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Tuesday, October 25, 2005

A 1942-style British armoured cruiser (UPDATED)

I have thought about what a British armoured cruiser might have been like, if it were laid down in 1942. It has 9-9.2in BLR, 12-4.5in DP, 48-40mm AA, and 28-20mm AA guns. The armour basis is now 8in. The speed is a modest 32 knots. I initially underestimated the displacement that would be necessary. I also gave too long of an armoured citadel. I have shortened the armoured length. This allowed the armour basis to increase to 8in, instead of 7in. This is the Springsharp report:
GB/CA/1942, Great Britain Armoured Cruiser laid down 1942

Displacement:
 17,687 t light; 18,366 t standard; 19,750 t normal; 20,857 t full load

Dimensions: Length overall / water x beam x draught
 718.89 ft / 715.00 ft x 78.00 ft x 25.00 ft (normal load)
 219.12 m / 217.93 m x 23.77 m  x 7.62 m

Armament:
      9 - 9.20" / 234 mm guns (3x3 guns), 380.00lbs / 172.37kg shells, 1942 Model
   Breech loading guns in turrets (on barbettes)
   on centreline ends, majority forward, 1 raised mount - superfiring
      12 - 4.50" / 114 mm guns (6x2 guns), 45.56lbs / 20.67kg shells, 1942 Model
   Dual purpose guns in turrets (on barbettes)
   on side, all amidships
      48 - 1.57" / 40.0 mm guns (12x4 guns), 2.00lbs / 0.91kg shells, 1942 Model
   Quick firing guns in deck mounts 
   on side ends, evenly spread, 7 raised mounts - superfiring
      28 - 0.79" / 20.0 mm guns in single mounts, 0.24lbs / 0.11kg shells, 1942 Model
   Quick firing guns in deck mounts 
   on side ends, evenly spread, 18 raised mounts - superfiring
 Weight of broadside 4,070 lbs / 1,846 kg
 Shells per gun, main battery: 120

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 8.00" / 203 mm 490.00 ft / 149.35 m 17.00 ft / 5.18 m
 Ends: Unarmoured
   Main Belt covers 105 % of normal length

   - Torpedo Bulkhead:
  1.00" / 25 mm 490.00 ft / 149.35 m 21.00 ft / 6.40 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 8.00" / 203 mm 5.00" / 127 mm  8.00" / 203 mm
 2nd: 4.00" / 102 mm 4.00" / 102 mm  4.00" / 102 mm
 3rd: 1.00" / 25 mm       -         -
 4th: 1.00" / 25 mm       -         -

   - Armour deck: 3.00" / 76 mm, Conning tower: 8.00" / 203 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 120,428 shp / 89,839 Kw = 32.00 kts
 Range 7,800nm at 15.00 kts
 Bunker at max displacement = 2,492 tons

Complement:
 832 - 1,082

Cost:
 £9.516 million / $38.064 million

Distribution of weights at normal displacement:
 Armament: 519 tons, 2.6 %
 Armour: 6,557 tons, 33.2 %
    - Belts: 2,770 tons, 14.0 %
    - Torpedo bulkhead: 381 tons, 1.9 %
    - Armament: 1,226 tons, 6.2 %
    - Armour Deck: 2,054 tons, 10.4 %
    - Conning Tower: 126 tons, 0.6 %
 Machinery: 3,146 tons, 15.9 %
 Hull, fittings & equipment: 7,464 tons, 37.8 %
 Fuel, ammunition & stores: 2,063 tons, 10.4 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   29,889 lbs / 13,558 Kg = 76.8 x 9.2 " / 234 mm shells or 4.4 torpedoes
 Stability (Unstable if below 1.00): 1.18
 Metacentric height 4.7 ft / 1.4 m
 Roll period: 15.1 seconds
 Steadiness - As gun platform (Average = 50 %): 53 %
   - Recoil effect (Restricted arc if above 1.00): 0.35
 Seaboat quality  (Average = 1.00): 1.07

Hull form characteristics:
 Hull has a flush deck
 Block coefficient: 0.496
 Length to Beam Ratio: 9.17 : 1
 'Natural speed' for length: 26.74 kts
 Power going to wave formation at top speed: 52 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 4.00 degrees
 Stern overhang: 2.00 ft / 0.61 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  27.00 ft / 8.23 m
    - Forecastle (20 %): 19.00 ft / 5.79 m
    - Mid (50 %):  19.00 ft / 5.79 m
    - Quarterdeck (15 %): 19.00 ft / 5.79 m
    - Stern:  19.00 ft / 5.79 m
    - Average freeboard: 19.64 ft / 5.99 m
 Ship tends to be wet forward

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 97.3 %
  - Above water (accommodation/working, high = better): 161.0 %
 Waterplane Area: 37,016 Square feet or 3,439 Square metres
 Displacement factor (Displacement / loading): 116 %
 Structure weight / hull surface area: 136 lbs/sq ft or 663 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 1.00
  - Longitudinal: 1.05
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is adequate
 Room for accommodation and workspaces is excellent

1 comment:

Roberto Iza Valdés said...
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