Page 132 - NAVAL SCIENCE 3 TEXTBOOK

SH IP CONSTH UCTIO N AND DA~IAGE CONTROL 137

The term lW!(/t"er deck includes all parts of decks that ar(' The top of a mast is called the trtlck. The pigsrick is <1 slender
exposed to the w(';Hher. Blilwarks are a sort of low, solid-steel fence vertical ex1ension above the Illast from which the ship's commis-
along the gunwale of the main deck, fitted with sCllppers, rubber sion pennant is flown. The galT extends abaft of the mainmast. It
or metal drains that allow water to run off the deck during rain or is from the gaff that the national ensign is flown when the ship is
heavy seas. under \Va)'. The small vertical pole at the bow on the forecastle and
Any deck above the main deck, fOrCCi.lstle deck, or poop deck is the slightly raked (diagonal) pole at the stern are called the jack-
called a sllpcrstnlctllre dcck. These decks ilre generally called lel'e/s. staffand the j7ngstnjrrespcctivci)'. When a Navy ship is at anchor or
The first level above the main deck is the 01 (pronounced oh-one) moored, it flies the jack on the jackstall and the national ensign on
level, the second the 02 level, and so on. These decks mily have the tlagstaA-' from 0800 hours to SUllset.
other names related to their use, such as boat deck, signal bridge, The stack of a ship supplies air to the main propulsion engines
<md llilvigating bridge. and exhausts smoke and hot gases from them. Nuclear-powered
ships do not need stacks, because their reactors requirc no air for
Superstructure combustion, so thc)1 produce no smoke or gas.
The slIperslrllctllre of a ship includes all structures above the
main deck. It will vary according to the type of ship, but 1110st war- Watertight Integrity
ships have ;:1 pilothouse, bridge, signal bridge, chart roOl11, combat
In order to pre\'ent the spread of flooding, watertight bulkheads
information center, "radio shack," and probably a sea c.lbin for the
<lre built in naval ships to divide the hull into a series of watertight
captain.
compartments. This is called watertight iniL'Srit)', meaning sound-
The superstructure is topped by the II/asl. It will be at least one
\'ertical pole fitted with a horizontal yardarm that ex1ends above ness or without leaks. The more watertight compartments a ship
has, the more secure it will be from flooding. \Vatertight integrity
the ship and carries flag halyards (ropes) and navigational and sig-
is intended to limit flooding, which (;:lJl cause a ship to list (lean) to
nallights. The mast may also be in the form of a structural tripod.
port or starboard, lose trilll (be "down" by the bow or stern), mpsize
On most ships there <llso will be electronic devices, radar anten-
(tip over), or sink.
nas, radio aerials, and meteorological instruments on the mast or
\·Vatertight doors and hatches allow access through bulkheads
the yardarm. iVlost Navy ships have only one lll<lst, but Illany mcr-
and decks, respectively. Any ship could be made almost unsinkable
chant ships and somc naval vessels have two. The one forward is
called the foremast, and the one aft of this is called the mni/ll//asl; if it were divided into enough watertight compartments, but too
the mainmast is lIsllall)r taller than the foremast, making it nor- much compartmentation would interfere with the arrangement of
milll)' the highest structure above the main dcck. mechanical equipment, ilnd C;'lSC of movement within the ship. A
strong watertight bulkhead ilt the after end of the forepeak tank

The principal parts of a typical auxiliary ship. With the exception of cargo holds and booms, all of these features are found on warships as well.