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Saturday, July 22, 2006

A rather odd design study for a GB/BB/1909 battleship

My friend Cliff was interested in exploring the space of possible battleship designs. The GB/BB/1909 design had rather thin turret and barbette armour (8in) and very thick deck armour (7in). The design study does not have a specification. I have an inboard profile and armour weights broken down. I also have a 26,000 ton Standard displacement and dimensions. The Cp is specified as 0.61. The drawing is annotated with armour thicknesses and the weights mention the deck thickness and the A/T bulkhead thickness (2in). I have adjusted the speed to be that which is achievable. The barrel lengths indicate that the guns are greater than 12in, so I moved up to 13.5in guns. This is the Springsharp report:
GB/BB/1908 Design Study, Great Britain Battleship laid down 1908 (Engine 1917)

Displacement:
    24,739 t light; 25,701 t standard; 27,700 t normal; 29,299 t full load

Dimensions: Length overall / water x beam x draught
    570.00 ft / 570.00 ft x 105.00 ft x 26.00 ft (normal load)
    173.74 m / 173.74 m x 32.00 m  x 7.92 m

Armament:
      8 - 12.00" / 305 mm guns (4x2 guns), 864.00lbs / 391.90kg shells, 1908 Model
      Breech loading guns in turrets (on barbettes)
      on centreline ends, evenly spread, 2 raised mounts - superfiring
      10 - 6.00" / 152 mm guns in single mounts, 108.00lbs / 48.99kg shells, 1908 Model
      Quick firing guns in deck mounts with hoists
      on side, all amidships
    Weight of broadside 7,992 lbs / 3,625 kg
    Shells per gun, main battery: 90

Armour:
   - Belts:        Width (max)    Length (avg)        Height (avg)
    Main:    10.0" / 254 mm    340.00 ft / 103.63 m    16.00 ft / 4.88 m
    Ends:    Unarmoured
      Main Belt covers 92 % of normal length

   - Torpedo Bulkhead:
        2.00" / 51 mm    340.00 ft / 103.63 m    26.00 ft / 7.92 m

   - Gun armour:    Face (max)    Other gunhouse (avg)    Barbette/hoist (max)
    Main:    10.0" / 254 mm    7.00" / 178 mm        10.0" / 254 mm
    2nd:    4.00" / 102 mm    4.00" / 102 mm        4.00" / 102 mm

   - Armour deck: 7.00" / 178 mm, Conning tower: 10.00" / 254 mm

Machinery:
    Oil fired boilers, steam turbines,
    Direct drive, 4 shafts, 69,224 shp / 51,641 Kw = 25.00 kts
    Range 6,500nm at 15.00 kts
    Bunker at max displacement = 3,598 tons

Complement:
    1,073 - 1,395

Cost:
    £2.060 million / $8.241 million

Distribution of weights at normal displacement:
    Armament: 999 tons, 3.6 %
    Armour: 11,214 tons, 40.5 %
       - Belts: 2,488 tons, 9.0 %
       - Torpedo bulkhead: 654 tons, 2.4 %
       - Armament: 2,083 tons, 7.5 %
       - Armour Deck: 5,792 tons, 20.9 %
       - Conning Tower: 197 tons, 0.7 %
    Machinery: 2,538 tons, 9.2 %
    Hull, fittings & equipment: 9,988 tons, 36.1 %
    Fuel, ammunition & stores: 2,961 tons, 10.7 %
    Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
    Survivability (Non-critical penetrating hits needed to sink ship):
      56,145 lbs / 25,467 Kg = 65.0 x 12.0 " / 305 mm shells or 10.3 torpedoes
    Stability (Unstable if below 1.00): 1.20
    Metacentric height 7.6 ft / 2.3 m
    Roll period: 16.0 seconds
    Steadiness    - As gun platform (Average = 50 %): 62 %
            - Recoil effect (Restricted arc if above 1.00): 0.36
    Seaboat quality  (Average = 1.00): 1.25

Hull form characteristics:
    Hull has rise forward of midbreak
    Block coefficient: 0.623
    Length to Beam Ratio: 5.43 : 1
    'Natural speed' for length: 23.87 kts
    Power going to wave formation at top speed: 56 %
    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:        29.00 ft / 8.84 m
       - Forecastle (20 %):    26.00 ft / 7.92 m
       - Mid (72 %):        26.00 ft / 7.92 m (18.00 ft / 5.49 m aft of break)
       - Quarterdeck (15 %):    18.00 ft / 5.49 m
       - Stern:        18.00 ft / 5.49 m
       - Average freeboard:    24.00 ft / 7.32 m

Ship space, strength and comments:
    Space    - Hull below water (magazines/engines, low = better): 71.0 %
        - Above water (accommodation/working, high = better): 193.7 %
    Waterplane Area: 44,722 Square feet or 4,155 Square metres
    Displacement factor (Displacement / loading): 114 %
    Structure weight / hull surface area: 166 lbs/sq ft or 812 Kg/sq metre
    Hull strength (Relative):
        - Cross-sectional: 0.93
        - Longitudinal: 1.97
        - Overall: 1.00
    Hull space for machinery, storage, compartmentation is excellent
    Room for accommodation and workspaces is excellent
    Good seaboat, rides out heavy weather easily

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