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Monday, August 20, 2007

We should be able to do better: GB/DD/1921 small and somewhat fast

I wanted to see what could be done with a smaller British destroyer for 1921. I was able to achieve a 35 knot speed with 4-4.7in QF, 6-2pdr AA guns, and 6-21in TT. We should be able to achieve a higher speed than this. This is the Springsharp report:
GB/DD/1921 small and fast, Great Britain Destroyer laid down 1921 (Engine 1950)

Displacement:
 1,251 t light; 1,306 t standard; 1,429 t normal; 1,527 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
 (358.23 ft / 355.00 ft) x 33.00 ft x (11.00 / 11.46 ft)
 (109.19 m / 108.20 m) x 10.06 m  x (3.35 / 3.49 m)

Armament:
      4 - 4.70" / 119 mm 45.0 cal guns - 52.35lbs / 23.75kg shells, 150 per gun
   Quick firing guns in deck and hoist mounts, 1921 Model
   4 x Single mounts on centreline ends, evenly spread
  2 raised mounts - superfiring
      6 - 1.57" / 40.0 mm 45.0 cal guns - 1.97lbs / 0.89kg shells, 150 per gun
   Anti-air guns in deck mounts, 1921 Model
   6 x Single mounts on sides, forward deck aft
      Weight of broadside 221 lbs / 100 kg
      6 - 21.0" / 533 mm, 20.00 ft / 6.10 m torpedoes - 1.307 t each, 7.841 t total
 In 2 sets of deck mounted carriage/fixed tubes

Armour:
   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 1.00" / 25 mm 1.00" / 25 mm  1.00" / 25 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 2 shafts, 36,069 shp / 26,907 Kw = 35.00 kts
 Range 3,800nm at 14.00 kts
 Bunker at max displacement = 221 tons

Complement:
 116 - 151

Cost:
 £0.410 million / $1.642 million

Distribution of weights at normal displacement:
 Armament: 68 tons, 4.7 %
    - Guns: 60 tons, 4.2 %
    - Torpedoes: 8 tons, 0.5 %
 Armour: 27 tons, 1.9 %
    - Armament: 27 tons, 1.9 %
 Machinery: 691 tons, 48.4 %
 Hull, fittings & equipment: 465 tons, 32.6 %
 Fuel, ammunition & stores: 178 tons, 12.4 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   455 lbs / 206 Kg = 8.8 x 4.7 " / 119 mm shells or 0.3 torpedoes
 Stability (Unstable if below 1.00): 1.16
 Metacentric height 1.3 ft / 0.4 m
 Roll period: 12.4 seconds
 Steadiness - As gun platform (Average = 50 %): 53 %
   - Recoil effect (Restricted arc if above 1.00): 0.54
 Seaboat quality  (Average = 1.00): 1.06

Hull form characteristics:
 Hull has rise forward of midbreak,
   a normal bow and large transom stern
 Block coefficient (normal/deep): 0.388 / 0.398
 Length to Beam Ratio: 10.76 : 1
 'Natural speed' for length: 21.70 kts
 Power going to wave formation at top speed: 67 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 8.00 degrees
 Stern overhang: 0.00 ft / 0.00 m
 Freeboard (% = length of deck as a percentage of waterline length):
    Fore end,  Aft end
    - Forecastle: 16.00 %,  23.00 ft / 7.01 m,  21.00 ft / 6.40 m
    - Forward deck: 16.00 %,  21.00 ft / 6.40 m,  21.00 ft / 6.40 m
    - Aft deck: 53.00 %,  13.00 ft / 3.96 m,  13.00 ft / 3.96 m
    - Quarter deck: 15.00 %,  13.00 ft / 3.96 m,  13.00 ft / 3.96 m
    - Average freeboard:  15.69 ft / 4.78 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 169.6 %
  - Above water (accommodation/working, high = better): 176.0 %
 Waterplane Area: 7,425 Square feet or 690 Square metres
 Displacement factor (Displacement / loading): 73 %
 Structure weight / hull surface area: 33 lbs/sq ft or 159 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.45
  - Longitudinal: 2.25
  - Overall: 0.53
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent

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