HMS Indestructible

HMS Indestructible, British Indestructible-class battlecruiser laid down 1925 (Engine 1927)

Displacement:
	42,217 t light; 44,061 t standard; 46,919 t normal; 49,204 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
	(870.83 ft / 853.02 ft) x 104.99 ft x (29.53 / 30.73 ft)
	(265.43 m / 260.00 m) x 32.00 m  x (9.00 / 9.37 m)

Armament:
      6 - 16.00" / 406 mm 45.0 cal guns - 2,048.09lbs / 929.00kg shells, 100 per gun
	  Breech loading guns in turret on barbette mounts, 1925 Model
	  2 x 3-gun mounts on centreline, forward deck forward
		1 raised mount - superfiring
      12 - 6.00" / 152 mm 50.0 cal guns - 111.99lbs / 50.80kg shells, 150 per gun
	  Dual purpose guns in turret on barbette mounts, 1925 Model
	  4 x Twin mounts on sides, forward deck aft
		2 raised mounts - superfiring
	  2 x Twin mounts on sides, aft deck forward
      6 - 4.72" / 120 mm 40.0 cal guns - 50.00lbs / 22.68kg shells, 175 per gun
	  Dual purpose guns in deck mounts, 1925 Model
	  6 x Single mounts on sides, evenly spread
      40 - 1.57" / 40.0 mm 39.0 cal guns - 1.98lbs / 0.90kg shells, 1,800 per gun
	  Anti-air guns in deck mounts, 1925 Model
	  4 x 2 row octuple mounts on sides, evenly spread
	  1 x 2 row octuple mount on centreline, aft deck centre
      24 - 0.50" / 12.7 mm 62.0 cal guns - 0.08lbs / 0.04kg shells, 2,500 per gun
	  Machine guns in deck mounts, 1925 Model
	  6 x 4 row quad mounts on sides, evenly spread
      Weight of broadside 14,014 lbs / 6,356 kg

Armour:
   - Belts:		Width (max)	Length (avg)		Height (avg)
	Main:	14.0" / 356 mm	337.96 ft / 103.01 m	12.30 ft / 3.75 m
	Ends:	2.00" / 51 mm	515.03 ft / 156.98 m	12.30 ft / 3.75 m
	Upper:	6.00" / 152 mm	337.96 ft / 103.01 m	8.01 ft / 2.44 m
	  Main Belt covers 61 % of normal length
	  Main Belt inclined -15.00 degrees (positive = in)

   - Torpedo Bulkhead - Additional damage containing bulkheads:
		12.0" / 305 mm	337.96 ft / 103.01 m	28.08 ft / 8.56 m
	Beam between torpedo bulkheads 98.43 ft / 30.00 m

   - Hull void:
		0.00" / 0 mm	  0.00 ft / 0.00 m	0.00 ft / 0.00 m

   - Gun armour:	Face (max)	Other gunhouse (avg)	Barbette/hoist (max)
	Main:	16.0" / 406 mm	8.29" / 211 mm		14.0" / 356 mm
	2nd:	1.50" / 38 mm	1.00" / 25 mm		1.00" / 25 mm

   - Armoured deck - multiple decks:
	For and Aft decks: 6.25" / 159 mm
	Forecastle: 1.00" / 25 mm  Quarter deck: 1.00" / 25 mm

   - Conning towers: Forward 13.50" / 343 mm, Aft 7.50" / 191 mm

Machinery:
	Oil fired boilers, steam turbines,
	Geared drive, 4 shafts, 138,004 shp / 102,951 Kw = 28.86 kts
	Range 7,000nm at 16.00 kts
	Bunker at max displacement = 5,143 tons

Complement:
	1,593 - 2,072

Cost:
	£11.140 million / $44.560 million

Distribution of weights at normal displacement:
	Armament: 2,888 tons, 6.2 %
	   - Guns: 2,888 tons, 6.2 %
	Armour: 16,870 tons, 36.0 %
	   - Belts: 3,979 tons, 8.5 %
	   - Torpedo bulkhead: 4,217 tons, 9.0 %
	   - Armament: 2,912 tons, 6.2 %
	   - Armour Deck: 5,174 tons, 11.0 %
	   - Conning Towers: 589 tons, 1.3 %
	Machinery: 4,356 tons, 9.3 %
	Hull, fittings & equipment: 17,603 tons, 37.5 %
	Fuel, ammunition & stores: 4,701 tons, 10.0 %
	Miscellaneous weights: 500 tons, 1.1 %
	   - Hull below water: 125 tons
	   - Hull void weights: 125 tons
	   - Hull above water: 125 tons
	   - On freeboard deck: 75 tons
	   - Above deck: 50 tons

Overall survivability and seakeeping ability:
	Survivability (Non-critical penetrating hits needed to sink ship):
	  97,710 lbs / 44,321 Kg = 47.7 x 16.0 " / 406 mm shells or 20.2 torpedoes
	Stability (Unstable if below 1.00): 1.18
	Metacentric height 7.3 ft / 2.2 m
	Roll period: 16.3 seconds
	Steadiness	- As gun platform (Average = 50 %): 72 %
			- Recoil effect (Restricted arc if above 1.00): 0.71
	Seaboat quality  (Average = 1.00): 1.64

Hull form characteristics:
	Hull has a flush deck,
	  a straight bulbous bow and a cruiser stern
	Block coefficient (normal/deep): 0.621 / 0.626
	Length to Beam Ratio: 8.13 : 1
	'Natural speed' for length: 29.21 kts
	Power going to wave formation at top speed: 47 %
	Trim (Max stability = 0, Max steadiness = 100): 44
	Bow angle (Positive = bow angles forward): 25.00 degrees
	Stern overhang: 3.28 ft / 1.00 m
	Freeboard (% = length of deck as a percentage of waterline length):
				Fore end,	 Aft end
	   - Forecastle:	30.19 %,  31.17 ft / 9.50 m,  29.53 ft / 9.00 m
	   - Forward deck:	23.81 %,  29.53 ft / 9.00 m,  29.53 ft / 9.00 m
	   - Aft deck:	15.81 %,  29.53 ft / 9.00 m,  29.53 ft / 9.00 m
	   - Quarter deck:	30.19 %,  29.53 ft / 9.00 m,  29.53 ft / 9.00 m
	   - Average freeboard:		29.73 ft / 9.06 m
	Ship tends to be wet forward

Ship space, strength and comments:
	Space	- Hull below water (magazines/engines, low = better): 60.9 %
		- Above water (accommodation/working, high = better): 235.8 %
	Waterplane Area: 66,793 Square feet or 6,205 Square metres
	Displacement factor (Displacement / loading): 121 %
	Structure weight / hull surface area: 196 lbs/sq ft or 958 Kg/sq metre
	Hull strength (Relative):
		- Cross-sectional: 0.95
		- Longitudinal: 1.46
		- Overall: 1.00
	Excellent machinery, storage, compartmentation space
	Excellent accommodation and workspace room
	Ship has slow, easy roll, a good, steady gun platform
	Excellent seaboat, comfortable, can fire her guns in the heaviest weather

HMS Indestructible. Designed as a replacement for the Admiral-class battlecruisers. Ultimately, only 2 are built as a result of dissatisfaction amongst the Admiralty with the design, especially when compared with a number of competing fast battleships of the era.