@Garlic: Thank you very much. while I'll probably use just the German names it would be unfair to say that such list wouldn't beuseful to me sooner or later.
Anyway, I feel a bit guilty to post the next class of ships now. It felt such an idea-ripoff from your excellent Coire class, even if it's not actually the case (got the idea sometime ago by browsing Krakatoa's Fisherless RN). I Hope for some mercy.
Kimmei Class Fast Minelayer:
By the early 30's Koko no Kaigun minelaying fleet was strong of ten ships, with another four under construction and three more planned. Some of the designs were direcly influenced by the London Naval Treaty, resulting in large treaty-skirting designs like the Fusetsukan-19 class ships, which featured almost cruiser-like armament (although only one out of three was actually built to the original specifications). Yet, another class of Kokoan Minelayers built during the decade was the result of a wider array of requirements.
Maps at hand, The closesness of foreign territories to Koko was striking. Tojima (Koko's easternmost island) and Midway Island were located 480 nautical miles, away. Attu and the Aleutians were just over 320nm northeast of Wasureshima. Petropavlovsk, and Kamchatka, were no more than 450 nautical miles northwest of Kitajima. Such relatively short distances made the concept of a fast minelaying vessel highly appealing for the Naval Staff. Under such provisions design started in early 1932.
The first requirement was that the ships had to be fast enough to make a trip from Tojima to Midway and back in just a day, something that could be achieved only by reaching the speed of 40 knots. To compensate LNT limitations the ships were to sport at least six destroyer-sized guns and carry not less than 170 naval mines. Soon designers realized that some corner had to be cut before such units could be turned into reality, as neither the speed or required armament could be easily achieved or fitted at the same time. When the ships were finally approved in late 1933, as a class of four, things had been rounded up to the best possible compromise.
Named Kimmei, Yozei, Heizei and Takakura the ships were allocated to Hoshiguma (Kimmei and Takakura), Toumachi (Yozei) and Kousaten (Heizei) naval yards. All recieved former protected cruiser names instead of the usual numerical denomination of the other Minelayers, and they were also not part of the former pennant sequence. All to reflect their uniquesness. As the final design allowed, the ships could be used either as Fast Minelayers, high-speed transports or supply vessels and even as flagships for torpedo boat squadrons if needed.
Hull lenght was 131,2m at the waterline, for an overall one of 133,97. Beam was 12,1m and draft 3,9m. The ships displaced 2.779T standard and 3.563T full load. Two 127mm twin gun turrets -for a total of four barrels- were fitted on the forecastle as the main armament. Anti-air suite was originally planned at sixteen 13mm machine guns in four quadruple mounts, but by commissioning the aft mounts were replaced by two twin 25mm mounts. The hull was unarmoured, but with enough space to carry 190 Mk.6-Mod.1 naval mines, or 230 Type88 ones. Up to 44 depth charges could also be carried without reducing the mine complement. Contrary to most Japanese and Kokoan ship a degaussing coil system and cable were fitted inside the ship from the start and not subsequently added later. The engines were high-end ones, even if the planned top speed had been shelved from the envisioned 40 to 37,5 knots no half-measures were taken. Four boilers powered two geared steam turbines driving two three bladed propellers with a generated power of 80.000 shp. Endurance was estimated at 3.800 nautical miles at 15 knots, 1.760 at 26 knots, or 900 at 37 knots. At a continous 35 knot-speed they could do the Tojima-Midway trip in a little more than thirteen-and-a-half hours, while Attu could be reached in just eight-and-a-half hours at top speed.
All laid down between 1934 and 1937 and commissioned between 1936 and 1939, the four Kimmei-class ships easily surpassed their planned engine output, generating over 83.000shp without issues, achieving maximum speeds around 38,8 knots. The fastest of the four was Takakura, which clocked at 39,02 knots with the engines generating 83.692shp. surprisingly, endurance figures were equaled, with minor deviations from the planned fuel consumption. All had a full complement of 245 officers and men.
