The Yanlun, which appears to have been scrapped, was the first Chinese-built catamaran, and some sources suggest as many as three were built. According to a report in "Jiangsu Ship" magazine (page 21, Issue 2, 1996), dozens of high-speed catamarans in the Pearl River Basin have been put into shipping and have caused serious losses to the embankment, with an annual economic loss of hundreds of millions of yuan. There is even a view that on the Yangtze River, in order to avoid the scouring of the waves on the embankment and the influence of the navigating and pushing fleet, it is not suitable to use the displacement high-speed boat.
In 1969, the Netherlands built the first semi-submersible small waterplane area catamaran "Douglas" with a displacement of 1,200 tons and a speed of 9 knots. In 1973, the United States built the "Camalino" small waterplane surface test work ship, which has a displacement of about 200 tons and can carry helicopters.
A catamaran is a "ship" that is joined together in a reinforced frame at the top of two separate underwater hulls. There is a main engine and a propeller in each of the two hulls. The strong structure connecting the two hulls is called the connecting bridge and there are more cabins. It has the advantages of good stability, safety and comfort, and flexible operation. This project is very poorly attested and there do not appear to be any photographs that are unambiguously associated with this nomenclature.
The catamaran is a ship composed of two single hulls laterally fixed together. As a hull shape different from the traditional ship design, the stability of the catamaran can be relatively good and it is not easy to overturn the ship; With the design impact, the deck area is also significantly increased, with a larger deck area and cabin capacity than a single tonnage of the same tonnage. Since the 1960s and 1970s, with the rapid development of high-speed passenger transportation at sea, high-speed catamaran has been widely optimistic due to its large deck area, space and easy decoration. It has become a development in high-performance ships in recent decades. The fastest, most widely used, and most constructed catamaran, which has achieved great results in the civil field, has attracted the attention of the military with its excellent performance. The United States and China have successively developed a variety of dual-body configuration military-use ships.
The US Navy's 650-tonne "Sea Shadow" stealth test ship, "Ocean" warship, and the 3,400-ton "victory"-class acoustic survey ship have marked the start of a new type of small waterplane catamaran. The small waterplane catamaran is a unique type of ship newly developed in the early 1970s. The underwater part of the ship is a pair of submarine-like hulls, and the upper body of the ship is supported above the water surface by narrow and long pillars. Because the area of the waterline is small, it is called a small waterplane catamaran; it is also called a semi-submarine catamaran because its lower body is submerged in the water. Because the waterline area of the small waterplane catamaran is small, the sailing wave is small, and the buoyancy part of the ship is submerged in the water, which will neither wave nor be affected by the sea wave.
Therefore, this type of ship has stronger wind resistance than the single ship, and has good airworthiness and can maintain high speed and balanced sailing in large wind and waves. The small waterplane catamaran also has a spacious deck area that is ideal for aircraft takeoff and landing, as well as for combat combat of missiles and artillery weapons. The small waterplane catamaran can be 30 to 45% shorter than the traditional drainage vessel, 60 to 70% wide, and 60 to 70% draught. Due to the wide hull and the large pitch of the propellers, the ship can flexibly turn and reverse in situ at low speeds, and the maneuverability is very good. On the ship using this type of ship, its vitality will be greatly improved through reasonable layout and invisible treatment, which is one of the important directions for the development of future ships.
However, from the current point of view, the small waterplane catamaran is expensive, and a 500-ton "Sea Shadow" ship costs more than 200 million US dollars. In addition, the small waterline surface ship itself has many shortcomings: deep draft, low-speed performance, complex structure and so on. Therefore, there are still many difficulties to be overcome in the development of new ships such as small waterline double-body frigates and destroyers.
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