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A look around
The American “fleet submarine” of the late
1930s and 1940s had two hulls. The inner pressure hull was circular,
a long tube closed at bow and stern, designed to resist water pressure,
welded rather than riveted, and divided into compartments. Between the
torpedo rooms there were two decks or levels inside of the pressure hull.
Compartments
Starting at the bow inside the pressure hull were:
- forward torpedo
room,
- space where officers and chiefs slept and officers ate and on the
deck below the forward battery of six-foot high cells,
- control room with radio room at the aft end and below the pump
room for machinery and above it the conning tower,
- the galley or kitchen, mess and recreation room, and crew sleeping
compartment and below the aft battery,
- two engine rooms each with two Diesels and generators and water distillers
in the forward one,
- maneuvering room where electrician mates controlled the flow
of electricity to power the submarine and below it four electric motors
geared to power two screws,
- the after torpedo room.
The controls for diving, keeping the submarine sealed, and many other
functions were in the control room. The conning tower above it was a
small pressure hull. In
its six-foot high space several men were on duty to steer, read and report
sonar, radar, fire control with the TDC, and use the two periscopes.
Above the conning tower was the bridge for control of the submarine
on the surface. Aft of the bridge was the opening for drawing air into
the hull for the Diesels and for crew’s breathing. Aft of the bridge
and “main air induction” was the cigarette deck that after
the first months usually included a 20mm gun; a smaller deck in front
of the bridge had another 20mm gun. On the main deck was a deck gun,
that after the early months was a 4- or-5 inch gun. Nearby was watertight
store for shells for ready access.
Outside of the pressure hull was a second hull, with
a high clipper bow, streamlined for maximum surface speed. Between these
two hulls were tanks for fuel, compressed air, drinking water, and sanitary
and other tanks. Between the hulls near the center of gravity of the
ship was the main ballast tank and near the bow and stern were trim tanks
and tanks flooded to compensate for the weight (a ton) of each torpedo
as it was fired to “keep” the
submarine “trimmed.”
At the bow and stern diving planes controlled the submarine’s
diving and rising by deflecting the sea to raise or lower the bow or
stern. The bow planes folded up against the hull when on the surface,
while the stern planes remained in place.
Diving
When surfaced, the submarine like any ship floats because it weighs less
than the water it displaces, and thus has "positive
buoyancy". In World War II often the submarine had almost no positive
buoyancy so it could dive more quickly. To dive vents were opened at
the top of ballast tanks, releasing air, to admit sea water through
openings at the bottom, making the submarine heavier until it had close
to "neutral
buoyancy"
and could be raised or lowered with the diving planes. However as
it went deeper, the hull was compressed by sea pressure and had
less buoyancy, so the diving
officer had to adjust diving planes or how much sea water was in
the ballast tanks. When the periscope was raised, that hollow tube
changed buoyancy!
To surface compressed air "blows the ballast tanks" clear
of sea water so with positive buoyancy she would rise, aided by the diving
planes.
The crew dives
To dive crew cleared the bridge, sealing the hatch to
the conning tower. The motor machinist mates shut down the Diesels. The
electrician mates in maneuvering shifted to battery power for the motors.
The main air induction was closed, forward diving planes deployed out,
and ballast tanks flooded from the sea. The diving officer in the control
room directed the crew controlling diving planes and ballast tanks, making
adjustments as needed by flooding or blowing ballast and adjusting diving
planes to keep the submarine “trimmed” at
the depth required by the skipper in the conning tower above him. There
was no room for error or for having to think what to do. Team work and
practice enabled all that to happen every time in 35 seconds
with no room for failures.
Diving
planes were controlled with large steel wheels; movement of the diving
planes was power assisted, but when running silent they were manually
controlled that required great muscular effort. Planesmen were sometimes
relieved frequently so fresh muscles took over.
"Trim dive"
Our submarines at night were usually on the surface to recharge
batteries, throw out the day’s garbage
in weighted bags, blow the sanitary tank, and woe to the officer of the
deck who let the smell be drawn into the submarine. At dawn the submarine
normally dove for a “trim
dive” so
the diving officer knew he had compensated for fuel used and other weight
shifts so he could keep the submarine level. As skippers became more
aggressive, they surfaced as soon as the diving officer "had his
trim"
to remain on the surface in daytime to search with radar, sonar, and
sight. Always they were ready to dive so as to be unseen.
Today's nuclear submarines do not normally dive and surface frequently.
They often dive after leaving port and reaching deeper seas and surface
again when necessary to transfer personnel or material onto or off of
the submarine and at the end of the patrol weeks or months later.
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