Before the start of the Pacific War, in November 1941, all four recieved a blue paintscheme to reduce visibility from the air. The four sisters departed for the Aleutians a few weeks after the occupation of Attu, based there they made multiple sorties to lay minefields around Umnak and Unalasaka. During one of those missions, in January 1942, Heizei suffered minor damage from near-misses when she was attacked by enemy planes, requiring two weeks of repair at Kumoi Arsenal. Overall, the initial minelaying operations in aleutian waters were considered succesful overall, between January and May 1942 naval mines laid by the four Kimmei class ships damaged the Light cruiser Concord, five destroyers -two seriously- and one merchant. All four sailed again together carriyng supplies for troops during operation AL/MI before returning home after the Kido Butai was ambushed off Midway. Their speed led them to be ordered south to Rabaul, where they landed their mine complement and started to operate as fast transports to support land operations around Guadalcanal. It was during one of those operations -on October 28th- that Yozei was caught at dawn while speeding back towards Rabaul by planes of the USS Enterprise and sunk after suffering five bomb hits.
The three survivors continued their supply runs until February 1943, when US troops evacuated Guadalcanal, then embarked again their mine load for operations against Espiritu Santo. In late March 1943, during one of those missions, Kimmei was caught by planes launched by the Recerchean carrier HMRS Eyre: After jettisoning all her mines the Kokoan minelayer reversed course and made 38,4 knots towards a nearby rain squall, eventually losing her pursuers, but not before suffering a single bomb hit on the quarterdeck that wrecked the mainmast, anti-air platforms and aft deckhouses. The ship returned to Koko for two months of repair.
In early October 1943 Heizei and Takakura were also recalled to Kokoan home waters, then based at Midway, to counter renewed USN presence along the Hawaiian island chain. All three alternated supply runs and minelaying missions for the rest of the year and the first months of 1944. By May all had recieved a minor refit: a few portholes on the lower decks were closed over, depth charge sotwage was increased to 66 charges, the forward quad 13mm machine guns were replaced with two twin 25mm ones and ten singles were also added for a total of eighteen barrels. A type13 air-searh radar was fitted and the blue camouflage revised, adding disruptive black patches and a second, darker, shade of blue.
During one of those minelaying missions, on May 27th 1944, Takakura was sighted by the USS Snapper (SS-185) which fired all her eight bow and stern tubes. Six torpedoes hit the minelayer, causing a sympathetic detonation of both the mine and depth charge warheads. Takakura exploded and sank leaving only 13 survivors.
After the shocking loss of Takakura, the two surviving units were temporariliy withdrawn from offensive minelaying and assigned to supply runs between Toumachi and Midway and between Teshigawa and Attu. In October 1944 they were refitted again: nearly all portholes were plated over and the anti-aircraft armament completely renewed by fitting nine triple and eight single 25mm machine guns, for a total of 35 barrels. Mine complement was reduced to 156 warheads, while depth charge inventory was increased to 100. An hydrophone was fitted at the bow. Randar and fire-control suite was largely upgraded, a Type33-kai surface search radar was fitted on the foremast, supplemented by Thiarian R2FA air-search radar and R6R high-frequency director finder. An R12CAD anti-air fire-control radar was also fitted on the main gun director. Such loaded their maximum achievable speed dropped to 37,6 knots. In January 1945 a new experimental gray, black and two-tone blue disruptive camouflage-scheme was painted on both ships, while boat complement was vastly reduced.
Such modified Kimmei and Heizei kept serving as minelayers and fast transports in the Aleutian theatre. Here Kimmei met her end on August 12th, shortly before the American invasion of Kiska, bombed by US B-24s. Heizei, now the only survivor, was refitted again in late October 1945. All 25mm machine guns were landed and replaced by nine twin 40mm mounts, totaling 18 barrels. When Koko uprisings started, Heizei was berthed at Teshigawa, were she remained for the rest of the conflict. When the Pacific War ended she landed two of the 40mm mounts and all of her mines and depth charges. She was repainted into standard gray and had her name and Kokoan flag added on her side.
Thanks to her speed she then operated as a repatriation vessel after beign stripped of all her remaining armament. Even so, because of all the wartime strain, she was good of no more than 36,8 knots. After fulfilling this last duty, Heizei was finally decommissioned in June 1947 and scrapped shortly after.
Ships in class: (laid down-launched-commissioned - fate)
Kimmei 1934-1935-1936 - Sunk 1945
Yozei 1935-1936-1937 - Sunk 1942
Heizei 1936-1937-1938 - Decommissioned 1947
Takakura 1937-1938-1939 - Sunk 1944