Ship stabilizer

from Wikipedia, the free encyclopedia
Roll around the longitudinal axis (x), pitch around the transverse axis (y), yaw around the vertical axis (z)

As ship stabilizers referred to different systems by means of which the rotational movement of the vessel in the wind and wave about its longitudinal axis , the so-called rolling , can be either completely prevented or at least significantly reduced.

There is hardly any possibility of influencing the pitching , the movement of the ship around its transverse axis through opposing upward and downward movements of the stern and bow .

Intended use

Stabilizers are mainly used on passenger ships to prevent seasickness from occurring , but also on ferries and container ships , which could cause major damage due to the cargo slipping or even capsizing the ship. On warships , stabilizers can be used to improve safety when aircraft or helicopters land. The accuracy of the ship's artillery is the greater, the less the ship rolls at the moment of shooting.

The stabilizing effect of counterweights or ballast tanks against heeling (list side) is not referred to as a ship stabilizer , but as trimming .

Types of stabilizers

Rolling keel

Rolling keel

With this system, flat steel profiles are welded on both sides of a ship, which run under the waterline from fore to aft across the greatest width of the hull and dampen the rolling, i.e. the movement around the longitudinal axis.

Properties:

  • Low effectiveness
  • Inexpensive and maintenance-free
  • Permanent braking effect

Fin stabilizers

Scheme
Extended fin on port of the German research vessel Polarstern (in dry dock)

This system uses movable fins on the ship's hull to straighten the ship under the pressure of the water current.

The idea was patented in 1898, but it was not implemented in practice until 1925 in Japan at the Mitsubishi-Nagasaki shipyard . From the 1930s onwards, the Denny-Brown system, which was further developed by the Scottish shipyards William Denny and Brothers Limited and Brown Brothers & Company, became established .

At first the fins consisted of a construction that was rigidly placed on the fuselage. They were later retractable in the hull to reduce water resistance in calm weather. As a rule, the angle of attack of the fins can be adjusted hydraulically to the rolling movement of the ship. The position of the fins is optimized on the basis of the speed, angular position, angular speed and rarely also the angular acceleration of the ship. The parameters change with the size, weight and payload of the ship.

Properties:

  • Very high effectiveness
  • Take up little or no space within the ship
  • Braking effect as soon as the fins are extended
  • Loss of effectiveness when the ship comes to a standstill

Tank stabilizers

With this technology, the rolling counteracts the intake and the regulated flow of water through several ballast tanks connected to one another by pipes .

The invention dates back to the end of the 19th century, but only celebrated a breakthrough with a further development by the German inventor H. Frahm and the use of a U-shaped tank system in the passenger ship RMS Laconia of the shipping company Cunard Line from 1912.

Properties:

  • Less effective than fin stabilizers
  • Works even if the ship no way through the water makes
  • High space requirements within the ship
  • Static heeling can also be compensated

Gyro stabilizers

With this technique, one or more large gyroscopic instruments inside the ship counteract the rolling movement.

In 1904 Ernst Otto Schlick first invented a large ship gyro constructed as a steam turbine , which was first successfully used in practice in 1906. However, due to unsatisfactory results in the transmission of the gyroscopic movement in further ship tests, Schlick's ship gyro was not widely used.

The American inventor Elmer Ambrose Sperry developed a gyroscope stabilizer in his company Sperry Gyroscope Company . In contrast to Schlick's work, the gyroscopes inside the ship were aligned by electric motors to counteract the rolling movement. The system was first used in various smaller ships and submarines towards the end of the 1920s, and finally on a large scale on the Conte di Savoia passenger ship . It could actually slow down the roll considerably, but often held the ship in the extreme positions of the roll movement for a long time, so that the effect was not satisfactory and the system often had to be switched off for safety reasons depending on the weather conditions. Sperry Marine now belongs to Group Northrop Grumman and is one of the leading producers for Stabilizers ( English fin stabilizers ).

See also

Web links

Commons : Ship stabilizers  - Collection of images, videos and audio files

Individual evidence

  1. ↑ Tristan Perez, Ship Motion Control , Springer Verlag, Berlin / Heidelberg, 2005, ISBN 978-1-85233-959-3 , p. 123 f.
  2. ↑ www.northropgrumman.com