The J/CA/1921 design

The J/CA/1921 design in an incremental improvement over its predecessor. The main differences are an increase to 10-8in guns, to 8-4.7in AA guns, and to 12-24in TT, instead of 16-21in TT. The speed and range are unchanged. The displacement was only slightly increased. The roll is still snappier than I would like with a roll period of 13.8 seconds. This is the Springsharp report:

J/CA/1921, Japan Heavy Cruiser laid down 1921 (Engine 1931)

Displacement:
 12,109 t light; 12,602 t standard; 13,800 t normal; 14,758 t full load

Dimensions: Length overall / water x beam x draught
 660.10 ft / 655.00 ft x 62.00 ft x 19.00 ft (normal load)
 201.20 m / 199.64 m x 18.90 m  x 5.79 m

Armament:
      10 - 8.00" / 203 mm guns (5x2 guns), 256.00lbs / 116.12kg shells, 1921 Model
   Breech loading guns in turrets (on barbettes)
   on centreline ends, majority forward, 2 raised mounts - superfiring
      8 - 4.70" / 119 mm guns in single mounts, 51.91lbs / 23.55kg shells, 1921 Model
   Anti-aircraft guns in deck mounts with hoists
   on side, all amidships
      24 - 2.24" / 57.0 mm guns (12x2 guns), 5.65lbs / 2.56kg shells, 1921 Model
   Anti-aircraft guns in deck mounts 
   on side, all amidships, 6 raised mounts - superfiring
 Weight of broadside 3,111 lbs / 1,411 kg
 Shells per gun, main battery: 120
 12 - 24.0" / 609.6 mm above water torpedoes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 3.50" / 89 mm 450.00 ft / 137.16 m 16.00 ft / 4.88 m
 Ends: Unarmoured
   Main Belt covers 106 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
  1.00" / 25 mm 450.00 ft / 137.16 m 18.00 ft / 5.49 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 4.00" / 102 mm 2.00" / 51 mm  2.00" / 51 mm
 2nd: 2.00" / 51 mm       -         -

   - Armour deck: 2.00" / 51 mm, Conning tower: 4.00" / 102 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 117,999 shp / 88,027 Kw = 33.00 kts
 Range 7,500nm at 15.00 kts
 Bunker at max displacement = 2,156 tons

Complement:
 636 - 827

Cost:
 £3.168 million / $12.671 million

Distribution of weights at normal displacement:
 Armament: 389 tons, 2.8 %
 Armour: 2,862 tons, 20.7 %
    - Belts: 1,040 tons, 7.5 %
    - Torpedo bulkhead: 300 tons, 2.2 %
    - Armament: 347 tons, 2.5 %
    - Armour Deck: 1,126 tons, 8.2 %
    - Conning Tower: 50 tons, 0.4 %
 Machinery: 3,529 tons, 25.6 %
 Hull, fittings & equipment: 5,329 tons, 38.6 %
 Fuel, ammunition & stores: 1,691 tons, 12.3 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   16,101 lbs / 7,304 Kg = 62.9 x 8.0 " / 203 mm shells or 2.0 torpedoes
 Stability (Unstable if below 1.00): 1.23
 Metacentric height 3.6 ft / 1.1 m
 Roll period: 13.8 seconds
 Steadiness - As gun platform (Average = 50 %): 51 %
   - Recoil effect (Restricted arc if above 1.00): 0.64
 Seaboat quality  (Average = 1.00): 1.02

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.626
 Length to Beam Ratio: 10.56 : 1
 'Natural speed' for length: 25.59 kts
 Power going to wave formation at top speed: 57 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 4.00 degrees
 Stern overhang: 3.00 ft / 0.91 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  30.00 ft / 9.14 m
    - Forecastle (20 %): 25.00 ft / 7.62 m
    - Mid (50 %):  25.00 ft / 7.62 m (17.00 ft / 5.18 m aft of break)
    - Quarterdeck (15 %): 17.00 ft / 5.18 m
    - Stern:  17.00 ft / 5.18 m
    - Average freeboard: 21.40 ft / 6.52 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 154.4 %
  - Above water (accommodation/working, high = better): 138.4 %
 Waterplane Area: 30,428 Square feet or 2,827 Square metres
 Displacement factor (Displacement / loading): 106 %
 Structure weight / hull surface area: 113 lbs/sq ft or 550 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.99
  - Longitudinal: 1.08
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent