Japan - Never built IJN ships.

in order to avoid open a million threads for every single never-where IJN ship i' gonna draw from now on i will collect them in this thread.

here you will find (i will update the thread each time i will complete one of them):
DONE - the 1941 Type A Heavy Cruiser
DONE - the Tone class Heavy Cruiser as originally planned
DONE - the Myoko class Heavy Cruiser preliminary designs
DONE - the 1930 Fujimoto studies for a treaty replacement of the Fuso class Battleship
DONE - the 1944 proposed AA refit for Noshiro (Agano class CL)
DONE - the Kai-Agano (or C-44) Class Light Cruiser
DONE - The Nagato class Battleship as originally designed
DONE - the Mogami class Cruiser as originally designed
DONE - the G6/G8 Class Carrier designs (also known as proto-Soryu)
DONE - the partial and full 1943 AA conversion proposals for Suzuya and Kumano
DONE - the 1938 C-39 class Cruiser (or Proto-Agano)
DONE - the 1936/39 Tenryu Class AA conversion proposals
DONE - the light cruiser Oyodo as planned in 1939
DONE - the 1942 G-15 Class Carrier (also known as Kai-Taiho)
-the Ibuki class Heavy Cruiser and it's never completed carrier conversion (CA version done)
-whatever it may come in the future that it's not present in my worklist currently.

The 1941 Type A Heavy Cruiser:

This ship was designed in early 1941 for the Dai-Roku-Ji Kaigun Gunbi Hojū Keikaku (Sixth Naval Armaments Supplement Program), also known as Maru 6 Keikaku (Circle Six Program) but the plan was quickly shelved and replaced with the 1941 wartime construction program in september 1941.
the 1941 Type A cruiser was planned as an eight-ship class, 218 meters long, armed with twelve 8-inch (203mm) guns in triple turrets and twelve 3.9-inch (100mm) guns in twin turrets (the same model that would eventually see service with the Akizuki class destroyers) and a 5.5-inch(140mm) planned armour belt would have been a match even for the Des Moines heavy cruisers (at least in terms of dimensions and firepower).
From a personal point of view tough theese ships had a flaw, the 4 quadruple torpedo tubes fitted there at the stern; knowing how subsceptible to explode was the Long Lance when hit in battle there is a real risk of wrecking the entire stern loosing steering and propellers at the same time, as the japanese CAs proved also a bit subsceptible to had their stern crippled by torpedo hits (a fact that Takao, Myoko, Haguro and Chikuma learned at their expense).

The Tone clas cruiser as initially designed:
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The ships would have sported 4 triple 6-inch guns on the forecastle, with japan withdrawal from treaty limitations the ships where quickly redesigned and the barbette reworked to house Type 3 8-inch turrets without the need to modify them like it was done on Mogami.

The Ibuki Class Heavy Cruiser:
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the ships design is based on the Mogami class cruiser Suzuya, this because she sported more modifications when compared to the lead ship especially when it comes to stability and engine layout; superstructure was further cut down aft in a way similar to the one seen on the Tone class, mainmast was moved aft like it was done on the first two Takao class ships.
The radar suite was also similar to the one fitted on Tone, torpedo armament was increased to 4 quadruple launchers (it was 4 triple on mogami) and it was planned to fit a type 21 air search radar on the foremast by the time of completion; the gun's barbettes where designed since the beginning with a roller path of 5 meters (instead 5,7 on Mogami, wich was planned as a light cruiser) to fit the 8-inch guns turret without implement modifications to them like it was done with their half-sisters, still the guns of turret 2 cannot be trained below 12° like the older Mogamis.
After the battle of midway it was decided to convert her into an aircraft carrier, and her sister, already under construction, was canceled and scrapped.

The early 1923 Myoko class design:
[ img ]

Dating early 1923, features no torpedo armament (following Yuzuru Hiraga remarks about their dangerous placement just above the engine room), anti-aircraft suite composed of four 4.7-inch (120mm) single guns, and no shelter deck near the bridge; still, the most evident feature is the absence of trunked funnels, a smaller bridge structure and the fire-control platform mounted on top of a tripod mast surmounting the bridge.

