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Thursday, March 06, 2008

An Atlanta-style light cruiser

I wanted to see what an Atlanta-style fast light cruiser would be like. I call my design the "US/CL/1940 AA". My ship has 16-5in/38 DP guns and has a 34 knot speed:
US/CL/1940 AA, United States Light Cruiser laid down 1940 (Engine 1950)

Displacement:
 7,687 t light; 7,951 t standard; 8,625 t normal; 9,165 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
 (546.43 ft / 540.00 ft) x 54.00 ft x (20.50 / 21.43 ft)
 (166.55 m / 164.59 m) x 16.46 m  x (6.25 / 6.53 m)

Armament:
      12 - 5.00" / 127 mm 38.0 cal guns - 58.00lbs / 26.31kg shells, 150 per gun
   Dual purpose guns in turret on barbette mounts, 1940 Model
   4 x Twin mounts on centreline ends, evenly spread
  2 raised mounts - superfiring
   4 x Twin mounts on centreline ends, evenly spread
  4 double raised mounts
      4 - 5.00" / 127 mm 38.0 cal guns - 58.00lbs / 26.31kg shells, 150 per gun
   Dual purpose guns in turret on barbette mounts, 1940 Model
   2 x Twin mounts on sides, forward deck aft
      12 - 1.57" / 40.0 mm 45.0 cal guns - 2.00lbs / 0.91kg shells, 150 per gun
   Breech loading guns in deck mounts, 1940 Model
   2 x Quad mounts on sides, aft deck forward
  2 raised mounts - superfiring
   1 x Quad mount on centreline, aft deck aft
      Weight of broadside 952 lbs / 432 kg
      8 - 21.0" / 533 mm, 22.00 ft / 6.71 m torpedoes - 1.501 t each, 12.009 t total
 In 2 sets of deck mounted side rotating tubes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 4.00" / 102 mm 355.00 ft / 108.20 m 12.00 ft / 3.66 m
 Ends: Unarmoured
   Main Belt covers 101 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
  0.60" / 15 mm 355.00 ft / 108.20 m 20.50 ft / 6.25 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 2.00" / 51 mm 1.00" / 25 mm  2.00" / 51 mm
 2nd: 2.00" / 51 mm 1.00" / 25 mm  2.00" / 51 mm

   - Armoured 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 5.00" / 127 mm,  Aft 0.00" / 0 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 88,421 shp / 65,962 Kw = 34.00 kts
 Range 5,400nm at 16.00 kts
 Bunker at max displacement = 1,214 tons

Complement:
 446 - 581

Cost:
 £3.858 million / $15.432 million

Distribution of weights at normal displacement:
 Armament: 214 tons, 2.5 %
    - Guns: 202 tons, 2.3 %
    - Torpedoes: 12 tons, 0.1 %
 Armour: 1,952 tons, 22.6 %
    - Belts: 700 tons, 8.1 %
    - Torpedo bulkhead: 162 tons, 1.9 %
    - Armament: 288 tons, 3.3 %
    - Armour Deck: 757 tons, 8.8 %
    - Conning Tower: 45 tons, 0.5 %
 Machinery: 2,115 tons, 24.5 %
 Hull, fittings & equipment: 3,406 tons, 39.5 %
 Fuel, ammunition & stores: 938 tons, 10.9 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   11,828 lbs / 5,365 Kg = 189.2 x 5.0 " / 127 mm shells or 1.9 torpedoes
 Stability (Unstable if below 1.00): 1.02
 Metacentric height 2.1 ft / 0.6 m
 Roll period: 15.7 seconds
 Steadiness - As gun platform (Average = 50 %): 51 %
   - Recoil effect (Restricted arc if above 1.00): 0.56
 Seaboat quality  (Average = 1.00): 1.03

Hull form characteristics:
 Hull has a flush deck,
   an extended bulbous bow and large transom stern
 Block coefficient (normal/deep): 0.505 / 0.513
 Length to Beam Ratio: 10.00 : 1
 'Natural speed' for length: 26.50 kts
 Power going to wave formation at top speed: 62 %
 Trim (Max stability = 0, Max steadiness = 100): 49
 Bow angle (Positive = bow angles forward): 9.00 degrees
 Stern overhang: 2.00 ft / 0.61 m
 Freeboard (% = length of deck as a percentage of waterline length):
    Fore end,  Aft end
    - Forecastle: 20.00 %,  28.00 ft / 8.53 m,  24.00 ft / 7.32 m
    - Forward deck: 30.00 %,  24.00 ft / 7.32 m,  21.00 ft / 6.40 m
    - Aft deck: 35.00 %,  21.00 ft / 6.40 m,  18.00 ft / 5.49 m
    - Quarter deck: 15.00 %,  18.00 ft / 5.49 m,  18.00 ft / 5.49 m
    - Average freeboard:  21.40 ft / 6.52 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 140.9 %
  - Above water (accommodation/working, high = better): 176.3 %
 Waterplane Area: 20,299 Square feet or 1,886 Square metres
 Displacement factor (Displacement / loading): 125 %
 Structure weight / hull surface area: 97 lbs/sq ft or 473 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.93
  - Longitudinal: 2.02
  - Overall: 1.01
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent

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