CB CLASS

by Cristiano D'Adamo

Technical Specifications

Submarines of the "CB" class

Italian CB-2 Submarines - Construction Details
1. The following is a translation of a report prepared by an officer of the Italian Navy concerning Italian 35-ton submarines of the type known as “CB” or “CB-2”. Five of these vessels were reported to have been turned over to the Rumanians, and their Italian crews interned in Rumania, following the Italian Armistice. The Rumanian ensign is reported to have been hoisted on the vessels (see reference (a)). It is now reported that these five submarines are: CB1, 2, 3, 4, 6.

CB 10 docked in Taranto in October 1943, following the Italian armistice.
(Photo National Archives)

“CB SUBMARINES”

2. 
Displacement: 35 tons
Length: 15 meters
Beam: 2.10 meters
Draft: 2.5 meters

Contain two compartments:

A – Navigation Room
B – Engine Room

The two compartments are separated by a light bulkhead which is gas-proof at a low pressure.

The navigation room seen from the engine room. 
The two compartments were separated by a light bulkhead 
which was gas-proof only at low pressure.
(Photo Cepparo)
3. Navigation Room

Toward the bow in direct contact with the pressure hull (Calotta elicoidale) are installed two (2) Calzoni pumps to which are attached air vents, the flooding of tanks, and operation of the rudder and hydroplanes. In the upper part of the pressure hull is the air vent for N.5 ballast tank. Proceeding aft on the left, there are the radio reception and transmission equipment. Continuing aft, there are:

(a) The valve of the air containers, installed in the cofferdam (between bulkheads?), and composed of fifteen (14) two hundred (200) kg. Flasks.

(b) The torpedo compensator air vents, operable only manually.

(c) The air vents of 1 and 3 ballast tank, and starboard diving tank, on the left; and the 2 and 4 ballast tanks, and the starboard diving tank, on the right. Below these air vents are the air valves for the sections to which the air vent pertain.

A very good view of the forward compartment. 
This is a picture of CB 20, later renamed P901 and used by the Yugoslavian Navy. 
Today, it is on display at the Teknicki Muzej of Zabrab.
(Photo Pavolich)

(d) Forward of this panel is the intake ventilator (in corresponding position to port is the expulsion ventilator; with one or the other, it is possible to ventilate the nearby space or the battery compartment).

(e) To port, forward of the air vents are the Calzoni controls for flooding of blowing, which (with skill) can also be operated manually.

(g) To starboard in the same position, forward of the air vents, is the switchboard of the electrical motor and of all auxiliary motors.

(h) Under this board are two (2) trimming pumps with their controls.

(i) To port, facing the switchboard are the air controls for blowing the diving tanks and 1, 2, 3, 4, and 5 ballast tanks; for the charging the Calzoni air flasks for launching torpedoes, and for the air for the siren.

(j) Two third of the way forward from this section, between the two hatches, is the fixed periscope (periscopio fisso).

Radioman Nannini while he is operating the radio equipment. This was the only part of the vessel where one could almost stand up. In general, movement within the boat required the three crewmembers to crawl.
(Photo Cepparo)
4. Engine Room

(a) Directly abaft the bulkheads, to port, is the gyro-compass, while to starboard is the hydrogen consumer (il bruciatore idrogeno).

(b) Slightly to starboard of the midship is an Isotta Fraschini diesel engine, from which the shaft extends aft with two couplings, between which is located the Marelli electric motor. Abaft the coupling of the electric motor is the reduction gear and the small pump circulating water in the cooling system of the electric motor. In the ceiling of the engine room, above the electric motor, are two reserve air-flasks.

(c) To port, under the transformer (convertitrice) of the gyro-compass is the oxygen flask.

Another photo of the CB 20. This the aft compartment (engine room). 
Both the diesel and electric engines are well visible.
(Photo Pavolich)

5. Other Details

(a) Abaft the forward hatch are the ventilation pipes.

(b) Forward of the bulkhead are:

i. The control of the diesel exhaust valve;
ii.The diesel operating controls;
iii. The control switchboard of the hydrogen consumer;
iv. The Brandfield, with safety lock;
v. The magnetic compass housing

(c) Batteries

Batteries are installed in four (4) groups beneath the )gas-proof_ deck of the navigation room and consist of three hundred eight (308) cells.

(d) Armament

Two torpedoes in external tubes, with internal fire control near the forward hatch.
Note: This document was declassified by NARA. Authority NND765068, dated May 9th, 2002.
 

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