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Saturday, December 17, 2005

My latest design for a British 8in-gun cruiser laid down in 1918

My opinion is that a satisfactory 8in cruiser design could not be restricted to 10,000 tons, standard. The design I propose hear is much larger, and is pretty well protected, as well as having an 8in gun armament and a 4in armour basis. The maximum speed is 32 knots with a 6,500nm range at 15 knots. I suspect that the ship should have lighter machinery (instead of 27.7 SHP/ton), and that this would cure the complaints about belt length. Contemporary Japanese ships had much lighter machinery. This is the Springsharp report:
GB/CA/1918, Great Britain Heavy Cruiser laid down 1918

Displacement:
 12,720 t light; 13,243 t standard; 14,500 t normal; 15,506 t full load

Dimensions: Length overall / water x beam x draught
 616.96 ft / 615.00 ft x 63.00 ft x 23.00 ft (normal load)
 188.05 m / 187.45 m x 19.20 m  x 7.01 m

Armament:
      8 - 8.00" / 203 mm guns (4x2 guns), 256.00lbs / 116.12kg shells, 1918 Model
   Breech loading guns in turrets (on barbettes)
   on centreline ends, evenly spread, 2 raised mounts - superfiring
      8 - 4.70" / 119 mm guns in single mounts, 51.91lbs / 23.55kg shells, 1918 Model
   Quick firing guns in deck mounts with hoists
   on side, all amidships
      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, evenly spread
      24 - 1.57" / 40.0 mm guns (6x4 guns), 2.00lbs / 0.91kg shells, 1918 Model
   Breech loading guns in deck mounts 
   on side, evenly spread
 Weight of broadside 2,639 lbs / 1,197 kg
 Shells per gun, main battery: 150
 12 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 4.00" / 102 mm 570.00 ft / 173.74 m 14.00 ft / 4.27 m
 Ends: Unarmoured
   Main Belt covers 143 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
  1.00" / 25 mm 570.00 ft / 173.74 m 22.00 ft / 6.71 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 4.00" / 102 mm 3.00" / 76 mm  4.00" / 102 mm
 2nd: 2.00" / 51 mm 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, 
 Direct drive, 4 shafts, 108,215 shp / 80,728 Kw = 32.00 kts
 Range 6,500nm at 15.00 kts
 Bunker at max displacement = 2,263 tons

Complement:
 659 - 858

Cost:
 £2.538 million / $10.150 million

Distribution of weights at normal displacement:
 Armament: 330 tons, 2.3 %
 Armour: 3,299 tons, 22.7 %
    - Belts: 1,263 tons, 8.7 %
    - Torpedo bulkhead: 464 tons, 3.2 %
    - Armament: 502 tons, 3.5 %
    - Armour Deck: 1,019 tons, 7.0 %
    - Conning Tower: 51 tons, 0.4 %
 Machinery: 3,904 tons, 26.9 %
 Hull, fittings & equipment: 5,188 tons, 35.8 %
 Fuel, ammunition & stores: 1,780 tons, 12.3 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   15,585 lbs / 7,069 Kg = 60.9 x 8.0 " / 203 mm shells or 2.0 torpedoes
 Stability (Unstable if below 1.00): 1.19
 Metacentric height 3.5 ft / 1.1 m
 Roll period: 14.2 seconds
 Steadiness - As gun platform (Average = 50 %): 52 %
   - Recoil effect (Restricted arc if above 1.00): 0.57
 Seaboat quality  (Average = 1.00): 1.04

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.569
 Length to Beam Ratio: 9.76 : 1
 'Natural speed' for length: 24.80 kts
 Power going to wave formation at top speed: 58 %
 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:  28.00 ft / 8.53 m
    - Forecastle (20 %): 24.00 ft / 7.32 m
    - Mid (67 %):  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: 21.68 ft / 6.61 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 154.2 %
  - Above water (accommodation/working, high = better): 136.4 %
 Waterplane Area: 27,539 Square feet or 2,558 Square metres
 Displacement factor (Displacement / loading): 105 %
 Structure weight / hull surface area: 115 lbs/sq ft or 561 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.97
  - Longitudinal: 1.36
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent

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