Launching

This chapter identifies the various means of transferring a ship from the land on which

it is constructed to the water. The traditional end launching process is described as this

is the most complex method. End launching is now less common as most newer

shipyards have a building dock. Other methods are less common and include side

launching, a ship lift, a floating dock, or a pontoon.

Whilst many modern shipyards now construct ships in building docks and float

them out and some utilize ship lifts, a good number of long-established shipyards are

still launching ships in the traditional manner. A significant advance has been

provided by computer programs that allow prior assessment of the performance of the

ship and the loading it may experience during the launch, both on the ways and in the

water.

Launching involves the transference of the weight of the ship from the keel blocks,

shores, etc. on which it was supported during construction, to a cradle on which it is

allowed to slide into the water. Normally the vessel is launched end on, stern first, but

a number of shipyards located on rivers or other narrow channels are obliged to

launch the vessel sideways. Vessels have been launched bow first, but this was a rare

occurrence as the buoyancy and weight moments, as well as the braking force, are

generally more favorable when the vessel is launched stern first. There is also a danger

of damage to propellers and rudders as the ship leaves the end of the slipway.

Ship Construction. DOI: 10.1016/B978-0-08-097239-8.00015-5

Copyright
2012 Elsevier Ltd. All rights reserved.

End launches

On release of a holding mechanism the launching cradle with the ship slides down the

ground ways under the action of gravity. When the stern has entered the water the

vessel is partly supported by buoyancy and partly by the ground ways. If this

buoyancy is inadequate after the center of gravity of the ship has passed the way ends,

the ship may tip about the way ends, causing large pressures on the bottom shell and

on the ends of the ground ways. To avoid this the greatest depth of water over the way

ends should be utilized, and the ground ways extended into the water if necessary.

Where this proves impossible it becomes necessary to strengthen the way ends and

provide shoring in the bottom shell region, which is likely to be damaged. These

remedies are often expensive.

As the vessel travels further into the water the buoyancy becomes sufficient to lift

the stern. The vessel then pivots about the forward poppets, i.e. the fore end of the

launching cradle. These are designed to take the load thrown on them by the pivoting

action, the load being widely distributed

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