There are a number of complications. Two of them are that firstly, when when the wind direction is within about 45 degrees against the direction you want to go,

There are a number of complications. Two of them are that firstly, when when the wind direction is within about 45 degrees against the direction you want to go, you have to tack, and secondly, a reasonably efficient sailboat is fastest when it is on a reach, with the wind coming from the side. https://physics.stackexchange.com/questions/186515/why-is-a-beam-reach-the-fastest-point-of-sail-on-modern-sailboats https://physics.stackexchange.com/questions/186515/why-is-a-...