By Dominique Martin


A boat is a craft that can float on water and move around, run or not by its occupants. It meets the needs of maritime or fluvial transport and allows various activities such as the transport of persons or goods, war at sea, fishing, boating, or other services such as the safety of other ships. The used boats for sale by owner have accompanied man in his evolution.

Finally, the hardware includes various pieces of equipment needed for maneuvering. Finally, from a certain size, every vessel carries a lifeboat or a liferaft ensuring the safety of people in case of shipwreck. The buoyancy of a vessel can be achieved in different ways. For a boatcraft, hull weight is offset by the buoyancy equal to weight of volume of water displaced (hence the term displacement). This is the case of all large ships and most 'classics'.

The term may involve any floating structure that can effectively advance be led (as opposed to the raft), but other names are preferred in some cases: we speak to craft a boat small (of order of few meters long).

On a human-powered boat, a system to control the direction may not be necessary. It is under mechanical propulsion or sailing. The most common device is a rudder, which comprises a rudder blade, immersed in rear plane of shell, steerable to generate a lateral force for rotating the rotating vessel. The rudder is deflected over the bar, manually operated or automatic pilot. The rudder can be removed when the propellant is adjustable: outboard engine pods or Z-drive.

These first boats have a simple function, which is to be able to walk on water, mainly for hunting and fishing. The oldest canoes were discovered through archaeological explorations are carved from softwood, using simple stone tools. There are about five thousand years, builders living along the river in Denmark Amose invent stitched edging, allowing progressively increase the size of the boats.

The balance and stability of a vessel are studied firstly statically (weight distribution) and dynamic (wave action and wind). Ways to compensate for excessive heel are moving crew on small sailboats, sail trim according to speed, fixed ballast (located at the bottom of keel) or swivel, the ballast can be filled with water. The plate is offset in same way.

However, the driving resistance is growing very fast for a ship to travel when the Froude number reaches 0.4; to exceed this speed, you either lighten and refine the hull either use an additional dynamic lift allowing the hull of "planing" and reduce the resistance: shells "trippy." This is the case dinghy racing as the 49ers, the "outboard", stars and some fast ships passengers.

For this, the fast boats are often thinner, with smaller appendages; the water friction is also reduced by regular maintenance of the hull on which is deposited in animals and algae, by coating a antifouling. Wave resistance can be reduced by adding a bulbous bow and regular shapes and thin. Another special form are swamp boats which are slidable not only on water, but in the marshes on the grasses. Submarines are carefully balanced according to technical principle.




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