Thanks for the comments guys. Kasier's break down was very helpful and I must agree B1 was the best choice.
Here is a revised version, by no means the final design. It has more draught, a torpedo bulkhead (one 1in and one 0.5in bulkhead) and an 8in inclined belt. (I'm still doing calcs to see if this is overkill or not)
Princess Royal Class, Great Britain Heavy Cruiser laid down 1936
Displacement:
18,676 t light; 19,666 t standard; 21,806 t normal; 23,518 t full load
Dimensions: Length overall / water x beam x draught
720.92 ft / 710.00 ft x 76.00 ft x 26.00 ft (normal load)
219.74 m / 216.41 m x 23.16 m x 7.92 m
Armament:
12 - 9.20" / 234 mm guns (4x3 guns), 510.00lbs / 231.33kg shells, 1936 Model
Breech loading guns in turrets (on barbettes)
on centreline ends, evenly spread, 2 raised mounts - superfiring
8 - 4.50" / 114 mm guns (4x2 guns), 45.56lbs / 20.67kg shells, 1935 Model
Dual purpose guns in deck mounts with hoists
on side, all amidships, all raised mounts - superfiring
8 - 2.24" / 57.0 mm guns (4x2 guns), 5.65lbs / 2.56kg shells, 1935 Model
Anti-aircraft guns in deck mounts
on side ends, evenly spread, all raised mounts - superfiring
36 - 0.66" / 16.8 mm guns (6x6 guns), 0.14lbs / 0.06kg shells, 1935 Model
Anti-aircraft guns in deck mounts
on side ends, evenly spread, 4 raised mounts - superfiring
Weight of broadside 6,535 lbs / 2,964 kg
Shells per gun, main battery: 150
8 - 24.5" / 622.3 mm above water torpedoes
Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 8.00" / 203 mm 500.00 ft / 152.40 m 10.00 ft / 3.05 m
Ends: Unarmoured
Main Belt covers 108 % of normal length
- Torpedo Bulkhead:
1.50" / 38 mm 500.00 ft / 152.40 m 24.00 ft / 7.32 m
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 7.00" / 178 mm 4.00" / 102 mm 7.00" / 178 mm
2nd: 1.00" / 25 mm 0.50" / 13 mm 2.00" / 51 mm
3rd: 0.50" / 13 mm - -
4th: 0.50" / 13 mm - -
- Armour deck: 3.50" / 89 mm, Conning tower: 3.00" / 76 mm
Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 116,000 shp / 86,536 Kw = 32.13 kts
Range 10,000nm at 16.00 kts
Bunker at max displacement = 3,852 tons
Complement:
896 - 1,166
Cost:
£8.666 million / $34.662 million
Distribution of weights at normal displacement:
Armament: 636 tons, 2.9 %
Armour: 6,059 tons, 27.8 %
- Belts: 1,657 tons, 7.6 %
- Torpedo bulkhead: 666 tons, 3.1 %
- Armament: 1,162 tons, 5.3 %
- Armour Deck: 2,524 tons, 11.6 %
- Conning Tower: 50 tons, 0.2 %
Machinery: 3,255 tons, 14.9 %
Hull, fittings & equipment: 8,526 tons, 39.1 %
Fuel, ammunition & stores: 3,130 tons, 14.4 %
Miscellaneous weights: 200 tons, 0.9 %
Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
32,118 lbs / 14,568 Kg = 82.5 x 9.2 " / 234 mm shells or 4.6 torpedoes
Stability (Unstable if below 1.00): 1.08
Metacentric height 3.8 ft / 1.2 m
Roll period: 16.3 seconds
Steadiness - As gun platform (Average = 50 %): 60 %
- Recoil effect (Restricted arc if above 1.00): 0.82
Seaboat quality (Average = 1.00): 1.08
Hull form characteristics:
Hull has a flush deck
and transom stern
Block coefficient: 0.544
Length to Beam Ratio: 9.34 : 1
'Natural speed' for length: 30.42 kts
Power going to wave formation at top speed: 54 %
Trim (Max stability = 0, Max steadiness = 100): 56
Bow angle (Positive = bow angles forward): 20.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 30.00 ft / 9.14 m
- Forecastle (20 %): 25.00 ft / 7.62 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: 22.15 ft / 6.75 m
Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 99.5 %
- Above water (accommodation/working, high = better): 150.9 %
Waterplane Area: 38,981 Square feet or 3,621 Square metres
Displacement factor (Displacement / loading): 122 %
Structure weight / hull surface area: 146 lbs/sq ft or 711 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.98
- Longitudinal: 1.26
- Overall: 1.00
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is excellent
On the 57mm issue I have a few points.
First the gun is semi-automatic, revised specs are now; 6pdr shell will have around 1.1lbs of HE filling. Rate of fire will be around 95rpm and effective ceiling 15,500ft. Now it may be noticed some of my 1935 designs mount both 6pdr and 2pdr guns, a sign that the heavier gun lacks the RoF of the 2pdr and that it may fail in service. I was planning improved versions from 1939 onwards anyway and such a gun is a prototype system. These CAs may have quad or octuple 2pdr instead when they commission anyway, only weight concerns (and space) have stopped me putting 2pdrs on as well. The RoF in practice will be much lower than 95rpm since the guns are belt loaded. No doubt that will cause problems too. I must admit future developments I planned do include the Mollins autoloader system.