WARSHIP PROTECTION AS APPLIED TO SOME OCEAN LINERS
It was shown in the previous chapter that the most completely protected vessel, so far as its flotation is concerned, is the warship, and plans were given of a battleship whose hull below the water-line was subdivided into no less than five hundred separate watertight compartments. Facts were cited from the naval operations in and around the harbour of Port Arthur, which prove that the battleship is capable of sustaining an enormous amount of injury below the water-line without going to the bottom.
Now, if it were possible to apply subdivision to the large ocean liners on the liberal scale on which it is worked out in ships of war, it would not be going too far to say that they would be absolutely unsinkable by any of the usual accidents of collision. The 60,000-ton Titanic, were she subdivided as minutely as the warship shown on page 143, would contain at least 1,500 separate compartments below her lower deck, and under these conditions even the long rent which was torn in her plating would have done no more than set her down slightly by the head. Her pumps would have taken care of the leakage of water through the bulkheads, and the ship would have come into New York harbour under her own steam.
But a warship and a passenger ship are two very different propositions. The one, being designed to resist the attack of an implacable enemy, who is using every weapon that the ingenuity of man can devise to effect its destruction, is built with little if any regard to the cost. The other, built as a commercial proposition for the purpose of earning reasonable dividends for its owners, and exposed only to such risks of damage as are incidental to ocean transportation, is constructed as economically as reasonable considerations of strength and safety may permit.
Another important limitation which renders it impossible to give a passenger ship the elaborate subdivision of a warship, is the necessity of providing large cargo spaces and wide hatchways for the convenient handling and stowage of the freight, upon which a large
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Courtesy of Scientific American
Longitudinal bullkheads from an inner skin through machinery spaces. Transverse bulkheads extend two decks (20 feet) above water line, the height increasing towards the ends.
Longitudinal Section and Plan of the Imperator
proportion of the passenger-carrying vessels chiefly depend for their revenue.
On the other hand, the main features of warship protection may be so applied to the large merchant ship as to render her as proof against collision with icebergs, derelicts, or with other vessels, as the warship is against the blow of the ram, the mine, or the torpedo. And the merchant ship of the size of our largest ocean liners has the great advantage over the warship (provided that the average size of her compartments be not too greatly increased) that her great size is in itself a safeguard against sinking.
By way of showing what can be done in applying warship principles of subdivision to merchant vessels, we shall consider in some detail three notable ships, the Mauretania, the Kronprinzessin Cecilie, and the recently launched Imperator.
The Mauretania and her sister, the Lusitania, were built under an agreement with the British Government, who stipulated that they would provide a sum sufficient to pay for the new vessels not to exceed $13,000,000, secured on debentures at 2¾ per cent, interest. The two ships were to be of large size and capable of maintaining a minimum average ocean speed of 24½ knots in moderate weather. The government also agreed that if the ships fulfilled these conditions, the Cunard Company was to be paid annually $750,000.00. In return for this extremely liberal assistance, the Cunard Company agreed to employ them in the British mail-carrying service; to so construct them that they would be available for use as auxiliary cruisers; and to hold them at the instant service of the government in case of war. In addition to holding the ships at the service of the government, it was agreed that all the officers and three-fourths of the crew should be British subjects, and that a large proportion should belong to the Royal Naval Reserve. The ships were thus to be utilised as a training school for officers and seamen, and with this point in view a record of the personnel was to be made each month.
The particulars of these two ships as finally constructed are as follows: Length over all 790 feet; beam, 88 feet; displacement, 46,000 tons; and horsepower, 70,000. Both vessels greatly exceeded the contract speed of 24½ knots, the Lusitania having maintained over 25½ knots
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and the Mauretania 26 knots for the whole run across the Atlantic.
The purpose of the present chapter is to show how successfully the methods of underwater protection employed in naval ships may be applied to passenger ships of the first class; and the Mauretania is given first consideration, for the reason that she is the best example afloat to-day of a merchant ship fully protected against sinking by collision. The protective elements may be summed up as consisting of multiple subdivision, associated with a complete inner skin and a watertight steel deck, answering to the heavy protective deck at the water-line of the warship. By reference to the hold plan on page 129 it will be noticed that she is subdivided by 22 transverse bulkheads, 12 of which extend entirely across the ship and 10 from the side inboard to the longitudinal bulkheads. The space devoted to the turbine engines is subdivided by two lines of longitudinal bulkheading, and the compartment aft of the engine-room spaces is divided by a longitudinal bulkhead placed upon the axis of the ship. Altogether there are 34 separate watertight compartments below the water-line. The most important feature of the subdivision is the two lines of longitudinal bulkheads, which extend each side of the boiler-rooms and serve the double purpose of providing watertight bunker compartments and protecting the large boiler-room compartments from being flooded, in the event of damage to the outer skin of the ship. The main engine-room, containing the low-pressure turbines, is similarly protected against flooding.
