Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
  • B63B1/02—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement
  • B63B1/10—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls
  • B63B1/12—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls the hulls being interconnected rigidly
  • B63B1/121—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls the hulls being interconnected rigidly comprising two hulls

Definitions

• the present invention relates to a hull or a hull construction for use in connection with a multi-hull vessel.
• the invention relates particularly to a hull construction for use in connection with a vessel with two juxtaposed hulls which besides ensuring buoyancy gives improved sailing characteristics.
• the still water drag includes the actual frictional drag and the so-called wave drag.
• the frictional drag may constitute approx. 70% of the overall drag and it normally varies proportionally with the so-called wet surface of the vessel, i.e. the area of that part of the hull which is submerged at a certain moment.
• the wave drag is due to the waves provoked by the vessel itself, as the high pressure at the fore part of the hull results in a bow wave top and a system of so-called roaches is created at the aft part of the ship.
• These two wave systems will, depending on the hull configuration, either enhance or weaken each other.
• a correct configuration of the hull lines at the end of the foreship makes it possible to reduce the wave drag.
• the wave drag may be reduced partially by providing a so-called bulb, i.e. an approximately cylindrical device which is mounted at the prow under the water surface.
• the sea drag is the contribution to the overall drag of the vessel by the movement thereof into the sea. This drag depends especially on the vessel's speed and course in relation to the direction of propagation of the waves and the relation between the wave length and the length of the vessel.
• the hulls are configurated so that large vertical acceleration components are avoided when sailing, which is essential for the comfort experienced by the passengers during the journey, as it is known that vertical acceleration components in particular cause symptoms of seasickness.
• the acceleration components are also essential for deciding whether to fasten or to lash the cargo on board the vessel.
• the vertical acceleration components are a particularly important parameter which is essential to the vessel's being accepted by line operators.
• SWATH-hull Small Water Area Twin Hull
• This hull form is characteristic in that it includes an elongated, cylindrical underbody which is connected to that part of the hull which is above the waterline by means of a tapered and approximately vertical hull portion which cuts through the water surface.
• This configuration solves the vertical acceleration component problem to a certain degree but gives birth to new problems, as the wet surface of the vessel is large compared to conventional catamaran constructions.
• the construction also involves an increased draught, which limits its use in waters and harbours with little depth.
• the vessel must be driven by means of a propeller assembly which is mounted at the end of the submerged, cylindrical parts.
• the Australian designer Lock Crowther developed two-hull vessel constructions where the fore part of the hull had a bulb-shaped cross-section. These hull constructions have the particularity that the underwater part of the hull continues into the part above water via an inflected curve, thus allowing the exterior half contour of the hull to be described as an S-shaped curve. The wet surface of the hull is thus reduced compared to the SWATH-hull, while the hull retains a relatively broad underwater part which is broader than the waterline sections that lie relatively close to the keel of the hull.
• the hull has a hull portion which is relatively tapered at the contact point between the hull and the sea surface.
• this solution is a compromise solution, as the configuration involves a reduction of the wet surface of the underwater part compared to SWATH-vessels, which, as mentioned before, is advantageous, the frictional drag being thus reduced, but at the same time it has been proven that the hull shape becomes more sensitive to wave movements, thereby inducing higher accelerations as a consequence of the vertical wave force component which acts directly on the curved hull surfaces at the waterline.
• An advantageous propulsion means when sailing with catamarans is the so-called water jets which are built-in in the hull of the ship's stern below the waterline.
• the vessel is thus propulsed by means of water which is introduced into these water jets at the bottom of the vessel and subsequently ejected at the stern of the hull in the stern direction under high pressure.
• the utilization of water jets makes particular demands on the hull configuration, since they are voluminous, thereby requiring the hull to be shaped with a considerable stern breadth. Therefore, out of consideration for the ship's stability, the draught must be reduced uniformly from the prow to the broad stern.
• German Patent No. 1 456 226 describes a two-hull ship construction which is designed taking into consideration the frictional drag and the wave drag.
• the hull construction in this publication is not configurated specifically in consideration of the vertical acceleration components of the vessel or the vessel's loading and unloading characteristics.
• the only thing described in the publication is a substantially S-shaped hull construction with a midship section with even sides, as for 85% of the hull frame, i.e. that frame which is placed at a distance of 85% of the ship's overall length calculated from the aft, it is indicated that the hull has a maximum bredth in its lower area which is bigger than the smallest bredth in an upper area. Consequently, the two hull sides are symmetrical in relation to a vertical longitudinal plane.
• European Patent No. 0 497 748 describes a hull construction for a multi-hull vessel, especially for a catamaran, which construction supposedly constitutes an improvement in relation to the above mentioned SWATH-hull, in particular regarding stability.
• This known hull construction is described in more detail by a series of parameters defining the relation between the distance from the hull's base line to the centre of mass of the hull's underwater body, the hull draught, etc.
• the inventors in the present invention have determined by tests, according to the below mentioned, that the relations indicated in this European Patent do not lead to an optimal construction from the point of view of the minimization of the ship's drag and maximization of the ship's stability, and particularly stability in relation to vertical accelerations, optimal construction, and further, that other construction parameters certainly are of greater importance for achieving the above mentioned optimization of the hull construction from the point of view of the minimization of the ship's drag and maximization of the ship's stability.
• a hull construction for a multi-hull vessel which hull has body plan sections of the hull a generally symmetrical form and sides which each describe a substantially S-shaped curve, which construction is characterized in that the fore part of the of the hull has the feature that the inflection point V 1 for the lower part of the S-shaped hull curve is below the deadweight line and in a minimum height above the hull's base line amounting to 50% of the distance between the hase line and the deadweight line, and that the inflection point V 2 for the upper part of the S-shaped hull curve is above the deadweight line at a minimum height of 125% of the distance between the base line and the deadweight line.
• the fore half of the hull may thus have the feature that the inflection point V 1 for the lower part of the S-shaped hull curve is at a height of 55-80% of the distance between the base line and the deadweight line, and that the inflection point V 2 for the upper part of the S-shaped hull curve is at a height of 130-155% of the distance between the base line and the deadweight line.
• the aft half of the hull may further have the feature that the inflection point V 1 for the lower part of the S-shaped hull curve is at a height of 55-110% of the distance between the base line and the deadweight line, and that the inflection point V 2 for the upper part of the S-shaped hull curve is at a height of 130-155% of the distance between the base line and the deadweight line.
• the sides of the hull describe an approximately S-shaped curve along the whole length of the hull, as the inflection points may have a height above the base line which falls constantly towards the hull stern.
• the hull may advantageously have a flat bottom at the stern and be provided with a bulb.
• the hull's 70%-frame defined similarly to the above mentioned 85%-frame may have the feature that the perpendicular distance from the hull's center line to the inflection V 1 for the lower part of the S-shaped hull curve is between 1.6% and 2.2% of the maximal length of the hull, preferably between 1.85% and 2.1%, and that the inflection point V 1 is at a height of between 50% and 75%, preferably between 55% and 70% of the distance between the base line and the deadweight line.
• the perpendicular distance from the hull's center line to the inflection point V 2 for the upper part of the S-shaped hull curve may be between 0.8% and 1.2% of the maximal length of the hull, preferably between 1.85% and 1.1%, and that the inflection point V 1 is at a height of between 125% and 150%, preferably between 130% and 145% of the distance between the base line and the deadweight line.
• the hull construction may advantageously take an amphora-like shape in its fore part, meaning that the sides converge relatively steeply toward the base line, constituting a sharp keel.
• the 70%-frame may at a height above the base line amounting to 25% of the distance between the base line and the deadweight line have the feature that the perpendicular distance from the hull's center line to the S-shaped hull curve is between 1.2% and 1.55% of the hull's maximum length, preferably between 1.3% and 1.45%.
• a reduction of the vertical accelerations is achieved in the fore part of the vessel.
• the passengers' indoors rest areas may advantageously be placed in the fore part of the vessel.
• the above mentioned placing of the indoors rest areas combined with the reduction of vertical accelerations provided by the invention is particularly advantageous.
• Utilization of an embodiment of the hull according to the invention and in connection with a multi-hull vessel construction with a superstructure for transport of both passengers and movable cargo, such as vehicles, further ensures particular advantages, particularly in connection with the ship's mooring in the harbour, when the vehicles, including trucks or automobiles, are loaded on board the vessel from the vessel's bow to the stern.
• a vessel with a large trim momentum is provided, the trim alteration being little.
• the vessel's rotation around a thwartships axis is limited to a great extent, which brings along advantages regarding the demands that must be made to the harbour installations, including the access ramps, which may thus be shorter.
• maximum length of the hull in the present application is to be construed as the largest underwater length of the hull.
• Fig. 1 shows an example of an embodiment of a ship's hull according to the present invention, described, in conformity with the shipbuilding industry, by a series of frame sketches which show the external contour of the hull in a series of chosen vertical sections which extend vertically through the length of the vessel.
• Frame sketches for the hull's aft half are shown to the left of the figure, i.e. left of the ship's vertical plane of symmetry.
• These frame sketches show the exterior contour of the hull in the sections 0, 2, 4, wherein line 0 shows the hull's aft contour, while line 4 shows the contour in the vicinity of the hull's half length.
• the line BL designates the so-called base line which corresponds to a horizontal plane or waterline section which is parallel to the lowermost part of the hull's keel.
• the position of the so-called deadweight line which is indicated in the figure by the designation DWL, is determined at the design stage and is represented by a line which extends parallel to a horisontal plane through the hull's base line BL and at a height that corresponds approximately to the ship's deepest draught in saltwater in a summer zone, the so-called summer load waterline. Sections parallel to the deadweight line are referred to as waterline sections and the area thereof is usually referred to as "water plane area". The distance between the base line and the deadweight line is indicated by the letter T.
• the ship's hull shown in Fig. 1 may particularly be used in connection with two-hull vessel constructions for freight or passenger transport in unprotected waters. Two identical hulls of the above presented kind are thus placed in parallel and are used to support a ship's superstructure with a given, desirable load capacity, the hulls' buoyancy inclusive the specific dimensions of the ship's hulls being adapted to this load capacity. The way the ship's superstructure connects the hulls is not shown in greater detail.
• the ship's hull is provided at the prow with a bulb.
• This bulb may extend from approximately frame sketch 9 to frame sketch 10 and, moreover, serves to reduce the wave drag on the ship's hull at a given speed and draught in a usual way.
• the hull's stern is relatively broad, the fitting of water jets being possible without any noteworthy problems.
• the hull sides may have a generally S-shaped contour from frame sketch no. 0 to about no. 9. In the aft half the sides are still slightly S-shaped, but here they have a flatter bottom.
• any frame sketch has the feature that the lines that demarcate the hull have two inflection points V 1 and V 2 .
• the inflection point V 1 in which the perpendicular distance from the center line to the exterior contour of the hull is the largest is below the DWL.
• the inflection point V 2 in which the perpendicular distance from the center line to the exterior contour of the hull takes on the minimum value, is considerably above the DWL.
• the exterior contour of the fore part i.e. from about frame sketch no. 5 to about frame sketch no. 9, has an amphora-like shape, since the hull has in any given perpendicular section a maximum breadth in an inflection point V 1 which is placed at a relatively large distance from the base line and close to the DWL, and that the hull frame sharpens uniformly towards the underside or the keel, the hull contour having in the same frame sketch an upper inflection point V 2 which is placed at a large height above the DWL.
• Configurating the hull in this manner provides a particularly seaworthy construction with a minimized wet surface and particularly advantageous sailing features, the water plane area in the section at the DWL being small.
• the local draught falls towards the stern where the hull may have an almost flat bottom.
• the upper as well as the lower inflection points may be connected by a continuous curve which is not necessarily straight, but may have a continuously increasing height above the base line towards the stern.
• the figure illustrates schematically the approximate position of the inflection points in the 80%-frame, i.e. the frame which is placed at a distance of 80% of the ship's overall length, measured from the aft.
• the hull according to the invention is narrowed in the region in the immediate vicinity of the DWL, the water plane area being reduced in this region.
• the waves produced by the vessel when sailing cause, as mentioned before, a wave drag.
• the size of the resulting waves and, consequently, of the resulting wave drag depends on the water plane area.
• the resulting wave drag will decrease with increasing wave heights.
• an extension of the wet surface will take place when sailing, large areas of the hull being surrounded by water.
• the decrease in the resulting wave drag is larger than the corresponding increase in the frictional drag, and, consequently, the overall wave drag, which is the sum of the resulting wave drag and frictional drag, will decrease.
• the particular configuration of the hull means that the longitudinal variation of the LCB, i.e. the longitudinal position of the buoyancy center, is small and limited between a position in which the ship is empty and, respectively, loaded.
• the vessel will thus be lying approximately horizontally both in a fully loaded state and in an empty state. This is advantageous, as the access ramps for automobiles may thus be built shorter, the vessel during unloading moving mainly only upwards, without heeling over, i.e. without the prow moving further upwards compared to the stern.
• Fig. 3 The measurements shown in Fig. 3 are made at a typical wave height of 2 m and a period of 5.5 s.
• Fig. 4 shows a semi-SWATH catamaran, i.e. a multi-hull ship which as a whole is referred to as 10.
• the multi-hull vessel 10 comprises two hulls, 12 and 14, which are connected to each other by means of a deck 24.
• the hull 10 defines a fore end or bulb 16, both hulls 12 and 14 at the backmost ends being provided with water jets 20 and 24.
• the deck 24 constitutes a car deck, whereupon there is placed a superstructure 26 comprising a restaurant, a cafeteria and a rest-room wherein the passengers may spend their time during the journey.
• Fig. 4 shows also a line along which the frames are designated the same referal numbers as in the Figs. 1 and 3.
• the following table presents values for the position of the inflection points V 1 and V 2 for the hull in Fig. 1 and for a maximum draught of 3.35 m and a hull length of 68.9 m.
• the position of the inflection points is indicated by the height h inflection point above the base line as a percentage of the maximum draught T and by the perpendicular distance ⁇ inflection point from the center line CL as a percentage of the maximum hull length.
• the indicated hull may be used in a two-hull construction with a superstructure designed to transport 120 automobiles and 450 passengers.
• the hull length is in this case determined as the distance from the stern to the tip of the bulb.
• the hull described in detail in Fig. 1 and above is used in a semi-SWATH catamaran designed by applicant and having the following specifications: Overall length 76.10 m, beam 23.40 m, deadweight 250 t, vehicle deck area (24) 1520 m 2 , car capacity 120 units, passenger capacity 450 persons, passenger seating capacity 500 persons, gas turbine engines 2 units, power 12.4 MW/unit, full load service speed 23.60 knots, fuel capacity 2 x 18 t, specific fuel consumption 241 g/kWh, range at maximum speed 240 nautical miles.
• the multi-hull vessel 10 shown in Fig. 4 is designed to be made of aluminium as an entirely welded hull.

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• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• Ocean & Marine Engineering (AREA)
• Other Liquid Machine Or Engine Such As Wave Power Use (AREA)
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• 1996
  • 1996-02-19 PT PT96902903T patent/PT807051E/pt unknown
  • 1996-02-19 DE DE69607600T patent/DE69607600T2/de not_active Expired - Fee Related
  • 1996-02-19 ES ES96902903T patent/ES2150657T3/es not_active Expired - Lifetime
  • 1996-02-19 AU AU47128/96A patent/AU708359B2/en not_active Ceased
  • 1996-02-19 WO PCT/DK1996/000075 patent/WO1996025322A1/en not_active Ceased
  • 1996-02-19 EP EP96902903A patent/EP0807051B1/en not_active Expired - Lifetime
  • 1996-02-19 DK DK96902903T patent/DK0807051T3/da active
• 2000
  • 2000-07-05 GR GR20000401596T patent/GR3033911T3/el not_active IP Right Cessation

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