It’s a bit mindboggling, but by exploiting physics and geometry, a sailboat can reach speeds faster than the wind propelling it. Steve Mould demonstrates how in this video using some cool tabletop set-ups. Like a wing, a sail generates force by changing the direction of the incoming air. But the optimal speed for a sail is the one where the the flow doesn’t get deflected from its initial path at all (middle). If the sail were moving slower than this, the air would get pushed aside, creating a force that accelerates the boat. If the sail were moving faster, the air’s deflection would generate low pressure that would slow the boat down. Given this ideal match, it’s straightforward to show that, with the right sail angle, a boat can cover more distance than the air pushing it does in the same amount of time (right). Part of the mark of a great sailor is knowing how to manipulate this relationship to maximize your boat’s speed! (Image and video credit: S. Mould)
Missed some of our earlier Olympics coverage? Check out how to optimize oar lengths for rowing, volleyball aerodynamics, and the ideas behind future swim technologies.