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Thursday, August 10, 2006

I underestimated the size needed for the Ger/CA/1917 design

I had only specified a 14,000 ton Standard displacement for the Ger/CA/1917 design, but the specifications were for a ship with a 6in belt, 4in deck, and 8-9.4in guns. The stable Springsharp design ballooned to almost 17,000 tons standard, which should not have been a surprise. the design is for a fast, belted cruiser. This is the Springsharp report:
Ger/CA/1917, Germany Heavy Cruiser laid down 1917 (Engine 1931)

Displacement:
 16,365 t light; 16,987 t standard; 18,400 t normal; 19,530 t full load

Dimensions: Length overall / water x beam x draught
 666.57 ft / 665.00 ft x 69.00 ft x 23.00 ft (normal load)
 203.17 m / 202.69 m x 21.03 m  x 7.01 m

Armament:
      8 - 9.40" / 239 mm guns (4x2 guns), 415.29lbs / 188.37kg shells, 1917 Model
   Breech loading guns in turrets (on barbettes)
   on centreline ends, evenly spread, 2 raised mounts - superfiring
      10 - 6.00" / 152 mm guns in single mounts, 108.00lbs / 48.99kg shells, 1917 Model
   Breech loading guns in deck mounts with hoists
   on side, all amidships, 2 raised mounts - superfiring
 Weight of broadside 4,402 lbs / 1,997 kg
 Shells per gun, main battery: 100

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 6.00" / 152 mm 435.00 ft / 132.59 m 10.00 ft / 3.05 m
 Ends: Unarmoured
   Main Belt covers 101 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
  1.00" / 25 mm 435.00 ft / 132.59 m 21.00 ft / 6.40 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: 3.00" / 76 mm 3.00" / 76 mm  3.00" / 76 mm

   - Armour deck: 4.00" / 102 mm, Conning tower: 6.00" / 152 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 123,957 shp / 92,472 Kw = 32.00 kts
 Range 7,500nm at 15.00 kts
 Bunker at max displacement = 2,543 tons

Complement:
 789 - 1,026

Cost:
 £2.825 million / $11.302 million

Distribution of weights at normal displacement:
 Armament: 550 tons, 3.0 %
 Armour: 5,018 tons, 27.3 %
    - Belts: 1,094 tons, 5.9 %
    - Torpedo bulkhead: 338 tons, 1.8 %
    - Armament: 989 tons, 5.4 %
    - Armour Deck: 2,507 tons, 13.6 %
    - Conning Tower: 90 tons, 0.5 %
 Machinery: 3,707 tons, 20.1 %
 Hull, fittings & equipment: 7,090 tons, 38.5 %
 Fuel, ammunition & stores: 2,035 tons, 11.1 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   24,861 lbs / 11,277 Kg = 59.9 x 9.4 " / 239 mm shells or 3.0 torpedoes
 Stability (Unstable if below 1.00): 1.10
 Metacentric height 3.4 ft / 1.0 m
 Roll period: 15.7 seconds
 Steadiness - As gun platform (Average = 50 %): 55 %
   - Recoil effect (Restricted arc if above 1.00): 0.83
 Seaboat quality  (Average = 1.00): 1.10

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.610
 Length to Beam Ratio: 9.64 : 1
 'Natural speed' for length: 25.79 kts
 Power going to wave formation at top speed: 57 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 3.00 degrees
 Stern overhang: -2.00 ft / -0.61 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  30.00 ft / 9.14 m
    - Forecastle (20 %): 26.00 ft / 7.92 m
    - Mid (71 %):  26.00 ft / 7.92 m (18.00 ft / 5.49 m aft of break)
    - Quarterdeck (15 %): 18.00 ft / 5.49 m
    - Stern:  18.00 ft / 5.49 m
    - Average freeboard: 24.00 ft / 7.32 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 124.3 %
  - Above water (accommodation/working, high = better): 198.6 %
 Waterplane Area: 33,881 Square feet or 3,148 Square metres
 Displacement factor (Displacement / loading): 109 %
 Structure weight / hull surface area: 131 lbs/sq ft or 640 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.97
  - Longitudinal: 1.35
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent

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