Question about Type VII ballast tanks

[Catfish]

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

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

[KMS Mordekaiser]

Hello! I just registered at Subsim. I am excited to participate in this forum, because I am incredibly fascinated by WWI and WWII submarines. Also, I found this forum stumbling around during some research.
Be warned though: I have MANY questions.

One of these involves the saddle tanks of the Type VIIC and the stability bulges of the Italian Navy's Submarines (WWII).

From plans of a VIIC it seems the tanks were placed at the upper body of the ship. Would it be logical to place them along the whole side instead of just the upper area?

I put in an image of the plans I am referring to.

[Aktungbby]

KMS Mordekaiser!

[Onkel Neal]

Originally Posted by Penguin

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

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.

Originally Posted by Catfish

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

Greetings,
CF

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.

Originally Posted by sober

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

You know me...here's the Wolfpack Training section

Originally Posted by Catfish

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 plan...... 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

Outstanding, put into terms I can understand.

Originally Posted by Feldpost

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)

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.

Wolfpack Crash Dive procedure, Step #15: Chief closes vent valves for negative tank and blows tanks to control dive before desired depth is reached. After execution of the order "Flood" and the boat has a noticeable descending tendency, the negative buoyancy tanks are expressed (blown by compressed air), by the Chief, who will call out, “Express”. It is critical that the Chief perform the crash dive operation competently, otherwise the boat could dive out of control, below safe depth, or with a dangerous down angle.

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

[Gotmilk]

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?

[Feldpost]

Ahoi Gotmilk,

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

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

[John Pancoast]

Originally Posted by Feldpost

[OFFTOPIC]
Maybe the swedes including Neal are creating the first UBoot game which can be labeled as Submarine Simulation
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...

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

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
[/OFFTOPIC]

Hopefully there will be options as you say, for those who aren't interested in all this.
Fwiw, be wary of the road that things appear to be going down. Ultra-detailing desired by some was a major part in killing off flight-sims.

[Aktungbby]

Mambo!

[Fidd]

Originally Posted by THE_MASK

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

Actually I think the Dive Officer has the reverse of this, as once the boat is in trim he has nothing else to do. It'd be great if one could elect to operate the 'planes and tanks to a greater degree of difficulty, and higher workload if desired. To do so it would be best if difficulty-levels were on a per-boat or even per-player basis, rather than per-lobby, allowing both boat crews and individual players to select the difficulty with which they wish to contend.

Personally, I'd like nothing better than working harder to maintain PD, or adjusting longitudinal trim and the regulated tank to deal with loss of weight due torpedoes being fired. (etc)