Methods of Ship launching
Ship launching. There are three principal methods of conveying a new ship from building site to water, only two of which are called ” ship 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.
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.
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“. Nevertheless the words “slip” and “slipway” are also used for all dry-docking installations that use a ramp.
In its simplest form, a slipway is a plain ramp, typically made of concrete, steel, stone or even wood. The height of the tide can limit the usability of a slip: unless the ramp continues well below the low water level it may not be usable at low tide. Normally there is a flat paved area on the landward end.
When used for building and repairing boats or small ships (i.e. ships of no more than about 300 tons), the vessel is moved on a wheeled carriage, which is run down the ramp until the vessel can float on or off the carriage. Such slipways are used for repair as well as for putting newly built vessels in the water.
When used for ship launching and retrieving small boats, the trailer is placed in the water. The boat may be either floated on and off the trailer or pulled off. When recovering the boat from the water, it is winched back up the trailer.
Swanage lifeboat being winched back up its slipway after a ship launch.
Slipways in the harbour of South Shields, Tyne and Wear, England
To achieve a safe launch of some types of land-based lifeboats in bad weather and difficult sea conditions, the lifeboat and slipway are designed so that the lifeboat slides down a relatively steep steel slip under gravity. It is winched back up afterward.