Italian submarine Smeraldo

History
Kingdom of Italy
Name	Smeraldo
Builder	Cantieri navali Tosi di Taranto, Taranto
Laid down	1931
Launched	27 July 1933
Fate	Lost, September 1941
General characteristics
Class and type	Sirena-class submarine
Displacement	691 t (680 long tons) (surfaced); 850 t (837 long tons) (submerged);
Length	60.18 m (197 ft 5 in)
Beam	6.45 m (21 ft 2 in)
Draft	4.7 m (15 ft 5 in)
Installed power	1,350 kW) (diesels); 800 hp (600 kW) (electric motors);
Propulsion	2 shafts; diesel-electric; 2 × diesel engines; 2 × electric motors;
Speed	14 knots (26 km/h; 16 mph) (surfaced); 7.5 knots (13.9 km/h; 8.6 mph) (submerged);
Range	5,000 nmi (9,300 km; 5,800 mi) at 8 knots (15 km/h; 9.2 mph) (surfaced); 72 nmi (133 km; 83 mi) at 4 knots (7.4 km/h; 4.6 mph) (submerged);
Armament	1 × single 100 mm (3.9 in) deck gun; 2–4 × single 13.2 mm (0.52 in) machine guns; 6 × 533 mm (21 in) torpedo tubes (4 bow, 2 stern);

Smeraldo was one of a dozen Sirena-class submarines, the second sub-class of the 600 Series of coastal submarines built for the Regia Marina (Royal Italian Navy) during the early 1930s.

Design and description

The Sirena class was an improved and enlarged version of the preceding Argonauta-class submarines. They displaced 691 metric tons (680 long tons) surfaced and 850 metric tons (837 long tons) submerged. The submarines were 61.5 meters (201 ft 9 in) long, had a beam of 5.7 meters (18 ft 8 in) and a draft of 4.7 meters (15 ft 5 in). Their crew numbered 45 officers and enlisted men.^[1]

For surface running, the boats were powered by two 675-

propeller shaft. When submerged each propeller was driven by a 400-horsepower (298 kW) electric motor. They could reach 14 knots (26 km/h; 16 mph) on the surface and 7.5 knots (13.9 km/h; 8.6 mph) underwater.^[2] On the surface, the Sirena class had a range of 5,000 nautical miles (9,300 km; 5,800 mi) at 8 knots (15 km/h; 9.2 mph);^[1] submerged, they had a range of 72 nmi (133 km; 83 mi) at 4 knots (7.4 km/h; 4.6 mph).^[2]

The boats were armed with six 53.3-centimeter (21 in)

13.2-millimeter (0.52 in) machine guns.^[1]