The J/DD/1921 design

The J/DD/1921 design really indicates a problem with how Springsharp computes the speed and power for small ships. The real Japanese destroyers from 1918 to 1921 achieved much higher speeds with less power for similar dimensions and displacement. The J/DD/1921 is having to compensate for that by going to lighter weight machinery, because a power that is too high is required to reach only 35 knots. The J/DD/1921 design has a greater range than its predecessor, 4,500nm at 15 knots. Otherwise, the armament and overall design is the same. This is the Springsharp report:

J/DD/1921, Japan Destroyer laid down 1921 (Engine 1937)

Displacement:
 1,429 t light; 1,462 t standard; 1,650 t normal; 1,800 t full load

Dimensions: Length overall / water x beam x draught
 337.26 ft / 335.00 ft x 31.00 ft x 13.00 ft (normal load)
 102.80 m / 102.11 m x 9.45 m  x 3.96 m

Armament:
      4 - 4.70" / 119 mm guns in single mounts, 51.91lbs / 23.55kg shells, 1921 Model
   Quick firing guns in deck mounts with hoists
   on centreline, evenly spread
   Aft Main mounts separated by engine room
      1 - 3.00" / 76.2 mm guns in single mounts, 13.50lbs / 6.12kg shells, 1921 Model
   Anti-aircraft gun in a deck mount with hoist
   on side amidships, 1 raised gun
      8 - 2.24" / 57.0 mm guns (4x2 guns), 5.65lbs / 2.56kg shells, 1921 Model
   Anti-aircraft guns in deck mounts 
   on side, all amidships, 2 raised mounts - superfiring
 Weight of broadside 266 lbs / 121 kg
 Shells per gun, main battery: 0
 6 - 21.0" / 533.4 mm above water torpedoes

Machinery:
 Oil fired boilers, steam turbines, 
 Direct drive, 2 shafts, 50,513 shp / 37,683 Kw = 35.00 kts
 Range 4,500nm at 15.00 kts
 Bunker at max displacement = 338 tons

Complement:
 129 - 168

Cost:
 £0.528 million / $2.112 million

Distribution of weights at normal displacement:
 Armament: 33 tons, 2.0 %
 Machinery: 924 tons, 56.0 %
 Hull, fittings & equipment: 472 tons, 28.6 %
 Fuel, ammunition & stores: 221 tons, 13.4 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   348 lbs / 158 Kg = 6.7 x 4.7 " / 119 mm shells or 0.2 torpedoes
 Stability (Unstable if below 1.00): 1.39
 Metacentric height 1.5 ft / 0.5 m
 Roll period: 10.5 seconds
 Steadiness - As gun platform (Average = 50 %): 55 %
   - Recoil effect (Restricted arc if above 1.00): 0.50
 Seaboat quality  (Average = 1.00): 1.10

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.428
 Length to Beam Ratio: 10.81 : 1
 'Natural speed' for length: 18.30 kts
 Power going to wave formation at top speed: 70 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 3.00 degrees
 Stern overhang: 1.00 ft / 0.30 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  24.00 ft / 7.32 m
    - Forecastle (20 %): 21.00 ft / 6.40 m
    - Mid (37 %):  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: 16.20 ft / 4.94 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 194.6 %
  - Above water (accommodation/working, high = better): 87.3 %
 Waterplane Area: 6,511 Square feet or 605 Square metres
 Displacement factor (Displacement / loading): 54 %
 Structure weight / hull surface area: 30 lbs/sq ft or 146 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.41
  - Longitudinal: 2.97
  - Overall: 0.50
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is cramped