An easy graphical method of obtaining generalised first order yacht performance

Extract

For many years, a first order understanding of aircraft performance has been possible from lift drag curves or forward speed/sinking speed curves for gliders. These presentations of performance are not sufficiently accurate for detailed aircraft performance analysis, but their understanding has enabled generations of aircraft engineers to grasp the importance of various aerodynamic parameters.

A new method of presenting the sailing vector triangles is described. When the locus of the possible vector triangles is drawn in the new presentation, a large portion approximates to a straight line parallel to or making a small angle with the Xaxis in the neighbourhood of the best speed to windward. A geometrical construction is given, which defines the best speed to windward point. It becomes self-evident that, as is well known, most yachts sail at nearly 45 degrees to the true wind when sailing at their best windward condition.