[Nisgeis]

Hi Dave,

Do you know what shape the Main Ballast Tanks No. 1 and No.7 that are part of the forward and after torpedo rooms were internally? The drawings in the fleet boat manual has them shown as a U shaped tank, with the outer sides being rounded and the top and middle sections being flat plates, the upper two parts of the U forming the deck of the torpedo rooms. This doesn't seem like a very good shape to withstand pressure, from an engineering point of view as they have large flat surfaces and sharp angles in the corners. There is no signs of any extra thickness in the pressure hull at the top/deck of the torpedo room to compensate for this shape.

Are the fuel ballast tanks actually built as a U shape, with flat sides to the pressure hull?

Also, after having a look at the pictures of the sections being constructed before assembly, it appears that the bulkheads are a single sheet welded at the ends of the pressure hull. Were the bulkheads made to fit inside the pressure hull, or were they the same diameter as the pressure hull. IE, when two sections were joined was it pressure hull - pressure hull, or was it pressure hull - bulkhead - pressure hull?

I also have a question about Normal Fuel Oil Tank number one. Was it completely sealed externally, with only valves to drain and fill from the inside in the forward topedo room? Even the fuel filling lines seem to be routed throught the torpedo room, so were there any hull openings at all through the pressure hull where Normal Fuel Oil Tank number one is?

Finally, how thick are the dividers between the ballast tanks? The drawings seem to indicate that they are fairly thick - were they?

Oh yeah I almost forgot. The conversion process for Fuel Ballast Tanks to Main Ballast Tanks was to remove some blanking plates - I'm assuming these were over the vents, as you wouldn't be able to replace ones over the flood ports at sea. The question is why have blanking plates - were the vent valves not secure enough?

Thanks for reading!