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Oar

The meaning of «oar»

An oar is an implement used for water-borne propulsion. Oars have a flat blade at one end. Rowers grasp the oar at the other end.

The difference between oars and paddles is that oars are used exclusively for rowing. In rowing the oar is connected to the vessel by means of a pivot point for the oar, either an oarlock, or a thole. The oar is placed in the pivot point with a short portion inside the vessel, and a much larger portion outside. The rower pulls on the short end of oar, while the long end is in the water. The oar is a second class lever with the water as the fulcrum, the oarlock as the load, and the rower as the force, force being applied to the oarlock by exertion of pressure against the water. An oar is an unusual lever since the mechanical advantage is less than one. The oar increases the small displacement of the end held by the rower, into a large displacement of the vessel through the water. The rower applies a large force through a small distance, which must be equaled by the small force the water applies operating over a longer distance, i.e. the work done by the rower must be balanced by the work done by the water.[1]

By contrast, paddles, are held in both hands by the paddler, and are not attached to the vessel.

Rowers generally face the stern of the vessel, reach towards the stern, and insert the blade of their oar in the water. As they lean back, towards the vessel's bow, the blade of their oars pivots in the oarlock, and the end in the water moves towards the stern, providing forward thrust.

For thousands of years vessels were powered either by sails, or by the mechanical work of rowers, or by paddlers. Some ancient vessels were propelled by both oars and sail, depending on the speed and direction of the wind.

Rowing oars have been used since the early Neolithic period. Wooden oars, with canoe-shaped pottery, dating from 5000–4500 BC have been discovered in a Hemudu culture site at Yuyao, Zhejiang, in modern China.[2][3] In 1999, an oar measuring 63.4 cm (2 ft) in length, dating from 4000 BC, was unearthed in Ishikawa Prefecture, Japan.[4]

Oars have traditionally been made of wood. The form is a long shaft (or loom) with a flat blade on the end. Where the oar connects to the boat there is a "collar" (or button), often made of leather, which stops the oar slipping past the rowlock. Oars usually have a handle about 150mm long, which may be a material sleeve or alternatively an ovoid shape carved to fit the hands.

This is a normal, usually wooden oar to which weight has been added at the inboard end so that the blade end is noticeably lighter and easier for a rower to operate without fatigue. The two methods of adding weight are to either have a much larger section in the oar immediately next to the handle for a distance of about 450 millimetres (18 in) or to drill an 18-millimetre (0.71 in) hole inside the handle for a distance of about 150 millimetres (5.9 in) and add about 12 oz of lead secured by epoxy resin glue. For a 7-foot (2.1 m) oar the balance point is about 12 inches outboard of the rowlock. Often surplus wood is removed from the blade's width and thickness and at the neck between the blade and the shaft to further reduce outboard weight. This type of oar is much better for long-range rowing.[according to whom?]

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