Tores mailbox VIIC and VIIC/41 operation and technical details

[NZSnowman]

Maciek & Don, have you seen any size measurements for the high pressure gas bottles?

I also found these pictures of U-106 high pressure gas bottles 

Estimating off the U-Boat plans the measurement are.

• Bottle width: Average 458 mm, SD = 21 mm, n = 9.
• Bottle length Type IX: Average 3779 mm, SD = 17 mm, n = 3.
• Bottle length Type VIIC’s: Average 2492 mm, SD = 20 mm, n = 4.

[Don Prince]

Hello Mr. Tore,


Echolot info taken from the German Type VIIC training manual...



"Each device consists of: transmitter, receiver and amplifier.  The shallow depth sounding device works noiselessly, while the deep depth device sends sound impulses which are audible.  Both devices are powered by the AC shallow and deep depth echo sounding converter located in the E-motor room.


The deep depth sounding device has three transmitters and three receivers which are mounted in the keel. The shallow depth sounding device has one transmitter and one receiver. Both are mounted on bottom of the hull, on the port side, near the munitions magazine."


Regards,
Don_

[tore]

Don.
I should have remembered the position, but I don`t, in spite of sleeping almost on the top of it for 3 years. My bunk, light blue, and the echosounder, red dot on the image below.
Tore

[Don Prince]

Hello Mr. Tore,


I had got a copy of the book which was in German about 5 or 6 years ago and struggled with the translation.  I Faxed each page to Captain Jerry Mason of the uboatarchive.net and he had Maciek to translate the book and it's on Captain Jerry's website. It took me several hours to find where I got the information in the first place.  Besides getting help from you about U-Boats, I need to start documenting where I got the info so I can find it again...  I don't have all that experience like you do in your head, and there is no one else around with the knowledge and who actually lived in the Type VII C U-Boat.


Kind regards,
Don_

[tore]

Don.
The funny part of it is when we did a schnorcheling test in 1953 being 28 days submerged towards Greenland, the echosounder and good drafts with sounding contours was one of the major navigation instruments at that time.
Tore

[SnakeDoc]

Hi Simon,

Maciek & Don, have you seen any size measurements for the high pressure gas bottles?

All high pressure air flask at type VIIC U-Boats have following dimensions:
capacity: 325 l
length: 2650 mm
diameter: 450 mm
Dehnung: 12% (it translates to lengthening but I'm not sure what it can mean)

so your estimation is very accurate.

Estimating off the U-Boat plans the measurement are.

• Bottle width: Average 458 mm, SD = 21 mm, n = 9.
• Bottle length Type VIIC’s: Average 2492 mm, SD = 20 mm, n = 4.

--
Regards
Maciek

[SnakeDoc]

Hi Simon,

Simon.
I guess the assumed image of the expansion tank of the IXC cutaway is probably the echosounder, I have previously been fooled by this image.
Tore

What make you think its the echosounder?

In the book "Die Sonaranlagen der deutschen U-Boote" by Eberhard Rössler there is a description of the Echolot (Echosounder), which says that three sonic transmitters were located at port side, at the height of the Diesel engine room (just behind the bulkhead between control room and Diesel engine room).
On the photo attached by Simon we can see (if I'm not mistaken) the Diesel engine room, looking aft. In my opinion, the marked element is the most aft of the three sonic senders.


Note, that at the bottom of the opposite fuel tank, this element does not exist (if it would be expansion tank, it had to be there).


--
Regards
Maciek

[SnakeDoc]

Don.
I should have remembered the position, but I don`t, in spite of sleeping almost on the top of it for 3 years. My bunk, light blue, and the echosounder, red dot on the image below.
Tore

On page 429 of the Skizzenbuch there is visible location of the ultrasonic transducers.


--
Regards
Maciek

[SnakeDoc]

Simon.
I guess the assumed image of the expansion tank of the IXC cutaway is probably the echosounder, I have previously been fooled by this image.
Tore

What make you think its the echosounder?

In the book "Die Sonaranlagen der deutschen U-Boote" by Eberhard Rössler there is a description of the Echolot (Echosounder), which says that three sonic transmitters were located at port side, at the height of the Diesel engine room (just behind the bulkhead between control room and Diesel engine room).
On the photo attached by Simon we can see (if I'm not mistaken) the Diesel engine room, looking aft. In my opinion, the marked element is the most aft of the three sonic senders.

I have attached the view of the bulkhead between Diesel engine room and control room (looking forward). The other (middle) sonic sender is visible there.


--
Regards
Maciek

[SnakeDoc]

Gentlemen,


regarding the expansion tank, reading the description of the ballast and fuel oil tanks in the German documents, I have found the following fragment:

Für Tauchbunker 2 und 4, Bb und Stb bei Betrieb als Tauchzellen.
Je 1 Sicherheitsrohr. Ist der Druckwasserschalter zu, stellt das Druckwasserrohr von Restwasser der Tauchzelle über Druckwassserschalter nach außenbords das Sicherheitsrohr dar.

Bei Betrieb als Treibölbunker ist ein Druckausgleich über die Druckwasserleitung bei offenem Druckwasserschalter möglich. Zur Vermeidung von Ölspuren ist die Druckwasserleitung in den Tauchbunkern in einen abgeschlossenen Raum zwischen zwei Spanten geführt. Verbunden ist dieser Raum mit dem Bunker durch ein gebogenes Übertrittsrohr, an diesen höchster Stelle ein Entölungsrohr angeschlossen ist.

I would translate it as follows (however please correct me if something is wrong):

For tanks 2 and 4, port and stb, used as ballast tanks.
Each tank is fitted with safety tube. When the pressurized cooling (compensating) water selection cock is closed, the residual water in the ballast tank overflows through the selection cock and safety tube overboard to the sea (my note: I guess - but I can be mistaken - that this description refers to the surfaced condition, when the pressurized cooling water is fed to the blown ballast tank).


When operating as fuel oil tank and when selection cock is opened, the pressure is equalized through the pressurized cooling (compensating) water system. To avoid the trail of the fuel oil, the pressurized cooling (compensating) water piping in the tank is enclosed in the space between two frames. This space is connected with the tank by means of the curved pipe (my note: maybe U-shaped pipe?). At the top of this curved pipe the de-oiling tube (my note: fuel oil venting/sounding/testing pipe?) is connected.

Maybe it somehow helps in further researches of the expansion tank.


--
Regards
Maciek

[Don Prince]

Hi Maciek,

That information could be interpreted is several ways... While running on the surface in the ballast mode:


1. The selector valve is in the Ballast configuration
2. The selector valve compensating water to the Ballast tank is shut
3. The selector valve now sends the compensating water to the Expansion tank at the bottom of the Ballast tank.
4. The small tube (Safety Tube) from the expansion tank is connected to the sea.


The "REPORT ON U-570 - H.M.S. GRAPH" on page 64 states...


They refer to the header tank under the tower as an expansion tank, and they also refer to a small tank at the bottom of each FBT (ballast tank) as an expansion tank. However, we refer to the tank under the winter garden as the header tank. Now their sentence makes sense...


"The expansion tank is always in open connection with the sea and thus the fuel tanks are always equalized and the only compensating water pressure which can be applied is due to the head of water in the expansion tank (Header Tank). This arrangement is necessary where direct blows are fitted and avoids the possibility of straining the tanks due to high pressure. The tanks are built of light plating and are tested to 15 lb. per sq. in."


Drawing attached.


Regards,
Don_

[tore]

Based on the info we have right now I have tried to put up  a sketch showing my assumtion of the ballast/ fueltank compensating system. The small "expansion" box of thin sheetmetal in the saddletank bottom is located between two frame lenghts remains the image documentation and I assume the fuel "drain" from the expansion box is connected to the testcock system under the casingdeck. The outlets under the casing deck shown on Simons image could possibly be the outlets from the sample funnels in the system.
Tore

[Don Prince]

Hello Mr. Tore,


The British report on U-570 states...  "The expansion tank is always in open connection to the sea..." In your drawing; If you are running in the ballast mode and submerged, then it looks like there is a possibility of having HP air entering the water compensating system with the small tube through the compensation tank at the bottom of the ballast tank when blowing the ballast.

I agree that the pipe in Simon's photo is most likely connected to the collector funnel on Plan 8a...


Regards,
Don_

[tore]

Don, if you follow the blue line on the image showing the ballast configuration you`ll see the ballasttank is in direct connection with the sea.
Tore

[Don Prince]

The "compensation water box" in your drawing...  Is that the expansion tank at rhe bottom of the ballast tank?  Why would it ever have fuel oil at the top?


Don_