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Thursday, February 23, 2006

Perhaps I was too ambitious with the J/CA/1923 design

I wanted to have a speed of 35 knots for the J/CA/1923 design, and to achieve that at this date required lighter weight machinery and a deeper draft. The higher speed is the only change between this design and its predecessor. The length, draft, freeboard, and displacement needed to grow to satisfy Springsharp. Perhaps, 34 knots would have been more reasonable, so that the range could have been increased. This is the Springsharp report:
J/CA/1923, Japan Heavy Cruiser laid down 1923 (Engine 1937)

Displacement:
 13,116 t light; 13,630 t standard; 14,800 t normal; 15,736 t full load

Dimensions: Length overall / water x beam x draught
 680.80 ft / 675.00 ft x 62.00 ft x 22.00 ft (normal load)
 207.51 m / 205.74 m x 18.90 m  x 6.71 m

Armament:
      10 - 8.00" / 203 mm guns (5x2 guns), 256.00lbs / 116.12kg shells, 1923 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, 1923 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, 1923 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 103 % 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 20.00 ft / 6.10 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, 148,942 shp / 111,111 Kw = 35.00 kts
 Range 7,500nm at 15.00 kts
 Bunker at max displacement = 2,107 tons

Complement:
 670 - 872

Cost:
 £3.967 million / $15.868 million

Distribution of weights at normal displacement:
 Armament: 389 tons, 2.6 %
 Armour: 2,874 tons, 19.4 %
    - Belts: 1,040 tons, 7.0 %
    - Torpedo bulkhead: 333 tons, 2.3 %
    - Armament: 356 tons, 2.4 %
    - Armour Deck: 1,094 tons, 7.4 %
    - Conning Tower: 52 tons, 0.4 %
 Machinery: 4,128 tons, 27.9 %
 Hull, fittings & equipment: 5,726 tons, 38.7 %
 Fuel, ammunition & stores: 1,684 tons, 11.4 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   14,745 lbs / 6,688 Kg = 57.6 x 8.0 " / 203 mm shells or 1.8 torpedoes
 Stability (Unstable if below 1.00): 1.19
 Metacentric height 3.4 ft / 1.0 m
 Roll period: 14.2 seconds
 Steadiness - As gun platform (Average = 50 %): 52 %
   - Recoil effect (Restricted arc if above 1.00): 0.68
 Seaboat quality  (Average = 1.00): 1.04

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.563
 Length to Beam Ratio: 10.89 : 1
 'Natural speed' for length: 25.98 kts
 Power going to wave formation at top speed: 58 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 5.00 degrees
 Stern overhang: 3.00 ft / 0.91 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  32.00 ft / 9.75 m
    - Forecastle (20 %): 26.00 ft / 7.92 m
    - Mid (50 %):  26.00 ft / 7.92 m (18.00 ft / 5.49 m aft of break)
    - Quarterdeck (15 %): 18.00 ft / 5.49 m
    - Stern:  18.00 ft / 5.49 m
    - Average freeboard: 22.48 ft / 6.85 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 163.3 %
  - Above water (accommodation/working, high = better): 135.2 %
 Waterplane Area: 29,554 Square feet or 2,746 Square metres
 Displacement factor (Displacement / loading): 104 %
 Structure weight / hull surface area: 115 lbs/sq ft or 562 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.97
  - Longitudinal: 1.30
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent

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