LIFT is a force that pulls the top of an airplane wing up and the outside part of a sail forward. The curve on the top of an airplane wing provides lift as the airplane speeds down the runway. A sail must have a concave wing-like curve to provide lift and power to pull the boat forward when heading towards the wind.
The air moving over a curved part of a wing has a longer distance to travel and therefore must go faster to have the same travel time as the air moving along the lower, flat surface of a wing. This creates a low pressure and considerable lift that can pull a sailboat forward. As you can see below, the shape of the sail on a sailboat is similar to the shape of an airplane wing.
DEMO: Take a piece of 8½ by 11-inch paper and hold it by the outside side edges between your thumbs and index fingers. Position your fingers about 1/3 of the way from the bottom of the paper, allowing the other 2/3 to extend away from your body. Move the paper close to your mouth. The 2/3 of the paper that extends beyond your fingers will naturally hang down. However, if you blow across and over the top of the paper and it will rise up – that’s LIFT!
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