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Monday, November 21, 2005

A British 1905 armoured cruiser

I found out quickly that to achieve a reasonable 1905 British armoured cruiser, we needed to use lighter machinery than 12 SHP/ton of machinery. In the real world, the Invincibles had somewhat lighter machinery than that (although only 12.44 SHP/ton). The problem is partly that my armour weight is 4,672 tons while the Invincibles had just 3,460 tons of armour. This is the Springsharp report:
GB/CA/1905, Great Britain Armoured Cruiser laid down 1905 (Engine 1907)

Displacement:
 13,369 t light; 13,900 t standard; 16,300 t normal; 18,220 t full load

Dimensions: Length overall / water x beam x draught
 555.00 ft / 555.00 ft x 76.00 ft x 26.00 ft (normal load)
 169.16 m / 169.16 m x 23.16 m  x 7.92 m

Armament:
      8 - 9.20" / 234 mm guns (4x2 guns), 380.00lbs / 172.37kg shells, 1905 Model
   Breech loading guns in turrets (on barbettes)
   on centreline ends, evenly spread
      16 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1905 Model
   Quick firing guns in casemate mounts 
   on side, all amidships
   12 guns in hull casemates - Limited use in heavy seas
 Weight of broadside 3,552 lbs / 1,611 kg
 Shells per gun, main battery: 100
 4 - 18.0" / 457.2 mm submerged torpedo tubes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 6.00" / 152 mm 400.00 ft / 121.92 m 16.00 ft / 4.88 m
 Ends: 4.00" / 102 mm 155.00 ft / 47.24 m 16.00 ft / 4.88 m
   Main Belt covers 111 % of normal length

   - Torpedo Bulkhead:
  1.50" / 38 mm 400.00 ft / 121.92 m 25.00 ft / 7.62 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 7.00" / 178 mm 5.00" / 127 mm  7.00" / 178 mm
 2nd: 5.00" / 127 mm 5.00" / 127 mm  5.00" / 127 mm

   - Armour deck: 2.00" / 51 mm, Conning tower: 7.00" / 178 mm

Machinery:
 Coal fired boilers, steam turbines, 
 Direct drive, 4 shafts, 45,828 shp / 34,187 Kw = 25.00 kts
 Range 5,200nm at 15.00 kts
 Bunker at max displacement = 4,321 tons (100% coal)

Complement:
 720 - 937

Cost:
 £1.250 million / $4.999 million

Distribution of weights at normal displacement:
 Armament: 453 tons, 2.8 %
 Armour: 4,672 tons, 28.7 %
    - Belts: 1,981 tons, 12.2 %
    - Torpedo bulkhead: 555 tons, 3.4 %
    - Armament: 980 tons, 6.0 %
    - Armour Deck: 1,059 tons, 6.5 %
    - Conning Tower: 97 tons, 0.6 %
 Machinery: 2,864 tons, 17.6 %
 Hull, fittings & equipment: 5,379 tons, 33.0 %
 Fuel, ammunition & stores: 2,931 tons, 18.0 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   23,223 lbs / 10,534 Kg = 59.6 x 9.2 " / 234 mm shells or 3.6 torpedoes
 Stability (Unstable if below 1.00): 1.28
 Metacentric height 5.2 ft / 1.6 m
 Roll period: 14.0 seconds
 Steadiness - As gun platform (Average = 50 %): 74 %
   - Recoil effect (Restricted arc if above 1.00): 0.35
 Seaboat quality  (Average = 1.00): 1.47

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.520
 Length to Beam Ratio: 7.30 : 1
 'Natural speed' for length: 23.56 kts
 Power going to wave formation at top speed: 50 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): -2.00 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 %): 23.00 ft / 7.01 m
    - Mid (67 %):  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: 20.60 ft / 6.28 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 110.3 %
  - Above water (accommodation/working, high = better): 157.4 %
 Waterplane Area: 28,630 Square feet or 2,660 Square metres
 Displacement factor (Displacement / loading): 116 %
 Structure weight / hull surface area: 123 lbs/sq ft or 601 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.95
  - Longitudinal: 1.62
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is adequate
 Room for accommodation and workspaces is excellent
 Ship has slow, easy roll, a good, steady gun platform
 Good seaboat, rides out heavy weather easily

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