Do you know why a sailboat can sail against the wind?

As the saying goes, "the layman looks at the bustle, the insider looks at the doorway", and it is generally believed that a sailboat is pushed by the wind, and sailing downwind can make the boat get the fastest speed. In fact, there are two forms of force that air exerts on the sail: one is dynamic pressure, that is, when the air flows, it can exert an impact force on the object blocking the way.

It is easy to understand that when a sailboat is sailing downwind, it is propelled by the dynamic force of the air. The other is static pressure: when the air flow velocity on both sides of the sail is different, a pressure difference occurs.

Why? This is done using Bernoulli's principle in fluid mechanics. The principle reveals that where the velocity of the gas flows, the lower the static pressure; The lower the flow velocity, the greater the static pressure (e.g., fold a small paper bridge with paper, blow air into the bridge hole, and bend the bridge deck downwards instead of drumming). In this way, the side with a small gas velocity creates a lateral pressure on the side with a large velocity, and this force is called the static pressure.

When a sailboat sails against the wind, it is under this static pressure that pushes forward.

The reason why the sail is able to generate static pressure is because the sail has an arc like a wing. Due to the different shapes of the wings and sails, when the air flow through the wing or sail, the air flow speed is faster on the upper side of the wing and the protruding side of the sail, and the air flow speed is slower on the other side. The pressure at the slower flow rate is stronger than the pressure at the fast flow, and it is this pressure difference that causes the wing to generate upward lift and also gives the sailboat forward momentum.

The pushing efficiency is highest when the bow is kept at an angle of 30-40 degrees to the direction of the sea breeze. In August 2000, the French-designed sailing yacht "Hydroptere" reached a speed of 35 knots (just under 70 km/h) with winds of only 15 knots. Isn't that counter-intuitive?

But that's the objective fact. <>

The sailing competition is a beautiful and challenging project, with a buoy on the sea surface to enclose a polygonal water, the participating sailboats sail around the standard, the wind on the sea surface, the wind direction is complex and changeable, which requires the contestants to "see the wind and rudder", show their own housekeeping skills, to meet the challenge. A sailboat cannot sail completely head-on against the wind. A 12-metre-long sailboat can sail upwind at an angle of 12 to 15 degrees to the wind.

If you want to go head-on with the direction of the wind, you must sail in a zigzag course. When driving against the wind, the smaller the angle between the boat and the wind direction, the slower the speed. The helmsman will speed up if he sails in a zigzag with a larger angle, but the range will be longer.

The main power for sailboats to sail against the wind is suction. According to the principle of aerodynamics, as the velocity of the fluid increases, the pressure decreases. In order for the air to bypass the outwardly curved sail, it has to pick up speed, so the pressure decreases, creating a suction force that pulls the sail to the side.

The suction force generated by the pressure drop on the leeward side of the sail is quite large, which can be 1 times greater than the force of the sail pushing the sail on the windward side.

The suction and thrust generated by the wind on both sides of the sail makes the boat move sideways; But the center plate prevents the boat from going sideways, so the wind breaks down into two components, one that pushes the sailboat forward, and the other that causes the boat to roll to the leeward side, and the helmsman leans out on the other side of the boat to keep the balance. <>

The principle of sailing against the wind is:The Bernoulli effect

In fact, the biggest power of a sailboat is the so-called ---Bernoulli effect, which means that when the air flows through an arc similar to a wing, it will produce a forward and upward attraction, and therefore, it is possible for the sailboat to go in a certain angle of headwind. When sailing downwind, the Bernoulli effect disappears, and the ship cannot reach its maximum speed.

In normal breezes, downwind sailing is the slowest because there is no Bernoulli effect except for the thrust of the wind, and in strong winds, it is easy to turn all the way to the other side because the thrust of the wind is concentrated on the port or starboard side.

The key to driving against the wind is 35 degrees on the left and right of the wind, but generally 45 degrees as the limit, which has a lot to do with the design of the ship, the concept of driving against the wind is quite close to the side hall of the wind, but when the wind is headwind, the lateral force is greater than the crosswind, and the forward force is less than the crosswind, which is easy to learn and difficult to master, beginners can practice the top wind at the beginning, because the sail will use a very clear method to correct the mistakes of your manuscript (hehe. Then crosswind driving will naturally be.

1. The sailboats themselves are not bent and have power devices, and they can only rely on the wind to stir the sails to sail. As a result, the sails are usually made very wide relative to the hull of the boat, so that the wind can be used more fully.

2. When the sailboat sails downwind, it can reach a very fast speed, but when it encounters a headwind, how does it sail? The sail hung on the mast can change its angle at any time depending on the direction of the wind. When a sailboat is sailing against the wind, it is necessary to turn the hull sideways so that the sail forms an angle with the hull, and one side of the sail is full of wind, and the other side is under less pressure, and the hull takes advantage of this pressure difference to keep moving forward.

Of course, if it moves forward in this way, there will be a certain deviation between the direction of travel of the ship and the direction of the destination, so after the sailboat has sailed for a period of time, the direction of the sail needs to be adjusted, so as to change the course and make the sailboat move forward in a zigzag shape.

When driving in the wind, it is the force of the wind on the sail that pushes the sailboat forward. So, what is the force that pushes the sailboat forward in a headwind? Let's talk about why sailboats are able to sail "against the wind".

The sailboat uses the thrust of the wind to move forward, in fact, no matter which direction the wind blows, it can always produce a force perpendicular to the sail surface, and it is this force that pushes the sailboat forward.

When driving downwind, it is the force of the wind on the sail that pushes the sailboat forward. If the destination of the voyage is in the direction of the headwind, the ship is moving forward, but the bow of the ship is off course. You don't have to worry about the shirt, you just need to constantly adjust the direction of the hull and sails as you move forward, so that the path of the sailboat is zigzag.

Sailing ships use the thrust of the wind, so it is difficult for the average person to imagine a sailboat going against the wind, but experienced sailors tell us that it can be done, and they often call it "wind boating".

Let's assume that the wind is blowing in the opposite direction from the front of the sailboat, and adjust the sail surface to the angle between the wind and the hull. At this point, the force exerted by the wind on the sail can be broken down into two components perpendicular to each other, one of which blows along the sail surface and has little effect on the sailboat, while the other component acts perpendicular to the sail surface. This perpendicular force to the sail can be further broken down into two perpendicular components, one perpendicular to the hull, which can be counteracted by a longitudinal flap mounted on the bottom of the boat, and the other component in the direction of the hull to propel the boat forward.

At this time, if the destination of the voyage is in the direction of the headwind, although the ship is advancing, the bow of the ship is off course. Don't worry, just keep adjusting the direction of the hull and sails as you move forward, so that the path of the sailboat is zigzag.