Japanese submarine Ro-4

The Type F submarines were designed by the Italian firm Fiat-Laurenti and built under license by Kawasaki at Kobe, Japan.[1] They were the Imperial Japanese Navy′s first true seagoing submarines,[1] and when the Japanese adopted a three-tiered classification system of its submarines as first-class (I), second-class or medium (Ro), and third-class (Ha) on 1 November 1924,[2] the Type F submarines were the earliest to receive the second-class classification,[1] as reflected in their low numbers in the Ro series,[1] and in fact they were the earliest Japanese submarine classified as anything higher than third-class. They had non-cylindrical hulls intended to provide extra internal space, but the Japanese considered the hulls weak despite the provision of additional scantlings during construction to reinforce them.[1]

The submarines of the F2 subclass displaced 700 tonnes (689 long tons) surfaced and 1,064 tonnes (1,047 long tons) submerged.[1] The submarines were 65.6 meters (215 ft 3 in) long and had a beam of 6.1 meters (20 ft 0 in) and a draft of 4.1 meters (13 ft 5 in).[1] They had a diving depth of 40 meters (131 ft).[1] For surface running, the submarines were powered by two 1,300-brake-horsepower (969 kW) Fiat diesel engines, each driving one propeller shaft.[1] When submerged each propeller was driven by a Savigliano 600-horsepower (447 kW) electric motor.[1] They could reach 14 knots (26 km/h; 16 mph) on the surface and 8 knots (15 km/h; 9.2 mph) underwater.[1] On the surface, they had a range of 3,500 nautical miles (6,500 km; 4,000 mi) at 10 knots (19 km/h; 12 mph);[1] submerged, they had a range of 80 nmi (150 km; 92 mi) at 4 knots (7.4 km/h; 4.6 mph).[1]

The submarines were armed with five 450 mm (18 in) torpedo tubes, three in the bow and two in the stern, and carried a total of eight Type 44 torpedoes.[1][3] As built, they were armed with a 7.7 mm machine gun.[1] Soon after completion, however, a 76.2 mm (3.00 in) deck gun was added.[1]

In the F2 subclass, the Fiat diesel engines were unreliable and the F2 subclass′s top surface speed of 14 knots (26 km/h; 16 mph) was well below the expected 17 knots (31 km/h; 20 mph).[1] Because of their disappointing performance, the Type F submarines did not serve as the basis for any later Japanese submarine classes.[1]

Ordered in 1918, Ro-4 was laid down as Submarine No. 32 on 22 December 1919 by Kawasaki at Kobe, Japan.[4] Launched on 22 June 1921,[4] she was completed and commissioned on 5 May 1922.[4]

Upon commissioning, Submarine No. 32 was attached to the Sasebo Naval District.[4] She was assigned to Submarine Division 23 on 8 May 1922.[4] On 1 December 1922, Submarine Division 23 was assigned to the Chinkai Defense Division on the southern coast of Chōsen.[4] Submarine No. 32 was renamed Ro-4 on 1 November 1924.[4]

Submarine Division 23 was reassigned to the Sasebo Defense Division in the Sasebo Naval District on 1 December 1924.[4] On 1 June 1925, the division was assigned to the 1st Fleet,[4] and on 1 December 1925 it returned to the Sasebo Defense Division in the Sasebo Naval District, where it remained for the rest of Ro-4′s active service.[4]

Ro-4 was stricken from the Navy list on 1 April 1932.[4] She was renamed Hulk No. 3020 and served as a stationary hulk through the end of World War II on 15 August 1945.[4]

• Gray, Randal, ed., Conway′s All the World′s Fighting Ships 1906–1921, Annapolis, Maryland: Naval Institute Press, 1985, ISBN 0 87021 907 3.
• navypedia.org "Fiat" 2 class submarines (18-GO) (1920 - 1922) Accessed 22 October 2020