The comparison of the hydrodynamic behaviour of three fast patrol boats with special hull geometries

For a group of interested parties, i.e. the Royal Netherlands Navy, Damen Shipyards at Gorinchem (NL), the Royal Schelde Group at Vlissingen (NL) and the United States Coast Guard from Baltimore (USA) the Shiphydromechanics Department of the Delft University of Technology and MARIN at Wageningen carried out an extensive research program on three conceptual designs of a 55 meter long monohull Patrol Boat. The boat should be capable of achieving 50 knots and in particular so in waves. The aim of the project was to investigate the feasibility of the designs in achieving a very high "all year round" operability under typical North Sea conditions.

The conceptual designs made for this Patrol Boat were designed according to:
• The Enlarged Ship Concept (ESC)
• The AXE Bow Concept (ABC)
• The Wave Piercer Concept (WPC)

The project consisted of a series of full scale measurements on board an existing Fast Patrol Boat of the UK Customs and a large series of towing tank measurements. These full scale tests were carried out in the winter period near the Scottish west coast and aimed at establishing operability criteria for the safe operation of fast ships in a seaway. Subsequently the three designs were tested for their calm water resistance and their behavior in head seas and following waves in the Delft towing tank. For the head seas conditions a large series of wave spectra have been used with an ever increasing significant wave height, starting from 2.0 and reaching as high as 4.5 meters and at three different forward speeds, i.e. 25, 35 and 50 knots. During these tests the motions, added resistance and vertical accelerations have been measured. In the following waves tests special attention has been given to the possible occurrence of deck wetness and bow diving. The limiting conditions in that respect have been established.
Here after both the Enlarged Ship Concept and the AXE Bow Concept designs were extensively tested as free running models at MARIN in Wageningen in their new Ship Motion Basin (SMB). Particular attention in these tests has been paid at stern quartering seas. These tests were specifically carried out to compare the designs on their possible sensitivity towards broaching and capsizing.
In the present paper a selection of the obtained results will be presented and discussed. An analysis of the results will be given and a comparison between the three concepts on their main issues regarding the seakeeping behavior will be presented and discussed.