[WWII] CB-class coastal midget submarine (Italy)

[copeab]

CB-class coastal midget submarine
Copyright 2011 by Brandon Cope

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 Constanta (a squadron of four MAS Classe 500 torpedo boats (p.W:GL35) were also part of this flotilla). One was sunk by aircraft that summer but the other five survived until the Italian surrender 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. Six were completed and used by the Italians, with five interned by the British in 1943 and the sixth (CB 7) taken by the Germans, then handed over to the Italian Social Republic, as well as the remaining ten which had been laid down. At least one was completed (most likely all ten) after September 1943, some 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 two confirmed Russian submarines sunk and one 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. Its 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 8 mph submerged.

Subassemblies: Light Cutter 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
Collars: 3/5

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
Size: 49’¥10’¥14’
Payload: 11.7 tons
Lwt: 45.1 tons
Volume: 320
Maint.: 71 hours
Price: $8,700
HT: 12
HP: 3,000 [Body], 120 [each torpedo collar]

wSpeed: 8.5
wAccel: 0.2
wDecel: 0.5(0.7)
wMR: 0.05
wSR: 4
Draft: 6'
Flotation Rating 50 tons.

uSpeed: 8
uAccel: 0.05
uDecel: 0.3(0.4)
uMR: 0.05
uSR: 4
uDraft: 14'
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).

[Michele]

Thanks for the interesting write-up, Brandon.
A few remarks.

- I wouldn't write "Costanza" for the name of that seaport. Sure that's its name in Italian sources, but I think in English one would use the Romanian form, Constanta.
- A total of 22 vessels were completed.
- These midgets sank two Soviet subs; this is confirmed by Soviet records. The third one is an unconfirmed claim.
- Those that were incomplete on the day of the armistice were only temporarily under German control. They were then handed over to the RSI Navy. The service history of these is somewhat interesting for RPG adventurers, because they were occasionally used to deploy agents down the coast. One of those also saw a mutiny, with the three crewmen surrendering to the Allies after having killed the commander.
- The five that weren't handed over to the Romanians nor captured by the Germans weren't "handed over" to the British. They reached the rest of the Regia Marina fleet in internment. Two of them later served for close coastal patrolling out of Malta, but with Italian co-belligerent crews. The Allies considered using these boats for sabotage missions against German-held ports, but that never happened - a GM could change that.

The sources are the good old Gino Galuppini and various others.

[copeab]

Originally Posted by Michele

Thanks for the interesting write-up, Brandon.

At least it was mostly right ;)

- A total of 22 vessels were completed.

Any idea if the others were used in their intended roles or where they were deployed?

I'll see about working in your comments as soon as I can.

I found conflicting numbers for displacement. Some sources list ~25 tons surfaced and ~35 tons submerged, while others list about 35 tons surfaced and 45 tons submerged. The latter numbers worked out better in the design (if the bilges are cleared, design weight drops to 37 tons) but I'm wondering which is right

[Michele]

Originally Posted by copeab

Any idea if the others were used in their intended roles or where they were deployed?

To simplify, I'd say there are three batches.

The first one was deployed to the Black sea, and saw some actual use there, and scored that couple of hits. Then it went to the Marina Regala Romana, which did not use them.

The second batch was with the Regia Marina, had a chance to scoot after the armistice, and saw almost no service because it was interned (the exception are those two on coastal patrol service at Malta, as mentioned).

The remaining batch was captured by the Germans, mostly while incomplete; and they were handed over to the RSI Navy (entirely, or mostly, the X MAS Flotilla). These were deployed in the Adriatic Sea for the good reason that were being built there, and there was neither much chance of success nor much sense in trying to deploy them elsewhere. In Trieste and Pola (now Pula, Croatia - don't forget that at the time Italy was bigger there than today).

If you really want some midget sub action in the Tyrrenian, however, you can look up the CA subs, three of them were in La Spezia. I thought that these would be more interesting than the CBs because apart from those three in La Spezia, one was in Bordeaux, and the reason why it was there was that it was planned to load it onto a dedicated modified mother sub, to carry it to... New York, and to use it for a propaganda attack there.

Nothing came of that, but, again, a GM could change this.

[copeab]

Originally Posted by Michele

If you really want some midget sub action in the Tyrrenian, however, you can look up the CA subs, three of them were in La Spezia. I thought that these would be more interesting than the CBs because apart from those three in La Spezia, one was in Bordeaux, and the reason why it was there was that it was planned to load it onto a dedicated modified mother sub, to carry it to... New York, and to use it for a propaganda attack there.

Nothing came of that, but, again, a GM could change this.

The reason I didn't do the CA was that none of my four books on submarines mentioned them (only one mentioned the CB, but a fair amount of data was provided for it). I came across the CA as I was wrapping up research on the B and decided to go ahead and finish and post that one instead.

The other Italian subs I'm considering doing, at the opposite end of the size spectrum, are the two R-class cargo subs.

[Phaelen Bleux]

What kind of chassis. . .?

[copeab]

Originally Posted by Phaelen Bleux

What kind of chassis. . .?

Light Cutter. Fixed.

[Ed the Coastie]

This is the kind of sub that would fit rather nicely into my Spellgate 2.0 game, especially the part about one of them being sent to attack New York. I can see the irrepressible Kylie and her new band of associates on the trail of some bad guy and venturing down into a flooded and long-forgotten subway tunnel, only to discover an old Italian midget sub that the bad guy is in the process of refurbishing...

[copeab]

Originally Posted by Ed the Coastie

This is the kind of sub that would fit rather nicely into my Spellgate 2.0 game, especially the part about one of them being sent to attack New York.

That's the CA class, not the CB class:

http://en.wikipedia.org/wiki/CA_class_midget_submarine

[Ed the Coastie]

True...but the inspiration is there nevertheless.