ChK-4 class Submarine Chaser:
In 1935 the last five units of the ChK-1 class were reordered to a modified design to further amend the stability issues that emerged after the Tomozuru incident. Compared to the earlier class the new design was shorter and had a smaller beam, for an overalllenght of 60,9m and a width of 5,6. draft was still 2,1m. Displacement was reduced to 291Tons. The ships were capable of a 21knot top speed, enough to joinly operate with the Kusentei-1 units, and had a range of 2.000nautical miles at 14knots. They were armed with a twin 40mm machine guns and 36 depth charges.
Contruction of the first unit began in 1936, with 8 extra units soon added to the order to bring the class up to 13 ships. ChK-4 was commissioned first in early 1937.
Starting with ChK-10 the ships had the bridge structure revised resulting in even less topweight, all other specification remained the same. The units were thus considered to be part of the ChK-10 subclass, but officially rated as a single class with all the other previosuly commissioned boats. The last unit of the class was ins ervice by 1940.
During the pacific war the ship operated together with the three chK-1 units, forming four Subchaser Divisions (or Kusentai). Nine were still afloat in 1945 to be taken in hand for modifications: a Type 13 air-search radar and a newer hydrophone were installed and four or five single 25mm machine guns (varying from ship to ship) were added. A camouflage pattern similar to that painted on the surviving ChK-1 units was also painted.
At the end of Koko Uprisings, in March 1946, four units of the class were still afloat: ChK-8,10,14 and 15. No.10 and 15 had been badly battered and were decommissoned immediately after the end of the war, while ChK-8 operated as a repatriation vessel before beign decommissioned in 1947.
ChK-14 was in better shape and was retained in service when Koko no Kaigun was reorganized into Koko Kaijou under the peace treaty provisions in May 1947. Renamed Shorai the ship was rearmed with a twin 40mm bofor mount and a few USN electronic and equipment and turned into an ASW training ship, serving into her nw guise until 1955 when she was decommissioned and finally scrapped.
Ships in class: (laid down-launched-commissioned - fate)
ChK-4 1936-1937-1937 - Sunk 1945
ChK-5 1936-1937-1937 - Sunk 1946
ChK-6 1937-1937-1937 - Sunk 1943
ChK-7 1937-1937-1937 - Sunk 1944
ChK-8 1937-1937-1937 - Decommissioned 1947
Chk-9 1937-1937-1938 - Sunk 1944
Chk-10 1938-1939-1939 - Decommissioned 1946
Chk-11 1938-1939-1939 - Sunk 1945
Chk-12 1938-1938-1939 - Sunk 1945
Chk-13 1938-1939-1939 - Sunk 1944
Chk-14 1939-1939-1939 - Renamed Shorai 1947, Decommissioned 1955
Chk-15 1939-1939-1939 - Decommissioned 1946
Chk-16 1939-1940-1940 - Sunk 1946