The purpose of this paper is to present a very general overview as to how basic concepts of aerodynamics and hydrodynamics can be utilized in the selection and trim of sails. I have used the term selection to go all the way back to the routes of designing and selecting a rig for a given boat. The paper introduces absolutely no data and, in fact, does not explore any existing data in detail. Its main purpose is to show that almost any decision on rig or sails on a sail boat is always a compromise of varying forces. Sometimes these compromises are conflicting dynamics of the hull and sails, other times the forces are man-made such as rule parameters.
Perhaps I could have done a more scientific job by choosing just one set of parameters that are in conflict and explored these in great detail showing how a conclusion can be reached from all the varying inputs into one particular problem involving rig, sails or hull. This type of thorough analysis, which would obviously require more exacting research to prove the hypothesis once defined, is not my strength. Therefore, it would be inappropriate for me to do such an analysis. My strength is in actually applying a large range of sailing theory to actual on-the-water sailing conditions.
What I hope to accomplish by this paper is to let sailors realize that when making a decision on a rig, a particular sail, or how to trim a particular sail, they first must decide what they want to accomplish with the rig, sail or sail trim. They must think about it in general terms as to what direction they should take aerodynamically or hydrodynamically to get the forces they want to achieve. Then they must go about the task with the full realization that there is no preset answer and that they must be willing to experiment in order to hone in on the optimum. The input variables of the hydrodynamics of a pitching yacht going to weather in a moderate breeze that is constantly receding and increasing in velocity as well as direction defies simple solutions. Thus, the best compromise is usually the best solution.