Experimental Validation of Innovative High-Speed Craft Spray Deflectors

Abstract: Hydrodynamic analysis of high-speed craft is a complex problem. For years naval architects have tried improving the eÿciency of the hull, changing its form, the number of hulls, adding spray rails or steps. Spray deflectors, an innovative modification of commonly used spray rails by a Swedish company called Petestep, might be the next advancement in that process. Experimental validation of this concept is the topic of this study. Previous years of towing tank tests showed compelling results, but were unable to draw definite conclusions, mainly due to inability to compare the results of bare hull and deflector hull tests which was a result of unequal trim achieved for equal input parameters (such as weight and speed).With amended test speed range and deflector design modifications, this project aimed to yield unambigu-ous results. Three spray deflectors were designed for di˙erent design speeds, tested and compared with bare hull tests for drag and trim. The results showed that deflectors did not change the running position of the hull compared to bare hull, allowing for an unequivocal drag comparison. Deflectors reduced drag by up to 4.9%.A number of design improvements were proposed as next steps in this research. A further successful proof of concept (increased stability, lower resistance and fuel consumption) could provide a substantial improvement in high-speed craft design resulting in a cheaper and a more comfortable ride with a lower environmental impact.