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Monday, May 08, 2006

The Ger/CS/1915 design

I somewhat struggled with the Ger/CS/1915 design, as I had trouble getting adequate seakeeping. The specifications in the Red Book were for 12 ships (S-8 to S-19), with a displacement of 2,400 tons and a speed of 35 knots. The dimensions specified were 355ft x 37ft, without a draft being mentioned. The armament was 4-6in QF guns and 4-23.6in TT. The pencil drawing looks like a large, German destroyer. The freeboard and draft are too great, but they seemed to be necessary for Springsharp. I was able to use heavier machinery than I had expected, once I got the draft and freeboard where they needed to be. This is the Springsharp report:
Ger/CS/1915, Germany Scout Cruiser laid down 1915 (Engine 1927)

Displacement:
 2,095 t light; 2,172 t standard; 2,400 t normal; 2,583 t full load

Dimensions: Length overall / water x beam x draught
 356.82 ft / 355.00 ft x 37.00 ft x 15.00 ft (normal load)
 108.76 m / 108.20 m x 11.28 m  x 4.57 m

Armament:
      4 - 6.00" / 152 mm guns in single mounts, 108.00lbs / 48.99kg shells, 1915 Model
   Quick firing guns in deck mounts with hoists
   on centreline ends, evenly spread, 1 raised mount
 Weight of broadside 432 lbs / 196 kg
 Shells per gun, main battery: 120
 4 - 23.6" / 600.0001 mm above water torpedoes

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 2 shafts, 52,011 shp / 38,800 Kw = 35.00 kts
 Range 4,250nm at 15.00 kts
 Bunker at max displacement = 411 tons

Complement:
 170 - 222

Cost:
 £0.439 million / $1.756 million

Distribution of weights at normal displacement:
 Armament: 54 tons, 2.3 %
 Machinery: 1,308 tons, 54.5 %
 Hull, fittings & equipment: 733 tons, 30.5 %
 Fuel, ammunition & stores: 305 tons, 12.7 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   583 lbs / 265 Kg = 5.4 x 6.0 " / 152 mm shells or 0.3 torpedoes
 Stability (Unstable if below 1.00): 1.34
 Metacentric height 1.9 ft / 0.6 m
 Roll period: 11.3 seconds
 Steadiness - As gun platform (Average = 50 %): 59 %
   - Recoil effect (Restricted arc if above 1.00): 0.62
 Seaboat quality  (Average = 1.00): 1.17

Hull form characteristics:
 Hull has rise forward of midbreak
   and transom stern
 Block coefficient: 0.426
 Length to Beam Ratio: 9.59 : 1
 'Natural speed' for length: 21.78 kts
 Power going to wave formation at top speed: 71 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 4.00 degrees
 Stern overhang: 0.00 ft / 0.00 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  26.00 ft / 7.92 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: 19.12 ft / 5.83 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 192.7 %
  - Above water (accommodation/working, high = better): 127.2 %
 Waterplane Area: 8,541 Square feet or 793 Square metres
 Displacement factor (Displacement / loading): 65 %
 Structure weight / hull surface area: 37 lbs/sq ft or 181 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.44
  - Longitudinal: 3.73
  - Overall: 0.55
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent

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