Static And Dynamic Forces and Wetted Lengths for a Planing Hull Model Forced in Roll

Abstract

An experimental program at the United States Naval Academy has been designed to investigate the transverse plane stability of planing hulls. An experimental mechanism to force a planing hull model in roll motion was designed and built. The first model tested was a wooden prismatic planing hull with a constant deadrise of 20o , a beam of 1.48 ft (0.45 m), and a total length of 5 ft (1.52 m). The model was forced in roll while fixed in pitch, heave, sway, yaw and surge. The tests were done at three model speeds, two displacements, three roll amplitudes, and four oscillation frequencies. In addition to the dynamic tests, the model was run at the same model speeds and displacements while held fixed in roll at seven heel angles between 0o and 30o . For both the dynamic and static roll conditions the heave and sway forces, along with the roll moment, were measured and underwater photography was taken. This paper will explore how the heave and sway forces and roll moments depend on heel angle and roll amplitude as well as how the wetted lengths (keel and chine) vary between the static and the dynamic roll conditions.