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Sunday, July 01, 2007

My fast German armoured cruiser design: Ger/CA/1917

I have this fast armoured cruiser design dating from the early 1970's that I have named the Ger/CA/1917, although my drawing is undesignated. This is a nominally 20,000 ton ship with 6-12in/50 and 8-6in/50 QF guns with a 33 knot speed. The armour basis is 6in with a 3in deck. The design requires 30 SHP/ton machinery. This is the Springsharp report:
Ger/CA/1917, Germany Armoured Cruiser laid down 1917 (Engine 1931)

Displacement:
 19,732 t light; 20,704 t standard; 21,916 t normal; 22,885 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
 (729.36 ft / 725.00 ft) x 80.00 ft x (23.00 / 23.82 ft)
 (222.31 m / 220.98 m) x 24.38 m  x (7.01 / 7.26 m)

Armament:
      6 - 12.00" / 305 mm 50.0 cal guns - 915.00lbs / 415.04kg shells, 150 per gun
   Breech loading guns in turret on barbette mounts, 1917 Model
   2 x Triple mounts on centreline, forward deck forward
  1 raised mount - superfiring
      8 - 6.00" / 152 mm 50.0 cal guns - 114.33lbs / 51.86kg shells, 150 per gun
   Quick firing guns in turret on barbette mounts, 1917 Model
   2 x Twin mounts on sides, forward deck aft
      Weight of broadside 6,405 lbs / 2,905 kg

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 6.00" / 152 mm 410.00 ft / 124.97 m 16.00 ft / 4.88 m
 Ends: Unarmoured
   Main Belt covers 87 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
  1.00" / 25 mm 410.00 ft / 124.97 m 23.00 ft / 7.01 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 6.00" / 152 mm 4.00" / 102 mm  6.00" / 152 mm
 2nd: 4.00" / 102 mm 3.00" / 76 mm  4.00" / 102 mm

   - Protected deck - multiple decks: 3.00" / 76 mm For and Aft decks

   - Conning towers: Forward 6.00" / 152 mm,  Aft 0.00" / 0 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 150,593 shp / 112,342 Kw = 33.00 kts
 Range 5,600nm at 15.00 kts
 Bunker at max displacement = 2,181 tons

Complement:
 899 - 1,170

Cost:
 £3.611 million / $14.446 million

Distribution of weights at normal displacement:
 Armament: 1,315 tons, 6.0 %
 Armour: 4,983 tons, 22.7 %
    - Belts: 1,680 tons, 7.7 %
    - Torpedo bulkhead: 349 tons, 1.6 %
    - Armament: 966 tons, 4.4 %
    - Armour Deck: 1,887 tons, 8.6 %
    - Conning Tower: 101 tons, 0.5 %
 Machinery: 4,503 tons, 20.5 %
 Hull, fittings & equipment: 8,930 tons, 40.7 %
 Fuel, ammunition & stores: 2,184 tons, 10.0 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   27,879 lbs / 12,646 Kg = 32.3 x 12.0 " / 305 mm shells or 3.3 torpedoes
 Stability (Unstable if below 1.00): 1.16
 Metacentric height 4.7 ft / 1.4 m
 Roll period: 15.5 seconds
 Steadiness - As gun platform (Average = 50 %): 53 %
   - Recoil effect (Restricted arc if above 1.00): 0.64
 Seaboat quality  (Average = 1.00): 1.05

Hull form characteristics:
 Hull has a flush deck,
   a normal bow and a cruiser stern
 Block coefficient (normal/deep): 0.575 / 0.580
 Length to Beam Ratio: 9.06 : 1
 'Natural speed' for length: 26.93 kts
 Power going to wave formation at top speed: 56 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 8.00 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 %,  31.00 ft / 9.45 m,  27.00 ft / 8.23 m
    - Forward deck: 30.00 %,  27.00 ft / 8.23 m,  23.00 ft / 7.01 m
    - Aft deck: 35.00 %,  23.00 ft / 7.01 m,  20.00 ft / 6.10 m
    - Quarter deck: 15.00 %,  20.00 ft / 6.10 m,  19.00 ft / 5.79 m
    - Average freeboard:  23.67 ft / 7.21 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 126.5 %
  - Above water (accommodation/working, high = better): 202.9 %
 Waterplane Area: 41,438 Square feet or 3,850 Square metres
 Displacement factor (Displacement / loading): 108 %
 Structure weight / hull surface area: 154 lbs/sq ft or 752 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.97
  - Longitudinal: 1.29
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent

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