Method of predicting course stability and turning qualities of ships

Abstract : An analytical method combining simplified potential flow theory and low aspect-ratio wing theory with empirical modifications for a real viscous fluid is used to predict the stability derivatives (first order hydrodynamic force and moment derivatives) of a family of hulls in order to estimate the dependence of geometric characteristics of course stability and turning or steering qualities. The hulls are Taylor Standard Series forms with after deadwood re moved and have the same length and prismatic coefficient but varying length-draft and beam draft ratios and skeg area. Comparison between the values calculated by this method and those obtained from experimental measurements shows good agreement. The analytical method can predict the relative effects of the geometrical characteristics. Calculated magnitudes are slightly different from the experimental. How ever, since the hulls tested have the same prismatic, the empirical modification for the rotary moment derivative which is a function of prismatic coefficient was fully tested.