The J/CL/1941 light cruiser design

The J/CL/1941 light cruiser design now has 15-6.1in QF guns, 12-5in DP, and 48-57mm AA guns in twin mounts. The torpedo armament has stayed at 8-24in TT. The speed is 37 knots, so the design is the embodiment of the original Mogami design, except that much more is required to achieve that then the original, too small displacement (to have been 8,500 tons standard). My main criticism of this design is that the armour basis is too light at 3in with a 2in deck. The roll period is now a very good 14.1 seconds and with the seakeeping ability, the result is a good, fast ship. The range might have been increased, but that would have required additional size. This is the Springsharp report:

J/CL/1941, Japan Light Cruiser laid down 1941 (Engine 1950)

Displacement:
 12,778 t light; 13,365 t standard; 14,400 t normal; 15,228 t full load

Dimensions: Length overall / water x beam x draught
 666.89 ft / 662.00 ft x 64.00 ft x 21.00 ft (normal load)
 203.27 m / 201.78 m x 19.51 m  x 6.40 m

Armament:
      15 - 6.10" / 155 mm guns (5x3 guns), 113.62lbs / 51.54kg shells, 1941 Model
   Quick firing guns in turrets (on barbettes)
   on centreline ends, majority forward, 2 raised mounts - superfiring
      12 - 5.00" / 127 mm guns (6x2 guns), 62.50lbs / 28.35kg shells, 1941 Model
   Dual purpose guns in deck mounts with hoists
   on side, all amidships
      48 - 2.24" / 57.0 mm guns (24x2 guns), 5.65lbs / 2.56kg shells, 1941 Model
   Anti-aircraft guns in deck mounts 
   on side, all amidships, 12 raised mounts - superfiring
 Weight of broadside 2,726 lbs / 1,236 kg
 Shells per gun, main battery: 180
 8 - 24.0" / 609.6 mm above water torpedoes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 3.00" / 76 mm 475.00 ft / 144.78 m 12.00 ft / 3.66 m
 Ends: Unarmoured
   Main Belt covers 110 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
  1.00" / 25 mm 475.00 ft / 144.78 m 19.00 ft / 5.79 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 3.00" / 76 mm 2.00" / 51 mm  2.00" / 51 mm

   - Armour deck: 1.00" / 25 mm, Conning tower: 3.00" / 76 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 188,126 shp / 140,342 Kw = 37.00 kts
 Range 7,500nm at 15.00 kts
 Bunker at max displacement = 1,862 tons

Complement:
 656 - 854

Cost:
 £8.429 million / $33.715 million

Distribution of weights at normal displacement:
 Armament: 341 tons, 2.4 %
 Armour: 1,925 tons, 13.4 %
    - Belts: 701 tons, 4.9 %
    - Torpedo bulkhead: 334 tons, 2.3 %
    - Armament: 296 tons, 2.1 %
    - Armour Deck: 556 tons, 3.9 %
    - Conning Tower: 38 tons, 0.3 %
 Machinery: 4,501 tons, 31.3 %
 Hull, fittings & equipment: 6,011 tons, 41.7 %
 Fuel, ammunition & stores: 1,622 tons, 11.3 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   13,566 lbs / 6,154 Kg = 119.4 x 6.1 " / 155 mm shells or 1.7 torpedoes
 Stability (Unstable if below 1.00): 1.21
 Metacentric height 3.6 ft / 1.1 m
 Roll period: 14.1 seconds
 Steadiness - As gun platform (Average = 50 %): 52 %
   - Recoil effect (Restricted arc if above 1.00): 0.60
 Seaboat quality  (Average = 1.00): 1.04

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.566
 Length to Beam Ratio: 10.34 : 1
 'Natural speed' for length: 25.73 kts
 Power going to wave formation at top speed: 62 %
 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:  33.00 ft / 10.06 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: 24.84 ft / 7.57 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 174.8 %
  - Above water (accommodation/working, high = better): 179.4 %
 Waterplane Area: 30,029 Square feet or 2,790 Square metres
 Displacement factor (Displacement / loading): 105 %
 Structure weight / hull surface area: 116 lbs/sq ft or 567 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.94
  - Longitudinal: 1.71
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent