Technology and Operations
This forum is for discussing technological & operational matters pertaining to U-boats.
Re: Pressure hull construction - VIIC boats
Posted by:
Scott
()
Date: November 11, 2002 07:12PM
The Outer Shell
The outer shell, which includes the end portions of the superstructure, enclosees the bow and stern buoyancy tanks, three main ballast tanks, five fuel ballast tanks, one normal fuel oil tank, two variables and the negative tank.
Later vessels had four fuel ballast tanks and tewo normal fuel oil tanks. Of interest is the fact that one of the tree main ballast tanks has flood valves, this fells under drain and trim systems.
The outer hull does not extend around below the pressure hull except well forward. In the way of the stern buoyancy tank and MBT 1 it extends across the top of the pressure hull. As a result of these characteristics, only the buoyancy tanks ans MBT 1 and 8 are single tnaks. All other tanks are twins with interconnection only to the extent permitted, by the piping connections in each case.
The ballast and fuel tanks are designed for internel preesure not exceeding 9 psi, althrough the variables and the negative tank withstand greater pressures.
Plating is normally run in horizontal strakes of 6mm (.24") material. In way of the variable (regelzelle) tanks there are three strakes, the upper and lower of which are 15mm (.59") while the middle one is 20mm (.79"). In the way of the negative tank there are two strakes, the upper of which is 15mm (.59") while the lower, extending in to the pressure hull at the bottom of the tank, is 20mm (.79"). The heavies plate extending all the way down serves to compensate in part for the flooding openings in the negative tank. Eleswhere in the outer shell, as well, heavy plates are worked in lieu of doublers as partial compensation for openings. Light 5mm (.20") plating is used on deck at the ends of the vessles.
Framing is 60X6 (2.36"X.24") bulb tees except in the way of the stern buoyancy tank where part of the frames are 75X50X8 (2.95"X1.97"X.31") bulb tees, and in the way of MBT 8 and the bow buoyancy tank where part of the frames are 60X40X5 (2.36"X1.58"X.20") angles. Frame spacing is 500mm (19.68") throughout.
Frames are discontinous in the way of the flood valves and larger flooding openings, and are terminated on longitudinal headers outboard of such openings. The hearders are in turn terminated on web frames on bulkheads fore and aft of the openings. Tank plating is normally 12mm (.47") in the part of the tank where frames are discontinous.
Tank bulkhead are 5mm (.20") bulkheads with light bulb tee 60X6 (2.36"X.24") or smaller radial stiffeners. Web frames are similarly constructed, but with fewer stiffeners and many lightening holes. The pressure bulkheads for the variable and negative tanks are 18mm (.71") and are dished inward, without stiffeners, on earlier vessles of the type, although it appears that stiffened plate bulkheads were used on later vessels.
Radial bracing of the outer shell frames is accomplished by means of 50X50X6 (.197"X1.97"X.23") angles bracketed to the pressure hull at one end and to the outer shell frames at the other end. Structure consists uniformly of a V assembly bracing the outer edge of the tank top and the upper portion of the frame. a single bracing menber at the point of greatest beam, and an N assembly which carries the compressive load around the turn of the tanks at the bottom. The lower angle of the N terminates on the longitudinal headers where these are fitted.
Except in the way of the variable and negative tanks, the tanks are built with flat tops. Tops of the variable and negative tanks, however, are rounded over and brought in normal to the pressure hull. There are drain pipes through the tanks to drain the waterway formed by the tank margin plate and the pressure hull.
Wwelding is employed except between strakes E and F, which are lapped and rivated, for frames at the ends of the vessels, and for propeller shaft fairwater, which are riveted to the plating. On earlier vessels of the type, the riveting extended the entire length of the vessel, but on the vessels actually been a lap weld was made from outer hull frames 1 to 118, and riveting was retained forward of frame 1128 and aft of 1 (frames are numberedfrom the stern post forward). The retained section is double riveted. The section in which welding has superseded riveting was formerly single riveted.
The shell plating is steel 42 (60000 psi tensile) specification KM 9104, except in the way of the variable tanks and negative tanks, which are specified to be of steel 52, (74000 psi tensile) specifiation KM 9104. Outer shell frames are steel 42, specification KM 9104.
Coming will be the Superstrucuture.
The outer shell, which includes the end portions of the superstructure, enclosees the bow and stern buoyancy tanks, three main ballast tanks, five fuel ballast tanks, one normal fuel oil tank, two variables and the negative tank.
Later vessels had four fuel ballast tanks and tewo normal fuel oil tanks. Of interest is the fact that one of the tree main ballast tanks has flood valves, this fells under drain and trim systems.
The outer hull does not extend around below the pressure hull except well forward. In the way of the stern buoyancy tank and MBT 1 it extends across the top of the pressure hull. As a result of these characteristics, only the buoyancy tanks ans MBT 1 and 8 are single tnaks. All other tanks are twins with interconnection only to the extent permitted, by the piping connections in each case.
The ballast and fuel tanks are designed for internel preesure not exceeding 9 psi, althrough the variables and the negative tank withstand greater pressures.
Plating is normally run in horizontal strakes of 6mm (.24") material. In way of the variable (regelzelle) tanks there are three strakes, the upper and lower of which are 15mm (.59") while the middle one is 20mm (.79"). In the way of the negative tank there are two strakes, the upper of which is 15mm (.59") while the lower, extending in to the pressure hull at the bottom of the tank, is 20mm (.79"). The heavies plate extending all the way down serves to compensate in part for the flooding openings in the negative tank. Eleswhere in the outer shell, as well, heavy plates are worked in lieu of doublers as partial compensation for openings. Light 5mm (.20") plating is used on deck at the ends of the vessles.
Framing is 60X6 (2.36"X.24") bulb tees except in the way of the stern buoyancy tank where part of the frames are 75X50X8 (2.95"X1.97"X.31") bulb tees, and in the way of MBT 8 and the bow buoyancy tank where part of the frames are 60X40X5 (2.36"X1.58"X.20") angles. Frame spacing is 500mm (19.68") throughout.
Frames are discontinous in the way of the flood valves and larger flooding openings, and are terminated on longitudinal headers outboard of such openings. The hearders are in turn terminated on web frames on bulkheads fore and aft of the openings. Tank plating is normally 12mm (.47") in the part of the tank where frames are discontinous.
Tank bulkhead are 5mm (.20") bulkheads with light bulb tee 60X6 (2.36"X.24") or smaller radial stiffeners. Web frames are similarly constructed, but with fewer stiffeners and many lightening holes. The pressure bulkheads for the variable and negative tanks are 18mm (.71") and are dished inward, without stiffeners, on earlier vessles of the type, although it appears that stiffened plate bulkheads were used on later vessels.
Radial bracing of the outer shell frames is accomplished by means of 50X50X6 (.197"X1.97"X.23") angles bracketed to the pressure hull at one end and to the outer shell frames at the other end. Structure consists uniformly of a V assembly bracing the outer edge of the tank top and the upper portion of the frame. a single bracing menber at the point of greatest beam, and an N assembly which carries the compressive load around the turn of the tanks at the bottom. The lower angle of the N terminates on the longitudinal headers where these are fitted.
Except in the way of the variable and negative tanks, the tanks are built with flat tops. Tops of the variable and negative tanks, however, are rounded over and brought in normal to the pressure hull. There are drain pipes through the tanks to drain the waterway formed by the tank margin plate and the pressure hull.
Wwelding is employed except between strakes E and F, which are lapped and rivated, for frames at the ends of the vessels, and for propeller shaft fairwater, which are riveted to the plating. On earlier vessels of the type, the riveting extended the entire length of the vessel, but on the vessels actually been a lap weld was made from outer hull frames 1 to 118, and riveting was retained forward of frame 1128 and aft of 1 (frames are numberedfrom the stern post forward). The retained section is double riveted. The section in which welding has superseded riveting was formerly single riveted.
The shell plating is steel 42 (60000 psi tensile) specification KM 9104, except in the way of the variable tanks and negative tanks, which are specified to be of steel 52, (74000 psi tensile) specifiation KM 9104. Outer shell frames are steel 42, specification KM 9104.
Coming will be the Superstrucuture.
