Construction, launch and fitting-out

The sheer size of Titanic and her sister ships posed a major engineering challenge for Harland and Wolff; no shipbuilder had ever before attempted to construct vessels of this size. The ships were constructed on Queen's Island, now known as the Titanic Quarter, in Belfast Harbour. Harland and Wolff had to demolish three existing slipways and build two new slipways, the biggest ever constructed up to that time, to accommodate the giant ships.[7]
Their construction was facilitated by an enormous gantry built by Sir William Arrol & Co., a Scottish firm responsible for the building of the Forth Bridge and London's Tower Bridge. The Arrol Gantry stood 228 feet (69 m) high, was 270 feet (82 m) wide and 840 feet (260 m) long, and weighed more than 6,000 tons. It accommodated a number of mobile cranes. A separate floating crane, capable of lifting 200 tons, was brought in from Germany.[63]
The construction of Titanic and Olympic took place virtually in parallel, with Olympic's hull laid down first on 16 December 1908 and Titanic's on 31 March 1909.[12] Both ships took about 26 months to build and followed much the same construction process. They were designed essentially as an enormous floating box girder, with the keel acting as a backbone and the frames of the hull forming the ribs. At the base of the ships, a double bottom 5 feet 3 inches (1.60 m) deep supported 300 frames, each between 24 inches (61 cm) and 36 inches (91 cm) apart and measuring up to about 66 feet (20 m) long. They terminated at the bridge deck (B Deck) and were covered with steel plates which formed the outer skin of the ships.[64]
The 2,000 hull plates were single pieces of rolled steel, mostly up to 6 feet (1.8 m) wide and 30 feet (9.1 m) long and weighing between 2.5 and 3 tons.[65] Their thickness varied from 1.5 inches (3.8 cm) to 1 inch (2.5 cm).[66] The plates were laid in a clinkered (overlapping) fashion from the keel to the bilge. Above that point they were laid in the "in and out" fashion, where strake plating was applied in bands (the "in strakes") with the gaps covered by the "out strakes", overlapping on the edges. Steel welding was still in its infancy so the structure had to be held together with over three million iron and steel rivets which by themselves weighed over 1,200 tons. They were fitted using hydraulic machines or were hammered in by hand.[67]