A containment boom is a temporary floating barrier used to contain an oil spill. Booms are used to reduce the possibility of polluting shorelines and other resources, and to help make recovery easier. Booms help to concentrate oil in thicker surface layers so that skimmers, vacuums, or other collection methods can be used more effectively. They come in many shapes and sizes, with various levels of effectiveness in different types of water conditions.Often the first containment method to be used and the last equipment to be removed from the site of an oil spill, they are "the most commonly used and most environmentally acceptable response technique to clean up oil spills in the United States.Booms used in oil spills can be seen as they rest on the surface of the water, but can have between 18 and 48 inches of material that hangs beneath the surface.[3] They're effective in calm water, but as wave height increases oil or other contaminants can easily wash over the top of the boom and render them useless.
The outhaul runs from the clew of the sail to the free end of the boom. Hauling in on (tightening) the outhaul increases foot tension in the main sail. Modern loose footed sails are cut so that the outhaul is also able to pull the clew downwards towards the boom.The sheet is attached midway along the boom or at the free end, typically by means of a block. The block is typically attached to the boom by means of a bail, which is a U-shaped piece of metal, flattened at the ends to allow attachment with screws or rivets. In smaller boats such as dinghies it is used to control the angle of the sail to the wind on each point of sail. On largest boats this function is largely assumed by the traveller and the main sheet is used to adjust the twist of the sail to present the luff of the sail to the wind all of the way up the mast. Easing the main sheet increases twist and the twist is usually adjusted so that the aft end of the top batten in the main sail runs parallel to the boom. The traveller is a track running from one side of the boat to the other upon which sits a car to which the other end of the sheet is attached. Moving the car from side to side alters the angle of the boom to the centreline of the boat while minimising the effect on the twist of the sail.The boom vang, kicking strap or kicker is an intricate set of pulleys (and, on yachts, a hydraulic ram) running diagonally between the boom and the lower portion of the mast. The kicker pulls the boom downwards. When the boat is running away from the wind the sheet will be fully eased and so the kicker becomes the primary means of controlling sail twist.
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