Japanese submarine Ro-21

History
Japan
Name	Submarine No. 39
Builder	Yokosuka Naval Arsenal, Yokosuka, Japan
Laid down	28 July 1919
Launched	26 October 1920
Completed	1 February 1922
Commissioned	1 February 1922
Renamed	Ro-21 on 1 November 1924
Stricken	1 April 1934
Fate	Sold 6 July 1935; Scuttled as artificial reef ca. 1935;
General characteristics
Class and type	Kaichū type submarine (K3 subclass)
Displacement	752 tonnes (740 long tons) surfaced; 1,013 tonnes (997 long tons) submerged;
Length	70.10 m (230 ft 0 in) overall
Beam	6.12 m (20 ft 1 in)
Draft	3.70 m (12 ft 2 in)
Installed power	2,900 bhp (2,200 kW) (diesel); 1,200 hp (890 kW) (electric motor);
Propulsion	Diesel-electric; 2 × Sulzer Mark II diesel engine, 75 tons fuel; 2 × electric motor; 2 x shafts;
Speed	16.5 knots (30.6 km/h; 19.0 mph) surfaced; 8.5 knots (15.7 km/h; 9.8 mph) submerged;
Range	6,000 nmi (11,000 km; 6,900 mi) at 10 knots (19 km/h; 12 mph) surfaced; 85 nmi (157 km; 98 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged;
Test depth	45.7 m (150 ft)
Crew	46
Armament	6 × 450 mm (18 in) torpedo tubes (4 x bow, 2 x external on upper deck); 10 x Type 44 torpedoes; 1 × 76.2 mm (3.00 in) gun;

Ro-21, originally named Submarine No. 39, was an Imperial Japanese Navy Kaichū-Type submarine of the Kaichū III subclass. She was commissioned in 1922 and operated in the waters of Japan. She was stricken in 1934.

Design and description

The submarines of the Kaichu III sub-class were a slightly improved version of the preceding Kaichu II subclass, the man difference being an increase in diving depth from 30 to 45.7 meters (98 to 150 ft).^[1] They displaced 752 tonnes (740 long tons) surfaced and 1,013 tonnes (997 long tons) submerged. The submarines were 70.10 meters (230 ft 0 in) long and had a beam of 6.12 meters (20 ft 1 in) and a draft of 3.70 meters (12 ft 2 in).

For surface running, the submarines were powered by two 1,450-brake-horsepower (1,081 kW) Sulzer Mark II diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 600-horsepower (447 kW) electric motor. They could reach 16.5 knots (31 km/h; 19 mph) on the surface and 8.5 knots (15.7 km/h; 9.8 mph) underwater. On the surface, they had a range of 6,000 nautical miles (11,000 km; 6,900 mi) at 10 knots (19 km/h; 12 mph); submerged, they had a range of 85 nmi (157 km; 98 mi) at 4 knots (7.4 km/h; 4.6 mph).

The submarines were armed with six 450 mm (18 in) torpedo tubes, four internal tubes in the bow and two external tubes mounted on the upper deck, and carried a total of ten Type 44 torpedoes. They were also armed with a single 76.2 mm (3.00 in) deck gun mounted aft of the conning tower.^[1]

Construction and commissioning

Ro-21 was laid down as Submarine No. 39 on 28 July 1919 by the Yokosuka Naval Arsenal at Yokosuka, Japan.^[2] Launched on 26 October 1920,^[2] she was completed and commissioned on 1 February 1922.^[2]

Service history

Upon commissioning, Submarine No. 39 was attached to the Yokosuka Naval District, to which she remained attached throughout her career.^[2] On 6 February 1922, she was assigned to Submarine Division 5 and to the Ominato Defense Division,^[2] and on 1 November 1924 she was renamed Ro-21.^[2] On 1 November 1925, Submarine Division 5 was reassigned to the Yokosuka Defense Division,^[2] then directly to the Yokosuka Naval District on 1 December 1926, and then to the Yokosuka Defense Division again on 10 January 1927.^[2]

Ro-21 was stricken from the Navy list on 1 April 1934.^[2] Her engines were removed at Uraga Shipyard, and on 6 July 1935 she was sold to the Fisheries Association of Miura District in Kanagawa Prefecture for use as an artificial reef. She subsequently was scuttled to serve as a breeding ground for fish and fishing reef.

