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Monday, March 12, 2007

I severely underestimated the displacement needed for the GB/BB/1941 design

While the battlecruiser worked well, I found that I had severely underestimated the displacment needed for a battleship with 9-18in guns and a speed of 28 knots. Unlike the battlecruiser, I included a light AA armament of sextuple 40mm guns. The belt is 15in and the deck is 7in, so the ship is reasonably well-protected. This is the Springsharp report:
GB/BB/1941, Great Britain Battleship laid down 1941

Displacement:
 59,031 t light; 62,186 t standard; 65,325 t normal; 67,836 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
 (920.54 ft / 915.00 ft) x 120.00 ft x (33.00 / 34.02 ft)
 (280.58 m / 278.89 m) x 36.58 m  x (10.06 / 10.37 m)

Armament:
      9 - 18.00" / 457 mm 45.0 cal guns - 2,940.86lbs / 1,333.95kg shells, 120 per gun
   Breech loading guns in turret on barbette mounts , 1941 Model
   3 x Triple mounts on centreline ends, majority forward
  1 raised mount - superfiring
      20 - 4.50" / 114 mm 45.0 cal guns - 45.95lbs / 20.84kg shells, 150 per gun
   Dual purpose guns in turret on barbette mounts , 1941 Model
   6 x Twin mounts on sides, forward evenly spread
  6 raised mounts
   4 x Twin mounts on sides, aft evenly spread
  4 raised mounts
      42 - 1.57" / 40.0 mm 45.0 cal guns - 1.97lbs / 0.89kg shells, 150 per gun
   Anti-air guns in deck mounts , 1941 Model
   3 x 2 row sextuple mounts on centreline ends, majority aft
  2 raised mounts - superfiring
   4 x 2 row sextuple mounts on sides, evenly spread
  4 raised mounts
 Weight of broadside 27,469 lbs / 27,469 kg

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 15.0" / 381 mm 570.00 ft / 173.74 m 16.00 ft / 4.88 m
 Ends: Unarmoured
   Main Belt covers 96 % of normal length

   - Torpedo Bulkhead:
  4.00" / 102 mm 570.00 ft / 173.74 m 35.00 ft / 10.67 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 16.0" / 406 mm 12.0" / 305 mm  15.0" / 381 mm
 2nd: 3.00" / 76 mm 2.00" / 51 mm  3.00" / 76 mm
 3rd: 1.00" / 25 mm       -         -

   - Armour deck: 7.00" / 178 mm, Conning tower: 12.00" / 305 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 132,552 shp / 98,884 Kw = 28.00 kts
 Range 8,500nm at 15.00 kts
 Bunker at max displacement = 5,650 tons

Complement:
 2,042 - 2,655

Cost:
 £31.625 million / $126.499 million

Distribution of weights at normal displacement:
 Armament: 4,343 tons, 6.6 %
 Armour: 25,973 tons, 39.8 %
    - Belts: 5,932 tons, 9.1 %
    - Torpedo bulkhead: 2,953 tons, 4.5 %
    - Armament: 5,507 tons, 8.4 %
    - Armour Deck: 11,163 tons, 17.1 %
    - Conning Tower: 419 tons, 0.6 %
 Machinery: 3,503 tons, 5.4 %
 Hull, fittings & equipment: 26,508 tons, 40.6 %
 Fuel, ammunition & stores: 6,294 tons, 9.6 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   127,372 lbs / 57,775 Kg = 43.7 x 18.0 " / 457 mm shells or 26.1 torpedoes
 Stability (Unstable if below 1.00): 1.14
 Metacentric height 8.5 ft / 2.6 m
 Roll period: 17.3 seconds
 Steadiness - As gun platform (Average = 50 %): 74 %
   - Recoil effect (Restricted arc if above 1.00): 0.77
 Seaboat quality  (Average = 1.00): 1.48

Hull form characteristics:
 Hull has a flush deck,
   a normal bow and small transom stern
 Block coefficient (normal/deep): 0.631 / 0.636
 Length to Beam Ratio: 7.63 : 1
 'Natural speed' for length: 34.78 kts
 Power going to wave formation at top speed: 45 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 9.00 degrees
 Stern overhang: 0.00 ft / 0.00 m
 Freeboard (% = length of deck as a percentage of waterline length):
    Fore end,  Aft end
    - Forecastle: 22.00 %,  35.00 ft / 10.67 m,  29.00 ft / 8.84 m
    - Forward deck: 30.00 %,  29.00 ft / 8.84 m,  25.00 ft / 7.62 m
    - Aft deck: 33.00 %,  25.00 ft / 7.62 m,  25.00 ft / 7.62 m
    - Quarter deck: 15.00 %,  25.00 ft / 7.62 m,  25.00 ft / 7.62 m
    - Average freeboard:  27.01 ft / 8.23 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 64.8 %
  - Above water (accommodation/working, high = better): 208.7 %
 Waterplane Area: 86,200 Square feet or 8,008 Square metres
 Displacement factor (Displacement / loading): 114 %
 Structure weight / hull surface area: 232 lbs/sq ft or 1,131 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.97
  - Longitudinal: 1.22
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is excellent
 Room for accommodation and workspaces is excellent
 Ship has slow, easy roll, a good, steady gun platform
 Good seaboat, rides out heavy weather easily

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