GB/CB/1921 Super Fast, Great Britain Light Battlecruiser laid down 1921 (Engine 1941)
Displacement:
34,937 t light; 36,283 t standard; 38,265 t normal; 39,851 t full load
Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(899.34 ft / 894.00 ft) x 97.00 ft x (33.00 / 33.95 ft)
(274.12 m / 272.49 m) x 29.57 m x (10.06 / 10.35 m)
Armament:
4 - 17.00" / 432 mm 45.0 cal guns - 2,480.00lbs / 1,124.91kg shells, 90 per gun
Breech loading guns in turret on barbette mounts , 1921 Model
1 x Twin mount on centreline, forward deck forward
1 x Twin mount on centreline, forward deck aft
12 - 5.50" / 140 mm 50.0 cal guns - 85.00lbs / 38.56kg shells, 150 per gun
Quick firing guns in deck and hoist mounts , 1921 Model
12 x Single mounts on sides, forward deck aft
Weight of broadside 10,940 lbs / 10,940 kg
Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 7.00" / 178 mm 490.00 ft / 149.35 m 8.00 ft / 2.44 m
Ends: Unarmoured
Upper: 5.00" / 127 mm 490.00 ft / 149.35 m 8.00 ft / 2.44 m
Main Belt covers 84 % of normal length
Main belt does not fully cover magazines and engineering spaces
- Torpedo Bulkhead:
1.50" / 38 mm 490.00 ft / 149.35 m 33.00 ft / 10.06 m
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 8.00" / 203 mm 5.00" / 127 mm 8.00" / 203 mm
2nd: 4.00" / 102 mm 2.00" / 51 mm 4.00" / 102 mm
- Armour deck: 3.00" / 76 mm, Conning tower: 8.00" / 203 mm
Machinery:
Oil fired boilers, steam turbines,
Geared drive, 6 shafts, 343,077 shp / 255,935 Kw = 40.00 kts
Range 6,500nm at 16.00 kts
Bunker at max displacement = 3,568 tons
Complement:
1,367 - 1,778
Cost:
£8.977 million / $35.910 million
Distribution of weights at normal displacement:
Armament: 1,883 tons, 4.9 %
Armour: 7,843 tons, 20.5 %
- Belts: 2,029 tons, 5.3 %
- Torpedo bulkhead: 897 tons, 2.3 %
- Armament: 1,482 tons, 3.9 %
- Armour Deck: 3,239 tons, 8.5 %
- Conning Tower: 196 tons, 0.5 %
Machinery: 9,067 tons, 23.7 %
Hull, fittings & equipment: 16,796 tons, 43.9 %
Fuel, ammunition & stores: 3,328 tons, 8.7 %
Miscellaneous weights: 0 tons, 0.0 %
Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
45,577 lbs / 20,673 Kg = 18.6 x 17.0 " / 432 mm shells or 4.9 torpedoes
Stability (Unstable if below 1.00): 1.15
Metacentric height 6.2 ft / 1.9 m
Roll period: 16.4 seconds
Steadiness - As gun platform (Average = 50 %): 53 %
- Recoil effect (Restricted arc if above 1.00): 0.59
Seaboat quality (Average = 1.00): 1.06
Hull form characteristics:
Hull has rise forward of midbreak,
a normal bow and small transom stern
Block coefficient (normal/deep): 0.468 / 0.474
Length to Beam Ratio: 9.22 : 1
'Natural speed' for length: 34.48 kts
Power going to wave formation at top speed: 58 %
Trim (Max stability = 0, Max steadiness = 100): 50
Bow angle (Positive = bow angles forward): 8.00 degrees
Stern overhang: -3.00 ft / -0.91 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 25.00 %, 38.00 ft / 11.58 m, 33.00 ft / 10.06 m
- Forward deck: 35.00 %, 33.00 ft / 10.06 m, 32.00 ft / 9.75 m
- Aft deck: 20.00 %, 24.00 ft / 7.32 m, 24.00 ft / 7.32 m
- Quarter deck: 20.00 %, 24.00 ft / 7.32 m, 26.00 ft / 7.92 m
- Average freeboard: 29.93 ft / 9.12 m
Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 127.6 %
- Above water (accommodation/working, high = better): 239.1 %
Waterplane Area: 58,358 Square feet or 5,422 Square metres
Displacement factor (Displacement / loading): 107 %
Structure weight / hull surface area: 186 lbs/sq ft or 907 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.95
- Longitudinal: 1.61
- Overall: 1.00
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is excellent
This is a forum for discussion of topics relating to the Dreadnought era, prior to the ascendency of naval aviation. We will be discussing history, ship design, and naval wargaming.
Friday, April 20, 2007
A Super Fast Battlecruiser variant
I had this design, but I had forgotten to use a transom stern. Having the small transom, in typical British 1921 style, allowed me to improve the overall qualities and decrease displacement. The GB/CB/1921 Super Fast carried 4-17in/45 BLR and 12-5.5in QF guns. The lower belt is 8in and the deck is 3in. The top speed is 40 knots and the ship has a range of 6,500nm at 16 knots. This is a photo that I struggled to produce using a chisle and hammer, which is all I have to work with in a locked down environment, and it shows (you should be able to click on it to get a larger photo):
This is the Springsharp report:

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