An extremely shallow draft fast battleship: GB/BB/1915 Design A

John Roberts, in his Battlecruisers book, has the specifications for the design studies for a fast battleship to be built in 1915 or 1916. The ship would have been the length of the Renown, with a greater beam, but an extremely shallow draft. That was to reduce the risk of torpedo attack. The armament was 8-15in and 12-5in guns. The armour basis was 10in. I gave the ship a 3in deck armour, as the deck armour was not specified. 3in may have been greater than the design was actually given. When I implemented Design A in Springsharp, I had to increase the displacement to achieve an adequate strength. This is the Springsharp report:

GB/BB/1915 Design A, Great Britain Fast Battleship laid down 1915

Displacement:
 31,754 t light; 33,182 t standard; 35,400 t normal; 37,175 t full load

Dimensions: Length overall / water x beam x draught
 796.17 ft / 794.00 ft x 104.00 ft x 23.50 ft (normal load)
 242.67 m / 242.01 m x 31.70 m  x 7.16 m

Armament:
      8 - 15.00" / 381 mm guns (4x2 guns), 1,687.50lbs / 765.44kg shells, 1915 Model
   Breech loading guns in turrets (on barbettes)
   on centreline ends, evenly spread, 2 raised mounts - superfiring
      12 - 5.00" / 127 mm guns in single mounts, 62.50lbs / 28.35kg shells, 1915 Model
   Breech loading guns in deck mounts with hoists
   on side, all amidships
 Weight of broadside 14,250 lbs / 6,464 kg
 Shells per gun, main battery: 90
 4 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 10.0" / 254 mm 535.00 ft / 163.07 m 8.00 ft / 2.44 m
 Ends: 5.00" / 127 mm 240.00 ft / 73.15 m 8.00 ft / 2.44 m
   19.00 ft / 5.79 m Unarmoured ends
 Upper: 7.00" / 178 mm 535.00 ft / 163.07 m 8.00 ft / 2.44 m
   Main Belt covers 104 % of normal length

   - Torpedo Bulkhead:
  2.00" / 51 mm 535.00 ft / 163.07 m 23.50 ft / 7.16 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 11.0" / 279 mm 9.00" / 229 mm  10.0" / 254 mm
 2nd: 5.00" / 127 mm 2.00" / 51 mm  5.00" / 127 mm

   - Armour deck: 3.00" / 76 mm, Conning tower: 11.00" / 279 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 88,293 shp / 65,866 Kw = 26.50 kts
 Range 5,600nm at 15.00 kts
 Bunker at max displacement = 3,993 tons

Complement:
 1,289 - 1,677

Cost:
 £4.474 million / $17.896 million

Distribution of weights at normal displacement:
 Armament: 1,781 tons, 5.0 %
 Armour: 10,896 tons, 30.8 %
    - Belts: 3,461 tons, 9.8 %
    - Torpedo bulkhead: 930 tons, 2.6 %
    - Armament: 2,775 tons, 7.8 %
    - Armour Deck: 3,474 tons, 9.8 %
    - Conning Tower: 256 tons, 0.7 %
 Machinery: 3,344 tons, 9.4 %
 Hull, fittings & equipment: 15,733 tons, 44.4 %
 Fuel, ammunition & stores: 3,646 tons, 10.3 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   61,481 lbs / 27,887 Kg = 36.4 x 15.0 " / 381 mm shells or 9.6 torpedoes
 Stability (Unstable if below 1.00): 1.17
 Metacentric height 7.2 ft / 2.2 m
 Roll period: 16.3 seconds
 Steadiness - As gun platform (Average = 50 %): 65 %
   - Recoil effect (Restricted arc if above 1.00): 0.62
 Seaboat quality  (Average = 1.00): 1.29

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.638
 Length to Beam Ratio: 7.63 : 1
 'Natural speed' for length: 28.18 kts
 Power going to wave formation at top speed: 45 %
 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:  31.00 ft / 9.45 m
    - Forecastle (20 %): 26.00 ft / 7.92 m
    - Mid (67 %):  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: 23.76 ft / 7.24 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 85.1 %
  - Above water (accommodation/working, high = better): 212.6 %
 Waterplane Area: 62,592 Square feet or 5,815 Square metres
 Displacement factor (Displacement / loading): 111 %
 Structure weight / hull surface area: 191 lbs/sq ft or 931 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 1.00
  - Longitudinal: 1.02
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is adequate
 Room for accommodation and workspaces is excellent
 Good seaboat, rides out heavy weather easily