|
Stabilization While Not Underway
{{no references, date=September 2018 Stabilisation while not underway, stabilisation at rest, zero-speed stabilisation or on-anchor stabilisation refers to the process of augmenting roll reduction for a vessel that is not underway. This process in some cases may be implemented through the use of equipment systems that are also used for roll stabilisation while underway. Vessels at anchor, at moorings, adrift, or keeping station are subjected to roll and pitch generating forces similar to those that affect vessels underway. Different strategies for mitigating the effects of these forces have been adopted. A variable system that uses " active fins" designed specifically for roll attenuation of a vessel while underway achieves lifting force through the flow of water over the fin's surface. By increasing the angle of attack of the fin to the water flow to some maximum working angle, a maximum lift force can be achieved for stabilising the hull. When these same systems are used for r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ship Motions
Ship motions are defined by the six degrees of freedom that a ship, boat or any other craft can experience. Reference axes The '' vertical/Z axis'', or ''yaw axis'', is an imaginary line running vertically through the ship and through its centre of mass . A yaw motion is a side-to side movement of the bow and stern of the ship. The '' transverse/Y axis'', ''lateral axis'', or ''pitch axis'' is an imaginary line running horizontally across the ship and through the centre of mass. A pitch motion is an up-or-down movement of the bow and stern of the ship. The '' longitudinal/X axis'', or ''roll axis'', is an imaginary line running horizontally through the length of the ship, through its centre of mass, and parallel to the ''waterline''. A roll motion is a side-to-side or port-starboard tilting motion of the superstructure around this axis. Rotational There are three special axes in any ship, called longitudinal, transverse and vertical axes. The movements around them a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marine Vessel
Any vehicle used in or on water as well as underwater, including boats, ships, hovercraft and submarines, is a watercraft, also known as a water vessel or waterborne vessel. A watercraft usually has a propulsive capability (whether by sail, oar, paddle, or engine) and hence is distinct from a stationary device, such as a pontoon, that merely floats. Types Most watercraft may be described as either a ship or a boat. However, numerous items, including surfboards, underwater robots, seaplanes and torpedoes, may be considered neither ships nor boats. Although ships are typically larger than boats, the distinction between those two categories is not one of size per se. *Ships are typically large ocean-going vessels; whereas boats are smaller, and typically travel most often on inland or coastal waters. *A rule of thumb says "a boat can fit on a ship, but a ship can't fit on a boat", and a ship ''usually'' has sufficient size to carry its own boats, such as lifeboats, dinghies, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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: * It is not aground * It is not at anchor * It has not been made fast to a dock A dock (from Dutch language, Dutch ''dok'') is the area of water between or next to one or a group of human-made structures that are involved in the handling of boats or ships (usually on or near a shore) or such structures themselves. The ex ..., the shore, or other stationary object. If a vessel is adrift and not being propelled by any instrument or device, it is said to be ''underway, not making way.'' "Under weigh" is a variation, coming from folk etymology, first used in 1749. "Under way" is likely from the Dutch ''onderweg'' or Middle Dutch ''onderwegen'' (lit. "under" or "among the ways"). Weigh is also a synonym for hanging or dangling, so t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anchor
An anchor is a device, normally made of metal , used to secure a vessel to the bed of a body of water to prevent the craft from drifting due to wind or current. The word derives from Latin ''ancora'', which itself comes from the Greek ἄγκυρα (ankȳra). Anchors can either be temporary or permanent. Permanent anchors are used in the creation of a mooring, and are rarely moved; a specialist service is normally needed to move or maintain them. Vessels carry one or more temporary anchors, which may be of different designs and weights. A sea anchor is a drag device, not in contact with the seabed, used to minimise drift of a vessel relative to the water. A drogue is a drag device used to slow or help steer a vessel running before a storm in a following or overtaking sea, or when crossing a bar in a breaking sea.. Overview Anchors achieve holding power either by "hooking" into the seabed, or mass, or a combination of the two. Permanent moorings use large masses (common ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moorings
