Last entry for the pre-WNT fleet plans (some two weeks later than I had planned but whatever...):
The third finalized design for Koko's Shi-Shi/Shi-Ni Kantai took off from one of the discarded IJN Hachi-Hachi Kantai proposals. Completely revisiting Design-B Koko designers increased both belt and deck armor sacrificing 1,5knots form the original intended top speed of 30knots. The ship was to be 258m long overall (255 at the waterline), 34m abeam and with a draft of 9,4m for a standard displacement of 46.243t and a full load of 50.615t. Oil firing boilers powering four turbine sets with 135.000shp would have propelled the ships to at least 28,5knots, enought to jointly operate wit the planned fast Nagato and Tosa designs. Endurance was to be 5.600nm at 16knots. Just as the American South Dakotas already under construction, the two Battleship planned for Koko would have sported twelve 409mm guns in triple turrets, a first for local shipyards, anticipating even Japan, who had planned the entire Hachi-Hachi Kantai around twin gunned Battleships. Secondary armament would have consisted of sixteen 140mm guns in casemate mounts, while for AA duties a battery of four 120mm high-angle guns in single mounts was to be installed. Eight above-water torpedo tubes were also planned. Main belt, inclined 15° in, would have been 305mm thick, with 152mm ends protecting the torpedo rooms and the steering gear. A second strake 140mm thick would have protected the casemate mounts, while main deck had a planned 130mm thicknes, with a 37mm extension above the steering gear. 25+19mm torpedo bulkheads were also planned. Conning tower was to be 369mm thick, while gun and barbette armor would had a maximum thickness of 305mm each.
Design had been finalized by December 1921: the two ships were supposed to be laid down by 1924, or 1925 at worst, but orders were never placed as the Washington Naval Conference and subsequent Treaty ratification first delayed, then killed the project.
A fourth and last Shi-Shi Kantai design was considered in late 1921 to complete the fleet, initial requirements called for six 460mm guns in three twin turrets with a required top speed of at least 28,5 knots, but a 30+knot ship was also considered and strongly advised by the Naval Staff. Further planning never took place as the Washington Naval Treaty was signed in 1922.