A German battleship design study with 15-11in guns

I had thought that a natural alternative for a German battleship would have 15-11in guns in triple turrets. I drew a pencil sketch and did some calculations. These were the origanally planned weights:

• Auxiliary machinery: 1,100 tons
• Hull: 6,960 tons
• Machinery: 833 tons
• Protection: 15,211 tons
• Armament: 1,656 tons
• Miscellaneous: 2,240 tons

The ship was to be 580ft x 100ft x 33.3ft with a normal displacement of 28,000 tons. The speed would be only 20 knots. I massaged the Springsharp design until I achieved a balanced design. The biggest deviation was a 23-knot speed. The Springsharp report had less protection, as well:

Ger/BB/1910 Design Study, Germany Battleship laid down 1910

Displacement:
 24,415 t light; 25,559 t standard; 28,000 t normal; 29,953 t full load

Dimensions: Length overall / water x beam x draught
 580.00 ft / 580.00 ft x 100.00 ft x 33.30 ft (normal load)
 176.78 m / 176.78 m x 30.48 m  x 10.15 m

Armament:
      12 - 11.00" / 279 mm guns (4x3 guns), 665.50lbs / 301.87kg shells, 1910 Model
   Breech loading guns in turrets (on barbettes)
   on centreline ends, evenly spread, 2 raised mounts - superfiring
      3 - 11.00" / 279 mm guns (1x3 guns), 665.50lbs / 301.87kg shells, 1910 Model
   Breech loading guns in a turret (on a barbette)
   on centreline amidships
      12 - 6.00" / 152 mm guns in single mounts, 108.00lbs / 48.99kg shells, 1910 Model
   Quick firing guns in casemate mounts 
   on side, evenly spread
   8 guns in hull casemates - Limited use in heavy seas
 Weight of broadside 11,279 lbs / 5,116 kg
 Shells per gun, main battery: 90

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 13.0" / 330 mm 380.00 ft / 115.82 m 17.00 ft / 5.18 m
 Ends: Unarmoured
   Main Belt covers 101 % of normal length

   - Torpedo Bulkhead:
  3.00" / 76 mm 380.00 ft / 115.82 m 31.00 ft / 9.45 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 13.0" / 330 mm 9.00" / 229 mm  14.0" / 356 mm
 2nd: 6.00" / 152 mm 6.00" / 152 mm  6.00" / 152 mm

   - Armour deck: 4.00" / 102 mm, Conning tower: 13.00" / 330 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Direct drive, 4 shafts, 46,342 shp / 34,571 Kw = 23.00 kts
 Range 6,200nm at 15.00 kts
 Bunker at max displacement = 4,394 tons

Complement:
 1,081 - 1,406

Cost:
 £2.307 million / $9.227 million

Distribution of weights at normal displacement:
 Armament: 1,410 tons, 5.0 %
 Armour: 10,693 tons, 38.2 %
    - Belts: 3,677 tons, 13.1 %
    - Torpedo bulkhead: 1,308 tons, 4.7 %
    - Armament: 2,571 tons, 9.2 %
    - Armour Deck: 2,879 tons, 10.3 %
    - Conning Tower: 258 tons, 0.9 %
 Machinery: 1,915 tons, 6.8 %
 Hull, fittings & equipment: 10,397 tons, 37.1 %
 Fuel, ammunition & stores: 3,585 tons, 12.8 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   42,210 lbs / 19,146 Kg = 63.4 x 11.0 " / 279 mm shells or 8.6 torpedoes
 Stability (Unstable if below 1.00): 1.06
 Metacentric height 5.6 ft / 1.7 m
 Roll period: 17.7 seconds
 Steadiness - As gun platform (Average = 50 %): 80 %
   - Recoil effect (Restricted arc if above 1.00): 0.58
 Seaboat quality  (Average = 1.00): 1.60

Hull form characteristics:
 Hull has raised forecastle, rise forward of midbreak
 Block coefficient: 0.507
 Length to Beam Ratio: 5.80 : 1
 'Natural speed' for length: 24.08 kts
 Power going to wave formation at top speed: 48 %
 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:  30.00 ft / 9.14 m
    - Forecastle (20 %): 30.00 ft / 9.14 m (0.00 ft / 0.00 m aft of break)
    - Mid (45 %):  30.00 ft / 9.14 m (22.00 ft / 6.71 m aft of break)
    - Quarterdeck (15 %): 22.00 ft / 6.71 m
    - Stern:  22.00 ft / 6.71 m
    - Average freeboard: 21.85 ft / 6.66 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 75.6 %
  - Above water (accommodation/working, high = better): 132.4 %
 Waterplane Area: 38,906 Square feet or 3,615 Square metres
 Displacement factor (Displacement / loading): 109 %
 Structure weight / hull surface area: 184 lbs/sq ft or 899 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.92
  - Longitudinal: 2.27
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is excellent
 Room for accommodation and workspaces is excellent
 Ship has slow, easy roll, a good, steady gun platform
 Excellent seaboat, comfortable, can fire her guns in the heaviest weather