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 proportion of
the passenger-carrying vessels chiefly depend for their revenue.
[Illustration: Courtesy of _Scientific American_
Longitudinal bulkheads form 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]
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 and
the _Mauretania_ 26 knots for the whole run across the Atlantic.
[Illustration: THE ROTOR, OR ROTATING ELEMENT, OF ONE OF THE
LOW-PRESSURE TURBINES OF THE IMPERATOR. DIAMETER OVER TIPS OF BLADES IS
18 FEET]
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 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_.
[Illustration: In addition to transverse and longitudinal bulkheads,
this ship has fire bulkheads in the passenger spaces.
THE 26,000-TON, 23½-KNOT KRONPRINZESSIN CECILIE, A THOROUGHLY PROTECTED
SHIP]
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 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.
[Illustration: 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]
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.
[Illustration: Courtesy of _Engineering_
SECTION THROUGH ENGINE-ROOM OF THE KAISER WILHELM II, SHOWING INNER
BOTTOM CARRIED UP SIDES OF SHIP, TO FORM DOUBLE SKIN]
The fire protection also includes both an 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.