Launching(redirected from launchings)
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In shipbuilding, launching is carried out either after the ship has been completely built or after completion of basic shipbuilding work, such as construction of the hull, mounting of the rudder, and installation of propellers. Launching by simple flotation (floating out) is used in building and repairing large-displacement ships in dry docks and floating docks. End and side launchings by gravity, that is, by sliding or rolling, are carried out from a slip or building berth on sliding ways or carriages that run on inclined tracks; these launching methods are used for ships of medium displacement.
End launching from a longitudinal building berth is usually carried out on ground ways located on both sides of the keel. Both ways extend underwater to a length calculated to make the ship float before it has traveled the entire length of the ways. Sliding ways are put under the ship before launching. Lubrication with grease, soap, mineral substances, paraffin, or petrolatum provides a low coefficient of friction between the runners of the sliding ways and the ground ways. The ship is launched stern first in order to avoid burying the end of the ship in water and to reduce the length of the run through water. Other means to reduce the length of this run include affixing braking boards to the sliding ways and throwing out anchors.
In side launching, four to ten ground ways are used. They may extend far into the water for floating-out launching or only to the water’s surface, or they may terminate several meters above the water. The list taken by the ship during side launching may be as great as 90°.
Provisions are made to prevent a spontaneous movement of the ship caused by gravity. They include special restraining devices made of cable, wood, or steel and launching triggers. If needed, the initial momentum for launching a ship can be supplied by a hydraulic winch, a tugboat, or levers. Mechanized launching is carried out with the aid of carriages, platforms with mechanical hoists, and loading cranes. Such launching is typical for lot building of small and medium-size ships. The launching of large ships is usually accompanied by a festive ceremony and a solemn ritual.
A. I. MAKSIMADZHI