Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Simon.
I believe this is OK. However the waterlevel when surfaced and dieselengines running would be as indicated on the drawings below.
Tore

[tore]

Simon.
I should perhaps mention you have a variation in the waterlevel between stopped and running diesels. The supplyline ends almost half way in the tank ( red) preventing the tank to be emptied at stopped engines. The overflow ( blue) ends almost at the top allowing a certain amount of "play" in the watertank volume, but always ensure a positive head surfaced and submerged.
Tore

[SnakeDoc]

Tore,


I have got picture of the aft side of the attack periscope well. Could you tell me, what are these four pipes with sight glasses?
The three pipes between them with outlets in one funnel look like drains of the air intake, exhaust and diesel engine intake trunk head valves.





http://www.kubische-panoramen.de/index.php?id_id=5378&p=i


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Thanks, regards

Maciek

[tore]

Maciek.
I am not 100% sure, but guess they are all drains from what you assume. Two drains from each of the two ventilation air inlet shaft, at least one from the main dieselair inletvalve,and I assume ( can`t remember) some from the schnorchel system. I shall study the matter a bit further and hopefully be able to give you further details. Unfortunately I am in a remote area for the summer and have only limited access to a very slow broadband so it takes time. 
Tore

[tore]

Maciek
I assume your question can be split in two answers. The pipes ending in a funnel are drains from the air ventilation inlet valves and main diesel inletvalve, see sketch below. The drain via sigthglasses ends in the bilge through a muffler and is checkdrain from the regulating and RFO tank 1 port and stb. and possibly also the check drain from the negative buoyancy tanks port and stb as I have not been able to trace this muffler drain in the fwd. controlroom, see sketches below. As usual the real systems are not a copy of the schematic sketches.

[NZSnowman]

Maciek
I assume your question can be split in two answers. The pipes ending in a funnel are drains from the air ventilation inlet valves and main diesel inletvalve, see sketch below. The drain via sigthglasses ends in the bilge through a muffler and is checkdrain from the regulating and RFO tank 1 port and stb. and possibly also the check drain from the negative buoyancy tanks port and stb as I have not been able to trace this muffler drain in the fwd. controlroom, see sketches below. As usual the real systems are not a copy of the schematic sketches.

Tore, I was looking at drain line for the Diesel Air Main Intake. It seen very high in the intake line and would leave a large amount of sea water in the intake line. This were a 2nd drain line?

[tore]

Simon
You are of course right, howewer this is a simple sketch possibly made by a German engineering officer to show the first type of standard schnorchel having a different airinlet as the next generation installed on U-995.  As the centerline of the valvespindle is wrongly offset, the drain gives a faulty impression of leaving substantial water in the shaft. The drain, I believe is more like a leakage check rather than a complete shaft drain. The sketch shows more the system than the real execution.
I assume it is a different need for drain for the diesel inlet air and the ventilation air. The diesel shaft  is acting almost like a very big drain having its outlet in the engine room bilge, in bad weather the water was constantly gushing down in the bilge and the bilge pump was running all the time. You would not like have the same amount of water in the ventilation shafts, hence a more elaborate drainage for this system at the main inlet.
Tore

[SnakeDoc]

Hi Tore,

The drain via sigthglasses ends in the bilge through a muffler and is checkdrain from the regulating and RFO tank 1 port and stb. and possibly also the check drain from the negative buoyancy tanks port and stb as I have not been able to trace this muffler drain in the fwd. controlroom, see sketches below.

Thanks for your explanation. What was the function of "check drain"? I'm little confused, as these pipes (with sightglasses) seem to be connected to the top part of regulating and RFO tanks. So aren't they rather vent lines? But if so, what for are these sight glasses? What can be observed there?


And these mufflers - I suppose they were to silence the air escaping from the flooded or pressurized tanks. But how do they work/look like?


--
Regards
Maciek

[SnakeDoc]

Hi,

And one more question - do you remember, what kind of electronic device is it? It is located in the forward part of control room, at port site.



Is it German, war-time? Was it installed, when U-995 served in Norwegian Navy?

Some time ago I have asked about this part of electronic equipment. Initially I was convinced, that this is post-war, unrelated with U-Boats, electronic device. But then accidentally I have found some informations which made me change my mind. I have started some researches and the results are in this article:
http://www.ubootwaffe.pl/en/u-boats/equipment/radar-of-german-u-boats
I hope you find it interesting. Any feedback is welcomed.


To answer my initial question, the device I have asked is part of FuMO 30 - early version of German radar for U-Boats.
I'm also 100% sure, that U 995 was not equipped with any active sonar gear (except echo depth sounding device).


--
Regards
Maciek

[tore]

Maciek.
 May be I better take one question at the time that's probably enough for an old man. Muffler comes in a wide range of design, the basic for a gas (air ) muffler is it destroys the vibration energy so the air escapes without noise. I never looked inside the U 995 air muffler but I am pretty sure it consisted of some kind of baffle plates and the air escaped though holes in the outer casing. If you look at the photo of the Kubische Panorama you are able to see the holes. Below is an example how a muffler looks inside.
Tore

[tore]

Maciek.
I agree with you check drain, was not the best word for the pipes. Venting and air supply is probably more correct. The purpose of the system  has two tasks. As you correctly are stating, venting. This is particularly important for the Q tank ( Untertriebzelle port and stb.) which is used for emergency quick diving and silencing is essential.
As the regulating tanks, are not connected to the pressure water compensating system , the pipes are used, when the regulating tanks are used as fueltanks, as  air pressurepipes to the tanks in order to transfer the fuel to the internal fuelsystem, as you see it is possible to use this LP air to the saddle ballast tanks 2 and 4 port/stb as well.
Tore

[tore]

Maciek
Sigthglasses are used for checking the drain from the tanks like fuel, water, air etc. An important item, you don`t want to have fuel in the bilge.
Obviously if you used funnels for these pipes the purpose of the mufflers are gone.
Tore

[tore]

Maciek.
Active sonar/ radar.
I think you are correct, I believe I can remember we did not have the active sonar. I read the article on the german radar development with interest and I can`t  contribute very much except to mention right after the war it was a general distrust of anything related to german radar. In my time I believe we had the original U- 995 equipment. We tried it several times with very little success. The worst experience was up at Lofoten Island, Northern Norway an early very foggy morning. These  island rise up from the sea like a wall 100- 300 meters and we  surfaced just outside the islands which were impossible to see and we tried out the radar. There was no echo, so we tried the old fashioned system, the whistle, and got immediately an echo. When the morning fog disappeared we discovered we were about 400- 500 meters from an impressive rockwall. After that we discarded the german radar, probably unjust, but in those days the navigators were still very skilled in navigating without electronics.
Tore

[SnakeDoc]

Hi Tore,


thanks for your answers.

May be I better take one question at the time that's probably enough for an old man. Muffler comes in a wide range of design, the basic for a gas (air ) muffler is it destroys the vibration energy so the air escapes without noise. I never looked inside the U 995 air muffler but I am pretty sure it consisted of some kind of baffle plates and the air escaped though holes in the outer casing. If you look at the photo of the Kubische Panorama you are able to see the holes. Below is an example how a muffler looks inside.

Thanks, I did not notice these holes - now it's clear for me.

As the regulating tanks, are not connected to the pressure water compensating system , the pipes are used, when the regulating tanks are used as fueltanks, as  air pressurepipes to the tanks in order to transfer the fuel to the internal fuelsystem, as you see it is possible to use this LP air to the saddle ballast tanks 2 and 4 port/stb as well.

Sigthglasses are used for checking the drain from the tanks like fuel, water, air etc. An important item, you don`t want to have fuel in the bilge.
Obviously if you used funnels for these pipes the purpose of the mufflers are gone.

Well, I must confess, I do not understand it. How can the fuel or water get to this pipe? During which operation? And when the fuel (or water) get there, does not affect the muffler?


The matter why the funnels are not used, is now clear for me.


--
Thanks, regards

Maciek

[SnakeDoc]

Active sonar/ radar.
I think you are correct, I believe I can remember we did not have the active sonar. I read the article on the german radar development with interest and I can`t  contribute very much except to mention right after the war it was a general distrust of anything related to german radar. In my time I believe we had the original U- 995 equipment. We tried it several times with very little success. The worst experience was up at Lofoten Island, Northern Norway an early very foggy morning. These  island rise up from the sea like a wall 100- 300 meters and we  surfaced just outside the islands which were impossible to see and we tried out the radar. There was no echo, so we tried the old fashioned system, the whistle, and got immediately an echo. When the morning fog disappeared we discovered we were about 400- 500 meters from an impressive rockwall. After that we discarded the german radar, probably unjust, but in those days the navigators were still very skilled in navigating without electronics.

Your recollection about unreliable German radar is consistent with few informations about its operational usage.
The story about  "old fashioned system" - the whistle is amazing.


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Thanks, regards
Maciek