Japanese cruiser Ibuki ( 1943 ) The Japanese cruiser was a heavy cruiser , the lead ship of her class , built for the Imperial Japanese Navy ( IJN ) during World War II . Before the ship was completed , she was ordered to be converted into a light aircraft carrier that could carry 27 aircraft . The conversion was delayed and finally stopped in March 1945 in order to concentrate on building small submarine s . " Ibuki " was scrapped in the Sasebo Naval Arsenal beginning in 1946 . Design and description . As originally designed the ship had a length of overall , a beam of and a draft of . " Ibuki " displaced at standard load and at ( full load ) . She was fitted with four Kampon geared steam turbine sets with a total of , each driving a propeller . Steam was provided by eight Kampon Ro Gō - type three - drum water - tube boilers intended to give the ship a maximum speed of . " Ibuki " carried of fuel oil which gave her an estimated range of at . Armament . The main armament of the " Ibuki " class was intended to be ten 50 - caliber 20 cm 3rd Year Type No . 2 guns mounted in twin turrets , three forward and two aft of the superstructure . The first two forward turrets were on the same level , but the third turret could superfire over the first two . The guns could depress to −5° and had a maximum elevation of + 55° and a maximum range of . The secondary armament was to consist of eight 40 - caliber 12 . 7 cm Type 89 anti - aircraft ( AA ) guns in twin mounts . They had a maximum range of , and a maximum ceiling of . The ships were also intended to be equipped with four twin 25 mm Type 96 light AA guns abreast the funnel . They had a maximum range of , and an effective ceiling of . The maximum effective rate of fire was only between 110 and 120 rounds per minute due to the frequent need to change the fifteen - round magazines . Two twin 13 . 2 mm Type 93 machine gun mounts were supposed to be mounted on the bridge with 2 , 000 rounds per gun . The " Ibuki " - class ships were intended to be armed with four rotating quadruple Type 92 torpedo tube mounts , two on each broadside . The ship carried 24 Type 93 torpedo s , commonly referred to in post - war literature as the " Long Lance " , 16 in the tubes and eight in reserve . Quick - reloading gear was installed for every mount that allowed the reserve torpedoes to be loaded in three to five minutes in ideal conditions . Early warning would have been provided by a Type 2 , Mark 2 , Model 1 air search radar mounted at the top of the foremast . A Type 93 passive hydrophone system would have been fitted in the bow . The ships were designed to carry three aircraft on a platform between the funnel and the mainmast . These would have consisted of one three - seat Aichi E13A and two two - seat Yokosuka E14Y floatplane s . They would have been launched by a pair of aircraft catapult s , one on each side of the aircraft platform . Armor . The ship ' s waterline armoured belt ran all the way down to the double bottom . It extended from the forward to the rear magazine s below the fore and aft turrets . Over the machinery spaces , it was thick and thick on the sides of the magazines . The outer ends of the fore and aft machinery compartments was protected by a transverse bulkhead . The magazines were protected by fore and aft transverse bulkheads thick . The thickness of the armored deck ranged from on the flat and on the slope . The sides of the conning tower were 100 millimeters thick while its roof was thick . The main gun turret s had of armor on all sides and on the roof . The barbette armor ranged from in thickness . Conversion . " Ibuki " s two aft turbine sets , the four aft boilers and the two innermost propeller shafts were removed with their propellers ; the exhaust uptakes for the remaining boilers were trunked together into a downward - curving funnel on the starboard side of the hull . The space made available was used for avgas tanks ( in capacity ) , additional fuel oil tanks , as well as bomb and torpedo magazines that had a capacity of 24 bombs and two torpedoes . The ship now could carry of oil , enough for at a speed of . The reduced power meant that " Ibuki " s top speed was only . As part of the conversion , the existing superstructure was razed , a new hangar deck was built above the existing upper deck and a full - length flight deck was added . It had a maximum width of , two aircraft elevators that serviced the single hangar and a small starboard island structure . The ship was bulged to improve her stability , which increased her beam to a maximum of below the waterline . " Ibuki " s trials displacement increased to and the additional weight increased her draft to . Initially , the ship was to have a very light armament of only 22 triple 25 - millimeter gun mounts , controlled by eight Type 95 fire - control director s , but this was modified in 1944 to substitute four 60 - caliber 8 cm Type 98 dual - purpose guns , mounted in two twin - gun turrets , and four 28 - tube launchers for anti - aircraft rockets for six of the triple 25 - millimeter gun mounts and two directors ( now Type 4s ) . This gave the ship a total of forty - eight 25 mm guns in 16 triple mounts . The Type 98 gun fired a , projectile . It had a muzzle velocity of that gave it a maximum range of , and a maximum ceiling of . The entire turret weighed and the guns could fire at a rate of 25 rounds per minute . At the top of the island , " Ibuki " was planned to have a rangefinder and a Type 21 radar . In 1944 , the Type 21 radar was moved to a retractable mount in the flight deck near the bow and a Type 22 surface search and a Type 13 air - search radar were going to be installed on the island . The ship retained the Type 93 hydrophone system . The ship ' s air group was designed to consist of 27 aircraft , 15 Mitsubishi A7M Reppū ( Allied codename : " Sam " ) fighters and a dozen Aichi B7A Ryusei ( " Grace " ) dive / torpedo bomber s . Construction . " Ibuki " was laid down at the Kure Naval Arsenal , Kure , on 24 April 1942 , but her construction was suspended on 30 June . Construction resumed a month later to allow the ship to be launched and clear her slipway for carrier construction . She was named after Mount Ibuki on 5 April 1943 as per the IJN ' s naming convention for first - class cruisers . The ship was launched on 21 May and construction was suspended in July while the IJN decided what to do with her . The navy considered completing " Ibuki " as a high - speed replenishment oiler , but decided to convert her into a light aircraft carrier on 25 August . While plans were prepared for the conversion , she was towed to the Sasebo Naval Arsenal , Sasebo , by the submarine tender 19 – 21 December . Completion of the ship was originally scheduled for March 1945 , but it was rescheduled for August because of delays . Work continued until 16 March 1945 , but it was ordered to halt when she was 80 % complete to concentrate on the construction of small submarines needed to defend Japan against an American invasion . She was anchored in Ebisu Bay , near Sasebo , and surrendered there on 2 September along with the rest of the Japanese military . " Ibuki " was scrapped in Sasebo Naval Arsenal Drydock No . 7 , 22 November 1946 – 1 August 1947 .