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Thursday, January 31, 2008

The GB/CL/1912 design

This is my 1912 version of my proposal for British light cruisers. These are designed from the beginning, like the old Town class, for overseas service, as well as with the fleet. This has three guns on the centerline, two aft and one forward, and six guns on the sidess. They have a six gun broadside that way. The main improvement is side armour to go with a 2in deck, although they have a much stronger gun armament, as well. This is the Springsharp report:
GB/CL/1912, Great Britain Light Cruiser laid down 1912 (Engine 1917)

Displacement:
 4,833 t light; 5,014 t standard; 5,626 t normal; 6,115 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
 (467.00 ft / 462.00 ft) x 46.00 ft x (17.00 / 18.16 ft)
 (142.34 m / 140.82 m) x 14.02 m  x (5.18 / 5.53 m)

Armament:
      7 - 6.00" / 152 mm 45.0 cal guns - 108.92lbs / 49.41kg shells, 150 per gun
   Quick firing guns in deck and hoist mounts, 1912 Model
   3 x Single mounts on centreline ends, evenly spread
   4 x Single mounts on sides, forward deck aft
      Weight of broadside 762 lbs / 346 kg
      4 - 21.0" / 533 mm, 20.00 ft / 6.10 m torpedoes - 1.271 t each, 5.084 t total
 In 2 sets of deck mounted side rotating tubes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 3.00" / 76 mm 400.00 ft / 121.92 m 8.00 ft / 2.44 m
 Ends: Unarmoured
 Upper: 3.00" / 76 mm 280.00 ft / 85.34 m 8.00 ft / 2.44 m
   Main Belt covers 133 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
  0.70" / 18 mm 400.00 ft / 121.92 m 17.00 ft / 5.18 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 4.00" / 102 mm 3.00" / 76 mm  4.00" / 102 mm

   - Protected deck - single deck: 2.00" / 51 mm For and Aft decks
 Forecastle: 2.00" / 51 mm  Quarter deck: 2.00" / 51 mm

   - Conning towers: Forward 4.00" / 102 mm,  Aft 0.00" / 0 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Direct drive, 2 shafts, 33,615 shp / 25,077 Kw = 27.00 kts
 Range 5,400nm at 15.00 kts
 Bunker at max displacement = 1,100 tons

Complement:
 324 - 422

Cost:
 £0.414 million / $1.655 million

Distribution of weights at normal displacement:
 Armament: 208 tons, 3.7 %
    - Guns: 202 tons, 3.6 %
    - Torpedoes: 5 tons, 0.1 %
 Armour: 1,584 tons, 28.2 %
    - Belts: 656 tons, 11.7 %
    - Torpedo bulkhead: 176 tons, 3.1 %
    - Armament: 174 tons, 3.1 %
    - Armour Deck: 551 tons, 9.8 %
    - Conning Tower: 27 tons, 0.5 %
 Machinery: 1,232 tons, 21.9 %
 Hull, fittings & equipment: 1,809 tons, 32.2 %
 Fuel, ammunition & stores: 792 tons, 14.1 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   7,811 lbs / 3,543 Kg = 72.3 x 6.0 " / 152 mm shells or 1.6 torpedoes
 Stability (Unstable if below 1.00): 1.11
 Metacentric height 1.9 ft / 0.6 m
 Roll period: 14.0 seconds
 Steadiness - As gun platform (Average = 50 %): 66 %
   - Recoil effect (Restricted arc if above 1.00): 0.45
 Seaboat quality  (Average = 1.00): 1.32

Hull form characteristics:
 Hull has rise forward of midbreak,
   a ram bow and a cruiser stern
 Block coefficient (normal/deep): 0.545 / 0.555
 Length to Beam Ratio: 10.04 : 1
 'Natural speed' for length: 21.49 kts
 Power going to wave formation at top speed: 55 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 9.00 degrees
 Stern overhang: -3.00 ft / -0.91 m
 Freeboard (% = length of deck as a percentage of waterline length):
    Fore end,  Aft end
    - Forecastle: 20.00 %,  23.00 ft / 7.01 m,  22.00 ft / 6.71 m
    - Forward deck: 17.00 %,  22.00 ft / 6.71 m,  22.00 ft / 6.71 m
    - Aft deck: 48.00 %,  14.00 ft / 4.27 m,  14.00 ft / 4.27 m
    - Quarter deck: 15.00 %,  14.00 ft / 4.27 m,  14.00 ft / 4.27 m
    - Average freeboard:  17.04 ft / 5.19 m
 Ship tends to be wet forward

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 147.9 %
  - Above water (accommodation/working, high = better): 136.2 %
 Waterplane Area: 14,762 Square feet or 1,371 Square metres
 Displacement factor (Displacement / loading): 119 %
 Structure weight / hull surface area: 75 lbs/sq ft or 368 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.95
  - Longitudinal: 1.55
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent
 Good seaboat, rides out heavy weather easily

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