Analysis of Wave Making Resistance And Optimization of Canting Keel Bulbs

Abstract

In upwind sailing conditions, bulbs of canting keel sailboats operate close to the water surface and therefore induce non-negligible changes in the wave system, thus influencing the wave making resistance of a sailboat. The bulb could produce relatively positive as well as negative effects, and therefore its design is suitable for optimization. A case study for a modern 100-foot canting keel sailboat is presented. The design space was explored to determine the bulb shape that would produce favorable interference with the hull wave system, reducing the total resistance of the sailboat for an upwind sailing condition, using the Response Surface Optimization (RSO) methodology developed by the authors. In the 1,000 bulb variations that were performed using an advanced parametric modeler, the volume and location of the center of gravity of the bulb were fixed so that the stability of the sailboat was not altered and, therefore, the computed total resistance became a direct measure of merit of the bulb design. An outlook is given to a combined optimization of hull and bulb in order to gain optimum improvement.