[caconym_]

I have to disagree, because a sailboat is a pure manifestation of the model that must be understood to understand how this vehicle works: a foil held at a fixed angle in a moving fluid, constrained to move only along a straight line at a fixed angle wrt. the motion of the fluid.

Understanding this vehicle requires heaping more complexity (the spiral motion) onto that same model, so in fact I think a sailboat is a great teaching aid here, as it's a clean waypoint on the journey to full understanding. Sailboats also exist, and have non-controversially demonstrated the surprising ability to sail with a downwind VMG higher than the environmental wind speed, which will help skeptics to engage with the problem.