Technology and Operations  
This forum is for discussing technological & operational matters pertaining to U-boats. 

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1 year ago
SnakeDoc
Hi, The only visual indicator of the German passive sonar (GHG) was the sound bearing indication dial. The operator trained the handle (adjusting time-phase array) to get the loudest sound. Simultanously, the bearing pointer at the dial is rotated respectively, so the bearing for loudest sound can be read off. Active sonar devices were fitted with so called "Kino-Anlage" developed
Forum: Technology and Operations
1 year ago
SnakeDoc
Hi, check this site: -- Regards Maciek
Forum: General Discussions
1 year ago
SnakeDoc
Hi, you are talking about Tauchretter manufactured by Dräger company. It was primarily used for escaping from the sunken U-Boat. It was a kind of rebreather, consisting of the oxygen flask, cartridge with the CO2 absorber, inflatable vest, the mouthpiece, goggles and nose clamp. It did not purify external air, but (in closed circuit) removed the CO2 from the exhausted air and enriched it w
Forum: Technology and Operations
1 year ago
SnakeDoc
Hi, I will be using term "hydrophones" for passive listening equipment and "sonar" for active listening equipment. Generally, during the war, Germans U-Boats were fitted with hydrophones, so called GHG (Gruppenhorchgerät). It consisted of set of sound receivers, fixed to the bottom part of the U-Boat bow. The signals from the receivers were transmitted to the set of del
Forum: Technology and Operations
1 year ago
SnakeDoc
Hi, Radar - FuMO Sonar - S-Gerät I don't know what other general terms you mean? Try this list: -- Regards Maciek
Forum: Technology and Operations
1 year ago
SnakeDoc
Hi, there were: two men at the diving station, operating fwd and aft diving planes (when submerged, when surfaced, these two men were at the bridge as a watch); ~ four men for operating: main drain pump, trim pump, the ballast tanks vent valves and negative buoyancy flood and vent valves, as well as operating the blowing manifold; sometimes the helmsman took his secondary station in the con
Forum: General Discussions
1 year ago
SnakeDoc
Hi, generally, Germans used the abbreviation "sm/Std" (Seemeile per Stunde) or even "sm". This unit was equal to one knot. However they did not order the speed of the U-Boat in terms of speed units, but in terms of engine telegraph orders (Grosse Fahrt Voraus, Kleine Fahrt Voraus and so on). Each order corresponded to the specific propellers rotation speed and thus to the s
Forum: Technology and Operations
1 year ago
SnakeDoc
Hi, I was not able to find a good photo of the torpedo hatch, but on this drawing: you can see the location of the hatch, as well as the torpedo in the loading position. Some interesting information you will also find here: These drawings show torpedo loading: -- Regards Maciek
Forum: Technology and Operations
1 year ago
SnakeDoc
Hi, Germans used two intercom systems: - a voice-powered telephone, whit a phone in each compartment; - a general announcement system, with speakers in each compartment. Some speakers (in conning tower, control room, forward and aft torpedo rooms) had terminals for connecting head-set with a additional speaker, for two-way communication. More information you can find here: paragraph: &q
Forum: Technology and Operations
1 year ago
SnakeDoc
Hi, it is an interesting question and the answer is not obvious. Before I try to answer, I will present some background. HMS Seal was captured in May 1940, with 6 Mark VIII wet-heater torpedoes, fitted with Type 3 contact pistol. It was the time just after Operation Weserübung, when the torpedo crisis totally revealed. The torpedo crisis was caused by three factors: 1. poor depth-keeping
Forum: Technology and Operations
1 year ago
SnakeDoc
Hi, it depends, what you mean as a maximum depth. Let's say it is 250 m. Assuming that U-Boat is going down only dynamically (i.e. when the boat has neutral buoyancy), the maximum trim is limited by batteries: they can be heeled up to 35° without spilling the acid. The maximum underwater speed is about 8 knots. It gives about 109 seconds that is almost 2 minutes. Practically it will
Forum: Technology and Operations
1 year ago
SnakeDoc
If you have any problem with translation, I can try to help. -- Regards Maciek
Forum: Modeling and schematics
1 year ago
SnakeDoc
Hi, try this: -- Regards Maciek
Forum: Modeling and schematics
1 year ago
SnakeDoc
Hi, well, generally, on the radio/sonar watch were always two people (even if the boat was not equipped with radar). The sound and radio equipment was operated by the same people (if boat surfaced/submerged, they simply changed their stations). The most common radars were: FuMO 29, FuMO 30 and FuMO 61. The FuMO 29/FuMO 30 set was located in the control room, so when surfaced, in th
Forum: Technology and Operations
1 year ago
SnakeDoc
Hi, type VII definitely. Which one? Hard to say, maybe U 98 or U 576. -- Regards Maciek
Forum: General Discussions
1 year ago
SnakeDoc
Hi, as far as I know, the raising of the U 864 was abandoned, and the wreckage site is going to be covered. Generally, the latest information can be found on the site of The Norwegian Coastal Administration: You can go there, and at the Norwegian or English version of the site, use the search engine to find phrase "U-846". Or you can try this link: -- Regards Macie
Forum: General Discussions
1 year ago
SnakeDoc
Hi, in the interrogation report by term "upper deck torpedo tubes" they meant "upper deck torpedo containers". In the later years of war, the usage of the upper deck containers was abandoned, because (due to allied air supremacy) there was no opportunity to transfer the torpedoes from the upper deck into the hull. Torpedoes in deck containers were also un-serviceable,
Forum: General Discussions
1 year ago
SnakeDoc
Hi, U 2540 was scuttled in the Flensburg Förde, near the lightship (i.e. near the position 54°50'18''N, 9°53'55'') at depth ~25-30 m. The boat was raised by means of two floating cranes: Ausdauer and Energie (2500 t capacity each). The lifted boat was moved to the Eckernförde Bay and put aground, where divers could work safely inside the hull. After drying th
Forum: Technology and Operations
1 year ago
SnakeDoc
Hi, more documents related to fuel oil you can see here: (series X - miscellaneous targets) -- Regards Maciek
Forum: General Discussions
1 year ago
SnakeDoc
Hi, well, diesel fuel is diesel fuel as you said, however some properties were important, i.e. specific gravity. Please check this report: the chapter "7. OIL SUPPLY IN THE FAR EAST" regarding the problems with fuel oil on the Far East. -- Regards Maciek
Forum: General Discussions
2 years ago
SnakeDoc
Hi, check this interrogation report: -- Regards Maciek
Forum: General Discussions
2 years ago
SnakeDoc
For German solutions, try here: Here you can find many information, how it was done in US Navy: -- Regards Maciek
Forum: Technology and Operations
2 years ago
SnakeDoc
Hi, it's an interesting question. Everybody know that 1st Flotilla was located in the former L'Ecole Navale (over the U-Boat bunker): Both buildings exist till today. While reading "Die Festung", I was wondering about location of the 9th Flotilla too. In the novel is a description of the route from the 9th Flotilla headquarter to U-Boat bunker and some other detai
Forum: General Discussions
2 years ago
SnakeDoc
Hi, here additional information about "Aruba" torpedo: In fact, the discussed torpedo beached on the Curacao. -- Regards Maciek
Forum: General Discussions
2 years ago
SnakeDoc
>> For example, let's say, that U-Boat is bow heavy (Vorlastig), with 6 degrees (the air-bubble is above null marking). I must correct myself - of course in the inclinometer there is no air-bubble (as the indicating medium), but water column level. So the above sentence should be as follows: >> For example, let's say, that U-Boat is bow heavy (Vorlastig), with 6 degree
Forum: General Discussions
2 years ago
SnakeDoc
Hi, Onkel Wrote: ------------------------------------------------------- > One thing has us stumped: after our visit to U-995, we are trying to understand what > the markings are on the Pappenburg gauge, and why there are two of these gauges. Is one for the each > scope? What do the marks mean? thanks! First thing: there are two instruments visible on the photos: 1. Papenberg
Forum: General Discussions
2 years ago
SnakeDoc
I forgot about one small issue. The diesel engine while working, needs cooling and lubricating. When engine is running, the cooling water and lubricating oil is forced to circulate by means of the pumps attached to engine and driven from the crankshaft. Of course, there is a problem, when the engine is stopped, and we want it to start up. First, the lubricating oil has to be forced between
Forum: General Discussions
2 years ago
SnakeDoc
Hi, well, German Diesels were started by means of the compressed air. There was a dedicated installation (see here: which admitted the compressed air through the valve in the cylinder head to each cylinder in proper sequence. As a result, the crankshaft started turning, and finally, the fuel was admitted and ignition occurred. In general this system was similar to the one used on US
Forum: General Discussions
2 years ago
SnakeDoc
Well, it looks like the Cameronia was damaged by torpedo dropped by Ju-88. It means, that the torpedo was F5b or (less likely) F5w type. It would be good to know the original label (it is unlikely, that on German torpedo was a "detonator ring" label). I have reviewed the documentation of both German aircraft torpedoes, and did not found anything similar to the part from the photo.
Forum: General Discussions
2 years ago
SnakeDoc
Great, thanks. Could you tell, where the label 'Detonator ring' is located? How exactly looks the label (in German)? -- Regards Maciek
Forum: General Discussions
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