Ship A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...

stabilizers (or stabilisers) are fins or rotors mounted beneath the waterline and emerging laterally from the hull to reduce a ship's roll due to wind or waves. ''Active fins'' are controlled by a

gyroscopic A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rot ...

control system. When the gyroscope senses the ship roll, it changes the fins' angle of attack so that the forward motion of the ship exerts force to counteract the roll. ''Fixed fins'' and

bilge keel A bilge keel is a nautical device used to reduce a ship's tendency to roll. Bilge keels are employed in pairs (one for each side of the ship). A ship may have more than one bilge keel per side, but this is rare. Bilge keels increase hydrodynamic r ...

s do not move; they reduce roll by hydrodynamic drag exerted when the ship rolls. Stabilizers are mostly used on ocean-going ships.

Function

Fins work by producing

lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Paternoster lift, a type of lift using a continuous chain of cars which do not stop ** Patient lift, or Hoyer lift, mobil ...

downforce Downforce is a downwards lift force created by the aerodynamic features of a vehicle. If the vehicle is a car, the purpose of downforce is to allow the car to travel faster by increasing the vertical force on the tires, thus creating more grip ...

when the vessel is in motion. The lift produced by the fins should work against the roll moment of the vessel. To accomplish this, two wings, each installed underwater on either side of the ship, are used. Stabilizers can be: *Retractable - All medium and large cruise and ferry ships have the ability to retract the fins into a space inside the hull in order to avoid extra fuel consumption and reduce the required hull clearance when the fins are not needed *Non-retractable - Used on small vessels such as yachts. Stabilizer movement is similar to that of

aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engine ...

ailerons. Some types of fins, especially the ones installed on larger ships, are provided with flaps, that increase the fin lift by about 15%. Stabilizer control needs to consider numerous variables that change quickly: wind, waves, ship motion, draft, etc. Fin stabilizers are much more efficient at higher velocities and lose effectiveness when the ship is under a minimum speed. Stabilization solutions at anchor or at low speed include actively controlled fins (such as the ''stabilisation at rest'' system developed by

Rolls-Royce Rolls-Royce (always hyphenated) may refer to: * Rolls-Royce Limited, a British manufacturer of cars and later aero engines, founded in 1906, now defunct Automobiles * Rolls-Royce Motor Cars, the current car manufacturing company incorporated in ...

that oscillate to counteract wave motion), and rotary cylinders employing the

Magnus effect The Magnus effect is an observable phenomenon commonly associated with a spinning object moving through a fluid. The path of the spinning object is deflected in a manner not present when the object is not spinning. The deflection can be expl ...

. The latter two systems are retractable, allowing for a thinner vessel profile when docking and reducing drag while cruising.

History

Ship stabilizing gyroscopes USS Henderson 1917

Leopold starts the stabilizer history with antiroll tanks installed on British warships in the end of 19th century. Another early stabilization technology was the anti-rolling gyro, or gyroscopic stabilization. In 1915 the gyroscopic stabilizer was mounted on US destroyer USS Worden (DD-16). The World War I transport USS ''Henderson'', completed in 1917, was the first large ship with gyro stabilizers. It had two 25-ton, 9-foot diameter

flywheel A flywheel is a mechanical device which uses the conservation of angular momentum to store rotational energy; a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, as ...

s mounted near the center of the ship, spun at 1100 RPM by 75 HP AC motors. The gyroscopes' cases were mounted on vertical bearings. When a small sensor gyroscope on the bridge sensed a roll, a

servomotor A servomotor (or servo motor) is a rotary actuator or linear actuator that allows for precise control of angular or linear position, velocity and acceleration. It consists of a suitable motor coupled to a sensor for position feedback. It also ...

would rotate the gyros about a vertical axis in a direction so their precession would counteract the roll. In tests this system was able to reduce roll to 3 degrees in the roughest seas. For about 20 years the effectiveness of the stabilizers was unclear (in part due to improved gunfire directors), and in the US Navy the feature remained experimental (gyrostabilizer on the

USS Osborne (DD-295) USS ''Osborne'' (DD-295) was a in the United States Navy following World War I. She was named for Weedon Osborne. Naval Service ''Osborne'' was laid down 23 September 1919 at Bethlehem Shipbuilding Corporation, Squantum, Massachusetts; lau ...

, active-tank stabilizer on USS Hamilton (DMS-18)) until 1950s. One of the most famous ships to first use an anti-rolling gyro was the Italian passenger liner , which first sailed in November 1932. It had three flywheels which were 13 feet in diameter and weighed 108 tons. Gyroscope stabilization was replaced by fin stabilization due to its lower weight and bulk, but it has seen renewed interest since the 1990s (Seakeeper, etc.). The fin stabilizer had been patented by Motora Shintaro of Japan in 1922. The first use of fin stabilizers on a ship was by a Japanese cruise liner in 1933. From the late 1930s the British were actively installing the Denny-Brown fin stabilizers onto their warships (over 100 installations by 1950). US Navy continued unsuccessful experiments with roll tanks until the successful fin stabilizer installations onto USS Gyatt (1956) and USS Bronstein (DE-1037) (1958). In 1934 a Dutch liner introduced one of the world's most unusual ship stabilizer systems, in which two large tubes were mounted on each side of the ship's hull with the bottom of the tubes open to the sea. The top of the tubes had compressed air or steam pumped in. As the ship rolled, the side it was rolling to would fill with water and then compressed air or steam would be injected to push the water down, countering the roll. In 2018, rocket and space technology company Blue Origin purchased the '' Stena Freighter'', a

roll-on/roll-off Roll-on/roll-off (RORO or ro-ro) ships are cargo ships designed to carry wheeled cargo, such as cars, motorcycles, trucks, semi-trailer trucks, buses, trailers, and railroad cars, that are driven on and off the ship on their own wheels or using ...

cargo ship, for use as a landing platform ship for its '' New Glenn'' launch vehicle booster stages. the ship is undergoing refit to prepare for its role of landing rockets. The rocket boosters will be recovered

downrange Downrange, or down range, is the horizontal distance traveled by a spacecraft, or the spacecraft's horizontal distance from the launch site. More often, it is used as an adverb or adjective specifying the direction of that travel being measure ...

of the

launch site A spaceport or cosmodrome is a site for launching or receiving spacecraft, by analogy to a seaport for ships or an airport for aircraft. The word ''spaceport'', and even more so ''cosmodrome'', has traditionally been used for sites capable ...

in the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

while the hydrodynamically-stabilized ship is

underway Underway, or under way, is a nautical term describing the state of a vessel. "Way" arises when there is sufficient water flow past the rudder of a vessel that it can be steered. A vessel is said to be underway if it meets the following criteria: ...

. The ship stabilization technology is designed to increase the likelihood of successful rocket recovery in rough seas, as well as helping to carry out launches on schedule.

References

Sources

* * {{cite journal , last1 = Leopold , first1 = Reuven , title = Innovation adoption in naval ship design , journal = Naval Engineers Journal , date = December 1977 , volume = 89 , issue = 6 , pages = 35–42 , issn = 0028-1425 , eissn = 1559-3584 , doi = 10.1111/j.1559-3584.1977.tb05537.x , pmid = , url = Watercraft components

Function

History

See also

References

Sources