Stabilizer (ship)
As ship stabilizers are called systems, by means of which the movement of a vessel can be prevented in the wind and wave, or at least significantly reduced.
The action focuses on balancing the roles designated as movement around the longitudinal axis of the ship. On motion about the transverse axis, which is also called stomping up and down by the stern and bow, there are only little influence.
On modern ships primarily computer- controlled fin stabilizers. With the appropriate size of the vessels and in conjunction with ballast tanks rolling movement is barely noticeable.
Purpose
Especially on passenger ships stabilizers are used to prevent the occurrence of seasickness, but also on ferries and container ships where major damage could occur due to shifting of cargo or would even be feared capsizing of the ship. On warships can more easily targeted with stabilizers, increases the accuracy of target acquisition or the safety of landing of aircraft or helicopters be improved.
Stabilizing effect also counterweights or systems from ballast tanks and pumps to heel ( list ) can be used. However, this is only a side effect. This is called trimming or, so far as it mainly one-sided weight distribution is balanced during the loading and unloading of anti-heeling systems.
Stabilizer types
Bilge keel
In this system, flat steel sections are on both sides of the vessel is welded to the back of the pre- run vessel below the water line on the hull, and the greatest width of the roll, so the movement around the longitudinal axis of vapors.
Features:
- Low effectiveness
- Cost-effective and maintenance-free
- Permanent braking effect
Stabilizers
This system uses movable fins on the hull, to raise up the ship by the pressure of the applied water flow.
The idea was patented as early as 1898, but a practical implementation was not until 1925 in Japan at the Mitsubishi Nagasaki shipyard instead. Then was able to sit down in the 1930s further developed by the Scottish shipyards William Denny and Brothers Limited and Brown Brothers & Company Denny-Brown system.
First, the fins were made of a longitudinally mounted to the hull rigid construction. In the course of development they are located on the side now and often they can be buried in the fuselage, just when there is no need, in order not to increase the water resistance unnecessary. In general, let the angle change hydraulically so that the orientation of the fins is continuously adapted to the rolling movement of the ship. For this purpose, a suitable fin angle is calculated from a higher speed, angular position, angular velocity and angular acceleration of the ship rarely. The parameters considered are strongly dependent on the technical characteristics of the vessel from such as size, weight, load etc.
Features:
- Very high efficiency
- Take up little or no space inside the vessel
- Braking effect when the fins are extended
Tank stabilizers
In this technique, the rolling is counteracted by the receptacle and the regulated flow of water through a plurality of tubes interconnected ballast tanks.
The invention dates back to the late 19th century, but enjoyed a breakthrough only with a development by the German inventors H. Frahm and the use of a U- shaped tank system in the passenger liner RMS Laconia of the Cunard Line from 1912.
Features:
- Less effective than fin stabilizers
- Works even if the ship does not speed through the water
- Even static angle may be union
Gyros
In this technique, one or more large counteract gyroscopic instruments within the vessel, the rolling movement.
First, Ernst Otto Schlick 1904 invented a constructed as a steam turbine, large ship gyro which was established in 1906 for the first time successfully applied in practice. Due to unsatisfactory results in the transfer of gyration in further experiments, however, the ship Schlick ship gyro was not widely prevalent.
The American inventor Elmer Ambrose Sperry developed in the company Sperry Gyroscope Company a gyroscope stabilizer. Unlike the silt gyro have been aligned in the interior of the vessel by means of electric motors, in order to counter the rolling motion. The system came towards the end of the 1920s, initially in several smaller ships and submarines, and finally a large scale in passenger ship Conte di Savoia used. It could actually slow down the rolling strong, the ship but often held some time in the extreme positions of the rolling motion, so that the effect was not satisfactory and the system had to be shut down frequently, depending on weather conditions for safety reasons. Sperry Marine is now part of Northrop Grumman Group and is a leading producer of fin stabilizers.