I redid a design study for a Ger/CB/1915 fast battlecruiser

My original concept was for a 40knot battlecruiser, but the best that could be reasonably done is 35 knots, which is not so bad. The problem with what I had done over 30 years ago is that I greatly underestimated the power it would take to drive the ship at 40 knots. I also neglected hull strength is my calculations. Springsharp uses a different weight budget than what I was using so it is difficult to compare. What is amazing is that I hoped for a standard displacement of 35,837 tons, with a full load displacement of 40,000 tons. The basic dimensions were:

• length: 900ft
• beam: 100ft
• hull depth: 58ft
• draft: 29.7ft deep load
• hull weight basis of only 0.24

The weight budget looked like this:

• full load: 40,000 tons
• fuel oil: 3,620 tons
• feed water: 543 tons
• standard displacement: 35,837 tons
• hull weight: 12,528 tons
• machinery: 7,200 tons
• armament: 2,875 tons
• protection: 8,974 tons
• miscellaneous: 2,860 tons
• auxiliary machinery: 1,400 tons

I had hoped to be able to achieve a range of 2,500 nm at 40 knots, with a fuel consumption of 62.5 tons per hour. The machinery basis was to be 30SHP/ton of machinery. This is my Springsharp report for the 35knot version:

Ger/CB/1915 Design Study, Germany Battlecruiser laid down 1915 (Engine 1931)

Displacement:
 39,493 t light; 41,071 t standard; 43,200 t normal; 44,903 t full load

Dimensions: Length overall / water x beam x draught
 901.78 ft / 900.00 ft x 100.00 ft x 32.00 ft (normal load)
 274.86 m / 274.32 m x 30.48 m  x 9.75 m

Armament:
     6 - 16.50" / 419 mm guns (2x3 guns), 2,425.00lbs / 1,099.96kg shells, 1915 Model
   Breech loading guns in turrets (on barbettes)
   on centreline, all forward, 1 raised mount - superfiring
     12 - 6.00" / 152 mm guns in single mounts, 108.00lbs / 48.99kg shells, 1915 Model
   Quick firing guns in deck mounts with hoists
   on side, all amidships
 Weight of broadside 15,846 lbs / 7,188 kg
 Shells per gun, main battery: 80

Armour:
  - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 8.00" / 203 mm 650.00 ft / 198.12 m 17.00 ft / 5.18 m
 Ends: Unarmoured
   Main Belt covers 111 % of normal length
   Main belt does not fully cover magazines and engineering spaces

  - Torpedo Bulkhead:
  2.00" / 51 mm 650.00 ft / 198.12 m 27.00 ft / 8.23 m

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

  - Armour deck: 3.00" / 76 mm, Conning tower: 9.00" / 229 mm

Machinery:
 Oil fired boilers, steam turbines,
 Geared drive, 4 shafts, 259,361 shp / 193,483 Kw = 35.00 kts
 Range 6,500nm at 15.00 kts
 Bunker at max displacement = 3,832 tons

Complement:
 1,497 - 1,947

Cost:
 £5.846 million / $23.385 million

Distribution of weights at normal displacement:
 Armament: 1,847 tons, 4.3 %
 Armour: 10,579 tons, 24.5 %
    - Belts: 3,655 tons, 8.5 %
    - Torpedo bulkhead: 1,299 tons, 3.0 %
    - Armament: 1,981 tons, 4.6 %
    - Armour Deck: 3,406 tons, 7.9 %
    - Conning Tower: 239 tons, 0.6 %
 Machinery: 7,756 tons, 18.0 %
 Hull, fittings & equipment: 19,312 tons, 44.7 %
 Fuel, ammunition & stores: 3,707 tons, 8.6 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   54,728 lbs / 24,824 Kg = 24.4 x 16.5 " / 419 mm shells or 6.6 torpedoes
 Stability (Unstable if below 1.00): 1.12
 Metacentric height 6.2 ft / 1.9 m
 Roll period: 16.8 seconds
 Steadiness - As gun platform (Average = 50 %): 61 %
   - Recoil effect (Restricted arc if above 1.00): 0.89
 Seaboat quality  (Average = 1.00): 1.22

Hull form characteristics:
 Hull has low forecastle, rise forward of midbreak
 Block coefficient: 0.525
 Length to Beam Ratio: 9.00 : 1
 'Natural speed' for length: 30.00 kts
 Power going to wave formation at top speed: 53 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 3.00 degrees
 Stern overhang: 0.00 ft / 0.00 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  34.00 ft / 10.36 m
    - Forecastle (20 %): 30.00 ft / 9.14 m (32.00 ft / 9.75 m aft of break)
    - Mid (67 %):  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: 28.15 ft / 8.58 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 112.9 %
  - Above water (accommodation/working, high = better): 222.6 %
 Waterplane Area: 61,361 Square feet or 5,701 Square metres
 Displacement factor (Displacement / loading): 106 %
 Structure weight / hull surface area: 208 lbs/sq ft or 1,014 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.96
  - Longitudinal: 1.44
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent
 Good seaboat, rides out heavy weather easily