Shock and vibration exposures in fast boats at sea can be more severe than in any other mode of transport. Shock mitigation seating plays a key part in reducing the possibility of injury, but seats must be suitable for the boat and for the way the boat will be used. The RNLI recently conducted an innovative sea trial programme to assess the performance of eight seats, from three manufacturers, for use in the Severn Class all-weather lifeboat. The trials were designed to maximise data capture while minimising crew exposure. Seat performance was measured with a range of occupants and operating conditions and the final seat selection was based on analysis of over 2,500 wave impacts. These "wave by wave" trials involved normal boat operation and were much more efficient to carry out than the more conventional, but often impractical, approach of attempting to carry out controlled, timed runs at specific speeds in specific sea states. Ahead of the trial, the seat manufacturer used information on RNLI crew demographics and craft operating conditions to optimise the seat. The seat configuration was determined from laboratory drop-tests at their in-house facility, with parameters chosen that were most likely to perform well in the Severn. The laboratory test procedure followed the methods defined by the UK's Ministry of Defence Protocol 1&2 and the US Navy's NSW/CCD-080-TR-2015/010 seat testing requirement. This paper describes the sea trials approach and seat design optimisation that led to the selection of the seat for use in the Severn Class.
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