Measurements of motions, loads and structural response on a fast FRP pleasure craft

Comprehensive sea trials including measurements of motions, loads and structural response aren’t usual events for pleasure crafts, especially of limited dimensions. However, the mass production of such craft by some shipyards and their prices largely justifies to carry out full scale tests in order to optimize not only the design itself but also building procedures for many reasons: among the others, the testing costs are shared by a large number of produced crafts. In facts, an optimized final design cannot be achieved by the mere application of the available rules and regulations, necessarily adopting simplified methods applicable to quite different craft types. This paper deals with the tests campaign carried out on a typical deep-V pleasure craft built in fiberglass, abt. 17,5m in length. Test equipment, sensors, instrumentation as well as the subsequent data analysis are described. The trials have been particularly devoted to study the structural behavior of the fore part of the structure, subject to impact phenomena. Motions and accelerations have been studied in relation with seakeeping performances and comfort, which is a target of paramount importance for pleasure crafts. Pressure sensors have been installed on the hull and their signals where collected together with signals from accelerometers and rate-gyros at a relatively high rate in order to describe also the narrow peaks better. Further to conventional accelerometers and rate-gyro sensors, a GPS-RTK system has been installed for the real time monitoring of the craft motions in the six-degree of freedom. Several strain gauges have been applied on the bottom shell plating and on the faceplate of stiffeners, giving a quite accurate map of the strain pattern of the structure.