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Saturday, July 30, 2005

Another shot at the Ger/DL/1914 design

I was able to make the Ger/DL/1914 design work fairly easily. I found, though, that very minor changes could make the design fail. What I have is a tightly balanced specification that achieved what I had desired, back in 1971. I wanted a destroyer of 1,250 tons displacement, with dimensions 320ft x 33ft, with a speed of 32 knots, and armed with 4-4in QF guns, 6-21in TT, and 30 mines. I had hoped that 25,000 SHP would provide sufficient power and that 250 tons of fuel would give an acceptable range. This is the Springsharp report:
Ger/DL/1914, Germany Destroyer Leader laid down 1914 (Engine 1927)

Displacement:
 1,072 t light; 1,110 t standard; 1,250 t normal; 1,362 t full load

Dimensions: Length overall / water x beam x draught
 322.73 ft / 320.00 ft x 33.00 ft x 10.50 ft (normal load)
 98.37 m / 97.54 m x 10.06 m  x 3.20 m

Armament:
      4 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1914 Model
   Quick firing guns in deck mounts with hoists
   on centreline, evenly spread
   Aft Main mounts separated by engine room
 Weight of broadside 128 lbs / 58 kg
 Shells per gun, main battery: 180
 6 - 21.0" / 533.4 mm above water torpedoes

Machinery:
 Oil fired boilers, steam turbines, 
 Direct drive, 2 shafts, 29,368 shp / 21,908 Kw = 32.00 kts
 Range 3,600nm at 15.00 kts
 Bunker at max displacement = 252 tons

Complement:
 104 - 136

Cost:
 £0.180 million / $0.722 million

Distribution of weights at normal displacement:
 Armament: 16 tons, 1.3 %
 Machinery: 649 tons, 51.9 %
 Hull, fittings & equipment: 378 tons, 30.2 %
 Fuel, ammunition & stores: 178 tons, 14.2 %
 Miscellaneous weights: 30 tons, 2.4 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   370 lbs / 168 Kg = 11.6 x 4.0 " / 102 mm shells or 0.3 torpedoes
 Stability (Unstable if below 1.00): 1.44
 Metacentric height 1.8 ft / 0.5 m
 Roll period: 10.4 seconds
 Steadiness - As gun platform (Average = 50 %): 57 %
   - Recoil effect (Restricted arc if above 1.00): 0.20
 Seaboat quality  (Average = 1.00): 1.13

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.395
 Length to Beam Ratio: 9.70 : 1
 'Natural speed' for length: 17.89 kts
 Power going to wave formation at top speed: 67 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 2.00 degrees
 Stern overhang: 2.00 ft / 0.61 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  21.00 ft / 6.40 m
    - Forecastle (20 %): 21.00 ft / 6.40 m
    - Mid (20 %):  21.00 ft / 6.40 m (13.00 ft / 3.96 m aft of break)
    - Quarterdeck (15 %): 13.00 ft / 3.96 m
    - Stern:  13.00 ft / 3.96 m
    - Average freeboard: 14.60 ft / 4.45 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 180.1 %
  - Above water (accommodation/working, high = better): 93.9 %
 Waterplane Area: 6,481 Square feet or 602 Square metres
 Displacement factor (Displacement / loading): 62 %
 Structure weight / hull surface area: 29 lbs/sq ft or 144 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.47
  - Longitudinal: 2.14
  - Overall: 0.55
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is adequate

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