The next step, the J/BB/1921 design

The next step for Japanese battleship development is to increase the caliber of the main armament to 18in. This version still seems to be not very well protected against gunfire. The anti-torpedo protection seems quite adequate, however. I was able to increase the speed to 30 knots without much problem, except raising the freeboard. Normal weight machinery suffices to provide the needed power. This ship seems comparable to what was contemplated, except perhaps for an increased displacement. There seems to be too much capability for the size, although perhaps that is just due to the low standard of protection. This is the Springsharp report:

J/BB/1921, Japan Battleship laid down 1921

Displacement:
 49,022 t light; 51,412 t standard; 55,500 t normal; 58,771 t full load

Dimensions: Length overall / water x beam x draught
 812.71 ft / 810.00 ft x 108.00 ft x 32.00 ft (normal load)
 247.71 m / 246.89 m x 32.92 m  x 9.75 m

Armament:
      8 - 18.00" / 457 mm guns (4x2 guns), 2,916.00lbs / 1,322.68kg shells, 1921 Model
   Breech loading guns in turrets (on barbettes)
   on centreline ends, evenly spread, 2 raised mounts - superfiring
      16 - 5.50" / 140 mm guns in single mounts, 83.19lbs / 37.73kg shells, 1921 Model
   Quick firing guns in casemate mounts 
   on side, all amidships, 8 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, evenly spread, 6 raised mounts
      24 - 2.24" / 57.0 mm guns in single mounts, 5.65lbs / 2.56kg shells, 1921 Model
   Anti-aircraft guns in deck mounts 
   on side, evenly spread, 16 raised mounts
 Weight of broadside 25,210 lbs / 11,435 kg
 Shells per gun, main battery: 90

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 13.0" / 330 mm 570.00 ft / 173.74 m 9.00 ft / 2.74 m
 Ends: Unarmoured
 Upper: 10.0" / 254 mm 570.00 ft / 173.74 m 8.00 ft / 2.44 m
   Main Belt covers 108 % of normal length

   - Torpedo Bulkhead:
  4.00" / 102 mm 570.00 ft / 173.74 m 30.00 ft / 9.14 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 13.0" / 330 mm 10.0" / 254 mm  13.0" / 330 mm
 2nd: 5.00" / 127 mm 5.00" / 127 mm  5.00" / 127 mm

   - Armour deck: 5.00" / 127 mm, Conning tower: 13.00" / 330 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 187,819 shp / 140,113 Kw = 30.00 kts
 Range 10,000nm at 15.00 kts
 Bunker at max displacement = 7,359 tons

Complement:
 1,807 - 2,350

Cost:
 £13.410 million / $53.641 million

Distribution of weights at normal displacement:
 Armament: 3,151 tons, 5.7 %
 Armour: 18,599 tons, 33.5 %
    - Belts: 4,775 tons, 8.6 %
    - Torpedo bulkhead: 2,531 tons, 4.6 %
    - Armament: 4,435 tons, 8.0 %
    - Armour Deck: 6,451 tons, 11.6 %
    - Conning Tower: 408 tons, 0.7 %
 Machinery: 6,468 tons, 11.7 %
 Hull, fittings & equipment: 20,804 tons, 37.5 %
 Fuel, ammunition & stores: 6,478 tons, 11.7 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   68,500 lbs / 31,071 Kg = 23.5 x 18.0 " / 457 mm shells or 10.2 torpedoes
 Stability (Unstable if below 1.00): 1.11
 Metacentric height 6.8 ft / 2.1 m
 Roll period: 17.4 seconds
 Steadiness - As gun platform (Average = 50 %): 51 %
   - Recoil effect (Restricted arc if above 1.00): 0.83
 Seaboat quality  (Average = 1.00): 1.02

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.694
 Length to Beam Ratio: 7.50 : 1
 'Natural speed' for length: 28.46 kts
 Power going to wave formation at top speed: 54 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 5.00 degrees
 Stern overhang: -2.00 ft / -0.61 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  31.00 ft / 9.45 m
    - Forecastle (20 %): 27.00 ft / 8.23 m
    - Mid (67 %):  27.00 ft / 8.23 m (19.00 ft / 5.79 m aft of break)
    - Quarterdeck (15 %): 19.00 ft / 5.79 m
    - Stern:  19.00 ft / 5.79 m
    - Average freeboard: 24.68 ft / 7.52 m
 Ship tends to be wet forward

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 98.7 %
  - Above water (accommodation/working, high = better): 182.2 %
 Waterplane Area: 69,736 Square feet or 6,479 Square metres
 Displacement factor (Displacement / loading): 98 %
 Structure weight / hull surface area: 217 lbs/sq ft or 1,061 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.98
  - Longitudinal: 1.17
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is adequate
 Room for accommodation and workspaces is excellent