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This "design" apparently did exist as a specification for the Maru 6 program -- but since the plan was pretty much shelved with the defeat at Midway, nothing came of it. Assumedly, most (if not all) records of its existence were destroyed. Certainly, no official drawings survived (if they ever existed)

So, I was wondering what is known about this design, and how much of the information floating around about it is true.

Apparently, in the book "未完成艦隊 1917~1950" (Unfinished Fleet 1917-1950, published in 2000), this cruiser (dubbed "Unzen") was meant to be an improvement of prior cruiser designs, created to cope with the Baltimore class (and other new US cruisers). The dimensions and displacement of the design was increased, and it was also intended to reduce the length of the citadel by using only 3 triple turrets (which, for the first time in a Japanese heavy cruiser, were to have been armored well, with 150mm on the face, since there were fears that concentrating the armament might make it easier to know out). This shorter citadel could also be armored more heavily.

Then, another turret was apparently added to counter the Des Moines class (which is strange, since that design hadn't even gotten to the "gunswapped improved Oregon City" stage yet), and turret armor was reduced back to the anti-splinter level due to stability concerns.

Main data is given as
"Standard displacement 14,580t Total length 218.3m Maximum width 21.2m Draft 7.2m
8 Ro-type shipbuilding boilers, 4 shipbuilding turbines, 4-shaft engine output 152,000hp speed 31kt
Armament: 4 x 20.3 cm triple guns (55 caliber), 6 x 10 cm twin anti-aircraft guns, 10x3 25mm, 4 x 61 cm quadruple torpedo tubes
Armor side 152mm (assumedly at 20 degrees angle as always, and I have also heard that over the machinery, the thickness was only 140mm), deck 40mm (unknown thickness of slopes/whether thickness changes over magazines), turret 25mm (in draft: 150mm)"

(highest-res version of that image I can find)
1741951487703.png
All of this data has been said to be fake/speculation, which I can believe -- a lot of the design data doesn't make much sense. But this is the only data that exists.


Similarly, the only drawing of the ship I can find is that one above (also said to be fake), which obviously made a large number of "artistic liberties" (errors) -- just compare this drawing to Ibuki and you can see a massive number of fundamental changes that don't make sense (like the relocation of aviation facilities and torpedoes aft). Maybe this can be explained as measures to shorten the citadel, but more likely it is due to speculation.
1741949084864.png
1741949200858.png

(Zao from World of Warships is directly based on this drawing, so I would assume that even Wargaming wasn't able to find any sekrit documents on this design)
1741950229472.png

What does everybody think? And does anybody have a higher-res version of that image?
 
Interestingly, someone appears to have made a model of the 'IJN CA 1941 Maru 6 Keikaku Type A' in recent times:
 
The design is complete BS. It has 1 catapult despite anything after Aoba always having 2? Not to mention wtf is that torpedo launchers placement oh my lord the japanese CA's never had their torpedos placed directly next to the catapults but always at midship or near it.
 
What does everybody think?
If I were to "reconstruct" that ship (say, for a hypothetical WoWS' better analogue), I would most likely made it just an improved  Ibuki. Same overall arrangement, but better armor, quintuple torpedo tubes, 100mm DP guns, new FCS and radars... you get it. Maybe even new main guns (203mm/55 ones that were contemplated in 1930s).
Maybe I would even give it three or four triple turrets instead of five twins, but that would be an extra layer of "what-if" on an already speculative design.

[rant] Also, I definitely wouldn't place the torpedo tubes as WoWS did it, because  Zao's torpedo launch angles are PAIN [/rant]
 
Knowing this was an 1941 design when Japan knew they will be at war with the US I doubt they would start developing a new gun or new gun turret. Indeed an Ibuki with fixed turret placement (all guns could elevate at 0°) 5-6 twin turrets, 10cm shielded mounts (Oyodo) and likely Hanger for Seaplanes. 4 Quad or Quintuple Torpedo Tubes , Improved armour around 152mm Belt, 76mm Deck.
 
