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Thursday, December 01, 2005

Another 1921 battlecruiser

I thought that I would extend my battlecruiser series to 1921 with a ship with 8-16.5in BLR, 16-6in QF, 6-4.7in AA, and 32-2pdr AA guns. The armour basis is a substantial 14in with a 5in deck. The speed of 32 knots has ballooned the displacement, but I felt that the ship should do better than the 31 knots of the preceding design. The combination of strength and seakeeping through a greater freeboard, along with the 32 knot speed is behind the great displacement for the rather small dimensions, although it is primarily the speed. I thought that for a 1921 design, a transom stern was appropriate, and it reduces the power requirement, and helps to keep the displacement as low as it is. This is the Springsharp report:
GB/CB/1921, Great Britain Battlecruiser laid down 1921

Displacement:
    49,896 t light; 51,920 t standard; 55,700 t normal; 58,724 t full load

Dimensions: Length overall / water x beam x draught
    867.38 ft / 865.00 ft x 106.00 ft x 32.00 ft (normal load)
    264.38 m / 263.65 m x 32.31 m  x 9.75 m

Armament:
      8 - 16.50" / 419 mm guns (4x2 guns), 2,246.06lbs / 1,018.80kg shells, 1921 Model
      Breech loading guns in turrets (on barbettes)
      on centreline ends, evenly spread, 2 raised mounts - superfiring
      16 - 6.00" / 152 mm guns (8x2 guns), 108.00lbs / 48.99kg 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
      on side, evenly spread, 2 raised mounts
      32 - 1.57" / 40.0 mm guns (8x4 guns), 1.95lbs / 0.89kg shells, 1921 Model
      Anti-aircraft guns in deck mounts
      on side, evenly spread
    Weight of broadside 20,070 lbs / 9,104 kg
    Shells per gun, main battery: 80
    4 - 21.0" / 533.4 mm submerged torpedo tubes

Armour:
   - Belts:        Width (max)    Length (avg)        Height (avg)
    Main:    14.0" / 356 mm    570.00 ft / 173.74 m    8.00 ft / 2.44 m
    Ends:    Unarmoured
    Upper:    10.0" / 254 mm    570.00 ft / 173.74 m    8.00 ft / 2.44 m
      Main Belt covers 101 % of normal length

   - Torpedo Bulkhead:
        4.00" / 102 mm    570.00 ft / 173.74 m    31.00 ft / 9.45 m

   - Gun armour:    Face (max)    Other gunhouse (avg)    Barbette/hoist (max)
    Main:    14.0" / 356 mm    10.0" / 254 mm        14.0" / 356 mm
    2nd:    4.00" / 102 mm    4.00" / 102 mm        4.00" / 102 mm

   - Armour deck: 5.00" / 127 mm, Conning tower: 14.00" / 356 mm

Machinery:
    Oil fired boilers, steam turbines,
    Geared drive, 4 shafts, 203,003 shp / 151,440 Kw = 32.00 kts
    Range 6,400nm at 18.00 kts
    Bunker at max displacement = 6,804 tons

Complement:
    1,812 - 2,356

Cost:
    £12.301 million / $49.203 million

Distribution of weights at normal displacement:
    Armament: 2,509 tons, 4.5 %
    Armour: 19,462 tons, 34.9 %
       - Belts: 4,666 tons, 8.4 %
       - Torpedo bulkhead: 2,615 tons, 4.7 %
       - Armament: 4,871 tons, 8.7 %
       - Armour Deck: 6,870 tons, 12.3 %
       - Conning Tower: 440 tons, 0.8 %
    Machinery: 6,990 tons, 12.6 %
    Hull, fittings & equipment: 20,935 tons, 37.6 %
    Fuel, ammunition & stores: 5,804 tons, 10.4 %
    Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
    Survivability (Non-critical penetrating hits needed to sink ship):
      75,345 lbs / 34,176 Kg = 33.5 x 16.5 " / 419 mm shells or 11.3 torpedoes
    Stability (Unstable if below 1.00): 1.08
    Metacentric height 6.3 ft / 1.9 m
    Roll period: 17.7 seconds
    Steadiness    - As gun platform (Average = 50 %): 51 %
            - Recoil effect (Restricted arc if above 1.00): 0.77
    Seaboat quality  (Average = 1.00): 1.03

Hull form characteristics:
    Hull has rise forward of midbreak
      and transom stern
    Block coefficient: 0.664
    Length to Beam Ratio: 8.16 : 1
    'Natural speed' for length: 33.54 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: -2.00 ft / -0.61 m
    Freeboard (% = measuring location as a percentage of overall length):
       - Stem:        34.00 ft / 10.36 m
       - Forecastle (20 %):    28.00 ft / 8.53 m
       - Mid (67 %):        28.00 ft / 8.53 m (20.00 ft / 6.10 m aft of break)
       - Quarterdeck (15 %):    20.00 ft / 6.10 m
       - Stern:        20.00 ft / 6.10 m
       - Average freeboard:    25.84 ft / 7.88 m

Ship space, strength and comments:
    Space    - Hull below water (magazines/engines, low = better): 93.6 %
        - Above water (accommodation/working, high = better): 201.3 %
    Waterplane Area: 74,274 Square feet or 6,900 Square metres
    Displacement factor (Displacement / loading): 104 %
    Structure weight / hull surface area: 207 lbs/sq ft or 1,009 Kg/sq metre
    Hull strength (Relative):
        - Cross-sectional: 0.99
        - Longitudinal: 1.08
        - Overall: 1.00
    Hull space for machinery, storage, compartmentation is adequate
    Room for accommodation and workspaces is excellent

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