No.251-class auxiliary submarine chaser

The No.251 class auxiliary submarine chaser (第二五一号型駆潜特務艇,) was a class of submarine chasers of the Imperial Japanese Navy (IJN), serving during World War II. 3 vessels were built in 1936 – 1939 under the Maru 2 Programme. They have two sub classes, this article handles them collectively.

Background

 * In 1934, the IJN planned an experimental model of high-speed coast defense submarine chaser. The IJN wanted over 20 kn, however the Navy Technical Department (Kampon) have not designed such a small-sized and high-powered diesels yet.
 * The IJN ordered hull design to the Thornycroft, and high-powered diesel design to the MAN, for study a small-sized high-speed boat.

Design

 * The Thornycroft drawings were not able to satisfy the IJN, because their designs center of gravity was too high, and bad drainage. The Kampon made a based on the Hayabusa class torpedo boat and finished hull designs.
 * The IJN was satisfied with MAN diesel specifications, however their designs were very complicated and very high-prices. The IJN bought two diesels and named MAN Mk.1 diesel (マ式1号ディーゼル,). Furthermore, the IJN ordered a copy of this diesel to the Kawasaki Heavy Industries and Mitsubishi Heavy Industries.
 * Also, 1 vessel was equipped with a Kampon turbine, because diesel engine was unsuitable for a mass production.

Service

 * The IJN deployed them to a mine warfare school after having finished their examination, because they were too small.
 * They became a training ship of the mine warfare school, and they acted in Tokyo Bay.

No.251-class

 * Project number K5A. 2 vessels were completed. They were equipped with MAN design diesels. The No.252 was equipped the copied MAN diesels by Kawasaki and Mitsubishi.

No.251

 * 14 December 1936: Laid down as the Submarine Chaser No.51 (第51号駆潜艇,) at Nihon Kōkan, Tsurumi Shipyard.
 * 9 June 1937: Launched.
 * 30 September 1937: Completed.
 * 15 November 1940: Classified to the Auxiliary submarine chaser, and renamed Auxiliary Submarine Chaser No.51 (第51号駆潜特務艇,).
 * (after): Assigned to the mine warfare school (Kurihama).
 * 30 April 1943: Renamed Auxiliary Submarine Chaser No.251 (第251号駆潜特務艇,).
 * 28 August 1944: Classified to the Support vessel (tugboat), and renamed No.1658 (公称第1658号,).
 * August 1945: The end of war at Uraga, later nothing more was heard.

No.252

 * 14 December 1936: Laid down as the Submarine Chaser No.52 (第52号駆潜艇,) at Nihon Kōkan, Tsurumi Shipyard.
 * 25 August 1937: Launched.
 * 25 July 1939: Completed.
 * 15 November 1940: Classified to the Auxiliary submarine chaser, and renamed Auxiliary Submarine Chaser No.52 (第52号駆潜特務艇,).
 * (after): Assigned to the mine warfare school (Kurihama).
 * 30 April 1943: Renamed Auxiliary Submarine Chaser No.252 (第252号駆潜特務艇,).
 * 15 February 1944: Classified to the Support vessel (tugboat), and renamed No.1650 (公称第1650号,).
 * August 1945: The end of war at Uraga, later nothing more was heard.

No.253-class

 * Project number K5B. 1 vessels was completed. She was equipped with Kampon turbine. She was classed in the No.251-class in the IJN official documents.

No.253

 * 9 January 1937: Laid down as the Submarine Chaser No.53 (第53号駆潜艇,) at Ōsaka Iron Works, Sakurajima Factory.
 * 15 July 1937: Launched.
 * 31 October 1937: Completed.
 * 15 November 1940: Classified to the Auxiliary submarine chaser, and renamed Auxiliary Submarine Chaser No.53 (第53号駆潜特務艇,).
 * (after): Assigned to the mine warfare school (Kurihama).
 * 30 April 1943: Renamed Auxiliary Submarine Chaser No.253 (第253号駆潜特務艇,).
 * 15 February 1944: Classified to the Support vessel (tugboat), and renamed No.1651 (公称第1651号,).
 * August 1945: The end of war at Uraga.
 * August 1946: Sink by unknown effect.