Seaspeed Marine Consulting was recently commissioned to undertake instrumented full scale sea trials on board a fleet of fast catamaran wind-farm support vessels, covering both calm water and rough water performance monitoring. The vessels ranged in size from 18 to 24 metres in length, all with speeds up to approximately 30 knots.
For the calm water trials, an MRU (motion reference unit), a high speed GPS system and a series of triaxial accelerometers along with a number of vessel system channels were used to monitor and characterise the vessels performance in terms of turning circles, crash stop and accelerations, lateral manoeuvring, speed vs rpm and trim (including effect of interceptors) and the effects of system failures on the manoeuvring capabilities of the craft. In addition the noise and vibration on the vessels were formally recorded in order to satisfy Class requirements and also to establish the benefits of resiliently mounted superstructures.
For the rough water trials, similar instrumentation was used along with a portable wave buoy for the monitoring of sea conditions. Seakeeping trials were undertaken over a range of speeds at each of the five main headings (head, bow, beam quartering and stern) for a variety of encountered sea conditions (each day revealed a new sea state). Vibration of the resilient superstructures in these rough conditions was also monitored in order to establish the dynamic effects of operations in a sea state on the mounting arrangements.
Further long term, high data rate monitoring trials were then undertaken on one of the vessels over a period of two months, from which useful operational data was recorded. This included the transit, loiter and passenger transfer modes of operation.
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Press release, May 15, 2013; Image: seaspeed