Cruiser Projects and Designs of the IJN

[gral_rj]

Girls and cruisers ? (I see myself out)

*snort* Not quite, but it has both of them. Just your typical les-yay manga with a military setting(although this one got further than most of those).

 

[40902nd]

Girls and cruisers ? (I see myself out)

That would be High School Fleet.

The Unebi is from the manga Kurogane Pukapuka-Tai.

The Unebi (the Second) is basically the mid-season upgrade the crew gets after the Unebi (a civilian cargo ship modified mid-construction into a commerce raider) gets sunk.
The USS Virgin, the USN equivalent/response, is a modified Wichita.

 

[Tzoli]

from what I understand, it looks like a table of required military forces at the end of 1940, after the collapse of naval treaty.
I made some translated version but it might be wrong to some extent

8x Battleships (戦艦) - Nagato class, Fuso class, Ise class, and Hiei + one more Kongo class?
4x Fast Battleships (高速戦艦) - 2x New fast battleships (新高戦, aka early concept of Yamato class), 2x Kongo class

4x Middle size Aircraft Carrier A (中空母 甲) - 18000t class (early concept of Shokaku class)
2x Middle size Aircraft Carrier B (中空母 乙) - Soryu, Hiryu
2x Large Aircraft Carrier (旧大空母) - Akagi, Kaga
2x Small Aircraft Carrier (小空母) - Hosho, Ryujo

8x Large Heavy Cruisers (大巡) - 10000t, Myoko class and Takao class
4x Middle size Heavy Cruisers (中巡) - 7100t, Furutaka class and Aoba class
4x Middle size Heavy Cruisers, modified (中巡改) - 8510t, Mogami class and Tone class (10in gun conversion was considered)

8x 5500t class cruisers (乙巡) as a flotilla leader + 4x 5500t class????

32x Large Destroyers (大駆) - DDs after Hatsuharu class?
48x First class Destroyers (一駆) - Fubuki class, Ayanami class, Akatsuki class + old DDs + 8 unfinished DDs?

etc.

As I've been commissioned to draw the 25cm armed Mogami variant, I've thought some more on it.

I can only see 3 possible layouts to be chosen for an upgunning out of which 2 was likely:

First variant:
5 twin 25cm/45 or /50 guns where the guns sit on the same cradle eg could not be elevated independently and the only way to maintain the same barbette diameter as the original 15,5cm gun turrets.
While it is possible and the IJN designers might looked at such turrets (Imagine a Japanese looking Pensacola like twin turret) and some turrets used this layout (14cm guns of Yubari and the 12,7cm guns of the Type A mounting of the Destroyers) it was not common.
This layout likely would allow a similar sized turret that of the 20cm twin or 15,5cm triple. but the extra weight of the barrels, loading mechanisms and ammunition would result even more serious hull issues and more strengthening and bulges was required to compensate.

Second variant:
3 twin 25cm turrets in likely in the 1st, 3rd and 5th positions if proper two-gun eg independently sleeved barrelled turrets was to be used. The choice on the number of turrets and their location dictated by the extra weight and larger size of these turrets necessitating a larger working circle ( there is no space available for growth for the 2nd turret and very small margin is for the 5th one) and larger barbettes to mount them.

Third variant:
This might be the easiest and most economical layout, using 5 single 25cm turrets either /45 or /50 guns. The single turret will not require modification to the barbette diameter and very likely would not be longer then the original 15,5cm and the actual 20 turrets eg it could fit in the previous spaces easily while still maitain a considerable firepower.

Other question is the / calibre and if new design gun or re-use old ones. /45 allows saving weight while /50 improves gun performance.

 

[Tzoli]

Based on this document:
https://www.secretprojects.co.uk/attachments/jp-guns-1928-1-png.742623/or
https://www.secretprojects.co.uk/th...un-super-a-cruiser-project.41917/#post-715248
Apparently all other gun proposals would use the same barbette diameter as the 15,5cm triple turret so the 24 and 25cm variants as well.
Discussion with a friend we concluded that the 24 and 25cm gun variants were quickly abandoned due to the weight of the mounting and the crampled insides would result in an unstatisfactory turret. This would mean the same turret size would be used (length wise) as the 20,3cm twin turret.
Based on the weights of the turrets in the image, I can guess that the twin 24cm would weight around 310 tons while the 25cm twin one around 350tons which is more then twice the weight of the twin 20cm one. This would mean it was more than likely that no more then 3 twin could be installed on the Mogami hull.

 

[Tzoli]

Here I now add 3 cruiser designs recently unearthed.

The Mogami 25cm upgun proposal:
https://www.deviantart.com/tzoli/art/Proposed-Mogami-Class-25cm-Upgunning-1316728122The 3x2 most likely variant:

and my 5x1 proposal to use all barbettes:

The 1936/37 maru 3 Big Gun Cruiser Proposal:
https://www.deviantart.com/tzoli/art/1318779202?action=published

And the 1940 C-43-I design, the B-65 preliminary with 25cm guns:
https://www.deviantart.com/tzoli/art/1319176991?action=published