Published online by Cambridge University Press: 04 July 2016
Using Glauert's analysis and taking into account the restraint due to the surface of the sea, lifting line theory is applied to calculate the distribution of loading, downwash velocity and vortex drag of a “Finn” dinghy's sail when upright. It appears that the loading can probably be represented with sufficient accuracy by
I=I0(sin θ+sin 2θ)
where k is largely dependent on the apparent twist in the sail and has a value generally of the order of 0-5, that the apparent twist may not be twist at all in the aerodynamic sense, and that the vortex drag is considerably greater than it would be if it were possible to make a sail to give elliptic loading.