The "final" 1923 Myoko class design:
[ img ]

Adopted in august 1923, it had the bridge structure changed to reach the shape it will feature as actually built, the spotting tripod was removed and the first two funnels trunked togheter, anti-aircraft armament was still composed of four 4.7-inch (120mm) single guns, to torpedoes where embarked and there was still no shelter deck abaft the bridge. despite beign labeled as "final" the Myoko class appearance will change before their commissioning, the torpedo armament composed of four triple fixed sets above the engine room initially considered and discarded was put back up, and the 4.7 inch guns where increased from 4 to 6; the last addition was the shelter deck added abaft the bridge when the ships where already under construction.

The 1930 Fujimoto design for a Fuso class replacement armed with 9x16.1-inch guns:
[ img ]

This design called for a treaty battleship armed with nine 16.1-inch (409mm) guns in three triple turrets, secondaries where composed by twelve 6-inch (152mm) guns in six twin turrets, unusally fitted outside the armour belt and (at least the forward turrets) protected with a shield from blast damage from the main guns; 4 twin 5-inch (127mm) AA guns mounted on sponsons at the fore and aft end of the superstructure completed the armament.
It was designed by Captain Fujimoto to replace the Fuso class Battleship, and like the one designed by Hiraga (planned to replace the Kongo class) plans to build her where canceld with the ratification of the london naval treaty in 1931.

The 1930 Fujimoto design for a Fuso class replacement armed with 12x16.1-inch guns:
[ img ]

A variant of the basic Fujimoto design, This one increased the main guns to twelve 16.1-inch (409mm) guns and moved 4 of the 6 twin 6-inch (152mm) guns inside the armoured citadel; given the heavy armament and dimension, with lenght exceding 260 meters this design will almost certainly had broken treaty limits if built.

Noshiro proposed CLAA conversion:
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in July 1944 a plan emerged to refit Noshiro as an anti arcraft cruiser, this called for the removal of the two type 98 80mm wing mounts to be replaced by four twin 100mm type 98 in shelded mounts, like the ones fitted on Oyodo, seventeen triple and eight single 25mm machine guns where also to be fitted for a total of 59 barrels; the plan do not materialized, and Noshiro eventualy got sunk in october 1944 during the Philippine Campaign.

The Kai-agano (also nown as C-44) Class Light Cruisers:
[ img ]

This class of light cruisers was designed in may 1941 for the Dai-Go-Ji Kaigun Gunbi Hojū Keikaku or Fifth Naval Armaments Supplement Program (also known as Maru 5 Keikaku or Circle Five Program) was an improved version of the agano-class, the hull was lenghtened by over 12 meters to a total lenght of 186,5 in order to fit a fourth 150mm (6-inch) twin turret aft of the mainmast, heavy anti-aicraft armament was to be composed of eight 80mm type 98 guns in four twin mounts fitted abaft the funnel; part of the hull lenghtening was also used to fit more powerful engines in order to mantain a top speed of 35 knots despite the increase of displacement, thus the funnel was also larger than the one of the standard Agano class.
Five ships (with hulls numbered from 810 to 814) where ordered in 1941, with other two (numbered 5037 and 5038) added in september 1942 under the Wartime Warship Construction Replenishment Program (Kai-Maru 5 Keikaku or Modified Circle Five Program) but eventually none of them was ever laid down neither recieved a name.

The Nagato class Battleship as originally designed:
[ img ]

the first design, dated 1916, shows more resemblance to the preceding Ise class because of the absence of the distinctive heptapodal foremast, initially concieved as a simple tripod like all the previous IJN battleships.

The Mogami class Cruiser as originally designed:
[ img ]

When construction started, and untill 1933, the planned layout for the Mogami class Cruisers was quite different from what she turned out once works where completed; according to the original design the ships looked much like a light cruiser version of the preceding Takao class CA, the aft superstructure, equipped with hangar for the floatplanes and the searchlight platforms were much like that of Takao, and while the bridge had a different shape and slighty smaller dimensions it's appearance recalled clearly that of their bigger siblings.
The capsizing of torpedo boat Tomozuru in february 1934 however called in question the stability of all recently-built IJN ships, to overcome stability issues that emerged after inspections the extent of the superstructure was drastically reduced, leading to the definitive silouetthe wich the Mogami class ships recieved at the time of their completions.

