Some time ago an idea popped out of my head: how to modernize the few armoured cruisers the Imperial Japanese Navy in ww2. And now here it is: The Modernized IJN Asama. Modern 20cm Twin Gun Turrets used on the new Heavy Cruisers replacing the old 1904 ones and practically double their range. Removed all of the casemate 152mm Guns and replaced them with 4 twin 155mm Gun Turrets similar ones found on the Oyodo, Mogami (Before Conversion to CA) and Yamato. AA Armament was limited to 2 twin 127mm AA guns but this is an old ship, I was lucky to find space for those AA guns at all! Trunked the two funnels into one and adopted the superstructure from the Oyodo.
IJN Asama, Imperial Japanese Navy Modernized Armoured Cruiser laid down 1896 (Engine 1936)
Displacement: 8 116 t light; 8 636 t standard; 8 979 t normal; 9 253 t full load
Dimensions: Length (overall / waterline) x beam x draught (normal/deep) (441,93 ft / 428,81 ft) x 67,26 ft x (24,38 / 24,90 ft) (134,70 m / 130,70 m) x 20,50 m x (7,43 / 7,59 m)
Armament: 4 - 7,99" / 203 mm 50,0 cal guns - 277,45lbs / 125,85kg shells, 200 per gun Breech loading guns in turret on barbette mounts, 1930 Model 2 x 2-gun mounts on centreline, evenly spread 8 - 6,10" / 155 mm 60,0 cal guns - 123,17lbs / 55,87kg shells, 300 per gun Breech loading guns in turret on barbette mounts, 1930 Model 4 x 2-gun mounts on sides, aft evenly spread 4 raised mounts 4 - 5,00" / 127 mm 40,0 cal guns - 51,70lbs / 23,45kg shells, 350 per gun Dual purpose guns in deck and hoist mounts, 1929 Model 2 x Twin mounts on sides, forward deck centre 2 raised mounts 18 - 0,98" / 25,0 mm 60,0 cal guns - 0,52lbs / 0,24kg shells, 2 500 per gun Anti-air guns in deck mounts, 1935 Model 6 x Triple mounts on centreline, evenly spread 6 double raised mounts Weight of broadside 2 311 lbs / 1 048 kg
Armour: - Belts: Width (max) Length (avg) Height (avg) Main: 7,01" / 178 mm 284,12 ft / 86,60 m 6,89 ft / 2,10 m Ends: 2,99" / 76 mm 144,69 ft / 44,10 m 6,89 ft / 2,10 m Upper: 5,00" / 127 mm 213,91 ft / 65,20 m 6,89 ft / 2,10 m Main Belt covers 102 % of normal length
- Torpedo Bulkhead - Additional damage containing bulkheads: 5,00" / 127 mm 278,71 ft / 84,95 m 22,83 ft / 6,96 m Beam between torpedo bulkheads 60,70 ft / 18,50 m
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max) Main: 0,98" / 25 mm 0,98" / 25 mm 5,98" / 152 mm 2nd: 0,98" / 25 mm 0,98" / 25 mm 5,98" / 152 mm 3rd: 0,98" / 25 mm 0,47" / 12 mm 5,98" / 152 mm
- Armoured deck - multiple decks: For and Aft decks: 2,01" / 51 mm Forecastle: 2,01" / 51 mm Quarter deck: 2,01" / 51 mm
- Conning towers: Forward 14,02" / 356 mm, Aft 2,99" / 76 mm
Machinery: Oil fired boilers, steam turbines, Geared drive, 2 shafts, 20 000 shp / 14 920 Kw = 21,80 kts Range 6 998nm at 10,00 kts Bunker at max displacement = 616 tons
Complement: 460 - 599
Overall survivability and seakeeping ability: Survivability (Non-critical penetrating hits needed to sink ship): 18 330 lbs / 8 315 Kg = 71,8 x 8,0 " / 203 mm shells or 5,1 torpedoes Metacentric height 3,2 ft / 1,0 m Roll period: 15,7 seconds
Hull form characteristics: Hull has a flush deck, a ram bow and a cruiser stern Length to Beam Ratio: 6,38 : 1 'Natural speed' for length: 20,71 kts Power going to wave formation at top speed: 49 % Ship tends to be wet forward
Ship space, strength and comments: Waterplane Area: 18 352 Square feet or 1 705 Square metres Structure weight / hull surface area: 128 lbs/sq ft or 623 Kg/sq metre Excellent machinery, storage, compartmentation space Excellent accommodation and workspace room Ship has slow, easy roll, a good, steady gun platform Good seaboat, rides out heavy weather easily
On the same hull as the A-49 proposal, on 173,7meters, the designers changed the turrets placements to a more regular all centreline positions with superfiring positions forward and aft and the 5th turret just aft of the second funnel. Armament did not changed (36cm/14inch) but displacement reduced by 100 tons to 27,000tons standard. We can see now the clear lines toward the Fuso class but this could also be considered a small scale Tosa, Kii or Amagi class, and probably this design led to those 5 turreted ship classes.
Another step towards Fuso Since A-51 the designers choose the 30cm (12inch) cannons as the main armament for these designs and with this A-52 variant they reached the smallest size of just 172meters. Featuring 4x3 30cm cannons on 26.000tons displacement. As you can see this is essentially the Japanese version of the Austro-Hungarian Viribus Unitis or Tagethoff class but with 30.5cm belt armour rather 28cm and a slightly longer hull.
I soon finish drawing these preliminary designs as I run out of useful data but now I show you this variant.
What is known about this design that it's length 173,7meters, same as the Design A-49, 27.300tons displacement, 44.000shp engine power and 12x 30cm cannons in 6 twin turrets. Despite the absolute similarity with the final Fuso design there are some differences: The length is 30meters short (202.7m was the Fuso), 2000tons less displacement, armament aren't 36cm but 30cm cannons and as the secondary armament aren't stated I've used the earlier 12x1 152mm Casemate guns (Fuso had 16 such guns), and lastly the engine power is 10% stronger (40.000 on Fuso)
So this could be seen as probably the smallest hull where you can place 6 twin turrets on the centreline in this arrangement.