Ceremonial ship launching

1908 launch of the Brazilian battleship Minas Geraes

Ceremonial ship launching is the process of transferring a vessel to the water. It is a naval tradition in many cultures, dating back thousands of years. It has been observed as a public celebration and a solemn blessing.

Ship launching imposes stresses on the ship not met during normal operation, in addition to the size and weight of the vessel, and it represents a considerable engineering challenge as well as a public spectacle. The process also involves many traditions intended to invite good luck, such as christening by breaking a sacrificial bottle of champagne over the bow as the ship is named aloud and launched.[1]

Methods

There are three principal methods of conveying a new ship from building site to water, only two of which are called "launching". The oldest, most familiar, and most widely used is the end-on launch, in which the vessel slides down an inclined slipway, usually stern first. With the side launch, the ship enters the water broadside. This method came into use in the 19th-century on inland waters, rivers, and lakes, and was more widely adopted during World War II. The third method is float-out, used for ships that are built in basins or dry docks and then floated by admitting water into the dock. If launched in a restrictive waterway drag chains are used to slow the ship speed to prevent it striking the opposite bank. [2]

Stern-first

Stern-first launch of the battleship USS Arizona in 1915 at the Brooklyn Navy Yard

Normally, ways are arranged perpendicular to the shore line (or as nearly so as the water and maximum length of vessel allows) and the ship is built with its stern facing the water. Modern slipways take the form of a reinforced concrete mat of sufficient strength to support the vessel, with two "barricades" that extend well below the water level taking into account tidal variations. The barricades support the two launch ways. The vessel is built upon temporary cribbing that is arranged to give access to the hull's outer bottom and to allow the launchways to be erected under the complete hull. When it is time to prepare for launching, a pair of standing ways is erected under the hull and out onto the barricades. The surface of the ways is greased. (Tallow and whale oil were used as grease in sailing ship days.)[3] A pair of sliding ways is placed on top, under the hull, and a launch cradle with bow and stern poppets is erected on these sliding ways. The weight of the hull is then transferred from the build cribbing onto the launch cradle. Provision is made to hold the vessel in place and then release it at the appropriate moment in the launching ceremony; common mechanisms include weak links designed to be cut at a signal and mechanical triggers controlled by a switch from the ceremonial platform.

On launching, the vessel slides backwards down the slipway on the ways until it floats by itself.[4]

Sideways launch of lake freighter Frank J. Hecker, St. Clair, Michigan. 1905

Sideways

Some slipways are built so that the vessel is side-on to the water and is launched sideways. This is done where the limitations of the water channel would not allow lengthwise launching, but occupies a much greater length of shore. The Great Eastern designed by Brunel was built this way as were many landing craft during World War II. This method requires many more sets of ways to support the weight of the ship.

Air-bag

Sometimes ships are launched using a series of inflated tubes underneath the hull, which deflate to cause a downward slope into the water. This procedure has the advantages of requiring less permanent infrastructure, risk, and cost. The airbags provide support to the hull of the ship and aid its launching motion into the water, thus this method is arguably safer than other options such as sideways launching.[5] These airbags are usually cylindrical in shape with hemispherical heads at both ends. The Xiao Qinghe shipyard launched a tank barge with marine airbags on January 20, 1981, the first known use of marine airbags.

Other Languages
беларуская: Спуск суднаў
català: Avarament
Deutsch: Stapellauf
Ελληνικά: Καθέλκυση
español: Botadura
한국어: 진수 (선박)
italiano: Varo (nautica)
日本語: 進水式
norsk nynorsk: Sjøsetjing
polski: Wodowanie
português: Botadura
русский: Спуск судов
svenska: Sjösättning