Notes

^ ^a ^b Gray, Randal, ed., Conway′s All the World′s Fighting Ships 1906–1921, Annapolis, Maryland: Naval Institute Press, 1985, ISBN 0 87021 907 3, p. 248.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ "RO-21 ex No-39". iijnsubsite.info. 2018. Retrieved 14 October 2020.

References

"Rekishi Gunzō"., History of Pacific War Vol.17 I-Gō Submarines, Gakken (Japan), January 1998, ISBN 4-05-601767-0
Rekishi Gunzō, History of Pacific War Extra, "Perfect guide, The submarines of the Imperial Japanese Forces", Gakken (Japan), March 2005, ISBN 4-05-603890-2
The Maru Special, Japanese Naval Vessels No.43 Japanese Submarines III, Ushio Shobō (Japan), September 1980, Book code 68343-44
The Maru Special, Japanese Naval Vessels No.132 Japanese Submarines I "Revised edition", Ushio Shobō (Japan), February 1988, Book code 68344-36
The Maru Special, Japanese Naval Vessels No.133 Japanese Submarines II "Revised edition", Ushio Shobō (Japan), March 1988, Book code 68344-37
The Maru Special, Japanese Naval Vessels No.135 Japanese Submarines IV, Ushio Shobō (Japan), May 1988, Book code 68344-39

[gray-1] Gray, Randal, ed., Conway′s All the World′s Fighting Ships 1906–1921, Annapolis, Maryland: Naval Institute Press, 1985, ISBN 0 87021 907 3, p. 248.

[ijnsubsiteRo21-2] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ "RO-21 ex No-39". iijnsubsite.info. 2018. Retrieved 14 October 2020.

[1]

[2]

v t e Kaichū type submarine
Ro-11-class (Type K1)	Ro-11 Ro-12
Ro-13-class (Type K2)	Ro-13 Ro-14 Ro-15
Ro-16-class (Type K3)	Ro-16 Ro-17 Ro-18 Ro-19 Ro-20 Ro-21 Ro-22 Ro-23 Ro-24 Ro-25
Ro-26-class (Type K4)	Ro-26 Ro-27 Ro-28
Ro-29-class (Toku-Chū/Type K5)	Ro-29 Ro-30 Ro-31 Ro-32
Ro-33-class (Type K6)	Ro-33 Ro-34
Ro-35-class (Sen-Chū/Type K7)	Ro-35 Ro-36 Ro-37 Ro-38 Ro-39 Ro-40 Ro-41 Ro-42 Ro-43 Ro-44 Ro-45 Ro-46 Ro-47 Ro-48 Ro-49 Ro-50 Ro-55 Ro-56
Preceded by: Type L submarine Followed by: Ko type submarine Imperial Japanese Navy submarines

v t e Shipwrecks and maritime incidents in 1935
Shipwrecks	2 Jan: Lexington 24 Jan: Mohawk 25 Jan: Rondo 20 Feb: Vila 24 Apr: HMAS Geranium, HMAS Mallow 25 Jun: USS Marcus 26 Jun: USS Sloat 9 Jul: Maheno 31 Jul: Verdi 1 Aug: HMAS Marguerite 3 Aug: Princess Ena 17 Sep: HMS L52 Unknown date: Chikuma, Ro-20, Ro-21, Ro-28
Other incidents	6 Jan: Havana 25 Jan: Dumana January (unknown date): Ruth Kellogg 2 Mar: Pommern 10 Apr: Aquitania 11 Apr: Letitia 12 May: USS Sicard 21 May: Naïade 25 May: I-24 May (unknown date): Ruth Kellogg 12 Jun: HMS Hastings 13 Jul: L'Espoir 1 Aug: Akatsuki, I-6 16 Aug: Letitia 4 Sep Prince Rupert 5 Sep: Doric 29 Sep: Rotterdam 17 Oct: Noemijulia Unknown date: Giulio Cesare
1934 1936