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The Hull (Pressure Hull)
Posted by: The Captain ()
Date: July 28, 2000 10:22PM

Robert,
I will try and explain the construction of the Type IXC40 boats. It will be in six parts. The first will be the pressure hull, second is the outer shell, third is the superstructure, forth is internal decking, fifth will be castings and last will be foundations. I hope this will help explain the construction of this type of submarine.

The Pressure Hull.

The vessel consists of a cylindrical pressure hull with truncated conical sections at the ends and cast end bulkheads, a conning tower of oval horizontal section with a cast top, a system of exterior ballast and fuel tanks enclosed in a ship-shaped envelope, and a light superstructure with accompanying conning tower fairwater and bridge. A box keel is fitted below the pressure hull. The designer's submergence depth is 100m. (328').

The cylindrical pressure hull has a diameter of 4400mm (14.42') and is made of 18mm (.73") steel with inside bulb tee frames 200X11 (7.88" web depth X .43 web thickness) on 700mm (27.56") centers. The plating is gradually reduced throughout the taped sections fore and aft to 16mm (.63") and the frames are correspondingly reduced to 130X9 (5.12X.35). Frame spacing remains unchanged in the tapered sections.

The specification for the pressure hull plating and frames calls for a tensile strength of 74,000 psi with a yield point of 51,300 psi. The steel is known as No. 52; the specification for plates is KM 9104, and for frames is KM 9103.

Framing is modified in the way of the main motors, to provide clearance, by substituting double frames 160X9 (6.30"X.35") for the normal 200x11 frames.

In addition to the dished end bulkheads of cast steel, four other dished cast bulkheads are fitted, dividing the pressure hull into five pressure compartments. These bulkheads are 22mm thick; but material specifications, while unknown, are believed to be German cast steel 45.81 per KM 9106.

Further subdivision is provided by two light fabricated bulkheads, one in the battery compartment forward, and the other separating the maneuvering and engine space in the machinery compartment aft.

These are designed for a pressure differential of 3 psi only, but in practice serve no pressure purpose because they have so many non-tight openings.

Large openings in the pressure hull consist of the two torpedo hatches, one galley hatch, one engine room hatch, and openings overhead in the control room for conning tower hatch and two periscopes. There is also one removable patch in the way of the engine room and another overhead in the battery compartment.

Compensation for these openings is obtained in a number of different ways:

(1). For the torpedo hatches, a doubler (in some vessels a single thicker plate) is fitted, increasing the plate thickness from 17mm normal to 38mm (1.49"). The frames are cut in the way of the hatches, and are fitted with bearing pieces at the ends, against which strongbacks are wedged and secured in position by toggle pins.

(2). The galley and engine room hatches have no compensation other than their trunks, which are tubes with 20mm (.79) walls.

(3). The overhead openings in the control room are compensated for by increasing the hull plating to 22mm, by trunking each opening and by fitting angles inside and outside the hull on each trunk. This sounds a little overdone. Further, as the openings make two frames discontinous, the adjacent through frames are increased to 200X15 (7.87x.59).

(4). The patch in the engine room has double butt straps, double riveted, on the plating. Frames are butt, with double butt straps on the webs having 6 rivets on each side.

(5). The battery patch consists merely of a plate riveted to a frame about 1.5" thick which is welded into the hull plating.

Within the pressure hull the forward and aft trim tanks, and the WRT tanks, are the only structural tanks designed for more than a gravity pressure head. The remaining structural tanks consist of four fuel oil tanks, the lubricationg oil tanks, the fresh water tanks and the sanitary tanks.

The conning tower is a relatively small oval cylinder mounted vertically on the pressure hull. Plating thickness is 40mm (1.18"). Frames are vertical. The structure is closed at the top by an elaborate steel casting incorporating periscope and hatch rings, and ribs extending to the top of the frames. The specified plating material is indentified as special Wh n/A, not further identifiable. The cover casting is of chrome-molybdenum-vanadium steel.

The entire pressure hull is welded except for the patches mentioned above. Butt joints are employed on the shell, and where heavier plating adjoins lighter plating, the heavier plating is scarfed to the lighter thickness at the weld. Where the shell is welded to the cast end bulkheads and where the conning tower plating joins the cover casting, however, the outer surface are flush, but the inner surfaces are not, and a fillet of weld metal has been built up from the plate to the thickness of the casting. Intermittent welding is used only on the stiffeners for the two light fabricated bulkheads. The cast type of pressure bulkhead is welded to a ring on its periphery, which in turn is welded to the pressure hull. The door frames in these bulkheads are riveted.


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Subject Written By Posted
The Hull (Pressure Hull) The Captain 07/28/2000 10:22PM
RE: The Hull (Pressure Hull) Robert Eno 07/29/2000 01:13PM
Re: The Hpressurz Hullzull (Pressure Hull) perew 05/16/2017 11:58PM


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