Ship size. The size of a ship usually is given in terms of
its displacement in long tons. Displacement means
the weight of the volume of water that the ship
displaces when afloat; in other words, the weight of
a ship by itself. The Navy uses standard
displacement, which is the weight of a ship when
ready for sea. All weights given in this chapter are
standard displacements, except where otherwise
noted. Cargo ships usually are measured in light
displacement (no cargo aboard) because of the wide
difference in the weights of cargo carried.
Ship armament. Armament describes the offensive
weapons a ship carriesguns, rockets, guided
missiles, and planes.
Ship armor. Armor means protective armorspecial
steel installed along the sides of the ship, on a deck,
and on some gun mounts and turrets.
Ship speed. The speed of a ship is stated in knots. A knot
is 1 nautical mile per hour (mph) or about 1 1/8
statute miles per hour. When a ship goes 20 nautical
miles an hour, its speed is said to be 20 knots (but
never 20 knots per hour). A land (or statute) mile is
5,280 feet. A nautical mile is about 6,080 feet, or
roughly 2,000 yards. A ship traveling at 20 knots is,
therefore, traveling at the rate of about 23 mph.
Ship class. Ships are said to be of a particular class. Do
not confuse this characteristic with type, which is
shown by a ships designation. The Forrestal, for
example, was the first of several aircraft carriers of
the same general advanced type and configuration
to be completed. The next three carriers completed
after the Forrestal are of the Forrestal class;
however, later CVs or CVNs (nuclear-powered
carriers) of other types are different classes (such as
the Kitty Hawk class, Nimitz class, and so forth).
Ship categories. Ships of the U.S. Navy are divided into
four categories that include combatant ships,
auxiliary ships, combatant craft, and support craft.
REVIEW 3 QUESTIONS
Q1. How is the size of a ship usually given?
Q2. What is meant by a ships armor?
Q3. What term is used to indicate the speed of a ship?
Ships of the U.S. Navy are divided into four
Depending on size and type, combatant ships may
have missions other than simply slugging it out with
a n e n e m y s h i p . C o m b a t a n t s h i p s a r e o f t wo
typeswarships and other combatants.
WARSHIPS.Most warships are built primarily
to attack an enemy with gunfire, missiles, or other
weapons. There are exceptions, however, that you will
see as we go along. The following types of ships are
included in the warship category: