Your vessel is drifting with the wind broad on the port beam. The Marconi sail is set and flapping free. When is the maximum drive attained as you sheet in the sail?

Correct Answer: Option A — When it first takes the shape of an airfoil

Maximum aerodynamic drive occurs the moment a sail transitions from fluttering to forming a clean airfoil shape. Laminar airflow across the curvature generates lift, which provides forward thrust in accordance with standard sailing aerodynamics and fluid dynamics.