Catamaran keel area

Induced Drag : An Equation is Worth 10**3 Words

Tom has a great understanding of the fundamentals & is very good at explaining them in ways that nontechnical people can understand. In this case, however, I think the equations are simple enough that it shouldn't be too confusing to show them.

A lot of sailors are familiar with the nondimensional form of the induced drag equation (for a wing with elliptical spanwise loading in an ideal fluid) :
(Induced Drag Coefficient) = (Lift Coefficient)**2 / (Pi * Aspect Ratio)

A lot fewer are familiar with the same equation in terms of dimensional quantities:
(Induced Drag) = (Lift / Span) **2 / (Pi * Dynamic Pressure)

Exactly what Tom said!

Doug Halsey (the other Doug)