Surface Wave Contours Associated With the Forebody Wake of Stepped Planing Hulls

Results of an extensive series of model tests that define the longitudinal surface wake profiles aft of prismatic hulls having deadrise angles of 10, 20, and 30 deg are presented. Empirical equations are developed that quantitatively define these profiles and are in a form that can be easily applied by designers of stepped planing hulls. These equations are applicable for an expected range of variations in trim angle, speed coefficient, and loading coefficient typical for these hulls. A brief introduction to the concept and to the hydrodynamic advantages of stepped planing hulls is presented to orient the reader to the importance of wake data in their design. Examples are presented that illustrate the application of these wake data for stepped planing hulls with wetted forebody chine to achieve maximum hydrodynamic lift/drag ratios. Finally, experimental results are presented that illustrate the potential resistance penalty associated with the operation of chines dry forebodies where the stagnation line crosses the step.