My attempt at a pre-Dreadnought design: GB/BB/1900

In the early 1970's, I did a Jane's Fighting Ships style drawing of the subdivision and armour for a pre-Dreadnought battleship. It is the next design in the Red Book. I just ran the design through Springsharp, and it seems to be too good, compared to real ships. As far as possible, I followed the specifications from way back:

Standard Displacement=  15,000 tons
Full Load displacement= 16,500 tons
Cp=0.61
Cm=0.97
Draft (maximum)=29.9ft
Length=     435ft
Beam=       75ft
Hull Depth= 50ft
Armour:
Lower Belt: 12in
Upper Belt:  8in
Barbettes:   9in
Turrets:     12in-7in
Casemates:   7in
Forward CT:  9in
Aft CT:      8in
Fore com tube: 5in
Aft com tube:  4.5in
Deck, Amidships: 3in
Deck, ends:      2in
A/T protection:  1in

This is the Springsharp report:

GB/BB/1900, Great Britain Battleship laid down 1900

Displacement:
 12,565 t light; 13,133 t standard; 16,000 t normal; 18,293 t full load

Dimensions: Length overall / water x beam x draught
 435.00 ft / 435.00 ft x 75.00 ft x 29.90 ft (normal load)
 132.59 m / 132.59 m x 22.86 m  x 9.11 m

Armament:
      4 - 12.00" / 305 mm guns (2x2 guns), 864.00lbs / 391.90kg shells, 1900 Model
   Breech loading guns in turrets (on barbettes)
   on centreline ends, evenly spread
      12 - 6.00" / 152 mm guns in single mounts, 108.00lbs / 48.99kg shells, 1900 Model
   Quick firing guns in casemate mounts 
   on side, all amidships
   4 guns in hull casemates - Limited use in heavy seas
 Weight of broadside 4,752 lbs / 2,155 kg
 Shells per gun, main battery: 90

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 12.0" / 305 mm 250.00 ft / 76.20 m 8.00 ft / 2.44 m
 Ends: Unarmoured
 Upper: 8.00" / 203 mm 250.00 ft / 76.20 m 8.00 ft / 2.44 m
   Main Belt covers 88 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Torpedo Bulkhead:
  1.00" / 25 mm 250.00 ft / 76.20 m 28.00 ft / 8.53 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 12.0" / 305 mm 7.00" / 178 mm  9.00" / 229 mm
 2nd: 7.00" / 178 mm 7.00" / 178 mm  7.00" / 178 mm

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

Machinery:
 Coal fired boilers, complex reciprocating steam engines, 
 Direct drive, 2 shafts, 17,562 ihp / 13,101 Kw = 19.00 kts
 Range 6,200nm at 15.00 kts
 Bunker at max displacement = 5,160 tons (100% coal)

Complement:
 710 - 924

Cost:
 £1.323 million / $5.292 million

Distribution of weights at normal displacement:
 Armament: 594 tons, 3.7 %
 Armour: 4,591 tons, 28.7 %
    - Belts: 1,823 tons, 11.4 %
    - Torpedo bulkhead: 259 tons, 1.6 %
    - Armament: 1,093 tons, 6.8 %
    - Armour Deck: 1,293 tons, 8.1 %
    - Conning Tower: 123 tons, 0.8 %
 Machinery: 2,744 tons, 17.2 %
 Hull, fittings & equipment: 4,636 tons, 29.0 %
 Fuel, ammunition & stores: 3,435 tons, 21.5 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   19,197 lbs / 8,707 Kg = 22.2 x 12.0 " / 305 mm shells or 2.9 torpedoes
 Stability (Unstable if below 1.00): 1.20
 Metacentric height 4.6 ft / 1.4 m
 Roll period: 14.7 seconds
 Steadiness - As gun platform (Average = 50 %): 100 %
   - Recoil effect (Restricted arc if above 1.00): 0.59
 Seaboat quality  (Average = 1.00): 2.00

Hull form characteristics:
 Hull has a flush deck
 Block coefficient: 0.574
 Length to Beam Ratio: 5.80 : 1
 'Natural speed' for length: 20.86 kts
 Power going to wave formation at top speed: 47 %
 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:  23.00 ft / 7.01 m
    - Forecastle (20 %): 20.00 ft / 6.10 m
    - Mid (50 %):  20.00 ft / 6.10 m
    - Quarterdeck (15 %): 20.00 ft / 6.10 m
    - Stern:  20.00 ft / 6.10 m
    - Average freeboard: 20.24 ft / 6.17 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 114.3 %
  - Above water (accommodation/working, high = better): 125.0 %
 Waterplane Area: 23,289 Square feet or 2,164 Square metres
 Displacement factor (Displacement / loading): 108 %
 Structure weight / hull surface area: 127 lbs/sq ft or 620 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.89
  - Longitudinal: 2.81
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 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