Fast battlecruisers, yet again

There is this page in the "Red Book" with specifications for a battlecruiser that could make (I hesistate to write it) 50 knots. It was to be 850ft x 105ft and 37,500 tons normal displacement. The armament was 6-18in/45 and 12-5in QF guns. It was to need 457,000 SHP to reach 50 knots, which is not possible. The hope was to be able to generate 548,000 SHP by pressing the machinery. I did a preliminary Springsharp design based on that, with a 40 knot speed. I had weights to work with from the specification:

• Hull=12,900 tons
• Aux. Mach.=1,500 tons
• Machinery=11,420 tons
• Armament=2,758 tons
• Protection=4,502 tons
• Misc.=2,880 tons

This is the Springsharp design that tried to come as close to that as possible. The hull weight was greater, in order to achieve a reasonable strength:

GB/CB/1916 Design Study, Great Britain Battlecruiser laid down 1916 (Engine 1950)

Displacement:
 34,837 t light; 36,405 t standard; 37,500 t normal; 38,376 t full load

Dimensions: Length overall / water x beam x draught
 851.89 ft / 850.00 ft x 105.00 ft x 37.00 ft (normal load)
 259.66 m / 259.08 m x 32.00 m  x 11.28 m

Armament:
      6 - 18.00" / 457 mm guns (2x3 guns), 2,916.00lbs / 1,322.68kg shells, 1916 Model
   Breech loading guns in turrets (on barbettes)
   on centreline ends, evenly spread
      12 - 5.00" / 127 mm guns in single mounts, 62.50lbs / 28.35kg shells, 1916 Model
   Quick firing guns in deck mounts with hoists
   on side, all amidships
 Weight of broadside 18,246 lbs / 8,276 kg
 Shells per gun, main battery: 80

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 4.00" / 102 mm 590.00 ft / 179.83 m 9.00 ft / 2.74 m
 Ends: Unarmoured
   Main Belt covers 107 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 6.00" / 152 mm 4.00" / 102 mm  5.00" / 127 mm
 2nd: 2.00" / 51 mm       -         -

   - Armour deck: 1.00" / 25 mm, Conning tower: 6.00" / 152 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 6 shafts, 397,020 shp / 296,177 Kw = 40.00 kts
 Range 4,000nm at 15.00 kts
 Bunker at max displacement = 1,971 tons

Complement:
 1,346 - 1,751

Cost:
 £7.306 million / $29.225 million

Distribution of weights at normal displacement:
 Armament: 2,281 tons, 6.1 %
 Armour: 3,181 tons, 8.5 %
    - Belts: 883 tons, 2.4 %
    - Torpedo bulkhead: 0 tons, 0.0 %
    - Armament: 1,139 tons, 3.0 %
    - Armour Deck: 1,015 tons, 2.7 %
    - Conning Tower: 145 tons, 0.4 %
 Machinery: 9,498 tons, 25.3 %
 Hull, fittings & equipment: 19,878 tons, 53.0 %
 Fuel, ammunition & stores: 2,663 tons, 7.1 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   28,420 lbs / 12,891 Kg = 9.7 x 18.0 " / 457 mm shells or 2.4 torpedoes
 Stability (Unstable if below 1.00): 1.14
 Metacentric height 6.9 ft / 2.1 m
 Roll period: 16.8 seconds
 Steadiness - As gun platform (Average = 50 %): 52 %
   - Recoil effect (Restricted arc if above 1.00): 0.81
 Seaboat quality  (Average = 1.00): 1.05

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.397
 Length to Beam Ratio: 8.10 : 1
 'Natural speed' for length: 29.15 kts
 Power going to wave formation at top speed: 58 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 3.00 degrees
 Stern overhang: -2.00 ft / -0.61 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  36.00 ft / 10.97 m
    - Forecastle (20 %): 32.00 ft / 9.75 m
    - Mid (75 %):  32.00 ft / 9.75 m (24.00 ft / 7.32 m aft of break)
    - Quarterdeck (15 %): 24.00 ft / 7.32 m
    - Stern:  24.00 ft / 7.32 m
    - Average freeboard: 30.32 ft / 9.24 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 126.7 %
  - Above water (accommodation/working, high = better): 238.9 %
 Waterplane Area: 54,861 Square feet or 5,097 Square metres
 Displacement factor (Displacement / loading): 93 %
 Structure weight / hull surface area: 228 lbs/sq ft or 1,113 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.91
  - Longitudinal: 2.30
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent