Question about Type VII ballast tanks
 

I'm researching the ballast tank system on Type VIIs to see how we will fit it in the game.

The Type VII had many tanks, including trim tanks, torpedo compensating tanks, MBT 1,2,3,4, & 5, regulatory tanks, and a pair? of negative tanks. I say pair, because they apparently wrap around the bottom of the sub? so you have a port and stbd pair of tanks for MBT 2, 4 and the negative tank that are connected beneath the boat?

The MBT 1, 3, and 5 seem to be a set of single tanks on the centerline of the sub.

The negative tank seems smaller that I would have expected.

In the pictures of the valves 1, 2, 3; they are painted black on U-995, any idea why? Are these possibly fuel lines?

The red bar handle, any idea what this does? What kind of valve it operates? It seems like a quick-opening valve of some kind.

The pair of red/blue chain-drive valves on the bulkhead, those are for the MBT 4, and another set are located on the opposite (stern) end of the control room, they open the vents for the MBT #2. That's what I think.

Any feedback or info is appreciated.

Hey Neal,

Not sure if this is helpful (didn't go through it, because lazy):
Type VIIC Manual (English)

According to the 1940 regulations, wheels and handles used for quick-release vents had to be painted red, in the 1944 regulations they also allowed green.
Source: http://www.u-boot-archiv.de/dieboote/farben.html

The exact location of the handle is hard to see on the pic. As it is located on the top, it could have been used for the fersh air conduits to the diesel engine or the internal fresh/used air pipes. Those start just start aft of the observation scope - close to the air vents for dive bunker 2 and 4.

I think you thought is correct, stern of the control room is MBT#2(?)

(maybe someone can help to translate :03:)
"Handrad für die Entlüftung des Tauchbunkers 2"
http://www.subsim.com/radioroom/pict...pictureid=9130
Source: "Vom Original zum Modell: Uboottyp VIIC"; ISBN 3-7637-6002-4

Also take a look at 00:04: https://www.youtube.com/watch?v=suY06PVK_bI
(flood the MBT#4 ?)


Maybe this background can help too (it's not WWII but possible it was similar)

Definition for Bundesmarine submarines:
http://www.subsim.com/radioroom/pict...pictureid=9128
http://www.subsim.com/radioroom/pict...pictureid=9129
Source: "Unterseebootbau"; ISBN 3-7637-5958-1

Lenz-/Seewasser: Seawater ;)
Kraftstoff: Fuel
Frisch-/Waschwasser: (not salty) Drinkwater
Schmieröl: oil
Lüftung: air
Druckluft: compressed air

edit: a shape of valves is given for its purpose in case of darkness

The main ballast tank (= ballast tank #3) was located within the pressure hull beneath the control room. The two (!) negative buoyancy tanks (not two pairs) were located port and starboard in the "saddle". I do not think they were connected, and i do not know whether they "met" underneath at all.
I have some plans, but none with a section at that point.
Each negative buoyancy tank (=Untertriebszelle) had a capacity of 2,15 tons of seawater.
Will post here if i find something.


Copy from the Subsim meet thread, regarding the procedure for the neg. b. tanks:


From the "Tauchvorschrift für Unterseeboote":

Untertriebszellen

131. Bei Booten mit Untertriebszellen wird wie folgt verfahren: Die Untertriebszellen werden, wenn das Boot alarmtauchklar ist, über Wasser gefüllt gefahren, so daß dem Boot ein der Größe der Zellen entsprechender Untertrieb gegeben ist. Nach der Ausführung des Befehls „Fluten“ und merklicher Falltendenz werden die Untertriebszellen auf den Befehl des L.I. „Ausdrücken“ ausgedrückt.

(131. If the boat has negative buoyancy cells, the procedures are as follows: The U.-cells are being flooded when the boat is running surfaced, and in "ready to submerge" state (edit: alarmtauchklar=all men at diving positions, boat prepared for emergency dive - so .. usual condition in enemy waters), so that there is an appropriate negative buoyancy. After execution of the order "Fluten" (edit: flood the tanks!) and a perceptible tendency of falling, the cells are being blown out by order of the LI (Leitender Ingenieur).

Der beste Zeitpunkt des Ausdrückens für mittlere Boote ist eine Tiefe von etwa 8 bis 10 m, für große Boote eine Tiefe von 10 bis 12 m. Erfahrungsgemäß beruht die Wirkung der Untertriebszellen in erster Linie im schnelleren Durchbrechen durch die Wasseroberfläche beim Tauchen. Da die schnelle Erreichung großer Tiefen fast ausschließlich von der Lastigkeit und der Fahrtstufe abhängig ist (etwa 25 bis 30°, 2 x G.F.), ist es falsch, die Untertriebszellen auf größerer Tiefe auszudrücken, da der äußerst geringe Vorteil in keinem Verhältnis zu der Gefahr steht, in die das Boot in einem solchen Falle geraten kann. Insbesondere steigen der Luftverbrauch und die Ausdrückdauer ganz erheblich.

(The best time for the blowing ballast of boats of middle size is a depth of 8-10 meters, for big boats a depth of 10-12 meters.
From experience the essential effect of the U.-cells is one of breaking through the water surface during a dive. Because the reaching of greater depths is almost entirely dependent of angle and speed (ca. 25 to 30°, 2x all ahead) it is wrong to blow them out at greater depth, because the advantage would not be in due proportion to the danger, the boat will be in. Especially wastage of air and the time of the blowing ballast increase badly.)

132. L.I.: „Ausdrücken“.

Daraufhin wird das Ventil „Ausdrücken Untertriebszellen“ aufgerissen und mit höchstmöglichem Druck (20 bis 30 at) ausgedrückt. [...]


(132. LI: "Blow ballast".
With this order the "Blow U.-cell" valve will be torn open, and be blown out by the utmost pressure (20-30 at). [...]

The general procedure was to have the U.-cells being fully blown at 19 meters of depth.

Anyone here has those three books from Lothar-Guenther Buchheim?
I mean those picture-books:
"Die U-Boot Fahrer"
"U-Boot Krieg"
"Zu Tode gesiegt"
Lots of pictures with explanations what can be seen on it, however not all.
If i find something about those trimming tanks..

(Assumption) From the shape and location i don't think these are fuel lines. That close to the conning tower and 'shaped' like air valves these could be valves for fresh air into the different compartments of the sub(?).


(Assumption) Quick 'Entlüftung der Tauchzelle #3' (flooding of cell #3); or more likely the 'Untertriebszelle' (for quick alarm diving)?
Where is it located? - Stern / port of command room? - On the far left of the picture the vertical-scale (could be a kind of fill/pressure-indicator for a cell), could be a hint too (but when stern/port than these could be an indicator for MBT#2)...

I just ran mad before my first post here since i got two Guenther Buchheim pictures-books and can't find them... but as i remember there are not that technical detailed :hmmm: but they would be great as source for graphical atmosphere impressions for 'Wolfpack' :up:

Regarding the last of the 5 pictures, the two handwheels over the fore bulkhead of the control room, Buchheim writes on page 47 of his book "Die U-Boot Fahrer" that these are for the "ventilation of the two saddle tanks in the boat's center". Since there are only two exterior (saddle) tanks at the center those can be either the control wheels for the two (aft) trim tanks, or for the two (fore) negative buoyancy tanks. :hmmm:

What does "ventilation" mean here, Bucheim writes "Entlueftung". Is this for letting pressure air into the tank for "ventilation"? Or is it for flooding, opening the upper valves?

What i red; were the negative-tanks (Untertriebszelle? - about 2x2m²) an aid to get the boat in stronger sea under the water line (assist to flood the main-cells especially in heavy waves from stern). I am sure there were also used for alarm-diving, but they have to been blown-free with compressed air as soon the destination depth was reached... (Source: "Unterseebootbau" page 26)

"Entlüftung" means to let the air out = flooding = opening the upper valves, nice find :up:

edit:
"ventilation of the two saddle tanks in the boat's center" => MBT #4 (Tauchbunker 4) are actualy two, port and stb. and are close to the center (slightly ahead)... i don't think that Bucheim ment a negative or trimm tank, these are the forward main-ballast tanks (?)...

Just a thought . Playing multiplayer single missions for 1 to 2 hours .
Is this turning into Neals Trimming Tanks simulator ?

This may also help:
http://www.uboatarchive.net/U-570/U-570DesignBook.htm

Greetings,
CF

Well, I just uploaded some pics for all you tank and cell geeks. :D
(I hope imgur doesn't screw up the quality, each scan is about 8Mb in size)

Pic 1 shows where the valves for the diving tank 2 and 4 are located (Entlüftungsventil Tauchbunker 2 + 4, bb = port) - you see a corresponding valve on the starboard side, too.

Pic 2 shows the location of all central-located tanks

Pic 3 shows shows that my previous assumption about the air pipe to the Diesel engine was wrong - you can see the pipe only branches to the engine room and the kitchen.

All drawings depict a 1944 type VII C
Source: Eberhard Rössler: Geschichte des deutschen U-Bootbaus, Band 1 - isbn: 3-86047-153-8

[OFFTOPIC]
Maybe the swedes including Neal are creating the first UBoot game which can be labeled as Submarine Simulation :up:
A submarine is nothing else than an underwater plane and good trimming is a fundemental in every flight-sim... from 'Silent Service' (C64) until SH5 we only got 'tactical' simulation of submarines, but 'Wolfpack' can also get the first submarine-simulation... :yeah:

When the team thinks, get that stuff early in development into the core engine b/c it could be needed someday :up:

I am sure there will be realism-settings later for just go and keep periscope depth, but to get a game-engine which also allows you to play the LI and try to keep periscope depth at BFT9 in north atlantic while the boss ordered to keep silent as possible :sunny:
[/OFFTOPIC]

The levers at the top of the control room, are for a fast opening of the upper tank valves = rapid flooding. No time to turn a wheel, just pull those levers and tear open the upper flooding valves for a crash dive.

The VIIC boats had 5 ballast tanks. They were located inside and outside of the pressure hull. The tanks located in the saddles have two parts: port and starboard! The yare therefore doubly listed in the table below.

According to the plans for type VIIc boats (from the Admiralty Technical Report on U-570), order of description:
Tank number
Between Frames
Capacity (tons sea water)
Fitted with


No. 1 (single) Main Ballast tank (rear end of the boat)
-10 to 0, external, aft of pressure hull above aft torpedo tube
31
Hand-worked vent, direct blow, exhaust blow - no Kingston valve, the bottom is open to the sea

No. 2 (double) Main Ballast and Reserve Fuel Oil tank
17-34, external, in saddle tank
11.4
Two kingston operating positions working four kingstons, one T-wrench operated emergency vent valve leading into a duct to a common quick-opening lever-operated vent for No. 2 port and No. 4 port fuel tanks, one after-end auxiliary vent leading into a duct to a common auxiliary vent for port and starboard tanks, direct blow, exhaust blow, compensating and blow-out connections. Saddle tank fuel tanks are tested to only 15 lbs./sq. in.

No. 2 Main Ballast and Reserve Fuel Oil tank
17-34, external, in saddle tank
11.4
As for No. 2 port, one T-wrench operated emergency vent valve leading into a duct to a common quick-opening lever-operated vent for No. 2 starboard and No. 4 starboard fuel tanks, one after-end auxiliary vent leading into a duct to a common auxiliary vent for port and starboard tanks.

No. 3 (single) Main Ballast. tank, internal
40-49, internal, below control room
47.75*
Four operating positions working six kingstons, direct blows, exhaust blows, two T-wrench operated emergency vent valves to port and starboard at the pressure hull to a duct which leads through the No. 2 Regulating tank at the end of which are two quick-opening lever-operated vents to the sea - tank tested to full diving depth so Kingstons could remain open at depth.

No. 4 (double) Main Ballast and Reserve Fuel Oil tank
45 1/2-62, external, in saddle tank
13.5
Two operating positions working four kingstons, one T-wrench operated emergency vent valve leading into a duct to a common quick-opening lever-operated vent for No. 2 port and No. 4 port fuel tanks, direct blow, exhaust blow, compensating and blow-out connections.

No. 4 Main Ballast and Reserve Fuel Oil tank
45 1/2-62, external, in saddle tank
13.5
As for No. 4 port, one emergency T-wrench operated vent valve leading into a duct to a common quick-opening lever-operated vent for No. 2 starboard and No. 4 starboard fuel tanks.

No. 5 (single) Main Ballast tank (at the bow of the boat)
80-106, external, forward of pressure hull surrounding forward torpedo tubes
25.3
One hand worked vent, direct blow, exhaust blow - there is no Kingston valve in this tank the bottom is open to the sea


Apart from those 5 'variable' flooding tanks, there were 'fixed' tight buoyancy tanks, 'variable' trimming tanks, fuel tanks being open to the sea at the bottom (Diesel swims on water) and fuel tanks being used for trimming - either by flooding them with seawater after being spent, or to be pumped around for trimming purposes.

I guess it is easy if you look at one system at a time :D

Generally the ballast tanks were blown out by compressed air stored in pressure bottles, not pumped out. Or, after surfacing or using a "Schnorchel" they could be fully blown out by the Diesels, having the advantage of the fatty exhaust fumes protecting the inner tanks from seawater.

During diving, tanks could only be blown out by air pressure. The bilge and auxiliary pumps were installed to empty the bilge and for trimming, not for emptying ballast tanks. Air pressure in the bottles were replenished by the Junkers compressor.

Ah whatever ;)

Nice, thanks! Someone told me all I needed to do was ask for help in this forum and there were people who would come forward. :salute:

Yes, that does help. So,it really does look like there are a series of tanks inside the "saddle tanks" blister. Wow, and that makes sense, you would not want one long tank fore and aft, any air in the tank for cause a surging effect, just like the tanker trucks I used to drive in another life. I'm still a little surprised they are not connected in some way, I guess being separate means its really important that they always fill and empty at the same rate, or the boat would take on a list.

You know me...here's the Wolfpack Training section :shucks:
http://www.subsim.com/radioroom/pict...pictureid=9131

Outstanding, put into terms I can understand. :up:

Yes, the procedure I found on uboatarchive specifically instructs the Chief to blow the negative almost immediately after the boat takes a "noticeable descending tendency" and passes periscope depth. This means that failure to operate efficiently could cause the boat to descend to rapidly and pass the maximum safe depth. I've read many accounts of this happening on boat where the Chief was unskilled, or there was a problem with the boat. It gives our game a tremendous opportunity to add realistic, skill-based gameplay to keep things interesting.

Thanks everyone, good stuff, and always glad to have the community involved. :rock:

Would like to continue this interesting conversation. Going trough uboat manuals and i see three things.

1) Blowing
2) Venting
3) Flooding

I know what blowing and flooding does. What does venting do? In many places it seems to be similar to flooding but then i see stuff like this in manual standing side by side

"Vent valve for main ballast tank 3"
"Flood valve for main ballast tank 3"

What is the difference?

Ahoi Gotmilk,

on VIIC is tank #3 the middle 'Tauchzelle' (bad translation 'diving cell' :hmmm:)

There are tanks to compensate torpedos, tanks to accelerate diving... but 'Tauchzellen' are for trimm...

These tanks get a valve to let the air out off the top "Vent"; or to let the Water in from the buttom "flood"; also to "blow" compressed air into them...
eg:
go Dive: both open
go Surface: 'Vent' close, 'flood' open and 'blow' out the water through the opened 'flood' with compressed air

now comes trim:
keep Periscope depth: 'vent' close, 'flood' open and the sub 'swims' under water on the pressured air inside that tank :up:

haha gotcha.

Thanks a lot. :)