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how does a boat speedometer work
The mileage of a ship in unit time. Calculated in nautical miles per hour, referred to as knots. It is one of the most important tactical and technical performance of ships. Usually, the speed of surface ships measured by log is divided into maximum speed, full speed, cruise speed, economic speed and minimum speed. Large ships such as aircraft carriers and missile destroyers have a speed of about 30 knots, while small ships such as missile speedboats and torpedo speedboats have a speed of 40 to 60 knots.
Speed refers to the mileage of a ship in unit time. According to the size, it can be divided into maximum speed, full speed, cruise speed, etc. as follows:
Maximum speed refers to the speed reached when the main power unit operates at maximum power; Full speed refers to the speed reached when the main power unit operates at the rated total power; Cruise speed is the speed commonly used by ships when cruising. Usually, the same type of ships specify a main engine speed as the cruise speed; Economic speed refers to the speed with the lowest cost determined according to ship transportation requirements, operating expenses and other factors; Minimum speed refers to the minimum speed at which the rudder can play a steering role. Submarine speed is divided into water speed, underwater speed and vent pipe speed (speed when using diesel engine underwater operation device, etc.).
Nautical log
Nautical log is a navigation instrument to measure the range and speed of ships. It is used to calculate navigation, integrated navigation and weapon equipment system to calculate firing parameters. There are relative log and absolute log. Compared with log, it has simple structure and is widely used, but it can only measure the speed and range relative to water. According to different principles, It can also be divided into rotary (including towed) log, hydraulic log and electromagnetic log, respectively according to the number of revolutions of the runner at the bottom of the ship (or the blade towed at the stern), the dynamic pressure of relative water flow and sea water (conductor) cut the difference of induced electromotive force in the electromagnetic place at the bottom of the ship to measure the speed and range. Among them, the electromagnetic log has high sensitivity and good accuracy at high and low speed. It can measure the backward speed and is easy to use. It is equipped and applied in most ships.
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