Inlets on Type VIIC hull

[dougie47]

Hello folks,
 
Merry Christmas to you and a Happy New Year in a few days.

I should really know this but I wonder if you might keep me right. It concerns the large inlets on the Type VIIB and VIIC. They are large on a 72nd model so it would be good to know precisely what they are for.

Here is a quick drawing -


First of all the 8 doors (in two groups of 4) at the bottom of the saddle tanks, in purple above. In Westwood's Anatomy book it says these are inlet valves for diving tank 2. I have read that when the saddle tanks were used as fuel oil tanks, the flood valves were kept closed. Also that when the tanks were used as ballast tanks, they were kept opened. Is this correct?

Can you also tell me how they closed? I have written in my notes of a few years ago "screened inlets (open to sea)" but am still unclear about them.

My other question regards the four doors at the bottom of the hull (see green rectangles above). In Westwood's book it says they are inlet valves for the main internal diving tank. Can anyone confirm this?

I have seen a photo of U 99 in dry-dock and it looks like these 4 doors are lying open, resting upon the keel bar at the very bottom of the boat. Am I right in saying that the opened doors rest upon this keel bar?
 
If there is anything I have wrong then please feel free to correct me.
 
Cheers,
 
Dougie

[uboatfan]

Hello Dougie,

i also wish Merry Christmas and a happy new year to all.

Do you know these Informations:
http://www.uboatarchive.net/U-570/U-570DesignBook.htm  (See Plate 28:  Flooding and venting system for ballast and buoyancy tanks )

and

http://www.uboatarchive.net/Diving/DivingRegulations.htm

May this helps.

As i knew the main ballast tank valves where mostly keep open. Du to this they are visible as you wrote.
The valve Inlets for balast tank system also keept mostly in open position du to a quick dive. In heavy weather this valves where closes to have a better stability of the boat.

Cheers,

uboatfan

[tore]

Dougie
Same to you. Your question concerns what in RN English is called Kingston, named after a British engineer who designed the valves sometime around 1890-1900. The valves are the floodvalves of the ballast(and Q) tanks and operated manually from inside the pressurehull on the VIICs. At sea they were normally open, but in harbour they were usually shut and secured. When the saddletanks were in fuelconfiguration they were shut. On my image below you see the mechanical system for operating the Kingston which at contemporary RN and US submarines were operated pneumatic/ hydraulic, usually Oleo systems. The 2x3 Kingstons on the bottom are for the MBT 3 and in order to protect the Kingston they were placed in a recess in the keel as the keel is used as a restbase for the submarine when resting at the seabed.
The 5th rectangular having a grating next to the forward 4 saddletank kingstons is a smaller kingston for the Q tank (Quick divingtank) and is operated from the controlroom next to the blowing/venting panel for the Q.

[dougie47]

Hello gentlemen,
 
Much obliged to you both for your comments, this is precisely what I was looking for.
 
I had guessed the purpose of the recess in the keel due to the shape (it is very similar also on the Type IIs) but it is great to have this confirmed.
 
I am particularly interested in the differences between the VIICs and VIIBs with regard to the valves. Firstly in the VIIB plan in Westwood's book there is no Kingston for the quick diving tank. Do you know if this did not feature on the VIIBs?
 
Secondly, there are 4 Kingstons on the bottom on VIIBs. For VIICs, some plans show 3 Kingstons and some plans 4 Kingstons. U 995 has three so it is evident that this VIIC/41 had three. Do you know if all VIICs and VIIC/41s had three Kingstons on the bottom? (period photos hardly ever show this area).
 
Many thanks for your help.
 
Cheers,
 
Dougie
 

[tore]

I am sorry Dougie I have a limited knowledge of the VIIB  however in the manual for the VIIC construction 1939 valid from July 1940 the text says on page 37: " On the mainballast tank 3 port and stb, side there are 3 rectangular, outward opening floodvalves which are operated by mean of four linkages rods from the control room." So you can be pretty sure the VIICs all including the VIIC/41 have 3 Kingstones on both sides.
Tore

[dougie47]

Hello Tore,
 
Given the dates on the manual then I would think all VIIC would have the 3 Kingstons on either side. Again this is exactly the information I was looking for so I am very grateful to you.
 
Cheers,
 
Dougie

[Rokket]

Interesting topic. I know Kingstons fro US Gato boats, didn't know they were from a Brit. Thanks Tore and Dougie.

[SnakeDoc]

Hi Gentlemen,

I am particularly interested in the differences between the VIICs and VIIBs with regard to the valves. Firstly in the VIIB plan in Westwood's book there is no Kingston for the quick diving tank. Do you know if this did not feature on the VIIBs?

The manual for type VIIB boats says, that they were not fitted with Q-tank.
 

Secondly, there are 4 Kingstons on the bottom on VIIBs. For VIICs, some plans show 3 Kingstons and some plans 4 Kingstons. U 995 has three so it is evident that this VIIC/41 had three. Do you know if all VIICs and VIIC/41s had three Kingstons on the bottom? (period photos hardly ever show this area).

The same manual says, that MBT 3 had 2x4 rectangular Kingstons.

--
Regards
Maciek

[dougie47]

Hi Maciek,

Many thanks for confirming this. That will be why there is no Q-tank opening on the plan or in the photo of U 99. I guess the Q-tank was an improvement brought about in the C model.

Thanks everyone for your replies, they have answered my questions perfectly.

Cheers,
 
Dougie