-
Figure 2-12.--Bottom structure.
rigidly fasten together the peak frames, the stem, and
the outside plating. Breast hooks are made of heavy
plate and are basically triangular in shape.
Deep transverse framing and transverse bulkheads
complete the stem assembly. The stem itself is
fabricated from castings, forgings, and heavy plate, or
in the case of smaller ships, heavy, precut structural
steel plate.
STERN STRUCTURE
The after-most section of the ship's structure is the
stem post, which is rigidly secured to the keel, shell
plating, and decks. On single-screw ships, the stem post
is constructed to accommodate the propeller shaft and
Figure 2-13.--Deep floor assembly for machinery foundations.
rudder stock bosses. The stem post as such is difficult
to define, since it has been replaced by an equivalent
shape. The external shape is shown in figure 2-14 and
structure of deep framing. This structure (fig. 2-15)
is commonly used on combatant ships. This form is
consists of both longitudinal and transverse framing that
essentially bulbous at the forefoot, tapering to a sharp
extends throughout the width of the bottom in the
entrance near the waterline and again widening above
vicinity of the stem. To withstand the static and
the waterline. Internally, the stem assembly has a heavy
dynamic loads imposed by the rudders, the stem
centerline member that is called the stem post. The stem
structure is strengthened in the vicinity of the rudder
post is recessed along its after edge to receive the shell
post by a structure known as the rudder bearing
plating, so that the outside presents a smooth surface to
housing.
cut through the water. The keel structure is securely
fastened to the lower end of the stem by welding. The
PLATING
stem maintains the continuity of the keel strength up to
the main deck. The decks support the stem at various
The outer bottom and side plating forms a strong,
intermediate points along the stem structure between the
watertight shell. Shell plating consists of approximately
keel and the decks.
rectangular steel plates arranged longitudinally in rows
or courses called strakes. The strakes are lettered,
At various levels and at regular intervals along the
beginning with the A strake, which is just outboard of
stem structure between the keel and the decks are
the keel, and working up to the uppermost side strake.
horizontal members called breast hooks. Breast hooks
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