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Hydrodynamic/Propulsive Efficiency

This simple program calculates a rough stimation of the hydrodinamic or propulsive efficiency of a given ship. The more water a hull displaces, the more power in the propulsion system is required to reach a certain speed. A ship should reach the higher speed possible with any given power. When the design of the hull is not particularly efficient, higher power will be required to achieve any given speed. A right design of the hull shapes and propellers structure is what makes the difference. When a hull is very heavy, designers pay more attention to these aspects, in order to achieve satisfactory prestations with the lesser requirements possible in the propulsion system. The Yamato was actually a severely underpowered ship, having the same shaft power than the Bismarck, but the design of the hull was a masterpiece. The Iowa class relied instead in a very powerful propulsion plant to reach a high speed. More modern warships, which are considerably lighter, such as the Kirov class, are actually overpowered and still their prestations are average. Since the Second World War speed has barely increased in warships, and the most modern of them get the worst rates, because of their superior propulsion power.

Below there is a list showing the values for some well-known historical large ships. The higher the number, the higher the hydrodynamic or propulsive efficiency of the ship.

PHP application by Sakhal TurkaystanPHP application by Sakhal Turkaystan

Displacement (tonnes - standard):
Power (shaft horse power):
Speed (knots - maximum):

Ironclad Caio Duilio: 21.7
Transatlantic Titanic: 21.3
Battleship Dreadnought: 16.8
Transatlantic Queen Mary: 16.1
Battleship Knyaz Suvorov: 15.4
Battleship Viribus Unitis: 15.1
Battleship Yamato: 12.8
Battleship Baden: 11.2
Battleship Vittorio Veneto: 9.7
Battlecruiser Derfflinger: 9.1
Aircraft carrier Enterprise: 8.9
Battlecruiser Hood: 8.9
Battleship Queen Elizabeth: 8.8
Battleship Bismarck: 8.3
Battleship Iowa: 7
Antisubmarine Cruiser Kiev: 7
Battleship Richelieu: 7
Cruiser Long Beach: 5.8
Battlecruiser Kirov: 5.6
Aircraft carrier Hornet: 5.6
Cruiser Ticonderoga: 3.9