Now, all of these bulkheads are carried up to a watertight connection with the upper deck, which, amidships, is over two decks, or say about 20 feet above the water-line, the exception being the first or collision bulkhead, which extends to the shelter deck. A most important feature of the protection, borrowed from warship practice, is that the lower deck, which, amidships, is located at about the water-line, is built of extra heavy plating, and is furnished with strong watertight hatches. It thus serves the purpose of a protective deck, and water, which flooded any compartment lying below the water-line, would be restrained by this deck from finding its way through to the decks above. The Mauretania, therefore, could sustain an
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Courtesy of Scientific American
In addition to transversal and longitudinal bulkheads, this ship has fire bulkheads in the passenger spaces.
The 26,000-Ton, 23½ Knot Kronprinzessin Cecilie, a Thoroughly Protected Ship
enormous amount of damage below the water-line without foundering. It is our belief that she would have survived the disaster which sank the Titanic. The first three compartments would have been flooded, it is true, but the water would have been restrained from her large forward boiler-compartment by the "inner skin" of the starboard bunkers. Furthermore, the watertight hatches of her lower, or protective, deck would have prevented that upward flow of water on to the decks above, which proved so fatal to the Titanic.
In dealing with the question of safety, the German shipbuilders have shown that thorough study of the problem which characterises the German people in all their industrial work. Although German ships of the first class, such as the Kronprinzessin Cecilie and the Imperator are not built to naval requirements, they embody many of the same protective features as are to be found in the Mauretania and Lusitania, and, indeed, in some safety features, and particularly in those built in the ship as a protection against fire, they excel them.
The existence of side bunkers, small compartments, and bulkheads carried well up above the
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This well-protected ship has side coal bunkers, and inner skin in engine-rooms. There are thirty-three compartments below the water-line.
Hold Plan of Kronprinzessin Cecilie
water-line, is due to the close supervision and strict requirements of the German Lloyd and the immigration authorities, and it takes but a glance at the hold plan of the Kronprinzessin Cecilie to show how admirably this ship and her sister are protected against collision. There are 21 transverse bulkheads, 18 of which are shown in the hold plan, the other three being sub-bulkheads, worked in the after part of the ship abaft of the machinery spaces. The four engines are contained in four separate compartments, and the boiler-rooms are entirely surrounded by coal-bunkers. These, the largest compartments, are protected throughout their entire length by the inner skin of the coal-bunker bulkheads. The engine-rooms are further protected by extending the inner floor of the double bottom up the sides as shown on page 176. Altogether, the hold plan shows 33 separate, watertight compartments. The collision bulkhead is carried up to the shelter deck, and the other bulkheads terminate at the main deck, which is about 19 feet above the normal water-line.
It is greatly to the credit of the Germans that they have given such careful attention to the question of fire protection. We have shown in a previous chapter that the long stretch of staterooms, with alleyways several hundred feet in length running through them, offer dangerous facilities for the rapid spread of a fire, should it once obtain a strong hold on the inflammable material of which the stateroom partitions and furnishings are composed. On the Kaiser Wilhelm II and Cecilie the passenger accommodations on the main deck are protected against the spread of fire by four steel bulkheads, which extend from side to side of the ship. Where the alleyways intersect these bulkheads, fire-doors are provided which are closed by hand and secured by strong clamps.
The fire protection also includes both an
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Courtesy of Engineering
outside and an inside line of fire-mains. Fire-drill, with full pressure on the mains, is carried on every time the ship is in port, the outside lines of fire-mains being used. Once every three months there is a fire-drill with the inside line of mains. Every time the ship reaches her home port, both fire-drills and lifeboat drills are carried out under the close inspection of German Government officials.
Now, the provision of fire bulkheads is such an excellent protection that it should be made compulsory upon every steamship of large carrying capacity. Moreover, they should be extended throughout the full tier of decks reserved for passenger accommodation. The bulkheads need not be of heavy construction, and they can be placed in the natural line of division of the staterooms, where they will cause no inconvenience.
Special interest attaches to the Imperator of the Hamburg-American Line, just now, because she is the latest and largest of those huge ocean liners, of which the Olympic and Titanic were the forerunners. This truly enormous vessel, 900 feet long and 96 feet broad, will displace, when fully loaded, 65,000 tons, or 5,000 tons more than the Titanic. A study of her hold plan and inboard profile, shown on page 163, proves that it is possible to provide for an even larger boiler and machinery plant than that of the Titanic, without making any of that sacrifice of safety, which is so evident in the arrangement of compartments and bulkheads on the Titanic. Not only are the bulkheads throughout the machinery and boiler compartments carried to the second deck above the water-line, but the same spaces, throughout their whole length, are protected by an inner skin in the form of the longitudinal bulkheads of the side bunkers. The large forward engine-room is also protected by two longitudinal bulkheads at the sides of the ship and the after engine-room is divided by a central longitudinal bulkhead. Protection against the spread of fire is assured by several bulkheads worked across the decks which are devoted to passenger accommodation.