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Publications
Bettencourt, J., Fonseca, N. and Guedes Soares, C. (2004), “A Procedure for the Optimization of the Hydrodynamic Performance of Sailing Yachts Keels”, Proceedings of the 1st International Symposium on Yacht Design and Production (MDY'04), 25-26 March, Madrid, Spain, pp. 58-68
One of the purposes of a yacht’s keel is the efficient generation of a substantial part of the total hydrodynamic side force that opposes the aerodynamic side force generated by the sail set when a yacht sails to windward. For a given required side force, the best keel will be the one that minimizes the boat’s resistance. This is the hydrodynamic optimal keel. The paper describes a methodology to find the optimal keel. A deterministic search algorithm is used to solve the Nonlinear Programming problem. The hydrodynamic properties of the candidate keels are assessed by a set of methods that tackle each of the sub problems that, altogether, make up the hydrodynamic problem of the fin keel, i.e., finding the side force and resistance components of a keel with a given plan form. Since the keel’s plan form is the most important feature related to the side force generation, the type of the sections is kept the same throughout the optimization procedure. The scenario is a yacht sailing to windward with constant hull speed, heel and leeway angles, assuming that the risk of keel stall and loss of hydrodynamic side force is negligible. Hull presence effects on the keel’s side force production are considered through the use of an empirical wing-fuselage interaction factor, and other sources of interference are neglected. Constraints on the optimal keel are of two types: equality constraints (the side force that is generated must equal a required value) and inequality constraints (the ratio of plan form area to windward sail area must be within specified limits). The results obtained with the application of this methodology to a specific case show that good improvements are attainable. The computational effort is small if the optimization parameters are carefully selected, particularly the inequality constraints values and the initial candidate keel.
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