How Sails Work or How Sailboats Sail into the Wind

You’re on a sailboat and the wind is blowing from behind you. The wind will push on the sails and your boat which is attached to the mast will be propelled forward. No mystery there right? But what about when the wind blows towards you or from the side. You’d think it would be impossible for you to move forward, right? Well think again, because not only will you go forward, but set your sails right and you can sail even faster than the wind. So how do sailboats work and sail into the wind? Short answer, your sailboat is actually an airplane on its side and your sail is one of the wings raised vertically. When sailing, the sailor will adjust the sails so the wind pushed on the inside of the sail keeping it stretched tight but also at an angle so some of the wind passes along the outer side of the sail as well. This is exactly what happens on wings of an airplane. The pilot controls the angle of attack, so some of the wind pushes the wings up from below and some of the wind, by following the curvature of the upper part of the wing, pulls the wings up as a result of the Coanda effect and Newton’s 3rd Law of Motion. This resultant force is called lift, and lift is what keeps airplanes flying and sailboats sailing. However unlike the wings of an airplane where the direction of lift is vertical, in case of sails the direction is horizontal. But that’s not the end of the story, because a keen observer will have noticed that the direction of lift created by the sails, while horizontal, is at an angle to where we actually want to go. We’re missing something here. Well no need to look far, because the secret sailors like to call the “keel” is hidden right beneath us. Remember that a sailboat is actually an airplane on it’s side. The sail is one the wings and the keel is the other one, hidden under water. When lift from the sails tries to move the boat at an angle, the water, which you can think of as much denser air, pushes on one side of the keel and pulls from the other side creating lift. In this regard keels are no different from sails or wings. However, unlike wings of an airplane which create lift in the same direction, up, the wings of a sailboat creates lift in different directions. Both at an angle from where you want to go, which individually would be unhelpful, but when the effects are taken together the result is the forward propulsion we were looking for. And that’s how sailboats work and sail into the wind, except for the “no-go” zone which is about 45 degrees on either side of the wind, where it’s physically impossible to create lift no matter how you angle the sail. You obviously need magic for that. What’s not magic is the Coanda effect and how wings work using Newton’s 3rd Law of Motion. You can find out more about it here in part 1 of how wings work. Or if you’re more a Bernoulli’s principle kind of person, check out part 2 of how wings work, here.

Channel: Stick Science

Views: 139,820

Keywords: Science, Physics, Chemistry, Stick Science, Sail, Sailboat, Lift, Airfoils, Wings, Airplanes, Force, Newton, Newton’s 3rd Law of Motion, Bernoulli’s Principle, 돛, 요트, 돛단배, 뉴턴 제3법칙, 뉴튼 제3법칙, 베르누이, 베르누이 법칙

Id: FCcKeOmYHFY

Length: 2min 59sec (179 seconds)

Published: Tue Sep 07 2021