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Wednesday, November 02, 2005

A fast armoured cruiser for 1921

The natural thing was to see what a 1921 British armoured cruiser, in the same vein, would look like. I initially tried 9-10in guns as a main armament, but that seemed too light for the size. The armament is still light with 9-12in BLR, 16-5.5in QF, 6-4.7in AA, and 24-2pdr AA guns. The armour basis is still just 9in and the maximum speed is still 33 knots. The displacement is a rather large 35,700 tons normal to achieve moderate results. This is the Springsharp report:
GB/CA/1921, Great Britain Armoured Cruiser laid down 1921

Displacement:
       32,643 t light; 33,848 t standard; 35,700 t normal; 37,182 t full load

Dimensions: Length overall / water x beam x draught
       814.10 ft / 812.00 ft x 96.00 ft x 28.00 ft (normal load)
       248.14 m / 247.50 m x 29.26 m  x 8.53 m

Armament:
    9 - 12.00" / 305 mm guns (3x3 guns), 864.00lbs / 391.90kg shells, 1921 Model
         Breech loading guns in turrets (on barbettes)
         on centreline ends, majority forward, 1 raised mount - superfiring
    16 - 5.50" / 140 mm guns (8x2 guns), 83.19lbs / 37.73kg shells, 1921 Model
         Quick firing guns in turrets (on barbettes)
         on side, evenly spread, 4 raised mounts
    6 - 4.70" / 119 mm guns in single mounts, 51.91lbs / 23.55kg shells, 1921 Model
         Anti-aircraft guns in deck mounts with hoists
         on side, evenly spread, all raised mounts
    24 - 1.57" / 40.0 mm guns (6x4 guns), 2.00lbs / 0.91kg shells, 1921 Model
         Anti-aircraft guns in deck mounts
         on side, evenly spread
       Weight of broadside 9,466 lbs / 4,294 kg
       Shells per gun, main battery: 90

Armour:
 - Belts:              Width (max)     Length (avg)            Height (avg)
       Main:   9.00" / 229 mm  600.00 ft / 182.88 m    17.00 ft / 5.18 m
       Ends:   Unarmoured
         Main Belt covers 114 % of normal length

 - Torpedo Bulkhead:
               2.00" / 51 mm   600.00 ft / 182.88 m    27.00 ft / 8.23 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:    5.00" / 127 mm  5.00" / 127 mm          5.00" / 127 mm
       4th:    1.00" / 25 mm         -                       -

 - Armour deck: 4.00" / 102 mm, Conning tower: 9.00" / 229 mm

Machinery:
       Oil fired boilers, steam turbines,
       Geared drive, 4 shafts, 170,392 shp / 127,112 Kw = 33.00 kts
       Range 6,000nm at 15.00 kts
       Bunker at max displacement = 3,335 tons

Complement:
       1,298 - 1,688

Cost:
       £7.529 million / $30.116 million

Distribution of weights at normal displacement:
       Armament: 1,183 tons, 3.3 %
       Armour: 11,888 tons, 33.3 %
          - Belts: 3,808 tons, 10.7 %
          - Torpedo bulkhead: 1,199 tons, 3.4 %
          - Armament: 2,388 tons, 6.7 %
          - Armour Deck: 4,283 tons, 12.0 %
          - Conning Tower: 210 tons, 0.6 %
       Machinery: 5,867 tons, 16.4 %
       Hull, fittings & equipment: 13,705 tons, 38.4 %
       Fuel, ammunition & stores: 3,057 tons, 8.6 %
       Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
       Survivability (Non-critical penetrating hits needed to sink ship):
         50,934 lbs / 23,103 Kg = 59.0 x 12.0 " / 305 mm shells or 7.1 torpedoes
       Stability (Unstable if below 1.00): 1.18
       Metacentric height 6.4 ft / 1.9 m
       Roll period: 15.9 seconds
       Steadiness      - As gun platform (Average = 50 %): 51 %
                       - Recoil effect (Restricted arc if above 1.00): 0.45
       Seaboat quality  (Average = 1.00): 1.03

Hull form characteristics:
       Hull has a flush deck
         and transom stern
       Block coefficient: 0.572
       Length to Beam Ratio: 8.46 : 1
       'Natural speed' for length: 32.69 kts
       Power going to wave formation at top speed: 54 %
       Trim (Max stability = 0, Max steadiness = 100): 50
       Bow angle (Positive = bow angles forward): 4.00 degrees
       Stern overhang: 0.00 ft / 0.00 m
       Freeboard (% = measuring location as a percentage of overall length):
          - Stem:              30.00 ft / 9.14 m
          - Forecastle (20 %): 23.00 ft / 7.01 m
          - Mid (67 %):                23.00 ft / 7.01 m
          - Quarterdeck (15 %):        23.00 ft / 7.01 m
          - Stern:             23.00 ft / 7.01 m
          - Average freeboard: 23.56 ft / 7.18 m
       Ship tends to be wet forward

Ship space, strength and comments:
       Space   - Hull below water (magazines/engines, low = better): 99.3 %
               - Above water (accommodation/working, high = better): 195.3 %
       Waterplane Area: 57,873 Square feet or 5,377 Square metres
       Displacement factor (Displacement / loading): 108 %
       Structure weight / hull surface area: 171 lbs/sq ft or 835 Kg/sq metre
       Hull strength (Relative):
               - Cross-sectional: 0.99
               - Longitudinal: 1.06
               - Overall: 1.00
       Hull space for machinery, storage, compartmentation is adequate
       Room for accommodation and workspaces is excellent

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