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Aerodynamically Alleviated Marine Vehicle
An aerodynamically alleviated marine vehicle (AAMV) is a high speed marine vehicle configuration that uses aerodynamically generated forces (lift) to 'alleviate' its weight. The advantage is that the hydrodynamic lift required to sustain the weight of the vehicle is diminished, leading to a diminished hydrodynamic drag. The vehicle is in constant contact with the water, therefore the aerodynamic surfaces operate in ground effect. The name derives from the "Aerodynamic Alleviation Concept", presented by L.J. Doctors to illustrate the positive effect of using a wing-like superstructure on a catamaran configuration.Doctors, L. J., “ANALYSIS OF THE EFFICIENCY OF AN EKRANOCAT: A VERY HIGH SPEED CATAMARAN WITH AERODYNAMIC ALLEVIATION”, International Conference on Wing In Ground Effect Craft (WIGs '97), RINA, 1997 Literature review In 1976, Shipps, among other air-supported waterborne vehicles, analyzed a new kind of race boats, known as 'tunnel hull' race boats. Two planing sponson ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Force
A force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. The concept of force makes the everyday notion of pushing or pulling mathematically precise. Because the Magnitude (mathematics), magnitude and Direction (geometry, geography), direction of a force are both important, force is a Euclidean vector, vector quantity. The SI unit of force is the newton (unit), newton (N), and force is often represented by the symbol . Force plays an important role in classical mechanics. The concept of force is central to all three of Newton's laws of motion. Types of forces often encountered in classical mechanics include Elasticity (physics), elastic, frictional, Normal force, contact or "normal" forces, and gravity, gravitational. The rotational version of force is torque, which produces angular acceleration, changes in the rotational speed of an object. In an extended body, each part often applies forces on the adjacent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chine (boating)
A chine in boat design is a sharp change in angle in the cross section of a hull. The chine typically arises from the use of sheet materials (such as sheet metal or marine ply) as the mode of construction. Rationale of chines Using sheet materials in boat construction is cheap and simple, but whereas these sheet materials are flexible longitudinally, they tend to be rigid vertically. Examples of steel vessels with hard chines include narrowboats and widebeams; examples of plywood vessels with hard chines include sailing dinghies such as the single-chined Graduate (dinghy), Graduate and the double-chined Enterprise (dinghy), Enterprise. Although a hull made from sheet materials might be unattractively "slab-sided", most chined hulls are designed to be pleasing to the eye and hydrodynamics, hydrodynamically efficient. Hulls without chines (such as clinker-built or carvel-built vessels) usually have a gradually curving cross section. A hard chine is an angle with little rou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wing-in-ground Effect Vehicle
A ground-effect vehicle (GEV), also called a wing-in-ground-effect (WIG), ground-effect craft, wingship, flarecraft or ekranoplan (russian: экранопла́н – "screenglider"), is a vehicle that is able to move over the surface by gaining support from the reactions of the air against the surface of the earth or water. Typically, it is designed to glide over a level surface (usually over the sea) by making use of ground effect, the aerodynamic interaction between the moving wing and the surface below. Some models can operate over any flat area such as frozen lakes or flat plains similar to a hovercraft. Design A ground-effect vehicle needs some forward velocity to produce lift dynamically, and the principal benefit of operating a wing in ground effect is to reduce its lift-dependent drag. The basic design principle is that the closer the wing operates to an external surface such as the ground, when it is said to be in ground effect, the less drag it feels. An airfo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
David W
David (; , "beloved one") (traditional spelling), , ''Dāwūd''; grc-koi, Δαυΐδ, Dauíd; la, Davidus, David; gez , ዳዊት, ''Dawit''; xcl, Դաւիթ, ''Dawitʿ''; cu, Давíдъ, ''Davidŭ''; possibly meaning "beloved one". was, according to the Hebrew Bible, the third king of the United Kingdom of Israel. In the Books of Samuel, he is described as a young shepherd and harpist who gains fame by slaying Goliath, a champion of the Philistines, in southern Canaan. David becomes a favourite of Saul, the first king of Israel; he also forges a notably close friendship with Jonathan, a son of Saul. However, under the paranoia that David is seeking to usurp the throne, Saul attempts to kill David, forcing the latter to go into hiding and effectively operate as a fugitive for several years. After Saul and Jonathan are both killed in battle against the Philistines, a 30-year-old David is anointed king over all of Israel and Judah. Following his rise to power, Dav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Center Of Gravity
In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may be applied to cause a linear acceleration without an angular acceleration. Calculations in mechanics are often simplified when formulated with respect to the center of mass. It is a hypothetical point where the entire mass of an object may be assumed to be concentrated to visualise its motion. In other words, the center of mass is the particle equivalent of a given object for application of Newton's laws of motion. In the case of a single rigid body, the center of mass is fixed in relation to the body, and if the body has uniform density, it will be located at the centroid. The center of mass may be located outside the physical body, as is sometimes the case for hollow or open-shaped objects, such as a horseshoe. In the case of a di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerodynamic Center
