Sailing against the Wind

boat angle φ

sail angle θ

wind velocity

forces

all forces

force on the sail

water reaction force

resultant (net) force

This oversimplified model shows that it is possible to sail in a zigzag against the wind. The force produced by the wind (red) is always perpendicular to the sail in this simple model. The reaction force of water acting on the boat (blue) is always perpendicular to the boat axis. The magnitude of this reaction force is just enough to make the net force (black) act along the boat's axis. You can change the magnitude and direction of any of these vectors using the controls.