an elongated streamlined body which has a prow which when seen in the horizontal plane is V-shaped above the waterline of the hull with a bulb under the waterline at one end and a square stern at the opposite end. The invention also relates to a motor driven cargo vessel with a hull of this kind.
Modern cargo vessels with a hull of the type mentioned above have a hull shape which is load capacity optimised. This means amongst others that the hull has a nearly flat bottom from the region behind the bulb in the prow to a short distance in front of the square stern where the bottom slants upwards towards the bottom edge of the square stern. The hull sides are completely vertical and pass over to the flat bottom via parts curved with a small radius. The advantages of this shape are obvious in, for example, container vessels, because it is possible to dimension the cargo space of the vessel according to the shape of container so that the maximum number of containers can be freighted with least possible wasted space. The disadvantages are, however, on the one hand that the vessel has a low shape stability and must be ballasted when it sails unloaded and on the other hand that it is not hydrodynamically optimised.
The purpose of the present invention is to provide a ship hull of the type mentioned in the introduction which can be hydrodynamically optimised and which has a higher shape stability than a cargo capacity optimised ship hull so that for example it does not need to be ballasted when it sails without cargo.
This is achieved according to the invention by the bottom of the hull, at least between the transition between the bulb and the hull and the waterline of the square stern, extending without any sharp changes along longitudinal lines which are curved over at least the largest part of the length and that the hull in cross-section having sides which at least over the largest part of their vertical extent from the waterline to the bottom plane are inclined to the vertical plane. With a hull of this type a 10% lower towing drag than a classic design of this hull calculated by the Holtrop-method is achieved but on the other hand it results in the bottom shape in the space in the fore and after-bodies of the hull being unsuitable for cargo such as, for example, containers.
The invention, however, is based on the idea of using such spaces for other purposes than for cargo so that a cargo ship with a hull according to the invention can lower the total transport cost compared to transporting in a conventional cargo capacity optimised vessel.
A preferred embodiment of a vessel with a hull according to the invention has in the forebody a first engine room with a plurality of diesel motor driven generators and in the afterbody a second engine room with a number of electric motors coupled to two propeller shafts. A vessel with a power requirement of approximately 4000 kW can, for example, have ten diesel motors each having an output of approximately 400 kW which without problem could be accommodated in the front half of the vessel, for example under the superstructure of the vessel.
The invention will be described in more detail with reference to the embodiments shown on the annexed drawings, where
FIG. 1 shows a lateral view of the hull of a vessel according to the invention,
FIG. 2 an enlarged frame plan of the hull in FIG. 1,
FIG. 3 a view from below of the hull of a vessel shown in FIGS. 1 and 2 and
FIG. 4 a perspective view of a container cargo vessel with a hull according to the invention.
In the Figures reference numeral 1 describes generally a ship's hull which has a prow 2 which is V-shaped when seen in the horizontal plane and a flat square stern 3 above the waterline 4. Under the waterline 4 the prow has a bulb 5. As is evident from the contour line 6 the bottom 7 runs in a continuous gentle curve without any sharp changes from the bulb 5 all the way to the waterline of the afterbody, which in the example shown forms the bottom edge of the squa
REFERENCES:
patent: 3511203 (1970-05-01), Buyscoll
patent: 4158416 (1979-06-01), Podesta
patent: 5299520 (1994-04-01), Wilts
Stig Gunnar Skoot, Elvstromb.ang.t med bulb, P.ang. Kryss & Till Rors, vol. 46, No. 3, Mar. 1975, p. 54.
AB Volvo Penta
Avila Stephen
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