In aerodynamics, the torques or moments acting on an airfoil moving through a fluid can be accounted for by the net lift and net drag applied at some point on the airfoil, and a separate net pitching moment about that point whose magnitude varies with the choice of where the lift is chosen to be applied. The aerodynamic center is the point at which the pitching moment coefficient for the airfoil does not vary with lift coefficient (i.e. angle of attack), making analysis simpler. : =0 where C_L is the aircraft lift coefficient. The lift and drag forces can be applied at a single point, the center of pressure, about which they exert zero torque. However, the location of the center of pressure moves significantly with a change in angle of attack and is thus impractical for aerodynamic analysis. Instead the aerodynamic center is used and as a result the incremental lift and drag due to change in angle of attack acting at this point is sufficient to describe the aerodynamic fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Degrees Of Freedom (mechanics)
In physics, the degrees of freedom (DOF) of a mechanical system is the number of independent parameters that define its configuration or state. It is important in the analysis of systems of bodies in mechanical engineering, structural engineering, aerospace engineering, robotics, and other fields. The position of a single railcar (engine) moving along a track has one degree of freedom because the position of the car is defined by the distance along the track. A train of rigid cars connected by hinges to an engine still has only one degree of freedom because the positions of the cars behind the engine are constrained by the shape of the track. An automobile with highly stiff suspension can be considered to be a rigid body traveling on a plane (a flat, two-dimensional space). This body has three independent degrees of freedom consisting of two components of translation and one angle of rotation. Skidding or drifting is a good example of an automobile's three independent degr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keel
The keel is the bottom-most longitudinal structural element on a vessel. On some sailboats, it may have a hydrodynamic and counterbalancing purpose, as well. As the laying down of the keel is the initial step in the construction of a ship, in British and American shipbuilding traditions the construction is dated from this event. Etymology The word "keel" comes from Old English , Old Norse , = "ship" or "keel". It has the distinction of being regarded by some scholars as the first word in the English language recorded in writing, having been recorded by Gildas in his 6th century Latin work '' De Excidio et Conquestu Britanniae'', under the spelling ''cyulae'' (he was referring to the three ships that the Saxons first arrived in). is the Latin word for "keel" and is the origin of the term careen (to clean a keel and the hull in general, often by rolling the ship on its side). An example of this use is Careening Cove, a suburb of Sydney, Australia, where careening was carried ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monohull
right A monohull is a type of boat having only one hull, unlike multihulled boats which can have two or more individual hulls connected to one another. Fundamental concept Among the earliest hulls were simple logs, but these were generally unstable and tended to roll over easily. Hollowing out the logs into a dugout canoe doesn't help much unless the hollow section penetrates below the log's center of buoyancy, then a load carried low in the cavity actually stabilizes the craft. Adding weight or ballast to the bottom of the hull or as low as possible within the hull adds stability. Naval architects place the center of gravity substantially below the center of buoyancy; in most cases this can only be achieved by adding weight or ballast. The use of stones and other weights as ballast can be traced back to the Romans, Phoenicians and Vikings. Modern ships carry tons of ballast in order to maintain their stability; even heavily laden cargo ships use ballast to optimize the distr ... [...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 aro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sponson
Sponsons are projections extending from the sides of land vehicles, aircraft or watercraft to provide protection, stability, storage locations, mounting points for weapons or other devices, or equipment housing. Watercraft On watercraft, a sponson is a projection that extends outward (usually from the hull, but sometimes other parts of the vessel) to improve stability while floating, or to act as a securing point for other equipment. Vessels with unstable body shapes or unevenly distributed weight are likely to feature sponsons to help prevent capsizing or other instabilities. On many vessels, these projections from the main body of the vessel can be attached and removed quickly and fairly easily. Canoes and kayaks sometimes feature sponson attachments as well, for stability in rough waters. These differ from outriggers, which extend a significant distance away from the body of the craft, and are employed on craft designed for open waters. A sponson's terminus is close to the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planing (sailing)
Planing ( ) is the mode of operation for a waterborne craft in which its weight is predominantly supported by hydrodynamic lift, rather than hydrostatic lift (buoyancy). Many forms of marine transport make use of planing, including fast ferries, racing boats, floatplanes, flying boats, seaplanes, and water skis. Most surfboards are planing or semi-planing hulls. Beyond planing, fast vessel designs have seen a transition to hydrofoil designs. History The earliest documented planing sailboat was a proa built in 1898 by Commodore Ralph Munroe. It was capable of speeds of more than twice the hull speed. Planing a sailing dinghy was first popularised by Uffa Fox in Britain. In 1928 Fox introduced planing to the racing world in his International 14 dinghy, ''Avenger''. That year he gained 52 first places, 2 seconds, and 3 third places out of 57 race starts. This performance was noticed by other designers who further developed them. Over the years many dinghies have acquire ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
