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Stabilization While Not Underway
{{no references, date=September 2018 Stabilisation while not underway, stabilisation at rest, zero-speed stabilisation or on-anchor stabilisation is the process of augmenting roll reduction for a vessel that is not underway. This process may in some cases be implemented through the use of equipment systems that are also used for roll stabilisation while underway. Vessels at 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 ', which itself comes from the Greek (). Anch ..., 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 fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ship Motions
Ship motions are the six degrees of freedom that a ship, boat, or other watercraft 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 angular movements around them—a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marine Vessel
A watercraft or waterborne vessel is any vehicle designed for travel across or through water bodies, such as a boat, ship, hovercraft, submersible or submarine. Types Historically, watercraft have been divided into two main categories. *Rafts, which gain their buoyancy from the fastening together of components that are each buoyant in their own right. Generally, a raft is a "flow through" structure, whose users would have difficulty keeping dry as it passes through waves. Consequently, apart from short journeys (such as a river crossing), their use is confined to warmer regions (roughly 40° N to 40° S). Outside this area, use of rafts at sea is impracticable due to the risks of exposure to the crew. *Boats and ships, which float by having the submergeable part of their structure exclude water with a waterproof surface, so creating a space that contains air, as well as cargo, passengers, crew, etc. In total, this structure weighs less than the water that would occupy the sa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Underway
Underway, or under way, is a nautical term describing the state of a vessel which is unconstrained from horizontal translational movement relative to the water and the ground. "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 The word dock () in American English refers 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). In British English, the term is not used the same way as in American Engl ..., 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 ''on ... [...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 ', which itself comes from the Greek (). 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 minimize 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. Anchoring Anchors achieve holding power either by "hooking" into the seabed, or weight, or a combination of the two. The weight of the anchor chain can be more than that of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moorings
A mooring is any permanent structure to which a seaborne vessel (such as a boat, ship, or amphibious aircraft) 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. They cause 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 moor ... [...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 (watercraft), hull to reduce a ship's ship motions#Rotational motions, roll due to wind or waves. ''Active fins'' are controlled by a gyroscope, 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 (force), 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lift (force)
When a fluid flows around an object, the fluid exerts a force on the object. Lift is the Euclidean_vector#Decomposition_or_resolution, component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag (physics), 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 is defined to act perpendicular to the flow and therefore can act in any direction. If the surrounding fluid is air, the force is called an aerodynamic force. In water or any other liquid, it is called a Fluid dynamics, hydrodynamic force. Dynamic lift is distinguished from other kinds of lift in fluids. Aerostatics, 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 (boat), Planing lift, in which only the lower po ... [...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 (Tohmei, 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' ca ... [...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 Property is a system of rights that gives people legal control of valuable things, and also refers to the valuable things themselves. Depending on the nature of the property, an owner of property may have the right to consume, alter, share, re ... 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 se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maritime Transport
Maritime transport (or ocean transport) or more generally waterborne transport, is the transport of people (passengers or goods (cargo) via waterways. Freight transport by watercraft has been widely used throughout recorded history, as it provides a higher-capacity mode of transportation for passengers and cargo than land transport, the latter typically being more costly per unit payload due to it being affected by terrain conditions and road/rail infrastructures. The advent of aviation during the 20th century has diminished the importance of sea travel for passengers, though it is still popular for short trips and pleasure cruises. Transport by watercraft is much cheaper than transport by aircraft or land vehicles (both road and rail), but is significantly slower for longer journeys and heavily dependent on adequate port facilities. Maritime transport accounts for roughly 80% of international trade, according to UNCTAD in 2020. Maritime transport can be realized over an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
