Gato/Balao class submarines had a typical concentric inner and outer hull arrangement. The outer hull was mostly thin (3/16") steel tanks surrounding the inner 7/8" HTS (high-tensil steel) pressure hull. From bow to stern there were usually about 14 tanks constructed mostly in pairs, port and starboard. These tanks contained seawater (ballast), fuel (fuel and fuel/ballast), and fresh water. Special tanks included the 'safety tank' (an extra-thick, depth-rated ballast tank) and the 'negative' tank (empty on the surface, this tank could be flooded rapidly through a large bottom valve to shorten diving time by precious seconds).
The inner pressure hull consisted of eight roughly cylindrical water-tight compartments called rooms plus a conning tower compartment attached above the control room. Each room was filled with a maze of pipes, conduits and operating equipment necessary for control, life and combat operations aboard a fighting vessel. Pipes ducts and conduits lining the hull carried ventilation, operating air, hydraulics, water, fuel and electricity between rooms. Crew must learn the location and operation of all valves, gauges, cranks, levers, knobs and switches to the point of finding them in total darkness in order to 'qualify in submarines' and earn the coveted Dolphins chest device. Space for crew was the minimum neeeded to move about, sleep, eat and study.
A sheet metal superstructure above the hulls streamlined sea water flow around the machinery for venting the ballast tanks, handling lines and anchors and exhausting engine gases. On top was a deck comprised of teak two-by-fours. A streamlined fairing or 'sail' surrounded the conning tower and enclosed the bridge, which was manned for surface maneuvering. At sea there were at least three persons -- Officer of the Deck (OOD) and two lookouts -- on the bridge. It was shielded by a 1/4-spherical plexiglass canopy. Operating equipment included a gyro-compass repeater, targeting binoculars and and communications gear (see below). Steering commands were given by shouting down the hatch to the helmsman in the forward end of the conning tower. Anyone wanting a breath of fresh air could visit the bridge if permission was obtained from the OOD.
Deck access from the inner hull was through five hatches, one each in the overhead (ceiling) of rooms except for the Maneuvering and Forward Engine rooms. Access to the Control Room was via the Conning Tower bridge hatch. While at sea, no one was allowed on deck except during recovery of fired practice torpedoes.
Movement between rooms is on decks of uniform height throughout and accessed through water-tight doors. Passageways were only slightly wider than a man's shoulders and lined with piping, valves, levers and gauges all carefully placed to bruise elbows. All decks were asphalt tile paved except for the engine rooms, which had steel mesh. The small but nearly 1/4-ton doors were fully depth-rated, had a tiny round window at eye-level known as a 'dead-light,' and had a series of latches called 'dogs' around their oval perimeters operated by a central spinning handle. Doors could be latched either open or shut. When the boat is 'rigged for sea,' doors (except for both Control Room doors) are shut and latched but not dogged. Dogging is only done if a room floods or requires pressure to prevent flooding through a leak.
Three communications systems provided information routing amongst the rooms: Sound-powered phones, the most basic and reliable, were used during battles for keeping sound to a minimum. Standard naval intercommunication (IC) phones were commonly used for non-operational conferences. Master communication of operational commands were divided into two paging systems, the 1MC (whole boat) and 7MC (bridge, conning tower, control and sonar shack). The 7mc was used when operational commands of a non-battle nature so sleeping off-watch crew and officers would not be disturbed. Sound-powered phone technology closely resembled that of Bell's first phones, consisting of diaphrams and coils and requiring no external power source. They maintain communications even if the boat's electrical system is interrupted during attack or accidental failure. The call telephone system consisted of boxes with a standard handset, a room selector switch and hand crank or 'growler' to get the destination's attention. Anyone picking up a handset could enter the conversation, however, for conference calls. This system required ship's DC power to operate.
The boat's batteries primarily provided the power to drive the boat's screws (propellers) via the large electric motors. The 250-volt direct current (DC) power also drove motor-generators to provide alternating current (60 cycle AC) for operating electronics and fluorescent lighting. There was also a 400-cycle AC power system to power attack equipment consisting of the torpedo data computer (TDC), compasses and repeaters which used battle-reliable shock resistant electomagnetic 'syncro-servo' devices.
Buoyancy is the property, discovered by Archimedes entering his bath, that equates weight to displacement. On the surface, submarine ballast tanks surrounding the pressure hull contain air. This makes the boat displace more weight in water than all the metal, air, food and men in the boat weigh, creating positive buoyancy; the boat floats. Open at the bottom through 'flood' valves or ports, the ballast tanks have vents at the top to release the air. When the vents are opened on the command "DIVE! DIVE!," sea water rushes into the floods forcing air out the vents. Now the boat displaces less sea water than it weighs, and sinks. When the tanks are fully submerged, the vents are all shut. To surface, air is routed into the tanks from high-pressure (3,000PSI) air tank banks through reducing valves to a 600PSI distribution system to blow the ballast water back out through the floods. The boat again displaces more water weight than itself, and rises. To remain on the surface, a low-pressure (10PSI), high-volume blower operates for several minutes to completely drain the main and fuel/ballast tanks. Additional tanks forward, central and aft, port and starboard, are used to trim the boat horizontally while submerged. Close accounting is kept of the volume of water (in pounds) distributed amongst these trim tanks to prevent the boat from seeking attitudes that would interfere with inter-room crew movement, torpedo inventory changes (such as firing), and fuel usage, as well as compensating for variations in seawater density. (TRIVIA: New diving officers were subject to 'trim parties,' a sort of 'civil disobedience' in which a dozen or so crew would alternately relocate betweeb the crew's mess and the Aft Torpedo room every 10 or 15 minutes, thereby upsetting the boat's trim, requiring the Diving Officer to order pumping too frequently. How many times would it take before he realized what was going on?)
The forwardmost room was the forward torpedo room. The longest room in the boat, Cubera's forward room contained six 21" torpedo tubes, up to 6 torpedoes in the tubes with 10 reloads in skids (intermingled with racks for crew sleeping). The room also held the operating gear for the bow diving planes and the forward mooring capstan and anchor chain winch. The pit log (measures water velocity) was located aft on the starboard side. In the middle of the room, in the overhead (ceiling) was the boat's only underwater escape 'trunk,' a sort of air-lock allowing ingress/egress while submerged. Just aft of that was a torpedo loading hatch. The boat's sonar equipment was in a 'shack' aft on the port side. Just forward of the shack were the torpedo alcohol tanks.
Torpedoes were of two types: MK-14 alcohol-burning steam powered with 600 pound warheads, or the shorter MK-37 electric ones. The first of five deck-access hatches was in the top of the escape trunk. The access ladder was secured with quick-release pins, and could be removed and rapidly re-installed. The Cubera officer's 'head' was located in the room's aft starboard corner, between the bulkhead and the pit log equipment.
Attack submarine batteries were divided into two banks of 252 cells each. Electrically, each battery could be separated into two groups of 126 cells each. The battery cells were about 18" x 14" and four feet tall, weighed 1,000 lb, and contained in spaces below the decks in the forward and aft battery rooms. The forward battery room above decks comprised the chief petty officers' and commissioned officers' sleeping quarters. It also held a gyrocompass repeater and the ship's office staffed by one yoeman. 'Officers country' also included a wardroom which doubled as an attack plotting center during battles, and a pantry for warming and serving meals, coffee and tea. Across the passageway, the officers enjoyed their own shower.
Primary control of the boat's bow and stern diving planes, air and electrical systems, and ballast tank flooding/venting were disbursed amongst complex vertical control panels in the control room. Below the control room deck was the Pump Room (not really a room, just the bilge area below the walking deck) which held the forward battery air conditioning, hydraulic, and trim system plants as well as the low-pressure ballast tank blower. The control room was primarily the diving control center. Large wheels were used to control hydraulic motors linked to the diving plane operating gear. Valve manifolds allowed crew to blow and pump from any tank to any other. Some like the ballast tank vents, could be operated hydraulically from the control room or manually at the valve operating gear in the adjacent room. For silent running, the hydraulic motors could be switched off and operated (with strenuous difficulty!) quietly by hand cranking the wheels. Ships communications radios and encryption gear occupied the port rear corner, known as the 'radio shack.' The main gyrocompass, located under a table in the center of the control room, provided signals for navigation/steering, radar/sonar reference and target attack plotting.
Not really a room (has no doors), the Conning Tower is a 9-foot diameter 14-foot long barrel welded onto the overhead (roof) of the Control Room. This is where attack observations are made through the periscopes, targets are tracked and torpedo gyro angles are set by the TDC. The ship's radar console was here, as well as the LORAN radio navigation aid and charting table. The main steering station is at its forward end, where course and speed commands are given by shouts from the Officer of the Deck (OOD) down to the helmsman. The helmsman steers via a large wheel controlling the rudder and monitors the boat's course on a gyrocompass repeater. Next to him is the engine-order telegraph, an electromechanical device linked to another one in the Maneuvering Room--more on that further on. When diving, the OOD orders lookouts and bridge visitors below, and shouts down the "DIVE, DIVE!" command via the 1MC system. He also sounds the klaxon horn dive alarm (ah-OOO-gah, ah-OOO-gah!). The starboard lookout slides down the ladder from the bridge, turns about 120 degrees and slides down the ladder to the Control Room to take up his position at the bow planes. He is closely followed by the port lookout who becomes the stern planesman, and the OOD. On his way through the Conning Tower, the OOD shuts the bridge hatch by hanging on a lanyard that pulls it shut, and the quartermaster of the watch dogs it down tight. The OOD descends to the Control Room to become the Diving Officer. When the engines are shut down, usually one junior engineman comes forward to man the trim manifold. He also operates the air manifold when required, to blow tanks for surfacing, before returning to the engine room for surface operations.
The majority of the crew sleeps here when off-watch, in about 30 berths. The berths are of two types. Most common are the 'hammock-style' prevalent in the Navy, consisting of a pipe frame with a heavy canvas web laced within it. About a dozen aluminum-boxed versions lined the outboard reaches. Both types of 'racks' supported thick matresses covered with fire and moisture-resistant vinyl zip covers. Fully loaded with provisions and torpedoes, the sleeping spaces frequently left less room for individual berths than there were crew, necessitating the practice of 'hot-racking,' in which the off-coming watch retired to a newly-vacated berth shared with another crewmember. The forward half of the room, separated from the berthing space by a simple noise-blocking door, comprises the crews mess and galley. The mess area had four tables, each seating six crew to feed 24 men at once. The galley was all-electric, of course, having a four-burner cook top and two ovens of different sizes. A pass-through window and shelf allowed the cook to supply the mess area with servings without leaving the galley. A militarized civilian-band radio above the pass-through provided music and news when in range of shore stations. A large coffee urn installed near the galley was in constant use. On the starboard side of the mess area against the hull outboard of the passageway was the scullery. It stored dishes and cutlery and was fitted with a double sink and drying rack. A garbage disposal unit (GDU) resembling a small torpedo tube mounted nearly vertical provided a means of ejecting garbage in special net bags. Bags were weighted to ensure they sank. There was also a 16mm film projector and screen for after-dinner theater entertainment. Aft of the scullery, on the starboard side was the After Battery deck hatch, accessed by a permanently-mounted ladder. A small passageway on the port side of the berthing area known as 'Hogan's Alley' held the corpsman's medical locker and was the ship's 'doctor's office.' (TRIVIA: Being assigned a berth in Hogan's Alley was somewhat of a prestige, as it removed the sleeper from fore-and-aft travel disturbances.) The aft four feet or so of the room was the 'latrine,' with two small sinks, to (mostly unused) shower stalls and across the hall, two 'head' closets.
U.S submarines, unlike the well-known German U-boats, were fleet boats. That is, they were at each generation, designed to be able to travel along with surface fleet elements (destroyers, cruisers, battleships and even carriers) to accomplish coordinated battle plans. That is why they had four diesels in two engine rooms. The engine rooms primarily each held a pair of 1,600 BHP (1,200 KW) diesel generator sets and their required air-jacking, fuel and lubrication oil purification and storage systems. Cubera's engines were General Motors model 16-278A V16-cylinder units specially designed for marine applications. U.S. fleet submarines are driven by huge DC electric motors whose armatures are actually wound on the screw shafts. They are powered by direct connection to the batteries, which can be switched through the control cubicles in the maneuvering room so that they are wired either in series or parallel to suit operating needs. The generators are only wired to charge the batteries. Each of Cubera's Engine Rooms also held a 60 cycle AC and 400 cycle ac motor-generator. The Forward room had a freshwater still and also held the airconditioning plant for the after battery and the air compressor to recharge the 3,000PSI ballast tank blow air banks.
The control cubicles to switch drive and charging power for the main motors straddled the passageway through Maneuvering. Below deck were the main motors, wound right on the drive shafts as mentioned. These motors were connected through operation of switching levers, ballast resistors and rheostats to adjust the boat's speed. All drive power was controlled at the Maneuvering cubicles. While surfaced, battery charging was also controlled here, and could be done while 'steaming' once two or more engines are running, either on the surface or submerged and snorkeling. There were also control panels to operate and synchronize the AC motor-generators. A small lathe was kept on the port side in case of the need to machine the odd replacement part or make a critical spring.
A smaller version of the Forward Torpedo Room, the After Room held four 21" torpedo tubes and up to fifteen crew berths and lockers, nestled amongst torpedoes as in the Forward Room. The After Room also had a third water closet and lavatory for the crew. Here too were the stern diving planes and steering operating gear.