Momi-class destroyer

Ashi

The Momi-class destroyers were a class of twenty-one second-class destroyers of the Imperial Japanese Navy. All were named for plants. Obsolete by the beginning of the Pacific War, the Momis were relegated to mostly secondary roles, with some vessels serving throughout the war as patrol vessels or high speed transports.

Background

Construction of the medium-sized Momi-class destroyers was authorized as part of the Imperial Japanese Navy's 8-4 Fleet Program from fiscal 1918–1920, as an accompaniment to the larger with which they shared many common design characteristics. These vessels were produced at several shipyards around Japan, and when formed into attack squadrons of two to four vessels, made up the backbone of the inter-war Imperial Japanese Navy.

The final seven vessels planned for this series were cancelled, and re-ordered as the new s in 1919, and by the mid-1920s the concept of the "second-class destroyer" had fallen out of favor due to the greater capabilities offered by the new generation of fleet destroyers.

Initial design

The Momi class was a development of the second-class destroyers, relying on the same basic hull. They were quite small, comparable to Royal Navy corvettes. The design incorporated features discovered on German destroyers awarded as reparations from World War I, including a lengthened forecastle with a break forming a well deck immediately forward of the bridge, and a front gun battery placed on a pedestal on the centerline so that it could be operated in heavy weather. This arrangement also offered the advantage of a low, semi protected area for the forward torpedo tubes albeit at the cost of becoming awash in heavy seas. Initial problems with stability during high-speed turns were later corrected by widening the beam and bringing up the waterline.

When compared with the Minekaze class, the smaller size necessitated a reduction from four boilers to three and the adoption of lighter-weight Parsons direct-drive turbines, resulting in a drop from 38,500 hp in the Minekaze class to in the Momi class. In addition, fuel capacity was lowered to 275 tons of oil fuel.

As gear turbine technology was not yet perfected, the navy experimented with a variety of power plants on the Momi class:

Turbines	Equipment for
Brown-Curtis turbines	Kaya, Warabi and Tade
Parsons impulse turbines	Hishi and Hasu
Escher Wyss & Cie Zoelly turbines	Sumire
Mitsubishi Shipbuilding High-pressure impulse turbine and low-pressure reaction turbine	Kaki
Kampon turbines	all others

The Momi class was heavily armed for its small displacement, with a main battery of Type 3 120 mm 45 caliber naval guns, the same as was used on the Minekaze-class, and a set of double torpedo launchers. Anti-aircraft protection was provided by two 7.7mm machine guns.

Early operational history

Due to their shallow draft, the Momi-class destroyers proved to be excellent for operation in coastal waters, and were used along the coast of China to support amphibious landings during the Second Sino-Japanese War.

A number of the Momi-class vessels were lost or disposed during the interwar period. Momi herself was turned over to trials in 1932, while Warabi was run down by the cruiser on 27 August 1927 off Maizuru, Kyoto. Kaya and Nashi were scrapped in 1939.

Also in 1939, Aoi, Fuji, Hagi, Hishi, Kiku, Satsuki, Tade, Tsuta and Yomogi were removed from front line combat service and converted into patrol vessels. In 1940, Ashi, Kaki, Nine, Sumire, and Take were disarmed, and re-rated as training ships.

By the time of the Pacific War, the Momi-class was reaching the end of its service life, and only three (Tsuga, Hasu and Kuri) remained in service as destroyers. An effort was made to upgrade their capabilities by removing the minesweeping gear from the stern and replacing with 36 to 48 depth charges and four depth charge launchers. The amidships Type 3 guns was replaced by two triple Type 96 AA guns from 1942 to 1943, and a Type 13 radar was added. Tsuga was sunk by air attack 15 January 1945. Hasu was surrendered and scrapped at the end of the war. Kuri was surrendered, but sank after striking a mine off Korea on 8 October 1945.

As patrol boats

File:Japanese Patrol Boat No.39 sinking after being torpedoed on 23 April 1943.jpg

Periscope photo of Patrol Boat #39 (Japanese escort vessel, originally the destroyer Tade, 1922) sinking after being torpedoed by Seawolf on 23 April 1943

File:Sinking after being torpedoed 02.jpg

Patrol Boat No. 39 (ex-Tade)

Beginning in 1939, nine Momi-class vessels were re-classified as patrol boats and converted for escort duty, having one boiler removed (dropping their power to and speed to just . Their torpedo tubes, minesweeping gear, and the amidships Type 3 gun mount were replaced by six Type 96 25 mm AT/AA Guns, 36 depth charges, and three depth charge throwers. As well, their names were dropped and they were simply numbered.

