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Tuesday, November 21, 2006

My first attempt at an It/DL/1927 design

I struggled to allow this design to reach even 36 knots, not the 37 or 38 knots that I would have liked. I would be open to suggestions about how to achieve that, while still having acceptable strength and seakeeping. This is intended to be a super-destroyer with 5-5.1in QF guns and the fastest speed possible. With the current version of Springsharp, much of the problem with small, fast ships is that Springsharp overestimates how much power is required to reach a given speed. This is the Springsharp report:
It/DL/1927, Italy Destroyer Leader laid down 1927 (Engine 1950)

Displacement:
 2,164 t light; 2,250 t standard; 2,450 t normal; 2,610 t full load

Dimensions: Length overall / water x beam x draught
 385.75 ft / 384.00 ft x 36.00 ft x 13.00 ft (normal load)
 117.58 m / 117.04 m x 10.97 m  x 3.96 m

Armament:
      5 - 5.10" / 130 mm guns in single mounts, 66.33lbs / 30.08kg shells, 1927 Model
   Quick firing guns in deck mounts with hoists
   on centreline, evenly spread
      2 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1927 Model
   Anti-aircraft guns in deck mounts with hoists
   on side, all amidships, all raised mounts - superfiring
      12 - 1.46" / 37.0 mm guns (6x2 guns), 1.55lbs / 0.70kg shells, 1927 Model
   Breech loading guns in deck mounts 
   on side, evenly spread, all raised mounts
 Weight of broadside 414 lbs / 188 kg
 Shells per gun, main battery: 150
 8 - 21.0" / 533.4 mm above water torpedoes

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 2 shafts, 69,926 shp / 52,165 Kw = 36.00 kts
 Range 4,200nm at 15.00 kts
 Bunker at max displacement = 359 tons

Complement:
 173 - 226

Cost:
 £1.114 million / $4.454 million

Distribution of weights at normal displacement:
 Armament: 52 tons, 2.1 %
 Machinery: 1,336 tons, 54.5 %
 Hull, fittings & equipment: 727 tons, 29.7 %
 Fuel, ammunition & stores: 286 tons, 11.7 %
 Miscellaneous weights: 50 tons, 2.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   549 lbs / 249 Kg = 8.3 x 5.1 " / 130 mm shells or 0.3 torpedoes
 Stability (Unstable if below 1.00): 1.30
 Metacentric height 1.7 ft / 0.5 m
 Roll period: 11.5 seconds
 Steadiness - As gun platform (Average = 50 %): 57 %
   - Recoil effect (Restricted arc if above 1.00): 0.59
 Seaboat quality  (Average = 1.00): 1.03

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.477
 Length to Beam Ratio: 10.67 : 1
 'Natural speed' for length: 19.60 kts
 Power going to wave formation at top speed: 70 %
 Trim (Max stability = 0, Max steadiness = 100): 55
 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:  25.00 ft / 7.62 m
    - Forecastle (20 %): 23.00 ft / 7.01 m
    - Mid (36 %):  23.00 ft / 7.01 m (15.00 ft / 4.57 m aft of break)
    - Quarterdeck (15 %): 15.00 ft / 4.57 m
    - Stern:  15.00 ft / 4.57 m
    - Average freeboard: 18.04 ft / 5.50 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 194.3 %
  - Above water (accommodation/working, high = better): 101.4 %
 Waterplane Area: 9,024 Square feet or 838 Square metres
 Displacement factor (Displacement / loading): 64 %
 Structure weight / hull surface area: 36 lbs/sq ft or 177 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.45
  - Longitudinal: 2.53
  - Overall: 0.53
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is adequate

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