DOCTORING A SHIP.

Manawatu Herald, Volume XLIV, Issue 2377, 10 January 1922, Page 4

DOCTORING A SHIP.

HOW OVERHAULING IS DONE

A liner entering a ship-repairing yard is the subject of almost as many questions as a patient visiting a doctor. She is often in greater danger when in a tidal basin than when she is plunging before a storm at sea. “Who is to pay the insurance In the ease of accident, how far will the owners’ liability extend? Who will pay the land-fire insurance?” These are but a few of the questions to be answered before she is handed over” to the repairers. These preliminaries settled, the vessel soon loses her neat appearance, and degenerates into her primitive condition of rust and dirt. It is impossible to keep, her clean when rivetters, platers, joiners, riggers, and carpenters are swarming over her, feverishly making as many alterations as possible before she is “docked.”

Two types of docks are used for inspecting the ship below waterline —the graving dock and the floating dock, but the latter is the more interesting. It is a strong box-steel structure, fitted with numerous lifting tanks, upon which are built the dock walls, containing pumps, control valves, power plant, and winches.

The carpenters consult the docking plan always carried on firstclass vessels, and proceed to erect (he keel blocks on the tank top. This is an important operation, because the ship—a. floating girdermust be evenly supported when she is lifted clear of the water.

The next move is to sink the dock. Every lifting tank is fitted with air and flooding valves. These valves are “eased,” the'water is allowed to flood the tgnks, and the mass of steel sinks slowly.

The engineer in charge consults the depth and level gauges, and at the desired moment a shrill whistle rings out and the attendants close all "valves. If all is tight the vessel is towed into position, the pumps empty a few tanks, and the dock rises- When “the grip” occurs and appears satisfactory, the pumps at e “opened up,” and soon the vessel *- lifted clear of the water. To prevent any possibility o£ accidents, the valves are all securely locked. An examination of the rudder, tail shafts, and plates is made, and new zincs are fitted. When steel ships were first built and brass sett connections fitted, it was discovered that the galvanic action set up by (he sea water and the two diffcienf metals ate away the plates, and made the ship leaky. A genius of a shipbuilder evolved the idea of fixing renewable zincs between the tun metals, thus saving the plates.