| The Type VIIC Untersee Boot
Lately, I've developed a healthy obsession for U-Boats, but I don't know why; maybe it's because I just got done watching Das Boot again. Anybody else interested in them? Some fascinating things I've learned quite recently about U-boats that had never occured to me before:
1. The streamlined, rakish outside of the U-boat that you usually see in pictures & movies is just an outer shell of sheetmetal; the heart of the U-boat is inside of the "hull", and is actually a cylindrical tube with all of the important stuff inside. The streamlined skin of the U-boat is attached to the center pressure hull by bracing; only about half of the volume of a U-boats hull is pressurized, the rest is open to the ocean water.
2. The fuel oil (typically diesel) is carried by the saddle tanks on the outside of the pressure hull, and are open on the bottom to the sea water. Since fuel oil is lighter than water (but not by not much), it stays in the top of the saddle tanks; it is actually "floating" on top of the seawater. As the U-boat uses the fuel oil by drawing it from the top of the saddle tanks, it is replaced by seawater, thereby maintaining the U-boats bouyancy.
3. All U-boats carried an anchor, just like a surface vehicle, though they were rarely used, since they usually tied up to a pier or a submarine pen.
4. The "heart" of the U-boat, the control room, doubled as an escape chamber if the U-boat sank; seawater was let into the control room up to the level of the conning tower, and pressurized air was released into the conning tower to equalize the pressure of the outside water. In this way, the hatch could be opened; otherwise, the pressure of the seawater would prevent the hatch from being opened. After the hatch was opened and the conning tower was submerged, the seamen were to swim out out of the conning tower hatch and up to the surface one by one.
5. The keel of a Type VII U-boat was composed mostly of iron bars to act as ballast, therby keeping the U-boat upright in even the most violent sea states.
6. Extra torpedoes were stored in the interstitial spaces between the pressure hull and the horizontal decking of the U-boat on the Type IX; however, tranferring the torpedoes from the outside of the pressure hull to the inside was a time-consuming task, and left the U-boat vulnerable for several hours on the surface. The Type VII carried all of her torpedoes on the inside of the pressure hull, with the extras stored "below deck" in the torpedo rooms. The U-boatmen billeted in the forward torpedo room actually looked forward to "action", as it meant there would be more elbow room in the forward torpedo room where most of them lived.
7. The main air inlet for the two on-board diesels was actually right underneath the "Wintergarten", the extra platform to the rear of the conning tower that usually carried the AA defenses (on later models of the U-boats; earlier models, pre-'42, had no AA armament). A large (approx. 40cm) duct brought fresh air from underneath the Wintergarten to the engine room for the diesels; this had to be opened before the diesels were started, or they would soon suck up all of the air inside of the U-boat and rupture seamen's eardrums.
If anybody else has any other interesting facts concerning U-boats, or simply wants to learn more about these interesting vessels, please contribute to this thread. I will do my best to post more interesting tidbits as I learn more about U-boats and, in particular, the Type VIIC.
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