Experimental Investigation of Seaplane Forebody Chine Details

The main blister spray generated by the main hull of a seaplane (flying boat) may damage or degrade performance upon impact with vessel components, particularly propellers, engines, or flight control surfaces. An experimental tow tank test was performed on two main hull variations with different spray suppression approaches applied to the forebody. One variant includes a recessed groove-type spray suppressor, and one variant includes a down-angle hard chine. This paper presents an intercomparison of performance between each variant for spray suppression, resistance, motions, and accelerations in a following sea condition. INTRODUCTION Hydrodynamically supported craft operating at planing speeds generate both whisker and main blister spray from the bottom shell, separating at the chines (Savitsky and Breslin 1958), see Figure 1. This spray originates close to the stagnation line, at the spray root, and contains a large volume of water being shed from the bottom shell. Of the two spray patterns, whisker spray tends to be a light spray reflected forward of the stagnation line, and which follows a trajectory roughly along the local deadrise angle of the hull. The main spray blister, however, is formed by the reflected spray rotating about the chine as the spray root approaches the chine outboard and forms a denser sheet of spray in the shape of a cone with a spray apex elevated significantly higher than the level of the chine and whisker spray (Savitsky and Morabito 2011). The main spray blister is more consequential to high-speed craft design including monohulls, catamarans, seaplanes, and wing-in-ground effect craft given its rise above the chine and potential impact with vessel components. Impact with vessel components may be a combination of a nuisance (noise / wetness on passengers), added resistance to the craft, or in the most serious cases cause damage to components. This paper focuses on the main spray blister for seaplane design, specifically for flying boats, which are seaplanes with a main hull for flotation and the planing surface during takeoff and landing. The dense main spray blister generated by the main hull may impact and damage components.