FIG. 6.
The salutary influence exerted by the Admiralty, in stipulating for increased sub-division of the hulls of all merchant vessels eligible for state employment in times of war, worthy of special recognition. A few years ago only thirty or forty large steamers in the merchant navy were so constructed, as regards sub-division, that they would have survived for a few minutes the effect of collision with other vessels or of grounding on rocks. Within recent years—greatly owing to the stipulations referred to, and to the desire f shipowners to comply with them for the reasons given—there are few, if any, of the many first-class mail steamers turned out, not so constructed.
FIG. 7.
FIG. 8.
Much valuable information on the subject was given in a paper on “Bulkheads,” read before the Institution of Naval Architects in March, 1883, by Mr James Dunn, of the Admiralty, whose experience in matters relating to the qualification of merchant ships for State employment eminently entitles him to be considered an authority. From diagrams contained in the paper, the effects of good and of inefficient sub-division of vessels are well illustrated. Figs. 5 to 8 in the present work represent some of these. They are concerned with two vessels, in one of which—an actual case—the bulkheads were well placed and cared for, and carried to a reasonable height as shown in Fig. 5; the result of a collision proving that under such conditions they were of immeasurable value, while in the other vessel, although having the same number and a similar disposition of bulkheads, their presence is rendered valueless by their being stopped at or about the water-line, as indicated in Fig. 7. In the first case, a steamer of nearly 5,000 tons, during a fog, ran into the vessel represented by Fig. 5 and 6, striking her abreast of No. 3 bulkhead, and opening up two compartments to the sea. The bulkheads, however, as has been said, were carried to a reasonable height, and the water could not get beyond them—they stood the test—the vessel did not sink, but kept afloat at the trim shown in Fig. 6, and in this condition steamed 300 miles safely into port. The second case—though a suppositionary one merely, yet representative of not a few merchant steamers now afloat—would not be attended with like results should such an accident happen as has been described. In vessels so bulkheaded, the water not being confined to the two holds, numbered 2 and 3, as it was in the previous actual case, would pour over the top of the dwarf bulkhead into the foremost hold, and the ship would soon assume the position indicated in Fig, 8: one not at all favourable, as may be readily believed, for the completion of a voyage to port.
These cases illustrate the value of minute and careful sub-division of the hulls of vessels by watertight bulkheads. Unless, however, the bulkheads are carried a few feet higher than the level of the water outside—and it is to be regretted that this is still not infrequently overlooked or neglected in merchant steamers—they are valueless, and, indeed, had better not be in the ship at all. They will contribute to the loss of the vessel by keeping the water at one end, and carrying her bows under, whereas if they are not fitted, the same volume of water will distribute itself throughout the bottom of the ship fore and aft, preserve the even trim of the vessel, and allow more pumps to cope with the inflow. Although her freeboard, or height of side above water will be reduced, she will still be seaworthy, the boiler fires may be kept burning, and the machinery going, sufficiently long for her to reach a port of safety. Readers appreciating the above considerations will readily see why it is that sailing vessels are usually fitted with only one transverse bulkhead—that near the bow—and understand how it is that the outcry sometimes made by inexperienced people about the absence of other bulkheads in emigrant sailing vessels is for most part unheeded by those on whom the responsibility falls.
From statistics presented in the paper above referred to, it is shown that during a period of six years, ending with December, 1882, the average loss per annum of ships not qualified for the Admiralty list was one in twenty-five; while of ships so qualified the annual average loss was only one in eighty-six. The chances of loss from any cause are thus seen to be nearly four times as great for a ship not constructed to qualify for the Admiralty list as for a vessel entered on that list. During the first four-and-a-half years of the period referred to, not one ship of those entered on the list was lost by collision although a considerable number had been in collision, and escaped foundering by reason of the safety afforded by their bulkheads. During 1882 six casualties happened to ships on the list, one of which—a case of collision—proved fatal. This was a case, however, such as no merchant steamer afloat at the time would have been capable of surviving. The whole of the ship—a small one—was flooded abaft the engine-room, the two after holds being open to the sea. The whole of the losses from the Admiralty list during the period referred to—eleven in number—have been from drifting on rocks, or otherwise getting fixed on shore, with the solitary exception above quoted. In the same period 76 ships have been lost which had been offered for admission to the list, but had not been found qualified; of these 17, or 22½ per cent., were lost by collision; and 10, or 13¼ per cent., were lost by foundering; most of the rest stranded or broke up on rocks. The risk of fatal collision, according to Mr Dunn, is about 1 to 100, irrespective of the class of ship, and the ships on the Admiralty list enjoy almost absolute immunity from loss by this cause.