The Ger/CL/1911 design study

This was a design study for a more conventional German light cruiser, although pushing the limits. The design is only feasible with very lightweight machinery (36 SHP/ton). I believe that the plan for the British Arethusa class was for 40,000 SHP from an 800 ton plant, which is 50 SHP/ton. The original specification was for a 4,240 ton Standard vessel with a speed of 32 knots. The armament was 4-6in QF guns and 8-21in TT. The belt was 2in, of limited coverage, with a 1in deck. This is the Springsharp report:

Ger/CL/1911 Design Study, Germany Light Cruiser laid down 1911 (Engine 1937)

Displacement:
 4,159 t light; 4,288 t standard; 4,640 t normal; 4,922 t full load

Dimensions: Length overall / water x beam x draught
 451.82 ft / 450.00 ft x 41.00 ft x 16.00 ft (normal load)
 137.71 m / 137.16 m x 12.50 m  x 4.88 m

Armament:
      4 - 6.00" / 152 mm guns in single mounts, 108.00lbs / 48.99kg shells, 1911 Model
   Quick firing guns in deck mounts with hoists
   on centreline ends, evenly spread
 Weight of broadside 432 lbs / 196 kg
 Shells per gun, main battery: 150
 8 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 2.00" / 51 mm 300.00 ft / 91.44 m 9.00 ft / 2.74 m
 Ends: Unarmoured
 Upper: 2.00" / 51 mm 120.00 ft / 36.58 m 8.00 ft / 2.44 m
   Main Belt covers 103 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 4.00" / 102 mm 3.00" / 76 mm  3.00" / 76 mm

   - Armour deck: 1.00" / 25 mm, Conning tower: 1.00" / 25 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Direct drive, 2 shafts, 59,993 shp / 44,754 Kw = 32.00 kts
 Range 4,500nm at 15.00 kts
 Bunker at max displacement = 633 tons

Complement:
 280 - 365

Cost:
 £0.424 million / $1.695 million

Distribution of weights at normal displacement:
 Armament: 54 tons, 1.2 %
 Armour: 630 tons, 13.6 %
    - Belts: 317 tons, 6.8 %
    - Torpedo bulkhead: 0 tons, 0.0 %
    - Armament: 69 tons, 1.5 %
    - Armour Deck: 238 tons, 5.1 %
    - Conning Tower: 6 tons, 0.1 %
 Machinery: 1,663 tons, 35.8 %
 Hull, fittings & equipment: 1,813 tons, 39.1 %
 Fuel, ammunition & stores: 481 tons, 10.4 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   3,815 lbs / 1,730 Kg = 35.3 x 6.0 " / 152 mm shells or 0.7 torpedoes
 Stability (Unstable if below 1.00): 1.17
 Metacentric height 1.8 ft / 0.5 m
 Roll period: 13.0 seconds
 Steadiness - As gun platform (Average = 50 %): 62 %
   - Recoil effect (Restricted arc if above 1.00): 0.38
 Seaboat quality  (Average = 1.00): 1.23

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.550
 Length to Beam Ratio: 10.98 : 1
 'Natural speed' for length: 21.21 kts
 Power going to wave formation at top speed: 63 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 4.00 degrees
 Stern overhang: -2.00 ft / -0.61 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  26.00 ft / 7.92 m
    - Forecastle (20 %): 24.00 ft / 7.32 m
    - Mid (32 %):  24.00 ft / 7.32 m (16.00 ft / 4.88 m aft of break)
    - Quarterdeck (15 %): 16.00 ft / 4.88 m
    - Stern:  16.00 ft / 4.88 m
    - Average freeboard: 18.72 ft / 5.71 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 125.2 %
  - Above water (accommodation/working, high = better): 107.4 %
 Waterplane Area: 12,878 Square feet or 1,196 Square metres
 Displacement factor (Displacement / loading): 106 %
 Structure weight / hull surface area: 70 lbs/sq ft or 340 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.90
  - Longitudinal: 2.67
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is adequate
 Good seaboat, rides out heavy weather easily