A mooring is any permanent structure to which a vessel may be secured. Examples include quays, wharfs, jetties, piers, anchor buoys, and mooring buoys. A ship is secured to a mooring to forestall free movement of the ship on the water. An ''anchor mooring'' fixes a vessel's position relative to a point on the bottom of a waterway without connecting the vessel to shore. As a verb, ''mooring'' refers to the act of attaching a vessel to a mooring. The term likely stems from the Dutch verb ''meren'' (to ''moor''), used in English since the end of the 15th century. Permanent anchor mooring These moorings are used instead of temporary anchors because they have considerably more holding power, for example because of lesser damage to the marine environment, and are convenient. Where there is a row of moorings they are termed a tier. They are also occasionally used to hold floating docks in place. There are several kinds of moorings: Swing moorings Swing moorings also know ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stabilizer (ship)
Ship 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 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 keels 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 or downforce 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 r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lift (force)
A fluid flowing around an object exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the force parallel to the flow direction. Lift conventionally acts in an upward direction in order to counter the force of gravity, but it can act in any direction at right angles to the flow. If the surrounding fluid is air, the force is called an aerodynamic force. In water or any other liquid, it is called a hydrodynamic force. Dynamic lift is distinguished from other kinds of lift in fluids. Aerostatic lift or buoyancy, in which an internal fluid is lighter than the surrounding fluid, does not require movement and is used by balloons, blimps, dirigibles, boats, and submarines. Planing lift, in which only the lower portion of the body is immersed in a liquid flow, is used by motorboats, surfboards, windsurfers, sailboats, and water-skis. Overview A fluid flowing arou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anti-rolling Gyro
Ship stabilizing gyroscopes are a technology developed in the 19th century and early 20th century and used to stabilize roll motions in ocean-going ships. It lost favor in this application to hydrodynamic roll stabilizer fins because of reduced cost and weight. However, since the 1990s, there is renewed interest in the device for low-speed roll stabilization of vessels (Seakeeper, Quick MC2, etc.). Unlike traditional fins, the gyroscope does not rely on the forward speed of the ship to generate a roll stabilizing moment and therefore can stabilize motor yachts while at anchor. However, the latest generation of "zero speed" fins stabilizers (CMC, Humphree, etc.) can stabilize yachts while at anchor thanks to their eccentricity with respect of the shaft. The World War I transport , completed in 1917, was the first large ship with gyro stabilizers. It had two 25-ton, diameter flywheels mounted near the center of the ship, spun at 1100 rpm by AC motors. The gyroscopes' cases were m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maritime Safety
Maritime safety as part of and overlapping with water safety is concerned with the protection of life (search and rescue) and property through regulation, management and technology development of all forms of waterborne transportation. The executive institutions are the national and transnational maritime administrations. Maritime accidents, while characterized by a level of safety of the order of 10−5 (1 serious accident per 100,000 movements), which is only slightly inferior to that of the field of air transportation (10−6) are a significant source of risk for insurance companies, transport companies and property owners. Beyond that, of course, ship owners and maritime institutions have to ensure that casualties at sea (mostly by drowning) are kept to the possible minimum. Organizational and human factors are critical antecedents to accidents such as MV Prestige, Herald of Free Enterprise, MS Sleipner, MS Estonia, Bow Mariner and Hoegh Osaka as well as the infamous Tita ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maritime Transport
Maritime transport (or ocean transport) and hydraulic effluvial transport, or more generally waterborne transport, is the transport of people (passengers) or goods (cargo) via waterways. Freight transport by sea has been widely used throughout recorded history. The advent of aviation has diminished the importance of sea travel for passengers, though it is still popular for short trips and pleasure cruises. Transport by water is cheaper than transport by air, despite fluctuating exchange rates and a fee placed on top of freighting charges for carrier companies known as the currency adjustment factor. Maritime transport accounts for roughly 80% of international trade, according to UNCTAD The United Nations Conference on Trade and Development (UNCTAD) is an intergovernmental organization within the United Nations Secretariat that promotes the interests of developing countries in world trade. It was established in 1964 by the ... in 2020. Maritime transport can be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
_and_battleship_in_typhoon_1944.jpeg "Click for more on -> Ship Motions")
.jpg "Click for more on -> Marine Vessel")
.PNG "Click for more on -> Stabilizer (ship)")
