My design for upgunning the Von der Tann

I thought that upgunning the Von der Tann would be challenging. The age of the ship and layout would be pretty restrictive. I went with two twin 17in turrets and two single 17in turrets, the last in echelon. I added bulges and raised the displacement considerably. I did not increase the protection, although the ship would be greatly helped by doing so. The rebuilt ship now has a speed of 26 knots and a main armament of 6-17in guns. This is the Springsharp report:

Von der Tann, upgunned, Germany Battlecruiser laid down 1914 (Engine 1907)

Displacement:
 21,604 t light; 22,911 t standard; 25,200 t normal; 27,032 t full load

Dimensions: Length overall / water x beam x draught
 562.66 ft / 562.66 ft x 87.27 ft (Bulges 92.52 ft) x 30.18 ft (normal load)
 171.50 m / 171.50 m x 26.60 m (Bulges 28.20 m)  x 9.20 m

Armament:
      4 - 16.93" / 430 mm guns (2x2 guns), 2,425.91lbs / 1,100.37kg shells, 1914 Model
   Breech loading guns in turrets (on barbettes)
   on centreline ends, evenly spread
      2 - 16.93" / 430 mm guns in single mounts, 2,425.91lbs / 1,100.37kg shells, 1914 Model
   Breech loading guns in turrets (on barbettes)
   on side, all amidships
      10 - 5.91" / 150 mm guns in single mounts, 102.98lbs / 46.71kg shells, 1914 Model
   Quick firing guns in casemate mounts 
   on side, evenly spread
   10 guns in hull casemates - Limited use in heavy seas
 Weight of broadside 15,585 lbs / 7,069 kg
 Shells per gun, main battery: 90
 4 - 17.7" / 450 mm above water torpedoes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 9.84" / 250 mm 351.05 ft / 107.00 m 9.84 ft / 3.00 m
 Ends: Unarmoured
 Upper: 8.86" / 225 mm 351.05 ft / 107.00 m 0.00 ft / 0.00 m
   Main Belt covers 96 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead and Bulges:
  0.98" / 25 mm 351.05 ft / 107.00 m 30.18 ft / 9.20 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 9.06" / 230 mm 3.54" / 90 mm  9.06" / 230 mm
 2nd: 9.06" / 230 mm 3.54" / 90 mm  9.06" / 230 mm
 3rd: 5.91" / 150 mm 0.79" / 20 mm  0.79" / 20 mm

   - Armour deck: 1.97" / 50 mm, Conning tower: 9.84" / 250 mm

Machinery:
 Coal fired boilers, steam turbines, 
 Direct drive, 4 shafts, 67,160 shp / 50,102 Kw = 25.50 kts
 Range 4,400nm at 14.00 kts
 Bunker at max displacement = 4,121 tons (100% coal)

Complement:
 999 - 1,300

Cost:
 £3.793 million / $15.172 million

Distribution of weights at normal displacement:
 Armament: 1,948 tons, 7.7 %
 Armour: 5,199 tons, 20.6 %
    - Belts: 1,497 tons, 5.9 %
    - Torpedo bulkhead: 386 tons, 1.5 %
    - Armament: 1,872 tons, 7.4 %
    - Armour Deck: 1,261 tons, 5.0 %
    - Conning Tower: 182 tons, 0.7 %
 Machinery: 4,198 tons, 16.7 %
 Hull, fittings & equipment: 10,260 tons, 40.7 %
 Fuel, ammunition & stores: 3,596 tons, 14.3 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   19,546 lbs / 8,866 Kg = 8.1 x 16.9 " / 430 mm shells or 2.8 torpedoes
 Stability (Unstable if below 1.00): 1.18
 Metacentric height 5.5 ft / 1.7 m
 Roll period: 16.6 seconds
 Steadiness - As gun platform (Average = 50 %): 56 %
   - Recoil effect (Restricted arc if above 1.00): 0.70
 Seaboat quality  (Average = 1.00): 1.12

Hull form characteristics:
 Hull has rise forward of midbreak, raised quarterdeck 
 Block coefficient: 0.561
 Length to Beam Ratio: 6.08 : 1
 'Natural speed' for length: 23.72 kts
 Power going to wave formation at top speed: 55 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): -2.00 degrees
 Stern overhang: -6.56 ft / -2.00 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  27.89 ft / 8.50 m
    - Forecastle (20 %): 27.89 ft / 8.50 m
    - Mid (35 %):  27.89 ft / 8.50 m (18.04 ft / 5.50 m aft of break)
    - Quarterdeck (15 %): 18.04 ft / 5.50 m (16.40 ft / 5.00 m before break)
    - Stern:  18.04 ft / 5.50 m
    - Average freeboard: 21.08 ft / 6.43 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 144.4 %
  - Above water (accommodation/working, high = better): 124.8 %
 Waterplane Area: 34,635 Square feet or 3,218 Square metres
 Displacement factor (Displacement / loading): 86 %
 Structure weight / hull surface area: 197 lbs/sq ft or 964 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.93
  - Longitudinal: 2.07
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent