Tores mailbox VIIC and VIIC/41 operation and technical details

[tore]

Don.
This was indeed many questions which all cannot be answered with yes or no. I post my answers in different posts starting the compensating tanks 1 and 2.
The purpose of the compensating tanks is to compensate for the changing the weigths of the submarine. The weigth is changing all the time, extra people are coming on board, fuel, freshwater and provision are consumed etc. Thus you have to compensate this by taking water in and out of the compensating tanks fairly often. Both the comp. saddletanks 1 and 2 have no direct contact with the sea, filling and pumping is done by connection to the bilge pumping system both for filling ( fine flood) and  emptying by the bilge pumps, see plate 6.
In order to further increase the reserve FO capacity a part of the compensating tanks are made as FO. reservetanks, called 1 port and stb.. The tanks are not always used as such. When RFO compensating tanks 1 port and stb are used as fuel oil tanks , the connection to the bilge system is shut and the tanks are connected to the fueloil system. See plate 9. If you have questions to the plates 6 and 9 shoot.
Tore

[SnakeDoc]

Don,

Is the Regulating and RFO tank 1 open to the Sea?  A while back I had the understanding that this tank had fuel oil floating on top of water and as the oil was used it was replaced with Sea water (a Self Regulation tank).  If so, then where is the opening for the sea water to enter the regulating and RFO tank 1?

Regulating and FRO Tank 1 (Regebunker 1) was not self-compensated tank. It was pressure-proof, flooded and emptied by means of the flooding and drain manifold (Flut und Lenzverteiler).

It looks like there are 3 blowing distributor systems
1.  the Main Blowing Distributor (Plate 17)
2.  the Exhaust Blowing Distributor (Plate 16)
3.  the Emergency Blowing Manifold (Plate 16 and Plate 17)


Q1.  is this correct. where are they located in the control room
Q2.  it looks like the Exhaust Blowing Distributor only affects D1 through- D5
Q3.  It looks like the other 2 blowing distributors affect all tanks except Regulating Tank 2 because this tank has no flood valve and has to be pumped???

Only main blowing manifold (compressed air) is located in the Control Room - right to the aft diving plane operator station.

The exhaust blowing manifold is outside the pressure hull - (more or less) over the main blowing manifold. Through the pressure hull are passing valve spindles, and only hand wheels are available for operation in the control room. These are eight, small, red hand wheels at the control room ceiling, over the main blowing manifold.

The emergency blowing manifold would be also located outside the pressure hull - in front of the conning tower, in the magnetic compass casing. Would be - because in late-war front going U-Boats it was not fitted (U-995 was not equipped with that). In the HMS Graph report this manifold is mentioned, but from survivors interrogation reports seems, that this manifold was fitted only for the time of U-Boat crew training (that is, when the vessel operated on the relative shallow waters of the Gdansk Bay or similiar).
Here is short discussion: http://models.rokket.biz/index.php?topic=921.msg12001#msg12001

The exhaust blowing manifold indeed affects only ballast tanks.

If there is a down U-boat and a diver hooks up the two lines in order to bring the U-boat to the surface, then all effort is for nothing if no one is conscious and able to open the Tide valves on D2, D3 and D4, and open the hull valves on ALL the other tanks???

All blowing valves of the emergency blowing manifold were located external - so available for diver. The flood valves of the ballast tank 3 was almost never closed when U-Boat was at sea. If the buoyancy gained by blowing all three main ballast tanks was not sufficient to rise the boat, the other measures had to be taken.

To know, how emergency blowing manifold could like, you can sea this diagram:

http://dreadnoughtproject.org/plans/KM_Uboot_Type_II_1934//bergungsplan_100dpi.jpg

--
Regards
Maciek

[SnakeDoc]

Tore,

The chief engineer is mostly stand by if something should go wrong and engineers would be required. During battlestation in our navy however, the chief engineer worked with the CO with distance bearing/ calculation. Down below is a picture with the CO on his knees at the navigation periscope and I calculating the distances during a dummy attack just to give you an idea.
When using the attack periscope the chief engineer was not in the tower but in the CR. At the attackperiscope the CO could get a lot of info directly, however we did not trust the German fruitmachine so the CE had to do some calculation passing messages up to the tower verbally.

Could you say something closer about Norwegian experience with German fruit-machine and  Norwegian practice of torpedo fire control, please?

--
Thanks, regards
Maciek

[tore]

Don
I believe Maciek has answered the rest of your questions in agood way. I would only add to the compensating tanks post I forgot to mention the air/ venting  system which we have touched upon previously as seen on plate 7 and 17,( the system with the sightglasses and muffler at the aft part of the attackperiscope casing). I guess using the dicussion on the Q system would help to understand the sketches.
Tore

[tore]

Maciek.
Torpedo firing and the fruitmachine was not really under my responsibility, that was the torpedopeoples job, so I am afraid I cannot help you very much. I did only the manual calculation using graphs and tables after receiving the COs info of speed, bearing etc. We had a student on board from the technical university in Trondheim taking his master on this "computer" it was of course the prehistoric computertime, but  I am sorry I cannot contribute in any sensible way.
Tore

[SG]

The purpose of the compensating tanks is to compensate for the changing the weigths of the submarine. The weigth is changing all the time, extra people are coming on board, fuel, freshwater and provision are consumed etc. Thus you have to compensate this by taking water in and out of the compensating tanks fairly often.
 

Tore, does it mean that you had to weight all the provisions in advance, before embarking them? What about the crew? did you know the weight of every single men aboard or you just assumed a mean weight of, for instance 70 kg per crewmember? also, did you take in consideration the possible weight loss of the people aboard or it was ininfluential?
How often did you calculate the weight change of the submarine?
thanks

[Don Prince]

Hello Mr tore,


I now know exactly where that Plate 17 came from....  The manual "U-Bootskunde für U-Boote Bauart VII C, Stand vom 15.7.40." - this manual has an appendix in the back of the book where you will find Plate 16 and Plate 17...


5.  Anblaseleitungen, Notausblaseund Raumnotluftleitung


Translate to English?


Regards,
Don_

[Don Prince]

Hello Mr. Tore,


Plate 16 = I assume the 1 vent valve in the diesel room to vent the trapped residual air in both D2 tanks is located in the roof area.  Do you have a photo of this valve?  Are the venting lines going from the back end of the tanks to the valve located internal or external to the pressure hull?


Regards,
Don_

[SnakeDoc]

Tore,

Torpedo firing and the fruitmachine was not really under my responsibility, that was the torpedopeoples job, so I am afraid I cannot help you very much. I did only the manual calculation using graphs and tables after receiving the COs info of speed, bearing etc. We had a student on board from the technical university in Trondheim taking his master on this "computer" it was of course the prehistoric computertime, but  I am sorry I cannot contribute in any sensible way.

Thank you Tore for your answer. It would be interesting to take master on such piece of equipment (as well as reading such scientific description).


--
Thanks, regards
Maciek

[SnakeDoc]

Don,

Plate 16 = I assume the 1 vent valve in the diesel room to vent the trapped residual air in both D2 tanks is located in the roof area.  Do you have a photo of this valve?  Are the venting lines going from the back end of the tanks to the valve located internal or external to the pressure hull?

As the vent valve of the Tauchbunker 2 is located outside the pressure hull, it is hard to get photo. But if you mean the drive for this valve - one is located in the control room - on the aft bulkhead - over the hatch to the petty officers room - large red wheel on the stb side (the wheel on the port side is the drive for the Tauchtank 1). In the diesel engine room, to the driving shaft going from control room, the other wheels are attached, so the vent can be operated also from the diesel engine room.
See also here: http://models.rokket.biz/index.php?topic=106.msg13275#msg13275


--
Regards
Maciek

[tore]

SG.
A full control of the weigths in and out is necessary. This is particularly elaborate after major refitting, preparing for long patrols,provision,fuel, torpedoes taken on board and compensating for shooting same etc. In my days a rough estimation of each person would be 75 kgs today you would probably add another 10 kgs pr. person I guess . Not only the weights taken on board, but the salinity and temperature of the sea had to be taken into consideration. In addition to weights taken on board you had to know where it was stowed as the tilting moment has to be taken into consideration for the trim as well. The influences of these shifting of weigths was many times based on experiences rather than calculations. As mentioned before f.i. prior to sounding the alarm for diving stations you knew that 400 liters had to be shifted from aft to forward trimtank. You could of course compensate a lot by the hydroplanes and the movement of a single person or normal watchchanging would not require a trim changing you compensated by the hydroplanes. The need for  fairly extensive corrections  is why there are  elaborate systems of compensating- and trimtanks as you want to have an optimal boat for easy handling of hydroplanes. Tanks were sounded every day and adjustment was carried out accordingly.
Tore

[tore]

Don.
Residueventing MBT 2
I believe Maciek has answered in a good way. I can only add that the drive rod from the controlroom goes into the engineroom and ends up at frame 21 in a bevelgear where it goes through the through the pressure hull. I am posting a photo showing the arrangement.
Tore

[tore]

Don.
Further to my previous post I am sending a bad photo showing the enginroom hand wheel for the residue ventingvalve, the rod continues to the CR.
Tore

[SG]

Very interesting, Tore. Thank you very much!!

[Don Prince]

Thank you Mr. Tore,


That explains a lot and I'm very grateful for your patients and understanding.  It looks like you have answered many of my questions before and I do apologize for being such a bother.


Several years ago, I started building an OTW Radio Controlled model of a Type VII C U-Boat "U-96" which has a fiberglass hull and a brass deck and tower.  The kit came with 2 flat tower side sheets and the laser cut out deck sections.  I had to manufacture the rest of the tower components from brass plate and rods and assemble everything with a small soldering gas torch.  It took me about 2 years to complete the U-Boat structure, but I have not installed the water tight chamber along with the all the electronics (receiver, servos. dive system, speed controller, depth controller, and pitch controller, plus tons of other stuff).  To complete my U-96 project it would take well over $3,000 and lots of time.  When it is completed, U-96 will be capable running on the surface, or diving to a predetermined depth in a lake or pool.  Today, U-96 sets on a table in my library as a huge 84 inch long accurate display model.


Sometime next week, I will take some new photos of U-96 and post them on this web site.  Oddly enough, this is the Accurate Model Parts site...


Regards,
Don_