State of the art model test procedures for launch and recovery

Current mission profiles for patrol vessels and frigates increasingly include the ability to launch and recover manned or unmanned boats. The recovery system design (e.g. stern ramp or cranes) must enable safe launch and recovery, not only in calm water but also in waves from various directions and at different vessel speeds. Validating in an early design phase the functionality and assessing the limits of the selected design by means of model testing in a wave tank can avoid costly modifications to the as built design. Based on the experience gained with several test campaigns for Rigid Inflatable Boat (RIB) launch and recovery, this paper describes the state of the art of model testing and its limitations and challenges. It describes the approaches chosen as well as the experience gained. The focus is on the model tests procedure, i.e. the requirement for the models and tests set-up, as well as on the test procedure and evaluation of the results. The paper gives insight into model test issues, e.g. on how to deal with learning curves of human helmsmen and the judgement of the tests. An overview is given of crucial points that have to be considered in model testing for launch and recovery systems in general. It is discussed which physical phenomena can be modeled correctly and where simplifications have to be accepted. At the end of the paper perspectives are given, including future developments in model testing technique that are desirable to improve the quality of the tests.