Type F submarine
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| Class overview | |
|---|---|
| Name | Type F submarines |
| Builders | Kawaski, Kōbe, Japan |
| Operators |  Imperial Japanese Navy |
| Preceded by | None |
| Succeeded by | Type L submarine |
| Subclasses |
|
| Built | 1917–1922 |
| In commission | 1920-1932 |
| Completed | 5 |
| Retired | 5 |
The Type F submarines (F型潜水艦, F-gata Sensuikan) were medium Imperial Japanese Navy submarines in commission during the 1920s. They were Japan's first true seagoing submarines and the earliest Japanese submarines classified as "second-class" or "medium" submarines.
The Type F submarines were designed by the Italian firm Fiat-Laurenti and built under license by Kawasaki at Kobe, Japan.[1] The Type F submarines 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.
As built, Type F submarines had no deck gun, but soon after they were completed each of them had a 76.2 mm (3 in)/40 gun installed on her deck.[1] The Type F submarines 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] Because of their disappointing performance, they did not serve as the basis for any later Japanese submarine classes.[1]
Class variants
The Type F submarines were divided into two subclasses:
Type F1 (Ro-1-class)
The F1 subclass was ordered under the 1915–1916 naval program.[1] Two were constructed between 1917 and 1920:[1][3][4]
| Name | Laid down | Launched | Completed | Notes, fate |
|---|---|---|---|---|
| Ro-1 ex-Submarine No. 18 |
5 January 1917 | 28 July 1919 | 31 March 1920 | Renamed Ro-1 on 1 November 1924. Stricken 1 April 1932. |
| Ro-2 ex-Submarine No. 21 |
1 July 1918 | 22 November 1919 | 20 April 1920 | Renamed Ro-2 on 1 November 1924. Stricken 1 April 1932. |
Type F2 (Ro-3-class)
The F2 subclass (Ro-3-class) was ordered in 1918.[1] It was an improved version of the F1 subclass with a modified bridge.[1] 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 intended 17 knots (31 km/h; 20 mph).[1] Additional F2 subclass units planned under the 1919 construction program were cancelled and replaced by the new Kaichū-type and Type L submarines.[1]
Three submarines of the F2 subclass were constructed between 1919 and 1922:[1][5][6][7]
| Name | Laid down | Launched | Completed | Notes, fate |
|---|---|---|---|---|
| Ro-3 ex-Submarine No. 31 |
28 October 1919 | 10 March 1921 | 15 July 1922 | Renamed Ro-3 1 November 1924. Stricken 1 April 1932. |
| Ro-4 ex-Submarine No. 32 |
22 December 1919 | 22 June 1921 | 5 May 1922 | Renamed Ro-4 1 November 1924. Stricken and hulked 1 April 1932. |
| Ro-5 ex-Submarine No. 33 |
1 March 1920 | 17 September 1921 | 9 March 1922 | Renamed Ro-5 1 November 1924. Stricken and hulked 1 April 1932. |