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Saturday, December 10, 2005

My attempt at a 1918 British light cruiser

Perhaps this is anachronistic, but I thought that having four twin 6in turrets was not unreasonable for a ship laid down in 1918. This is meant to be an incremental advance over my GB/CL/1916 design. It is not a great advance, except for the turrets. There is some increase in speed and range. I couldn't resist a Springsharp-specific "hack" of increasing the draft for more strength and increased seakeeping. This is the Springsharp report:
GB/CL/1918, Great Britain Light Cruiser laid down 1918

Displacement:
 8,996 t light; 9,290 t standard; 10,200 t normal; 10,928 t full load

Dimensions: Length overall / water x beam x draught
 556.36 ft / 555.00 ft x 56.00 ft x 20.00 ft (normal load)
 169.58 m / 169.16 m x 17.07 m  x 6.10 m

Armament:
      8 - 6.00" / 152 mm guns (4x2 guns), 108.00lbs / 48.99kg shells, 1918 Model
   Quick firing guns in turrets (on barbettes)
   on centreline ends, evenly spread, 2 raised mounts - superfiring
      4 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1918 Model
   Anti-aircraft guns in deck mounts with hoists
   on side, all amidships
      16 - 1.57" / 40.0 mm guns (4x4 guns), 1.95lbs / 0.89kg shells, 1918 Model
   Breech loading guns in deck mounts 
   on side ends, evenly spread
 Weight of broadside 1,023 lbs / 464 kg
 Shells per gun, main battery: 150
 8 - 21.0" / 533.4 mm above water torpedoes, 21 - 21.0" / 533.4 mm submerged torpedo tubes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 4.00" / 102 mm 425.00 ft / 129.54 m 12.00 ft / 3.66 m
 Ends: Unarmoured
   Main Belt covers 118 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 2.00" / 51 mm       -   2.00" / 51 mm

   - Armour deck: 2.00" / 51 mm, Conning tower: 4.00" / 102 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 97,206 shp / 72,515 Kw = 32.50 kts
 Range 5,800nm at 15.00 kts
 Bunker at max displacement = 1,639 tons

Complement:
 506 - 659

Cost:
 £1.826 million / $7.306 million

Distribution of weights at normal displacement:
 Armament: 128 tons, 1.3 %
 Armour: 1,835 tons, 18.0 %
    - Belts: 832 tons, 8.2 %
    - Torpedo bulkhead: 0 tons, 0.0 %
    - Armament: 142 tons, 1.4 %
    - Armour Deck: 821 tons, 8.0 %
    - Conning Tower: 41 tons, 0.4 %
 Machinery: 3,507 tons, 34.4 %
 Hull, fittings & equipment: 3,526 tons, 34.6 %
 Fuel, ammunition & stores: 1,204 tons, 11.8 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   4,601 lbs / 2,087 Kg = 42.6 x 6.0 " / 152 mm shells or 0.7 torpedoes
 Stability (Unstable if below 1.00): 1.28
 Metacentric height 3.3 ft / 1.0 m
 Roll period: 13.0 seconds
 Steadiness - As gun platform (Average = 50 %): 53 %
   - Recoil effect (Restricted arc if above 1.00): 0.32
 Seaboat quality  (Average = 1.00): 1.05

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.574
 Length to Beam Ratio: 9.91 : 1
 'Natural speed' for length: 23.56 kts
 Power going to wave formation at top speed: 61 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 3.00 degrees
 Stern overhang: -2.00 ft / -0.61 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  26.00 ft / 7.92 m
    - Forecastle (20 %): 23.00 ft / 7.01 m
    - Mid (67 %):  23.00 ft / 7.01 m (15.00 ft / 4.57 m aft of break)
    - Quarterdeck (15 %): 15.00 ft / 4.57 m
    - Stern:  15.00 ft / 4.57 m
    - Average freeboard: 20.60 ft / 6.28 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 169.4 %
  - Above water (accommodation/working, high = better): 142.8 %
 Waterplane Area: 22,191 Square feet or 2,062 Square metres
 Displacement factor (Displacement / loading): 103 %
 Structure weight / hull surface area: 94 lbs/sq ft or 458 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.95
  - Longitudinal: 1.56
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent

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