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Ships are complex systems, the detailed
description of which is beyond the scope of this Encyclopedia.
Furthermore, even ships of the same class tended to show
small
variations, and most ships were extensively modified as the war
progressed. In particular, both the Allies and the
Japanese
tended to add more antiaircraft
protection to a ship every time it was
refitted. Ship specifications given in this Encyclopedia are therefore
nominal values at
the
time ships of the class were first committed to the Pacific.
Warships of the Second World War benefited from a
number of improvements in engineering from the First World War. One was
improved metallurgy. High-strength steels gave the same strength
as older steels with less weight. Superior alloys for turbine blades
made it possible to run ships'
machinery at higher temperatures and pressures, yielding more power
with greater efficiency. Armor was
also superior in quality.
Another area of improvement was in hull forms. All
the major naval powers did extensive testing of hulls in model basins.
Curiously, American tests
demonstrated such advantages to twin-skeg hulls that they were used in
almost all major U.S. warships built during the war, including all
post-treaty battleships, while
British and Japanese model basin tests incorrectly
predicted that twin skegs would be counterproductive.
Welding began to replace riveting in ship
construction between the wars. Rivets required overlapping plates, and
a riveted joint did not have the strength of the solid plate. Welds
eliminated the need for overlapping plates, thereby reducing weight,
and a properly welded joint was as strong as the original metal. This
was particularly important in underwater protection systems. On the
other hand, welding was a relatively new technology and properly welded
joints were still difficult to achieve. Riveted joints had the
advantage that they tended to halt the propagation of cracks.
Finally, tremendous advances were made in naval
electronics, particularly radar,
which transformed naval warfare.
Displacement.
The
usual measure of the overall size of a warship was its standard
displacement, which was the total weight of the ship, measured in long
tons, when loaded for combat. For merchant vessels, the usual
measure was either the gross register tonnage (G.R.T.) or the
deadweight
tonnage. G.R.T. was the total volume of the ship in units of
100
cubic feet (2.83 cubic meters). Deadweight tonnage was the maximum
weight, in long tons, of
crew, passengers, and cargo that the ship could safely carry. In some
cases merchant ships are described by light
and fully loaded displacement; the deadweight tonnage would be slightly
less than the the difference between these two displacements.
Dimensions.
These are give as the overall length, beam (width), and draft
(maximum depth of the keel). For operational purposes, draft
was
most important, as it determined how closely a warship could approach
shore, and deep-draft vessels could not enter the shallowest harbors.
Beam theoretically could have limited passage through the Panama
Canal, but for this very reason all U.S. warships
launched before and
during the war were designed to fit through the Canal. The
ratio
of length to beam was one of the factors determining maximum speed (the
greater the ratio, the faster the ship, up to a value of about 10), but
speed is listed separately.
Maximum
speed.
This is the maximum speed the ship could sustain for any
length
of time.
Complement. This is the nominal size of the ship's crew. This number tended to go up as the war progressed.
Aircraft. This gives the length of the flight deck, the number of elevators and catapults, and the maximum number of aircraft a carrier could reasonably operate. Most carriers could carry more aircraft, but could not make effective use of them. For other classes of ships, this specification gives the number of seaplanes and seaplane catapults, if any.
Armament. This is the typical armament of the class at the time that members of the class were first committed to combat in the Pacific. Most ships upgraded their antiaircraft armament once or more during the war. Main armament was rarely upgraded without reclassification of the ship.
Protection.
Describes the armor protection of
the ship. In
general,
only a portion of an armored warship (called the citadel) was
protected. The citadel typically consisted of belts of armor
on
the sides of the ship, enclosed on top by one or more armored decks,
plus armor protection for the main gun turrets and the conning tower.
The bulkheads at the ends of the side armor belts were usually also
armored.
Not listed is the
general toughness of the ship, which is difficult to quantify. American
warships often used
Special Treatment Steel (STS) for internal structural members and
bulkheads,
which was
resistant to splinters. The British and Japanese likewise used Type D
Steel. Other
navies probably did something
similar. Toughness also depended on sound design, and it
was
not strongly correlated with the quality of the armor system.
Some unarmored destroyers were quite tough for their size,
while
the heavily armored Yamatos
appear to have had significant structural weakness, if the difficulty
of satisfactorily repairing torpedo
damage is any indication.
Machinery.
Gives the number of
shafts and boilers and the total shaft horsepower, which have some
bearing on the ability of the ship to survive flooding.
Bunkerage. This specifies the amount and type of fuel carried by the ship. It is important in determining refueling requirements. The amount of aviation gasoline carried by aircraft carriers and (when known) seaplane-carrying vessels is also listed.
Range.
This is given as the maximum distance that the fully
fueled ship could travel at its designed cruising speed before
refueling. Some
sources quote lesser ranges and higher speeds, indicating that the ship
rarely operated at its designed cruising speed. This was
particularly the case for lighter escort vessels (cruisers and
destroyers.)
Most warships consumed fuel prodigiously at maximum speed. Merchantmen, on the other hand, were designed to cruise at close to their maximum speed, there being no good reason to build excess speed capacity into a commercial vessel. The rule of thumb was that the power required to cruise at a particular speed was proportional to the cube of the speed. Thus, a ship running at 32 knots required ten times the power (and presumably ten times the fuel consumption) of a ship running at 15 knots, reducing its range by a factor of nearly 5.
The actual fuel consumption curve for a particular class departed slightly from the cube law. Wartime figures compiled for the Bagley class showed that these ships burned 1.8 times the fuel at 20 knots as at 15, 3.9 times as much as 25 knots, and 8.4 times as much at 30 knots. Thus the actual performance was slightly steeper than the cube law, with slightly better performance at moderate speeds and slightly worse performance at the highest speeds. Even so, the cube law was a fairly good rule of thumb.
The figures given are nominal. There was a marked
tendency for ships to consume fuel more quickly under wartime operating
conditions than experience in peacetime exercises suggested. This may
have been due to reduced opportunities for maintenance of engines and
for scraping the hull.
Sensors. This specifies the radars and sonars typically available to units of the class when committed to the Pacific. Like antiaircraft armament, these were upgraded frequently during the war.
Modifications. Most ships were modified during the war, typically to increase their light antiaircraft armament and to add or upgrade radar. This sometimes varied greatly from ship to ship within a class, so modifications may be described only in general terms.
Units in the Pacific. This table gives the names and fates of ships that saw service in the Pacific War. Starting locations are given for those ships already in the Pacific when war broke out. Ships completed at shipyards within the Pacific Theater are so indicated along with the yard.
For ships arriving from outside the Pacific Theater, arrival dates are given. Unless otherwise specified, the arrival date is the approximate date the ship transited the Panama Canal if it was an American ship or the approximate date the ship reached Durban if it was a British ship.
Production
Schedule. For certain
kinds of mass-produced ships, particularly Japanese standard vessels
and escorts, individual completion dates are not available, but
production rates are known or can be estimated.
The U.S. Navy classified most ships using a two- to four-letter
prefix.
References
The Pacific War Online Encyclopedia © 2007-2010 by
Kent G.
Budge. Index
