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Tuesday, April 11, 2006

The F/CL/1923 light cruiser design

The F/CL/1923 light cruiser design can now make 35 knots. The design was lengthened and the bow was raised and the rake was increased. The result was better seakeeping, while achieving a higher speed. The only other improvement is that the torpedo armament is now 8-21.6in TT. To achieve that, a pretty large displacement is required for a rather modest armament. I believe that not very light weight machinery is the reason. This is the Springsharp report:
F/CL/1923, France Light Cruiser laid down 1923 (Engine 1927)

Displacement:
 11,133 t light; 11,453 t standard; 12,300 t normal; 12,978 t full load

Dimensions: Length overall / water x beam x draught
 650.62 ft / 645.00 ft x 59.00 ft x 19.00 ft (normal load)
 198.31 m / 196.60 m x 17.98 m  x 5.79 m

Armament:
      8 - 6.10" / 155 mm guns (4x2 guns), 113.62lbs / 51.54kg shells, 1923 Model
   Quick firing guns in deck mounts with hoists
   on centreline ends, evenly spread, 2 raised mounts - superfiring
      4 - 3.54" / 90.0 mm guns in single mounts, 22.24lbs / 10.09kg shells, 1923 Model
   Anti-aircraft guns in deck mounts with hoists
   on side, evenly spread, all raised mounts
      16 - 1.85" / 47.0 mm guns (8x2 guns), 3.17lbs / 1.44kg shells, 1923 Model
   Anti-aircraft guns in deck mounts with hoists
   on side, all amidships, all raised mounts - superfiring
 Weight of broadside 1,049 lbs / 476 kg
 Shells per gun, main battery: 120
 8 - 21.7" / 549.9999 mm above water torpedoes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 3.00" / 76 mm 420.00 ft / 128.02 m 12.00 ft / 3.66 m
 Ends: 2.00" / 51 mm 132.00 ft / 40.23 m 8.00 ft / 2.44 m
   93.00 ft / 28.35 m Unarmoured ends
   Main Belt covers 100 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
  1.00" / 25 mm 420.00 ft / 128.02 m 18.00 ft / 5.49 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 3.00" / 76 mm 2.00" / 51 mm  3.00" / 76 mm

   - Armour deck: 2.00" / 51 mm, Conning tower: 3.00" / 76 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 2 shafts, 137,885 shp / 102,863 Kw = 35.00 kts
 Range 5,400nm at 15.00 kts
 Bunker at max displacement = 1,525 tons

Complement:
 583 - 759

Cost:
 £3.227 million / $12.906 million

Distribution of weights at normal displacement:
 Armament: 131 tons, 1.1 %
 Armour: 2,131 tons, 17.3 %
    - Belts: 704 tons, 5.7 %
    - Torpedo bulkhead: 280 tons, 2.3 %
    - Armament: 87 tons, 0.7 %
    - Armour Deck: 1,025 tons, 8.3 %
    - Conning Tower: 34 tons, 0.3 %
 Machinery: 4,352 tons, 35.4 %
 Hull, fittings & equipment: 4,519 tons, 36.7 %
 Fuel, ammunition & stores: 1,167 tons, 9.5 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   11,258 lbs / 5,107 Kg = 99.1 x 6.1 " / 155 mm shells or 1.5 torpedoes
 Stability (Unstable if below 1.00): 1.33
 Metacentric height 3.7 ft / 1.1 m
 Roll period: 12.8 seconds
 Steadiness - As gun platform (Average = 50 %): 53 %
   - Recoil effect (Restricted arc if above 1.00): 0.27
 Seaboat quality  (Average = 1.00): 1.06

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.595
 Length to Beam Ratio: 10.93 : 1
 'Natural speed' for length: 25.40 kts
 Power going to wave formation at top speed: 60 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 5.00 degrees
 Stern overhang: 3.00 ft / 0.91 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  30.00 ft / 9.14 m
    - Forecastle (20 %): 24.00 ft / 7.32 m
    - Mid (67 %):  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: 21.84 ft / 6.66 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 186.0 %
  - Above water (accommodation/working, high = better): 166.9 %
 Waterplane Area: 27,713 Square feet or 2,575 Square metres
 Displacement factor (Displacement / loading): 103 %
 Structure weight / hull surface area: 99 lbs/sq ft or 482 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.98
  - Longitudinal: 1.27
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent

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