The keel is essential in determining the boat's direction, it's just out of the scope of this paper, which concentrates on how the sail generates lift. That's t

The keel is essential in determining the boat's direction, it's just out of the scope of this paper, which concentrates on how the sail generates lift. That's the specific topic a lot of textbooks get wrong. I agree it would be cool if the paper also had a quick higher-level overview including how the forces from the hull/keel and sail interact, right now it feels like it lacks a bit of context! Thankfully this higher level is not so prone to error and I believe textbooks generally get it right, in a "spherical cows on a frictionless plane" sort of way. For example: http://www.real-world-physics-problems.com/physics-of-sailing.html http://www.real-world-physics-problems.com/physics-of-sailin...