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Sunday, March 30, 2008

A GB/CA/1921 design

This is another attempt at a fast, British 1921-style heavy armoured cruiser. The ship has 9-10in/50, 16-5.5in/50 QF, 6-4.7in AA, and 24-2pdr AA guns. The armour basis is 8in. This is the Springsharp report:
GB/CA/1921, Great Britain Armoured Cruiser laid down 1921 (Engine 1937)

Displacement:
 24,231 t light; 25,234 t standard; 26,899 t normal; 28,230 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
 (760.07 ft / 755.00 ft) x 88.00 ft x (26.00 / 26.99 ft)
 (231.67 m / 230.12 m) x 26.82 m  x (7.92 / 8.23 m)

Armament:
      9 - 10.00" / 254 mm 50.0 cal guns - 529.32lbs / 240.10kg shells, 120 per gun
   Breech loading guns in turret on barbette mounts, 1921 Model
   3 x Triple mounts on centreline ends, majority forward
  1 raised mount - superfiring
      16 - 5.50" / 140 mm 50.0 cal guns - 88.07lbs / 39.95kg shells, 150 per gun
   Quick firing guns in turret on barbette mounts, 1921 Model
   8 x Twin mounts on sides, aft deck forward
  4 raised mounts - superfiring
      6 - 4.70" / 119 mm 45.0 cal guns - 52.35lbs / 23.75kg shells, 150 per gun
   Anti-air guns in deck and hoist mounts, 1921 Model
   6 x Single mounts on sides, forward deck aft
  6 raised mounts
      24 - 1.57" / 40.0 mm 45.0 cal guns - 1.97lbs / 0.89kg shells, 150 per gun
   Anti-air guns in deck mounts, 1921 Model
   6 x 2 row quad mounts on sides, evenly spread
  6 raised mounts
      Weight of broadside 6,534 lbs / 2,964 kg

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 8.00" / 203 mm 435.00 ft / 132.59 m 16.00 ft / 4.88 m
 Ends: Unarmoured
   Main Belt covers 89 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
  1.00" / 25 mm 435.00 ft / 132.59 m 26.00 ft / 7.92 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 9.00" / 229 mm 6.00" / 152 mm  9.00" / 229 mm
 2nd: 4.00" / 102 mm 3.00" / 76 mm  4.00" / 102 mm

   - Armoured deck - multiple decks: 3.00" / 76 mm For and Aft decks
 Forecastle: 3.00" / 76 mm  Quarter deck: 3.00" / 76 mm

   - Conning towers: Forward 8.00" / 203 mm,  Aft 0.00" / 0 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 173,434 shp / 129,382 Kw = 34.00 kts
 Range 5,400nm at 17.00 kts
 Bunker at max displacement = 2,996 tons

Complement:
 1,049 - 1,365

Cost:
 £5.593 million / $22.373 million

Distribution of weights at normal displacement:
 Armament: 1,632 tons, 6.1 %
 Armour: 7,509 tons, 27.9 %
    - Belts: 2,386 tons, 8.9 %
    - Torpedo bulkhead: 418 tons, 1.6 %
    - Armament: 1,904 tons, 7.1 %
    - Armour Deck: 2,646 tons, 9.8 %
    - Conning Tower: 155 tons, 0.6 %
 Machinery: 4,807 tons, 17.9 %
 Hull, fittings & equipment: 10,284 tons, 38.2 %
 Fuel, ammunition & stores: 2,668 tons, 9.9 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   39,909 lbs / 18,103 Kg = 79.8 x 10.0 " / 254 mm shells or 4.9 torpedoes
 Stability (Unstable if below 1.00): 1.11
 Metacentric height 5.0 ft / 1.5 m
 Roll period: 16.4 seconds
 Steadiness - As gun platform (Average = 50 %): 54 %
   - Recoil effect (Restricted arc if above 1.00): 0.53
 Seaboat quality  (Average = 1.00): 1.08

Hull form characteristics:
 Hull has a flush deck,
   an extended bulbous bow and small transom stern
 Block coefficient (normal/deep): 0.545 / 0.551
 Length to Beam Ratio: 8.58 : 1
 'Natural speed' for length: 29.60 kts
 Power going to wave formation at top speed: 57 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 9.00 degrees
 Stern overhang: 0.00 ft / 0.00 m
 Freeboard (% = length of deck as a percentage of waterline length):
    Fore end,  Aft end
    - Forecastle: 20.00 %,  32.00 ft / 9.75 m,  28.00 ft / 8.53 m
    - Forward deck: 30.00 %,  28.00 ft / 8.53 m,  25.00 ft / 7.62 m
    - Aft deck: 35.00 %,  25.00 ft / 7.62 m,  25.00 ft / 7.62 m
    - Quarter deck: 15.00 %,  25.00 ft / 7.62 m,  25.00 ft / 7.62 m
    - Average freeboard:  26.37 ft / 8.04 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 105.3 %
  - Above water (accommodation/working, high = better): 220.6 %
 Waterplane Area: 47,286 Square feet or 4,393 Square metres
 Displacement factor (Displacement / loading): 114 %
 Structure weight / hull surface area: 159 lbs/sq ft or 775 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.97
  - Longitudinal: 1.34
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is adequate
 Room for accommodation and workspaces is excellent

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