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Friday, November 18, 2005

The next step is a high-speed light cruiser

I thought that a Barbiano-style light cruiser. The problem with my first attempt is that there is no belt, only turret, barbette, deck, and conning tower. My first attempt was to reach 36 knots with 8-6in guns. That goal proved achievable. I wanted a 555ft length and as low a displacement as possible. I assumed that a relatively high freeboard would be required. I also assumed that the design would use the lightest machinery that Springsharp would allow. I expect that I will do several iterations to achieve better performance. This is the Springsharp report:
GB/CL/1925, Great Britain Light Cruiser laid down 1927 (Engine 1950)

Displacement:
 5,962 t light; 6,177 t standard; 6,650 t normal; 7,029 t full load

Dimensions: Length overall / water x beam x draught
 555.36 ft / 550.00 ft x 51.00 ft x 21.00 ft (normal load)
 169.27 m / 167.64 m x 15.54 m  x 6.40 m

Armament:
      8 - 6.00" / 152 mm guns (4x2 guns), 108.00lbs / 48.99kg shells, 1927 Model
   Dual purpose guns in turrets (on barbettes)
   on centreline ends, evenly spread, 2 raised mounts - superfiring
      8 - 2.24" / 57.0 mm guns (4x2 guns), 5.65lbs / 2.56kg shells, 1927 Model
   Anti-aircraft guns in deck mounts with hoists
   on side, all amidships, all raised mounts - superfiring
      16 - 1.57" / 40.0 mm guns (8x2 guns), 1.95lbs / 0.89kg shells, 1927 Model
   Anti-aircraft guns in deck mounts 
   on side, evenly spread, 6 raised mounts
 Weight of broadside 940 lbs / 427 kg
 Shells per gun, main battery: 150
 4 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 1.00" / 25 mm 1.00" / 25 mm  1.00" / 25 mm

   - Armour deck: 1.00" / 25 mm, Conning tower: 1.00" / 25 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 102,857 shp / 76,731 Kw = 36.00 kts
 Range 5,400nm at 15.00 kts
 Bunker at max displacement = 852 tons

Complement:
 367 - 478

Cost:
 £2.371 million / $9.482 million

Distribution of weights at normal displacement:
 Armament: 118 tons, 1.8 %
 Armour: 410 tons, 6.2 %
    - Belts: 0 tons, 0.0 %
    - Torpedo bulkhead: 0 tons, 0.0 %
    - Armament: 84 tons, 1.3 %
    - Armour Deck: 319 tons, 4.8 %
    - Conning Tower: 8 tons, 0.1 %
 Machinery: 2,461 tons, 37.0 %
 Hull, fittings & equipment: 2,974 tons, 44.7 %
 Fuel, ammunition & stores: 688 tons, 10.3 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   4,804 lbs / 2,179 Kg = 44.5 x 6.0 " / 152 mm shells or 0.9 torpedoes
 Stability (Unstable if below 1.00): 1.21
 Metacentric height 2.6 ft / 0.8 m
 Roll period: 13.3 seconds
 Steadiness - As gun platform (Average = 50 %): 56 %
   - Recoil effect (Restricted arc if above 1.00): 0.42
 Seaboat quality  (Average = 1.00): 1.11

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.395
 Length to Beam Ratio: 10.78 : 1
 'Natural speed' for length: 23.45 kts
 Power going to wave formation at top speed: 59 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 5.00 degrees
 Stern overhang: 3.00 ft / 0.91 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  27.00 ft / 8.23 m
    - Forecastle (20 %): 24.00 ft / 7.32 m
    - Mid (37 %):  24.00 ft / 7.32 m (16.00 ft / 4.88 m aft of break)
    - Quarterdeck (15 %): 16.00 ft / 4.88 m
    - Stern:  16.00 ft / 4.88 m
    - Average freeboard: 19.20 ft / 5.85 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 133.6 %
  - Above water (accommodation/working, high = better): 145.8 %
 Waterplane Area: 17,220 Square feet or 1,600 Square metres
 Displacement factor (Displacement / loading): 106 %
 Structure weight / hull surface area: 93 lbs/sq ft or 453 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.92
  - Longitudinal: 2.07
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent

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