Link to part 1
Kumoi Class Light Cruiser (part 2, 1930-1940):
After tests of a spring catapult fitted on the forward flying off platform, done between 1929 and 1931, proved to be unsuccesful Kizu entered and left the yards repeatedly.
In 1931, she was briefly docked at Kumoi arsenal to disembarke the experimental spring-catapult, then returned to service. By mid 1932, she was recalled for modifications once again, this time at Toumachi naval Arsenal. During the works the flying off platform was removed and the hangar turned into flag space for the command crew. A Kure Type-2 catapult was fitted towards the stern, between gun mounts 6 and 7, the latter one was moved further astern to make space for the catapult turntable. Then the pole mainmast was removed and replaced with a tripod one, fitted with a derrick for aircraft-handling operations. A Nakajima E2N floatplane was retained as the spotter aicraft. With her modifications done, Kizu returned to service by early 1933.
Then in early 1934, under the first reamament plan approved by Morimoto's government, Kizu was docked once again, this time at Hoshiguma Navy Yard, for a major refit meant to improve her fire-control equipment. During the works the bridge was further extended aft, with new deckhouses housing the radio room added Lookout platforms were added adn the spotting top expanded, the 3,5m main rangefinder was replaced with a more advanced model. The main bridge was also enclosed, replacing the earlier canvas cover. the RDF equipment was upgraded and the two 76mm anti-air guns were landed, replaced by a quadruple and two twin 13mm machine guns. Finally, the main deck area was extended abaft the aircraft catapult. Such modified Kizu returned to service by the end of 1934.
Starting by mid-1934 Ayase, Kamu and Nayoro were also recalled for modernization, docking at Hoshiguma, Toumachi and Kousaten Yards respectively. As all three ships were supposed to join Kizu in Sentai-3 once recommissioned they were given roughly the same modifications of their already completed sister. Even so, they eventually differed. The three cruiser had their bridge structures and fire-control platofrms further enlarged and expanded, with a 4,5m rangefinder unit replacing the earlier 3,5m one. Given the increased topweight both the foremast and the forward funnel were cut down in height, giving the four stacks an uniform look. A Nakajima E4N was carried as the reconnassiance plane and the pole derrick was replaced by a built-up one, as to safely operate the heavier aicraft. Al ships were back in service by 1935.
Kumoi, the lead ship of the class, did not entered the yards until fall 1935. Because she was the only one of her class to operate as a Suirai Sentai flagship, and not as part of a surface Sentai, her modifications were deemed less extensive. Her bridge had less flag space and the fire-control-platform was not reworked as extensively, beign smaller like on Kizu. The lookout posts were also fitted differntly, and two 1,5m navigation rangefinders were installed on both sides of the bridge. Her searhlight platforms were expanded, with the four 90cm units that equipped the other sisters replaced by three 110cm ones. The foremat and funnel were shortened as well. Strangely, she did not recieved a built-up crane but was fitted with a simple pole, despite she was equipped with the far larger Kawanishi E7K seaplane. Kumoi was back in service by March 1936.
Strangely regarded more useful than the Yakogoros, despite the ships sported basically the same hull and the same main armament, and despite the much more advanced Kazami class was about to enter service, in 1938 the diet approved another large-scale refit for the cruisers, under the second rearmament bill that was approved two years earlier.
Kizu was once again the first ship to enter the yards, docked at Toumachi in 1938. during the works bridge space was further expanded and 1,5m navigation rangefinders fitted. The 3,5m main rangefinder was replaced by a new 6m unit, the onlder one beign moved at midship. The spotting top and fire-control paltforms were completely reworked, now housing torpedo directors, a dedicated greenhouse for fire-control and a type 94 main-gun director. All of this by further reducing topweight high the foremast. Searchlight platforms were reworked, and the former 90cm units were replaced by 110cm ones. A built-up derrick was fitted and an E7K seaplane embarked, the RDF replaced and the twin 13mm machine guns replaced by twin 25mm ones. Finally, foremast and first funnel were cut down in height. Kizu was recommissioned in 1939. Nayoro was refitted on the same lines during the year 1939.
A few weeks before Kizu returned to service, in late 1938, Ayase was docked at Toumachi to start an ever more comprehensive refit. She recieved four lookout stations, two 1,5m navigation rangefinders, larger binocular posts, expanded fire-control platforms and a heavily reworked and expanded bridge, also coupled with the largest flag space fitted on a Koko no kaigun light cruiser yet. Quadruple 13mm machine gun position ahead of the bridge recieved an enlarged and reworked platform, an auxiliary torpedo director was added between the funnels, the ventilation system above the engine room was reforked, with extra vents abaft the RDF room and the mainmast. The mainmast itself recieved two extra binocular paltforms. The main deck space was further expanded, completely covering the weather deck on both sides to the n°7 gun mount. Torpedo armament was also reworked, with the forward twin torpedo tubes were landed and their former position enclosed and turned into crew space. The aft torpedo mounts were removed and replaced by quadruple sets and equipped with 610mm Long Lance torpedoes. Finally, extra antenna works were added on the forecastle, and an Aichi E11A reconnaissance floatplane was carried, replacing the Nakajima E4N previously carried. Ayase was recommissioned in late 1940, Kamu looked identical once recommissioned a few months later.
By mid 1941 Kumoi, Nayoro and Kizu underwent further minor refits to be brought to Ayase standard.