Ship Launching

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SHIP LAUNCHING Presented By Mohankumar.M 709-B

Transcript of Ship Launching

Page 1: Ship Launching

SHIP LAUNCHINGPresented

ByMohankumar.M

709-B

Page 2: Ship Launching

The most commonly used method of launching a ship is one that has remained virtually unchanged for thousands of years. It is, perhaps, the simplest solution to the problem of moving a vessel from Point A on dry land to Point B much lower in the water.Basically, it involves transferring the ship's weight from the blocks that have supported her during construction to the launchways. These are greased timbers which help the ship to slide down into the water and consist of slidingways (attached to the bottom of the ship), and standingways (fastened to the ground). Everything is held securely in place until the moment of the launch when traditionally, a bottle is broken to trigger the release. The ship should then glide down the slipway under her own weight into a floating position.

TRADITIONAL LAUNCHING

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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, usually stern first, down an inclined SLIPWAY.The SIDE LAUNCH, whereby the ship enters the water broadside, came into 19th-century use 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 drydocks and then floated by admitting water into the dock. Technically, this is not a launch, although sometimes erroneously referred to as such.

METHODS OF LAUNCHING

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A slipway, boat slip or just a slip, is a ramp on the shore by which ships or boats can be moved to and from the water. They are used for building and repairing ships and boats. They are also used for launching and retrieving small boats on trailers and flying boats on their undercarriage. The nautical term “ways” is an alternative name for slipway. A ship undergoing construction in a shipyard is said to be on the ways. If a ship were scrapped there, she is said to be broken up in the ways.Nevertheless the words "slip" and "slipway" are also used for all dry-docking installations that use a ramp.

SLIPWAY

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As the word "slip" implies, in theory the ships or boats are moved over the ramp, standing on a sledge, with help of grease. Slipways are used to launch (newly built) large ships, but can only dry-dock or repair smaller ships. Pulling large ships against the greased ramp would require too much force. For dry-docking large ships, one must use carriages supported by wheels or by roller-pallets. These types of dry-docking installations are called "marine railways".

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Figure 1 - Balance of the forces while ship is sliding down the slipway

Figure 2 - Balance of the forces in the rotation phase

Figure 3 - Balance of forces in the tipping phase

Figure 4 - Balance of the forces in the final phase

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SIDE LAUNCHINGSidewise launching is achieved in a similar manner with a large number of shorter ways or carriages.

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A shiplift is a modern alternative for a slipway, a floating dry dock or a graving dry dock. A shiplift is used to dry dock and launch ships.It consists of a structural platform that is lifted and lowered exactly vertical, synchronously by a number of hoists.First, the platform is lowered underwater, then the ship is floated above the support, and finally the platform with ship’s support and ship is lifted and the ship is brought to the level of the quay.Nowadays, shiplift are most of the time supplied under rules of a classification authority. Lloyd's Register of Shipping is the authority with most experience in the certification or classification of shiplifts."SHIPLIFT" is the word that is normally used, the term used by Lloyd's register is "Mechanical Lift Dock".

SHIPLIFT

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Modern systems use electrical control and drive systems for the winches. Old fashioned electrically driven shiplift systems needed so much starting current that they often could only be used in the weekend when other electrical equipment was not in use. The modern shiplifts however do not have this disadvantage; they can start the movement in any desired curve.Many shiplifts use a transfer system for ships so that the vessels can be transported from the water to a parking place where they can be painted or repaired. One shiplift can serve many parking places, while a dry docking installation can only dock one ship.For large vessels the transfer system consists of a number of trolleys or cradles, supported by high capacity steel wheels. The wheels drive on heavy duty rails. The transport can be one directional, but in order to serve more parking places, two directional systems are used. These two directional systems make use of a traverser carriage or sometimes the wheels of the trolleys can be turned over 90 degrees. Above the wheels often hydraulic cylinders are located so that the ship can be transported upon a so called "fluid bed". The cylinders are also used to lower the ships on a static support, so that the transfer system with the active elements can be recovered.

ADVANTAGES OF SHIPLIFT OVER OTHER METHODS