The purpose of this paper, which is based on work done by CETENA is to assist the ship designer by presenting a method for expressing a merit rating characterising the seakeeping qualities of a proposed design, so enabling him to make an objective choice from alternative solutions at an initial design-stage. The rating is a mathematical factor based upon ship-speed, and indicates the percentage of its life that the ship will be fully operational from the seakeeping viewpoint. The method has been developed by (a) determining the phenomena that limit the ship's operability, and the maximum allowable intensity of each of these effects; (b) formulating a valid analytical expression for the long-term probability distribution of the sea conditions; (c) determining, on the basis of the geometrical characteristics of the hull, the maximum wave height beyond which the ship is no longer operational at a given speed; and (d) establishing, on the basis of the long-term probability distribution of sea conditions, the probability that this maximum wave height will be exceeded. These four steps are explained in detail, and the method is illustrated in an example in which three warships of different nationalities, having similar lengths and displacements, are compared from information on their body plans and overall weight distributions, the only essential elements for the application of the method. The comparison is made in respect of sea-state probability distributions in the areas: World-Wide, Northern North Atlantic, North Atlantic, and Mediterranean. Seven speeds, between zero and 30 knots, in head seas are considered in the comparison. It is concluded that it now seems possible to relate the operational efficiency limits of a ship to an overall merit rating expressed by the annual average speed which can be maintained in the geographical are under consideration, and that the comparison of hull designs on the basis of the seakeeping merit rating can be made independently of the geographical area (though the world-wide sea-state distribution might conventionally be used).

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  • Corporate Authors:

    International Periodical Press

    193 Heemraadssingel
    Rotterdam,   Netherlands 
  • Authors:
    • Chilo, B
    • Sartori, G
  • Publication Date: 1979-12

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  • Accession Number: 00310895
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: May 7 1980 12:00AM