Copyright 2011 by Brandon Cope

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CB-class coastal midget submarine

The CB boats were originally designed to be used as anti-submarine platforms, operating in coastal waters and the first six were built in January to May of 1941, with 72 planned but only 22 hulls laid down. The submarines were about the same length as the British X-craft (p.W:HS27) but with double the displacement. In early 1942, these submarines were transferred to the Black Sea and used offensively against Russian submarines, operating as part of the 101st Flotilla from the Romanian port of Costanza (a squadron of four MAS Classe 500 torpedo boats (pW:GL35) were also part of this flotilla)). One was sunk by aircraft that summer but the other five survived until the Armistice in September 1943, at which point they were turned over to the Romanians (most sources say the CBs were first taken by the Germans, then given to the Romanians, but one source claims the Italian sailors handed them over directly to the Romanians, to prevent them from falling into German hands. These served with the Romanian navy until 1944, when they were scuttled in the face of the Russian advance; four of the boats were raised and commissioned into the Russian navy, some lasting as long as 1955.

Sixteen more hulls were laid down and sources conflict as to how many were actually completed. Possibly six more were completed and used by the Italians, with five handed over to the British in 1943 and the sixth taken by the Germans. Of the remaining ten boats, all taken over by the Germans, and at least one was completed, using parts from the CB 7. Five of these ten were destroyed by Allied aircraft and a sixth sunk in a collision.

The actual wartime exploits of the little subs was not good – only one confirmed Russian submarine sunk and two more possibly sunk. The main problems was that the CB was quite slow on he surface and carried only two (weak) torpedoes, both factors distinct liabilities in offensive operations.

The CB has a crew of 4. It two 450mm torpedoes firing forward in unsealed, external collars. The engine burns 2.4 gallons of diesel fuel per hour of routine usage. The CB can travel 500 miles at 8.5 mph or 1,600 miles at 5.5 mph surfaced and 58 miles at 3.5 mph or 7 miles at 8mph submerged.

Subassemblies: Light Chassis chassis with Sub option +5, two Large Weapon torpedo collars +2 [L,R].
Powertrain: 60-kW marine diesel engine with 60-kW water screw and 650-gallon standard tanks; 37-kW electric motor with 55,000-kWs batteries†.
Occupancy: 4 CS Body Cargo: 5 (plus 93 waste space)

Armor
Body: 4/25

Weaponry
2¥450mm Torpedo Tubes [Collars: F] (2).

Equipment
Body: Autopilot; 55-VSP bilge; bilge pump; 2 bunks; 5-VSP cargo hold; 15-man/day life support†; fire extinguisher†; navigation instruments; precision navigation instruments; 10-man/days of provisions; large radio receiver and transmitter.
† Limited access.

Statistics

HT: 12
HP: 3,000 [Body], 120 [each torpedo collar]

Flotation Rating 50 tons.
 

Crush Depth 70 yards.

Design Notes
Design surface speed was 12 mph and underwater speed was 6.5 mph. Both have been adjusted to the historical, as well as surface draft (design was 3') and floation rating (design was 34 tons).