During 1941–1942, these vessels were modified again, to carry and launch a Toku Daihatsu-class landing craft, by having the aft smokestack removed and the stern modified with a sloping deck to the waterline, as well as providing accommodation for 150 naval infantry troops. All of these vessels except ex-Fuji (as Patrol Boat #36) were sunk during the course of the Pacific War.

List of ships

Construction data

Name	Kanji	Builder	Laid down	Launched	Completed	Fate
	樅	Yokosuka Naval Arsenal, Japan	23 January 1918	10 June 1919	27 December 1919	Decommissioned, 1 April 1932; renamed ; used for trials to 1936
			23 December 1918	10 June 1919	28 March 1920	Decommissioned, 1 February 1940 and scrapped
		Kawasaki Shipyards, Kobe, Japan	2 February 1918	26 August 1919	10 December 1919
		Kawasaki Shipyards, Kobe, Japan	2 December 1918	26 August 1919	25 December 1919	Decommissioned, 1 February 1940; converted to training ship; scuttled as breakwater at Akita port in 1948
		Uraga Dock Company, Japan	27 February 1919	20 October 1919	2 August 1920	Decommissioned, 1 April 1940; converted to training ship; re-converted to auxiliary ship 23 February 1945; scrapped 1948
		Ishikawajima Shipyards, Japan	5 March 1919	17 April 1920	20 June 1920	Sunk off Taiwan, 15 January 1945, in air attack; struck 10 March 1945
		Kure Naval Arsenal, Japan	5 September 1919	22 December 1919	31 March 1920	Decommissioned, 1 February 1940; converted to training ship, re-converted to auxiliary ship 15 December 1944; scrapped 1948
		Kure Naval Arsenal, Japan	5 December 1919	19 March 1920	30 April 1920	Mined off Pusan, 8 October 1945; struck 25 October 1945
		Kawasaki Shipyards, Kobe, Japan	20 January 1920	13 October 1920	10 December 1920	Converted to 1 April 1940; sunk at Palau, 30 March 1944 by air attack; struck 10 May 1944
		Kawasaki Shipyards, Kobe, Japan	1 April 1920	9 November 1920	10 December 1920	Converted to 1 April 1940; grounded 23 December 1941 at Wake Island; struck 15 January 1942
		Uraga Dock Company, Japan	28 February 1920	29 October 1920	20 April 1921	Converted to 1 April 1940; grounded 23 December 1941 at Wake Island; struck 15 January 1942
		Fujinagata Shipyards, Japan	6 December 1919	27 November 1920	31 May 1921	Converted to 1 April 1940; surrendered to Netherlands in July 1946 at Surabaya; scrapped 10 August 1946
		Ishikawajima Shipyards, Japan	3 May 1920	21 February 1921	25 May 1921	Converted to 1 April 1940; sunk 6 March 1943 in collision with off Kavien; written off 10 January 1945.
		Uraga Dock Company, Japan	10 November 1920	9 May 1921	23 March 1922	Converted to 1 April 1940; sunk off Borneo, by 24 January 1942; struck 10 April 1942
		Uraga Dock Company, Japan	2 March 1921	8 December 1921	31 July 1922	Retired, 12 October 1945; scuttled as breakwater in Fukui, 1946
		Fujinagata Shipyards, Japan	12 October 1920	28 September 1921	19 December 1921	Sunk 24 August 1927 in collision with off Cape Miho; struck 15 September 1927
		Fujinagata Shipyards, Japan	20 December 1920	15 March 1921	31 July 1922	Converted to 1 April 1940; torpedoed off Yonaguni by 23 April 1943; struck 1 July 1943
		Ishikawajima Shipyards, Japan	24 November 1920	14 December 1921	31 March 1923	Decommissioned, 1 February 1940; converted to training ship, re-converted to auxiliary ship 23 February 1945; scrapped 1948
		Kawasaki Shipyards, Kobe, Japan	16 October 1920	9 May 1921	30 June 1921	Converted to 1 April 1940; sunk at Lae by air attack 2 September 1942; struck 10 February 1943
		Kawasaki Shipyards, Kobe, Japan	15 November 1920	3 September 1921	29 October 1921	Decommissioned, 1 February 1940; converted to training ship, re-converted to auxiliary ship 15 December 1944; modified to Shin'yō suicide motorboat mothership 1945, scrapped 1947
		Ishikawajima Shipyards, Japan	26 February 1921	14 March 1922	19 August 1922	Converted to 1 April 1940: torpedoed Bashi Strait by 25 November 1944; struck 10 March 1945