THE train ferry must carry railway carriages, freight cars and sometimes locomotives on her main deck. In addition, sleeping and dining accommodation for passengers and, in many modem ships, a garage are essential. Since much of the heavy cargo is on deck, the hull - as will be seen - is a broad, shallow one, and there is ample space below the deck for machinery. To prevent any twisting due to corner loading, the hull must be stiffened with strong fore-and-aft girders.
The ship illustrated, the “Twickenham Ferry”, was designed for the Southern Railway cross-Channel service from Dover. She has a length overall of 360 ft, a maximum breadth of 63 ft and a draught of water of 12 ft 6-in for ordinary loading. The height of the train deck above water is 7 ft 6-in from the ordinary load line: thus the moulded depth is 20 ft. The speed is 16½ knots and, for manoeuvring purposes, the machinery has to be capable of obtaining revolutions astern which are 85 per cent of those corres-ponding to 16½ knots ahead. The train deck accommodates twelve sleeping cars and two baggage wagons or, alternatively, forty 25-ft goods wagons, on four sets of rails.
Two platforms are required, one on either side of the ship between the pair of tracks, so that passengers can alight and have access to the accommodation on the deck above the trains. The ship is built up forward to make her weather-worthy, and the trains are loaded aft on two tracks. The ends of these tracks correspond with similar tracks on the loading apron - as the device is called that links the shore rails to the deck rails.
Propulsion is by twin-screws, driven by geared turbines with a total of 5,000 hp. Steam is generated by four water-tube boilers with coal firing and mechanical stokers, so that coal enters the boiler without direct human aid. A special arrangement of main machinery control is made whereby the manoeuvring is controlled from the bridge, thus preventing any mistake during the somewhat delicate operations of manoeuvring astern to load and unload the ferry.