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Monday, December 26, 2005

The GB/DD/1923 design

The move to twin mounts in the GB/DD/1923 design may be premature, but it seemed an obvious move to make. The armament is increased to 6-4.7in QF, 1-4in AA, and 8-2pdr AA guns with 10-21in TT. The forecastle is raised and the freeboard was increased further to aid seakeeping. The draft is perhaps to deep, but it is a feature of Springsharp that increasing the draft generally improved seakeeping and strenght. This is the Springsharp report:
GB/DD/1923, Great Britain Destroyer laid down 1923 (Engine 1933)

Displacement:
 1,553 t light; 1,630 t standard; 1,750 t normal; 1,846 t full load

Dimensions: Length overall / water x beam x draught
 346.68 ft / 345.00 ft x 33.00 ft x 14.00 ft (normal load)
 105.67 m / 105.16 m x 10.06 m  x 4.27 m

Armament:
      6 - 4.70" / 119 mm guns (3x2 guns), 51.91lbs / 23.55kg shells, 1923 Model
   Quick firing guns in deck mounts with hoists
   on centreline ends, majority forward, 1 raised mount - superfiring
      1 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1923 Model
   Anti-aircraft gun in a deck mount with hoist
   on side amidships
      8 - 1.57" / 40.0 mm guns (2x4 guns), 1.95lbs / 0.89kg shells, 1923 Model
   Anti-aircraft guns in deck mounts 
   on side, evenly spread, all raised mounts
 Weight of broadside 359 lbs / 163 kg
 Shells per gun, main battery: 200
 10 - 21.0" / 533.4 mm above water torpedoes

Machinery:
 Oil fired boilers, steam turbines, 
 Direct drive, 2 shafts, 46,926 shp / 35,007 Kw = 36.00 kts
 Range 4,500nm at 12.00 kts
 Bunker at max displacement = 215 tons

Complement:
 134 - 175

Cost:
 £0.652 million / $2.609 million

Distribution of weights at normal displacement:
 Armament: 45 tons, 2.6 %
 Machinery: 944 tons, 54.0 %
 Hull, fittings & equipment: 564 tons, 32.3 %
 Fuel, ammunition & stores: 197 tons, 11.2 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   377 lbs / 171 Kg = 7.3 x 4.7 " / 119 mm shells or 0.2 torpedoes
 Stability (Unstable if below 1.00): 1.24
 Metacentric height 1.4 ft / 0.4 m
 Roll period: 11.7 seconds
 Steadiness - As gun platform (Average = 50 %): 55 %
   - Recoil effect (Restricted arc if above 1.00): 0.75
 Seaboat quality  (Average = 1.00): 1.11

Hull form characteristics:
 Hull has raised forecastle, rise forward of midbreak
   and transom stern
 Block coefficient: 0.384
 Length to Beam Ratio: 10.45 : 1
 'Natural speed' for length: 21.46 kts
 Power going to wave formation at top speed: 69 %
 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:  24.00 ft / 7.32 m
    - Forecastle (20 %): 22.00 ft / 6.71 m (21.00 ft / 6.40 m aft of break)
    - Mid (36 %):  22.00 ft / 6.71 m (14.00 ft / 4.27 m aft of break)
    - Quarterdeck (15 %): 14.00 ft / 4.27 m
    - Stern:  14.00 ft / 4.27 m
    - Average freeboard: 16.96 ft / 5.17 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 194.3 %
  - Above water (accommodation/working, high = better): 64.2 %
 Waterplane Area: 7,215 Square feet or 670 Square metres
 Displacement factor (Displacement / loading): 57 %
 Structure weight / hull surface area: 33 lbs/sq ft or 163 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.41
  - Longitudinal: 3.33
  - Overall: 0.51
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is cramped

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