Sailboat Hydrodynamic Drag Source Prediction and Performance Assessment

Velocity Prediction Programs used for sailboat hull, sail, and keel sizing trades, have found an important place in the designer's toolbox. Sail designers now recognize the benefits of applying aerodynamic panel methods. In addition, the 1983 and 1987 America's Cup competitions have drawn attention to use of computerized flow simulation methods for improving hydrodynamic performance. This paper highlights characteristics of methods capable of predicting sailboat hydrodynamic drag forces. Taken together the resistance components predicted include appendage surface friction drag, configuration and lift-induced drag, and configuration trim drag. All of the computer programs discussed in this paper were originally developed for aircraft aerodynamic applications. Since each method is based on some approximate model of real world flow physics, the need to establish a simulation experience base is emphasized and illustrated. VPP polar diagrams are used to link drag source benefits and penalties to sailboat performance. Micro-computer execution times are provided because the methods described operate in machines commonly found in the naval architect’s office.