The computation of the best windward and running courses for sailing yachts

The best course for a yachtsman to steer, for any course to windward, can be shown to be that which resolves the maximum speed in the direction of the true wind for any course lying between the reciprocal sailing vectors producing such a maximum. Outside these vectors it is nearly always quicker to steer a direct course, the exception being on the running points of sailing in light wind conditions. Unfortunately measurements of true wind bearing and speed are not possible on a moving yacht and measurements of only the apparent wind parameters, namely, apparent wind velocity and apparent wind angle ¿ less the leeway angle A, are possible. The other practical velocity measurement is the yacht´s speed through the water. The parameters available for the computation of the best course are therefore two velocities and one inaccurate angle¿the inaccuracy being due to leeway. Previously postulated solutions to the problem have confessed lack of feasibility due to the leeway error and due to the cost of the computation, for instance circuits employing 105 transistors consuming 5 W of power1. This paper explains measurement methods which are free of errors due to leeway and describes an electronic computer which will enable the best sailing vector to be found and indicated on both the close-hauled and running points of sailing. The additional power required to compute the best course from the input of established instruments measuring apparent wind velocity and sailed velocity is 0¿12 W.