by Vepr157 » Sun Jun 04, 2023 6:45 pm
Ah "limber hole" means a hole in the free-flooding superstructure allowing it to flood and drain quickly. What you are referencing are "flood holes."
In the early 20th Century, nearly all submarines had flood valves (Kingstons) that sealed the bottom of the main ballast tanks. To dive a submarine would have to open both the vents at the top of the MBTs and the Kingstons at the bottom. During WWI the Germans realized that the Kingstons were unnecessary and omitted them, relying solely on the vents to keep water in the MBTs. Air could only leave the MBTs through the flood holes under exceptional circumstances, probably well over 45 degrees of roll and/or nearly 90 degrees in pitch, in which case the submarine was probably in dire straits for other reasons. The small amount of water remaining within the envelope of the MBTs was accounted for in the design. The vents were reliable enough to rely on them alone to hold air in the MBTs, a practice called "riding the vents." After WWI, the U.S. Navy eliminated most of the flood valves on its submarines and all current U.S. nuclear submarines have simple flood holes (albeit covered with gratings to reduce noise).
The Type II and VII had Kingstons for their amidships, internal MBT, probably for safety in the unlikely event that the vents failed. However, they were normally left open. The Type IX apparently had Kingstons on one of its amidships MBTs as well.
One additional thing to consider is that other types of tanks do require Kingstons. Fuel-ballast tanks, which can be used as MBTs after the fuel in them is used up, require Kingstons when acting as fuel tanks. Negative and safety tanks also require Kingstons. Kingstons also are occasionally used when flow-induced noise and vibration is problematic, although these days it is more common to use vortex-dissipating gratings.
Jacob
Ah "limber hole" means a hole in the free-flooding superstructure allowing it to flood and drain quickly. What you are referencing are "flood holes."
In the early 20th Century, nearly all submarines had flood valves (Kingstons) that sealed the bottom of the main ballast tanks. To dive a submarine would have to open both the vents at the top of the MBTs and the Kingstons at the bottom. During WWI the Germans realized that the Kingstons were unnecessary and omitted them, relying solely on the vents to keep water in the MBTs. Air could only leave the MBTs through the flood holes under exceptional circumstances, probably well over 45 degrees of roll and/or nearly 90 degrees in pitch, in which case the submarine was probably in dire straits for other reasons. The small amount of water remaining within the envelope of the MBTs was accounted for in the design. The vents were reliable enough to rely on them alone to hold air in the MBTs, a practice called "riding the vents." After WWI, the U.S. Navy eliminated most of the flood valves on its submarines and all current U.S. nuclear submarines have simple flood holes (albeit covered with gratings to reduce noise).
The Type II and VII had Kingstons for their amidships, internal MBT, probably for safety in the unlikely event that the vents failed. However, they were normally left open. The Type IX apparently had Kingstons on one of its amidships MBTs as well.
One additional thing to consider is that other types of tanks do require Kingstons. Fuel-ballast tanks, which can be used as MBTs after the fuel in them is used up, require Kingstons when acting as fuel tanks. Negative and safety tanks also require Kingstons. Kingstons also are occasionally used when flow-induced noise and vibration is problematic, although these days it is more common to use vortex-dissipating gratings.
Jacob