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Wednesday, August 02, 2006

The Ger/CS/1905 suffers from the usual Springsharp problems

Small, fast warships are in issue in Springsharp. I suspect that part of the issue is the empirical equation used to compute speed of power works best for large warships. I struggled to get the Ger/CS/1905 design to have adequate seakeeping, while accepting a lower speed than desired. The design wants a 36 knot speed, but I accepted a 34 knot speed to get an acceptable result. The ship has 5-4in QF guns and 2-18in TT. A complicating factor is the 2in armour to flash off hits form 12pdrs and similar hits. The designed dimensions are 370ft x 38ft x 13ft with a Standard displacement of 2,480 tons. This is the Springsharp report:
Ger/CS/1905, Germany Scout Cruiser laid down 1905 (Engine 1945)

Displacement:
    2,373 t light; 2,446 t standard; 2,800 t normal; 3,083 t full load

Dimensions: Length overall / water x beam x draught
    371.75 ft / 370.00 ft x 38.00 ft x 13.50 ft (normal load)
    113.31 m / 112.78 m x 11.58 m  x 4.11 m

Armament:
      3 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1905 Model
      Breech loading guns in deck mounts with hoists
      on centreline, evenly spread
      Aft Main mounts separated by engine room
      2 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1905 Model
      Quick firing guns in deck mounts with hoists
      on side, all amidships
    Weight of broadside 160 lbs / 73 kg
    Shells per gun, main battery: 180
    2 - 18.0" / 457.2 mm above water torpedoes

Armour:
   - Belts:        Width (max)    Length (avg)        Height (avg)
    Main:    2.00" / 51 mm    220.00 ft / 67.06 m    8.00 ft / 2.44 m
    Ends:    Unarmoured
    Upper:    2.00" / 51 mm    140.00 ft / 42.67 m    8.00 ft / 2.44 m
      Main Belt covers 91 % of normal length
      Main belt does not fully cover magazines and engineering spaces

   - Gun armour:    Face (max)    Other gunhouse (avg)    Barbette/hoist (max)
    Main:    1.00" / 25 mm          -                  -
    2nd:    1.00" / 25 mm          -                  -

   - Conning tower: 3.00" / 76 mm

Machinery:
    Oil fired boilers, steam turbines,
    Direct drive, 2 shafts, 63,385 shp / 47,285 Kw = 34.00 kts
    Range 4,200nm at 18.00 kts
    Bunker at max displacement = 636 tons

Complement:
    192 - 250

Cost:
    £0.300 million / $1.198 million

Distribution of weights at normal displacement:
    Armament: 20 tons, 0.7 %
    Armour: 276 tons, 9.9 %
       - Belts: 252 tons, 9.0 %
       - Torpedo bulkhead: 0 tons, 0.0 %
       - Armament: 11 tons, 0.4 %
       - Armour Deck: 0 tons, 0.0 %
       - Conning Tower: 13 tons, 0.5 %
    Machinery: 1,427 tons, 50.9 %
    Hull, fittings & equipment: 650 tons, 23.2 %
    Fuel, ammunition & stores: 427 tons, 15.3 %
    Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
    Survivability (Non-critical penetrating hits needed to sink ship):
      802 lbs / 364 Kg = 25.1 x 4.0 " / 102 mm shells or 0.4 torpedoes
    Stability (Unstable if below 1.00): 1.46
    Metacentric height 2.3 ft / 0.7 m
    Roll period: 10.6 seconds
    Steadiness    - As gun platform (Average = 50 %): 51 %
            - Recoil effect (Restricted arc if above 1.00): 0.15
    Seaboat quality  (Average = 1.00): 1.02

Hull form characteristics:
    Hull has rise forward of midbreak
    Block coefficient: 0.516
    Length to Beam Ratio: 9.74 : 1
    'Natural speed' for length: 19.24 kts
    Power going to wave formation at top speed: 71 %
    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:        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): 170.3 %
        - Above water (accommodation/working, high = better): 148.6 %
    Waterplane Area: 9,509 Square feet or 883 Square metres
    Displacement factor (Displacement / loading): 77 %
    Structure weight / hull surface area: 33 lbs/sq ft or 161 Kg/sq metre
    Hull strength (Relative):
        - Cross-sectional: 0.44
        - Longitudinal: 2.13
        - Overall: 0.52
    Hull space for machinery, storage, compartmentation is cramped
    Room for accommodation and workspaces is excellent

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