The Roles of Skirt Planform and Deflection in Hovercraft Response

Abstract

A linearized theory of hovercraft response while moving over regular waves is modified to account for, firstly, a cushion planform other than rectangular and, secondly, deflections of the skirt enclosing the supporting cushion as a result of wave-induced variations in the internal pressures. Consideration is given to the pitching and heaving of a hovercraft whose plenum air chamber is divided into two compartments by a transverse barrier. Detailed calculations are carried out for a cushion planform whose forward part is hexagonal and for a vertically deflecting skirt hemline, but the results are more widely useful in suggesting the general nature of the roles of cushion planform and skirt dynamics. A method of representing the overall effect of skirt deflection is proposed, involving four dimensionless coefficients, and the effect of these coefficients on the dynamic characteristics is investigated.