The structure of some past and present rules is discussed and the general problem of optimum performance under the rule is considered. This requires a rational performance model, which would itself form the most equitable rating rule possible under the existing level of technical understanding of mechanics of sailing.
The theory of sailboat performance estimates is outlined and surveyed. New theories are presented on the performances of geometrically similar vessels and on the implications of optimum sail trim. Two rational ways are proposed for averaging performance over a probability distribution of operating conditions appropriate to different types of races. The theory suggests a new form for a rule, in which multiple ratings are assigned characterizing average potential speeds in various ranges of operating conditions.