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Sunday, October 30, 2005

My smaller, faster 1912 British Light Cruiser design

I wanted to see what might done on a smaller displacement that could reach 28 knots. I armed the resulting design with 6-5in QF guns, 2-3in AA guns, and 4-21in TT above water. The armour basis is 3in with a 1in deck. The gun shields are 3in, as well. This is the Springsharp report:
GB/CL/1912 Fast, Great Britain Light Cruiser laid down 1912

Displacement:
 4,167 t light; 4,305 t standard; 4,850 t normal; 5,286 t full load

Dimensions: Length overall / water x beam x draught
 443.75 ft / 440.00 ft x 44.00 ft x 15.00 ft (normal load)
 135.25 m / 134.11 m x 13.41 m  x 4.57 m

Armament:
      6 - 5.00" / 127 mm guns in single mounts, 62.50lbs / 28.35kg shells, 1912 Model
   Quick firing guns in deck mounts with hoists
   on centreline ends, evenly spread
      2 - 3.00" / 76.2 mm guns in single mounts, 13.50lbs / 6.12kg shells, 1912 Model
   Anti-aircraft guns in deck mounts 
   on side, evenly spread
 Weight of broadside 402 lbs / 182 kg
 Shells per gun, main battery: 180
 4 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 3.00" / 76 mm 310.00 ft / 94.49 m 12.00 ft / 3.66 m
 Ends: Unarmoured
   Main Belt covers 108 % of normal length

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 3.00" / 76 mm       -         -

   - Armour deck: 2.00" / 51 mm, Conning tower: 3.00" / 76 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Direct drive, 2 shafts, 37,013 shp / 27,611 Kw = 28.00 kts
 Range 4,250nm at 15.00 kts
 Bunker at max displacement = 981 tons

Complement:
 289 - 377

Cost:
 £0.395 million / $1.579 million

Distribution of weights at normal displacement:
 Armament: 50 tons, 1.0 %
 Armour: 1,046 tons, 21.6 %
    - Belts: 460 tons, 9.5 %
    - Torpedo bulkhead: 0 tons, 0.0 %
    - Armament: 51 tons, 1.0 %
    - Armour Deck: 516 tons, 10.6 %
    - Conning Tower: 19 tons, 0.4 %
 Machinery: 1,476 tons, 30.4 %
 Hull, fittings & equipment: 1,595 tons, 32.9 %
 Fuel, ammunition & stores: 683 tons, 14.1 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   5,442 lbs / 2,468 Kg = 87.1 x 5.0 " / 127 mm shells or 1.0 torpedoes
 Stability (Unstable if below 1.00): 1.32
 Metacentric height 2.4 ft / 0.7 m
 Roll period: 11.9 seconds
 Steadiness - As gun platform (Average = 50 %): 59 %
   - Recoil effect (Restricted arc if above 1.00): 0.21
 Seaboat quality  (Average = 1.00): 1.18

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.585
 Length to Beam Ratio: 10.00 : 1
 'Natural speed' for length: 20.98 kts
 Power going to wave formation at top speed: 59 %
 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:  25.00 ft / 7.62 m
    - Forecastle (20 %): 21.00 ft / 6.40 m
    - Mid (37 %):  21.00 ft / 6.40 m (13.00 ft / 3.96 m aft of break)
    - Quarterdeck (15 %): 13.00 ft / 3.96 m
    - Stern:  13.00 ft / 3.96 m
    - Average freeboard: 16.28 ft / 4.96 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 107.2 %
  - Above water (accommodation/working, high = better): 119.1 %
 Waterplane Area: 13,956 Square feet or 1,297 Square metres
 Displacement factor (Displacement / loading): 110 %
 Structure weight / hull surface area: 68 lbs/sq ft or 333 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.96
  - Longitudinal: 1.51
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is adequate
 Room for accommodation and workspaces is adequate

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