Ships – Hull or hull adjunct employing fluid dynamic forces to... – Having hydrofoil
Reexamination Certificate
2000-11-28
2002-08-20
Basinger, Sherman (Department: 3617)
Ships
Hull or hull adjunct employing fluid dynamic forces to...
Having hydrofoil
C114S061100, C114S125000, C114S283000
Reexamination Certificate
active
06435123
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
Present invention generally relates to marine vessels and particularly a hydrofoil assisted high speed hybrid hull featuring a slender central hull element and two or more side hull elements, the vessel basically operating as a hydrofoil stabilized super-slender monohull in the normal high speed mode.
2. Description of the Related Art
Among modern high speed vessels, the catamarans have over the two last decades gained a dominating market position over monohulls, particularly of size less than 100 meters. This type of vessel is characterized by its simplicity of operation, high stability and relatively high speed- and seakeeping capabilities, particularly in the speed regime of 30-35 knots. The marked, however, seems to continue putting increased demands to speed performance, and several catamarans making 45 knots, and exceptionally above 50 knots, have recently become a reality. Seakeeping performance has also become a major issue in modem high- speed marine transportation. These demands have resulted in larger propulsion power plant installations and the introduction of active motion damping systems, like T-foils located in the bow region and trim-tabs or interceptors located aft, for improvement of ride comfort. The introduction of T-foils, which basically are non permanent lift generating devices, however, is associated by a notable drag that reduces the speed with approximately 2-3 knots on a 40-45 knots catamaran.
Parallel with the increased speed demands on certain routes, most fast ferry operators are still reluctant to join this trend of development because of the associated sky-rocking fuel consumption. It is very likely that the catamaran technology, initially commercially developed during the early seventies, today have reached its optimum stage of development from a hydrodynamic point of view. Further reduction of drag is severely limited by the fact that the major drag component is related to hydrodynamic skin friction. To overcome this, either wetted surface area has to be reduced, or the skin friction has to be reduced by application of new technology, like air lubrication. Recognizing the lack of proven means to solve these technological challenges, it indicates that the catamaran concept, as we know it today, is no longer particularly suited to fully comply with the future marked needs in all respects. This view is supported by the increased attention concerning environmental issues paid by the public and authorities, which is likely to force through the development of novel concepts that performs better in this respect. Also the environment effects of the wave-making tendency of high speed crafts has become a growing regional concern.
The surface piecing hydrofoils were commercially developed in the mid fifties and produced in series by Rodriquez, Italy. As known, these are based on a monohull fitted with a forward- and aft-located surface piecing hydrofoil arrangement, which in the transverse section features a V-like shape of the foil span. Thus parts of the foil span protrude the waterline on both sides, and provide a transverse righting momentum when the craft heels causing the surface piercing foil span to be submerged. The hull is completely lifted out of the water at higher speed, being self stabilized in roll and pitch by the surface piecing hydrofoil arrangement. It is propelled by fully submerged propellers, mounted on inclined shafts. The advantages of this conceptual design over traditional monohulls of similar size were improved seakeeping and power-to-speed efficiency at service speed around 35 knots. The disadvantages were larger complexity, building costs, weight- and speed restriction. Therefore the design is generally limited to an overall length of around 40 m and maximum displacement of around 150 tons. The design became very popular as passenger ferries, and today there is still a large number of these operating around the world, particularly in previous Russian countries, Japan and the Mediterranean countries. According to the inventor's opinion, there is probably no other high-speed concept that has transported the same amount of passengers so far. Compared to modern type high speed crafts, like catamarans and monohulls, the design has lost it's popularity, and can no longer compete in terms of speed requirements and passenger comfort, though it still maintain an edge over these regarding speed-to-power efficiency.
On of the most significant steps in high-speed marine technology development came in the mid seventies when Boeing, USA, developed the Jetfoil. As the Rodriquez hydrofoils, the conceptual design is based on a monohull that is lifted clear of the waterline at higher speed, However, the foil system is based on the fully submerged type, which consists of a substantially plane fully submerged foil span supported by three vertical struts. As opposed to the surface-piercing hydrofoil, it is not self-stabilizing and therefore depends on controllable flaps integrated to the following edge of the foilspan. The primary foil is located aft extending to the full width of the craft, and provides the primary lift and roll stabilization. A lesser foil (T-foil) is located in the centerline forward and supported by a vertical strut. This provides a secondary lifting force as well as the required pitch controlling momentum. All foils can be tilted upward when the craft is in a fully displacement mode. The 27.4 m and 117 tons displacement Jetfoil design has a normal service speed in foil-born mode of around 45 knots. This design has the advantage of excellent seakeeping and high speed-to-power efficiency. The disadvantages, however, are high building costs, technical complexity, overall weight- and payload capacity restrictions.
In the early nineties, Kvaerner Fjellstrand and Westamarin, both Norway, developed the Foilcat concept. This is basically a catamaran fitted with a fully submerged foil system that lifts the craft clear of the waterline, and operates at a service speed of around 45 knots. The largest design is 35 m and has a maximum displacement of around 175 tons. It is described in Norwegian patent no. 175199. The design has basically the same advantages and disadvantages as the Jetfoils. This has limited its commercial acceptance. In order to reduce the large frictional resistance related to catamarans operating at speeds of around 45 knots, there is a resent trend towards developing foil assisted catamarans that is fitted with a fully submerged foil system for the purpose of lifting the hull partially out of the water. At the same time it is controlling the pitch, and to less degree roll and hive. Examples of these are U.S. Pat. No. 4,606,291 and U.S. Pat. No. 4,665,853. Since they are operating in a partial displacement mode, and as such still have two hulls submerged in the water, they are still left with a major frictional drag.
The trimaran design has gained increased reputation within the sailboat environment due to its high speed- and seakeeping capabilities. As known, the trimaran design consists of three fully submerged hull elements, including a long and narrow center hull and a pair of shorter outrigger hulls or sidehulls, integrated to the underside of a transverse bridging structure located midship or aft. However, this design is yet not brought into use in the high-speed ferry marked. Variations of this design are described in various patents and patent applications, like U.S. Pat. No. 4,348,972, U.S. Pat. No. 5,178,085, U.S. Pat. No. 5,529,009, JP 63130492, WO 93/07046, WO 94/20359, WO 97/10988 and EP455605. Some of these incorporate lifting devices in the form of T-foils fitted to the sidehulls and the center hull, for the purpose of damping roll and pitch motion. However, they all operate in a constant displacement mode with three hulls submerged.
A foil assisted hybrid marine vessel is described in U.S. Pat. No. 5,503,100. However, this particular invention seems to be impaired by a number of impracticable attributes that is likely to render the inven
Basinger Sherman
Berkowitz Marvin C.
Nath Gary M.
Nath & Associates PLLC
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