Hovercraft
air-cushion craft
A hovercraft uses high-pressure air to form an air cushion between the bottom of the boat and the water surface (or the ground) to lift the hull out of the water
Hovercraft, also called "aircraft", is a boat that uses the support of air to lift out of the water. As soon as this kind of ship appeared, it immediately attracted the attention of the shipbuilding community around the world.
A ship that uses the high-pressure air cushion between the bottom of the ship and the water surface to lift part or all of the hull to achieve fast sailing. The high-pressure air cushion is formed by pressing air into the bottom of the boat. There is a flexible apron (or a rigid apron) around the bottom of the boat to restrict the air from escaping, and the air pressure is used to lift the hull. In 1959, the United Kingdom built its first hovercraft, which sailed in the English Channel. Hovercraft are mostly passenger ships and are also used as ferries or transportation boats. Hovercraft can travel at speeds of up to 80 nautical miles per hour. According to the lifting height of the hovercraft, it can be divided into full-cushion type and partial-cushion type. Fully-cushioned hovercraft is also called fully floating hovercraft. There are flexible aprons around the bottom of the boat. Since it is fully padded, it has high speed and good adaptability. It can not only sail on the water, but also on flat ground and swamps. Its propulsion uses air propellers and air rudders to control the direction. Partially raised hovercraft, also known as side-wall hovercraft. Rigid side walls are set up on both sides of the hull, and flexible air sealing devices are set up at the bow and stern to maintain an air cushion. It can lift most of the hull and can only sail on the water. Its propulsion uses an underwater propeller-type water spray device. The sailing speed is higher than that of ordinary ships, but not as fast as that of a fully-cushioned hovercraft. Hovercraft structural materials require high strength and light weight. It is made of aluminum alloy, fiberglass or high-strength steel, and uses aircraft engines, high-speed diesel engines, etc. as power devices.
The idea behind the design of a hovercraft is to create an air cushion under the bottom of the boat so that the hull is not in direct contact with the ground and appears to be suspended in the air. This air cushion is sucked in air from above or around the hull by the engine, and then ejected from below the hull. Because the bottom of the boat is surrounded by rubber bands, like an elastic skirt, an air cushion is formed.
The biggest advantage of the hovercraft is that it can travel on the ground as well as on the water. It does not need to build roads when traveling on the ground, which is very convenient.
There are two main forms of hovercraft: full floating and side wall. The largest passenger hovercraft in the world is the British-made SRN4-III hovercraft. It adopts a fully floating type, which is propelled by an air propeller (just like an airplane propeller). The bottom of the boat is surrounded by an "apron" made of nylon rubber cloth. High-pressure air is shot from the bottom of the boat, between the bottom of the boat and the water surface. The air cushion is formed to support the weight of the hull to reduce sailing resistance. The average speed is 100 kilometers per hour and it can carry 416 passengers and 55 cars. The fastest is the American side-wall hovercraft, which reaches 167 kilometers per hour.
The largest hovercraft
The Russian Zubr-class air-cushion landing craft was designed and built by the St. Petersburg "Almaz" Central Design Bureau Shipbuilding Co., Ltd., with a total length of 57.4 meters and a width of 22.3 meters. , said to be the world's largest air-cushion warship. According to relevant NATO reports, Russia has built ten Zubr-class air-cushion landing craft since 1986.
The creation of the hovercraft
The hovercraft was invented by British engineer Cocker. In 1950, at the age of 40, Cocler fell in love with the shipbuilding industry. So he quit his original job and used all his savings to start a small shipbuilding company with his wife. At this time, what Cocler was thinking about was how to build a faster boat. He believed that the reason why the boat speed could not increase was the resistance caused by the friction between the bottom of the boat and the water surface. After repeated research, he found that if air was used as an "air cushion" between the ship and the water, it would be possible to reduce friction and thereby increase the speed of the ship. Cocler made this idea concrete. He put an empty coffee can on an empty cat food can and used a hair dryer as a power to conduct experiments. As a result, he was very satisfied with the lifting effect produced by the exhaust. Then he built a model boat about 0.5 meters long, conducted experiments in the river, and achieved success again.
Its principle is exactly the same as that of today's practical hovercraft.
At this time, Cocler was ready to sell his invention to entrepreneurs, but was rejected. The reason is very interesting, the ship builders consider it an airplane and not a ship. However, Halspery, general manager of the British Research and Development Corporation, had a unique vision and foresaw the importance of hovercrafts and helped Cocler obtain the patent. At that time, Cocler joined NEDC and began to officially build a hovercraft that was 9.1 meters long and 7.3 meters wide. The hovercraft successfully crossed the English Channel and became the first hovercraft in the world to actually sail. It also fully demonstrates the superiority of hovercraft.