The Royal Netherlands Sea Rescue Institution (KNRM) exploits a fleet of lifeboats around the North Sea coast of the Netherlands. The majority of this fleet consists nowadays of so called Rigid Inflatable Boats “RIB’s”. The largest vessels in the fleet are from the “Arie Visser” class, with a length of around 18.5 meters and a maximum speed of 35 knots. These are all weather boats on the North Sea and its coastal areas and self-righting. The Lifeboat Institution plans to replace the 10 boats in this class in the next 10 years. So an improved design (if possible) is sought for.
A design group has been composed for this purpose consisting of the Shiphydromechanics Department of the Delft University of Technology, Design office W. de Vries Lentsch, (the designers of the existing boats) and the High Speed Craft Department of Damen Shipyards.
Based on the requirements of the Sea Rescue Institution (KNRM) the group developed two new designs. These designs were initially derived using computer simulations and calculations. The emphasis in these new designs was on improved operability of the Search and Rescue boats in their typical working environment and improved habitability (i.e. noise and vibrations).
To assess the differences in performances of these designs in calm water and in waves an extensive test program has subsequently been set up and carried out with the three designs: i.e. the existing design Arie Visser and the two new designs.
Extensive full scale measurements on the existing boats of the “Arie Visser” class had already been carried out in the past and these results were used to specify the behaviour of the existing boats as a bench mark. Then the three designs, i.e. the Arie Visser, the Concept 1 and the Concept 2, have been tested for their resistance, sinkage and running trim in calm water. In addition their behaviour with high forward speeds in head irregular waves have been tested with emphasis on measuring motions and vertical accelerations.
Next their behaviour in high stern quartering, following and beam seas has been investigated with free sailing models in the Ship Model Basin of MARIN to compare the new designs with the existing one for difference in a possible tendency for bow diving and broaching behaviour in these high seas.
In addition severe breaking waves have been simulated in the towing tank and the models run through these both in head as well as following waves conditions.
The findings based on the computer simulations have been compared with the results from the measurements. The results of this research project will be summarized and presented in the present paper.