The G6 carrier project:
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Dated 1932 it was the first preliminar design for the aircraft carrier Soryu, it feature a double deck hangar similar to that fitted on Akagi but smaller, with a maximum capacity of 48 planes, three superimposted twin 8-inch gun turrets where planned to be placed on the forecastle.

The G8 carrier project:
[ img ]

Dated 1933, it was the second preliminar design for the aircraft Carrier Soryu, it featured a large sponson at the stern to maximize flight deck lenght and an unusual main armament composed of 6.1-inch guns mounted on the forecastle, below the flight deck.

The 1943 AA conversion proposals for Suzuya and Kumano:
Partial conversion for Suzuya:
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Full conversion for Kumano:
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According to page 492 of "Japanese Cruiser of the Pacific War": Plans were made during the end of 1942 / early 1943 to modify the Suzuya and Kumano to AA cruisers by removing all or part of the 20-cm. turrets and adding more twin Type 89 12.7-cm. HA-gun mounts.

The C-39 Class Light Cruiser:
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This is the first design for what will become the Agano Class, dated march 1938 it called for a 7.800t light cruiser armed with 6x 6-inch (150mm) guns in twin turrets, 4x 3.9-inch (80mm) anti-air guns in twin mounts and six 25mm machine guns in two triple mounts; torpedo armament was to be composed of two quadruple Type 92 torpedo tubes, a 6-boiler machinery was to be fitted for a top speed of 36knots.
The c-39 project was slighy bigger and a knot faster than the Agano that was actually built, as armament differed only in machine-gun layout; the cruiser profile was instead quite different particulary because of the absence of the distinctive trunked funnels, by that time a distinctiv mark of nearly all IJN warships.

The 1936 CLAA Tenryu conversion:
[ img ]

In 1936 a plan emerged to refit the tenryu class ships as anti-aircraft cruisers, this called for the removal of all four 5.5-inch (140mm) guns, to be replaced by eight Type89 5-inch (127mm) ones, argumented by four trilpe 25mm machine guns; the three funnels would have been trunked toghether to improve firing arcs, masts and superstructure would also be heavily redesigned and toped by two Type94 HA director equipped with 4,5-meter rangefinders; for ASW the plan called for two depth charge throwers and four depth charge chutes to be fitted on the fantail.

The 1939 cLAA Tatsuta conversion:
[ img ]

In 1939 the same conversion plan resurfaced again, this time replacing the 5-inch guns with the new Type 98 3.1-inch (80mm) guns then under developement; the plan was eventually rejected in favor of the Akizuki class Destroyers.

The light cruiser Oyodo as planned in 1939:
[ img ]

Oyodo was eventually built quite similar to how she was planned, yet some fittings were changed by the time construction starded. both mast were taller, with the fore one sporting a different tripod, the vent cowls for the first boiler rooms located just aft of the bridge were of a different design also; the aft RDF installation was planned to be located on top of the hangar, and not between it and the funnel, also the radio room above the aircraft facilities was placed more forward, housing two Type 95 machien gun directors, wich were placed on sponsons abreast the bridge structure when the cruiser was completed. Two 1,5m navigation rangefinder were also to be placed on both sides of the bridge structure just above the DP guns ones, but they were replaced by simple lookout posts, and a single one was fitted in an open fitting just in front of the main gun director.
Finally, the envisioned airwing was the full complement of six Kawanishi E15K1, then under developement; the Oyodo once built never carried more than two.

The Kai-Taiho project or G-15 class Aricraft Carrier:
[ img ]

Planned in 1942 as a follow-on of the IJN Taiho, it featured a 14-feet hull stretch, a 33-knot top speed and an anti-aircraft armament composed of 16 3.9-inch (100mm) guns in eight twin mounts and 66 25mm machine guns in 22 triple mounts.
Airwing, supposedly composed by at least 53 planes was to be made of Mitsubishi A7M2 "reppu" fighters, Yokouska D4Y "suisei" dive bombers, Aichi B7A2 "ryusei" torpedo/dive bombers and Nakajima C6N1 "myrt" reconnaissance planes.
Up to seven units were planned, none was eventually laid down.

Shipbucket

Japan - Never built IJN ships.

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