A Preliminary Investigation into Two Speed Operation of Ships

Some ship types, such as many surface warships, some motor yachts and some cruise ships are required to operate efficiently at two different speeds: low speed cruise; and high speed sprint. In the past, a single optimised hull form has been developed, with a balance between the different roles, based on the requirement set, and on the operations envisaged. In order to investigate the possibilities of reconfigurable hull and propulser configurations for the two speed regimes, a preliminary investigation was undertaken, based on a 90-100m Offshore Patrol Vessel (OPV). As a result of this work it has been shown that significant improvements in low speed powering performance, and hence range, for a monohull designed for high speed are possible by: 1. use of a retractable single screw thruster; 2. fitting waterjet inlet covers, and evacuating water from the inlet; 3. fitting an adjustable transom flap; and 4. making it possible to adjust the trim to trim by the bow. Larger improvements could be achieved if major changes to the stern shape are possible. The use of an adjustable bulbous bow has been shown to be of only marginal benefit, and is it is not recommended that this be considered further for this application. © 2006: Royal Institution of Naval Architects.