The effect of spray deflection on the performance of high speed craft in calm water

Hydrodynamic analysis of high speed craft is a complex problem. Naval architects have been improving the efficiency of high speed hulls by introducing hard chines, warping, adding spray rails and steps, or forcing air ventilation. Spray deflectors is a novel spray redirection technology inspired by spray rails. It has shown potential for further improving the performance of high speed craft. Spray deflectors run parallel to the stagnation line from the keel to the chine through the spray area. Previous numerical and experimental studies focusing on spray deflectors have been unable to draw definite conclusions regarding the efficiency and optimal design of the deflectors. This paper aims to experimentally investigate, through towing tank testing, the effect on the total resistance using spray deflectors to redirect the spray. Three spray deflectors were designed for different design speeds, tested, and compared in terms of the resulting bare hull for resistance, trim, and heave response. The new deflector designs did not affect the running position of the hull, allowing for an unequivocal resistance comparison. Deflectors reduced resistance by up to 5% with the highest reduction achieved when the stagnation line crossed the deflector at about a quarter beam from the chine.