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I think Zao is a reasonable interpretation of a "no war with the USA" cruiser design, as long as the catapults and torpedoes are moved to match Ibuki's (and all other IJN cruisers).
(Speaking of Ibuki, it should have the 203/55s in wows. Ibuki is just a Mogami with tiny differences after all, why it is at T9 is a mystery. You can tell their Japanese line was made back before WG had actual researchers. Zao is based off of a fanfic, and the ship line is poorly designed in terms of continuity.)

But as Tzoli said, taking the time to develop not just a triple turret, but one of a gun that hadn't finished development (the 203/55), is nonsensical considering the war situation. Little wonder why this entire specification was thrown out.

My expectation for a completed 1941 design would be a repeat Ibuki, perhaps with weight savings invested in better armor, comparable to what we see on the short-citadel Tones. If the "designed to counter the US 8-in cruisers is correct", perhaps something with 4x2 203/55 and better armor would be the end result? And of course the 100mm guns would be used, as in contemporary designs.
 
The same way Musashi and Mutsu are not on the same lvl as Yamato and Nagato, Gameplay... and lazyness
 
Yeah, I'm not sure what part of WoWS is worse: the nonsensical tiering and gimmicks of historical ships (Japanese cruiser line being 2 Tier 6es, 3 Tier 8s, and a fanfiction), or the sci-fi rocketships that defy physics and cast magic spells.

But enough about WoWS in the naval history section, it leads nowhere good
 
Knowing this was an 1941 design when Japan knew they will be at war with the US I doubt they would start developing a new gun or new gun turret. Indeed an Ibuki with fixed turret placement (all guns could elevate at 0°) 5-6 twin turrets, 10cm shielded mounts (Oyodo) and likely Hanger for Seaplanes. 4 Quad or Quintuple Torpedo Tubes , Improved armour around 152mm Belt, 76mm Deck
I should point out, that Japanese did not assume the PROLONGED war with USA. So the design works for "post-war" ships were perfectly possible in 1941. Considering that a new cruiser was intended to be a next generation design, and not a wartime replacement, it stand to reason that Japanese designers decided to took the time and plan for a radical design changes.
 
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As we lack anymore info then the proposal/design date (Around 1941), type (Heavy Cruiser) and armament (203mm Guns)
It's anyones guess what the IJN wanted or what was the base specifications.
Still we have multiple options:

Twin turret variants:

1. Simply an Improved Mogami with fixed turret placement (enough space between the 1st and 2nd turrets) and guns eg 203mm/50, 4x2 10cm DP-AA guns and improved armour say 120 and 150mm belt and 40 and 60mm Deck. Hull wise similar to Ibuki but a bit longer: say 200-202m WL and 21-21,5m wide. Engien would either remain 152K shp or improved to 160K shp to retain the speed.
Ibuki or Tone style simplified Bridge and or mixed with elements from Oyodo and Agano
This would likely require the least costs and least development time.

2. Enlarged Mogami with 5-6x2 203mm/50 Turrets and Uniform armour of 145-150mm Belt and 50-60mm Deck, possible but not necessary a small seaplane hanger (Smaller than Oyodo's). 4-6x2 10cm DP-AA and improved/modified bridge, taking into account the experiences with Mogami and Tone classes and maybe re-design the Takao bridge with the Tomozoru incident in mind. Longer and Wider hull with a 21,5-22m width and depending on turret number 205-225m Long to retain the high speed.

Triple Turret variants

3. Using the Enlarged Mogami hull as a basis but changing the armament to 3x3 203mm/50 guns and the usual 4-6 10cm DP-AA guns, alternatively a sort of mini B-65 battlecruiser look with appropriately reduced hull and superstructure elements.

4. Using the Tone as a basis for a Scouting oriented or Aviation Cruiser, all 3 triple 203mm/50 turrets forward and seaplane facilities aft like on Tone or my Tone-kai drawing. Hull is similar to that of the Enlarged Mogami

5. Modified version of the above but adding a 4th triple turret aft, seaplane hanger is optional, not installing it would likely allow a shorter hull

6. Using that fake design drawing as a basis but using actual 203mm/50 guns in 4 triple turrets and actual IJN design choices and elements. Or alternatively a sort of reduced B-65 design with 203mm turrets and smaller hull.

Al designs had 4 quad 61cm Torpedo Tubes.
 

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