The ship was sheathed and decked in steel plating, which added to the solidity of her structure. The steel used was mild (low-carbon) steel of high-grade “battleship” quality that had to be rolled out by machines. As an anonymous technician recalled: “You fed your heated steel plate from the furnace into the machine, where you could bend and curve it as required. The biggest plates on the ship were 30 feet long and weighed more than three tons each. The rolling machines were dangerous beasts. As one pushed the steel plates into them, it was all too easy to get one’s fingers, hands and arms dragged in too. There was no emergency stop button, and if one got caught there’d be nothing to stop one being dragged in bodily and crushed to death.”
The strakes (horizontal steel plates) on Titanic were numbered from A, first out from the keel bar, up to Z at the level of the Bridge deck. The joints between the inner and outer strakes of the steel plating were filled with liners of iron or steel. The entire system was both intricate and demanding, calling as it did for the highest precision on a very large scale. The average shell plate on Titanic amidships was 6 feet wide, 1 inch thick (though tapering at each end) and 30 feet long, adding up to a weight of 4.25 tons. Lower down, on the bottom of the ship, thicker plates were used, and various other parts of the ship required specialized plating. Keels in the shape of projecting fins were fitted along the bilge (the rounded part of the hull where the bottom joins the sides) for about 295 feet of Titanic’s length amidships to act as stabilizers.
In addition to all the work described above, expansion joints had to be allowed for. Two were fitted on Titanic—one at frame 49F and the other at 28A. All joints had to be caulked after the parts had been riveted together. This was done in the case of the Olympic-class and other large liners by using a variety of special blunt-ended chisels to nip the prepared edges of the joints tightly together, a process known as faying. This was vital to ensure absolute watertightness. And finally, the various openings in the steel hull—coal-ports, access doors, sidelight openings and so on—were made, and the doors and portholes fitted and made watertight.
The interior lower part of the hull on an Olympic-class ship near watertight bulkhead G. The outer plating is in place, riveted to the web frames, which in turn are attached to the Tank top. The inner sheathing has yet to be applied.
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