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Monday, July 16, 2007

A GB/CA/1921 design

This is my first attempt at a GB/CA/1921 design in Springsharp 3.0b2 Beta. I want a fast ship that is well-protected and which can fill the armoured cruiser role for the 1921 building program. For the size, the 9-9.2in/55 guns seem rather meager, but 10in guns seem to heavy and slow-firing. Still, the ship is large, with a 22,474 tons Standard displacement. The belt is 8in at the waterline and the deck is 3in. I want speed, so I made the sacrifices necessary to obtain a 33 knot speed and a range of 12,000nm at 16 knots. All that costs size. This is the Springsharp report:
GB/CA/1921, Great Britain Heavy Cruiser laid down 1921 (Engine 1927)

Displacement:
 21,612 t light; 22,474 t standard; 25,832 t normal; 28,518 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
 (721.59 ft / 715.00 ft) x 90.00 ft x (25.00 / 27.02 ft)
 (219.94 m / 217.93 m) x 27.43 m  x (7.62 / 8.24 m)

Armament:
      9 - 9.20" / 234 mm 55.0 cal guns - 420.00lbs / 190.51kg shells, 150 per gun
   Breech loading guns in turret on barbette mounts, 1921 Model
   3 x Single mounts on centreline ends, majority forward
  1 raised mount - superfiring
      6 - 4.70" / 119 mm 50.0 cal guns - 54.96lbs / 24.93kg 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
      16 - 1.57" / 40.0 mm 50.0 cal guns - 2.00lbs / 0.91kg shells, 150 per gun
   Anti-air guns in deck mounts, 1921 Model
   4 x 2 row quad mounts on sides, aft deck forward
      Weight of broadside 4,142 lbs / 1,879 kg

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 8.00" / 203 mm 470.00 ft / 143.26 m 8.00 ft / 2.44 m
 Ends: Unarmoured
 Upper: 5.00" / 127 mm 470.00 ft / 143.26 m 8.00 ft / 2.44 m
   Main Belt covers 101 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
  1.50" / 38 mm 470.00 ft / 143.26 m 25.00 ft / 7.62 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 8.00" / 203 mm 6.00" / 152 mm  8.00" / 203 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, 156,007 shp / 116,381 Kw = 33.00 kts
 Range 12,000nm at 16.00 kts
 Bunker at max displacement = 6,045 tons

Complement:
 1,018 - 1,324

Cost:
 £4.877 million / $19.506 million

Distribution of weights at normal displacement:
 Armament: 1,396 tons, 5.4 %
 Armour: 6,657 tons, 25.8 %
    - Belts: 2,068 tons, 8.0 %
    - Torpedo bulkhead: 652 tons, 2.5 %
    - Armament: 1,184 tons, 4.6 %
    - Armour Deck: 2,602 tons, 10.1 %
    - Conning Tower: 151 tons, 0.6 %
 Machinery: 4,924 tons, 19.1 %
 Hull, fittings & equipment: 8,634 tons, 33.4 %
 Fuel, ammunition & stores: 4,220 tons, 16.3 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   41,886 lbs / 18,999 Kg = 107.6 x 9.2 " / 234 mm shells or 5.6 torpedoes
 Stability (Unstable if below 1.00): 1.29
 Metacentric height 6.7 ft / 2.0 m
 Roll period: 14.6 seconds
 Steadiness - As gun platform (Average = 50 %): 55 %
   - Recoil effect (Restricted arc if above 1.00): 0.25
 Seaboat quality  (Average = 1.00): 1.09

Hull form characteristics:
 Hull has a flush deck,
   an extended bulbous bow and small transom stern
 Block coefficient (normal/deep): 0.562 / 0.574
 Length to Beam Ratio: 7.94 : 1
 'Natural speed' for length: 28.88 kts
 Power going to wave formation at top speed: 58 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 12.00 degrees
 Stern overhang: 0.00 ft / 0.00 m
 Freeboard (% = length of deck as a percentage of waterline length):
    Fore end,  Aft end
    - Forecastle: 30.00 %,  31.00 ft / 9.45 m,  26.00 ft / 7.92 m
    - Forward deck: 30.00 %,  26.00 ft / 7.92 m,  24.00 ft / 7.32 m
    - Aft deck: 25.00 %,  24.00 ft / 7.32 m,  24.00 ft / 7.32 m
    - Quarter deck: 15.00 %,  24.00 ft / 7.32 m,  24.00 ft / 7.32 m
    - Average freeboard:  25.50 ft / 7.77 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 101.7 %
  - Above water (accommodation/working, high = better): 213.8 %
 Waterplane Area: 46,545 Square feet or 4,324 Square metres
 Displacement factor (Displacement / loading): 123 %
 Structure weight / hull surface area: 142 lbs/sq ft or 693 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.97
  - Longitudinal: 1.35
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is adequate
 Room for accommodation and workspaces is excellent

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