Main Ballast tanks

The main ballast tanks are used to surface and submerge the boat. There are several controls for the main ballast tanks. At the forward and aft center of the control room are two large red hand-wheels. These are used to control the vents for the main ballast tanks, which when open, will flood the respective ballast tank, forward or aft. On the center starboard side of the control room is a single large red hand-wheel with five gauges above it. The central gauge shows the compressed air supply, while lower two show the amount of water in each of the trim tanks. The upper two are pressure gauges, a reading of 1 indicates that the ballast tank will be fully blown if the boat is brought to the surface. The hand-wheel is used to blow the tanks, and the main ballast tanks can be blown even with the vents open, however this is not recommended, as it is both slower, and requires a larger amount of compressed air, as the air will continuously be escaping the tanks. As with the negative tanks, the amount of compressed air required to blow the tanks increases with depth. Because of this it is recommended to use the dive planes to get to a shallow depth before blowing the tanks. Alternatively the tanks can be blown only partially. As the depth decreases, so does the pressure, and the air in the tanks will expand, gradually displacing more and more water as the boat ascends. The tanks need only be blown to the 45m2 mark to reach depth awash (7.5m) at which point the bridge can be maned and the diesels and compressor can be started. Decks awash does however not offer many advantages in game, and was not used much, if at all historically due to instability.