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"G3" project battlecruisers (4)


Name No Yard No Builder Laid down Launched Comp Fate
i   627 Beardmore, Dalmuir --- --- --- suspended 11.1921, cancelled 2.1922
ii   497 John Brown, Clydebank --- --- --- suspended 11.1921, cancelled 2.1922
iii   615 Fairfield, Govan --- --- --- suspended 11.1921, cancelled 2.1922
iv   1203 Swan Hunter, Wallsend --- --- --- suspended 11.1921, cancelled 2.1922

Technical data

Displacement standard, t


Displacement full, t


Length, m

250.1 pp 260.9 oa

Breadth, m


Draught, m

10.2 deep

No of shafts



4 sets geared steam turbines, 20 small-tube boilers

Power, h. p.


Max speed, kts

31 - 32

Fuel, t

5000 oil

Endurance, nm(kts)7000(16)
Armour, mm

main belt: 356 - 305, bulkheads: 305 - 254, turrets: 431 (face), decks: 203 - 102, CT: 305


3 x 3 - 406/45 BL Mk I, 8 x 2 - 152/50 BL Mk XXII, 6 x 1 - 120/40 QF Mk VIII, 4 x 8 - 40/39 2pdr QF Mk VIII, 2 - 622 TT (fwd, 20), 2 flying-off platforms, 2 airplanes



Standard scale images

'G3' final design
'G3' final design

Project history

The Royal Navy was well aware that it had ended the War in an inferior position vis a vis the American and Japanese navies. Despite the enormous preponderance of numbers, 305mm-gunned dreadnoughts were quite outclassed, and even the 343mm- and 381mm-gunned ships were outclassed by the latest 356mm- and 406mm-gunned 'super-dreadnoughts' laid down during the War. Drastic reconstruction would remedy the worst deficiencies of 381mm-gunned ships, but what was needed was a new class of ships capable of facing 406mm and even 457mm gunfire. There was also an urgent need to incorporate war lessons: Hood class, despite detailed improvements, was essentially a pre-Jutland design, and by 1921 there was a large body of fresh experience based on tests against German ships. The first design required was a class of four large battlecruisers, to be laid down in 1921. The concept which evolved was much closer to a fast battleship than anything previously considered and the US Navy's 'all-or-nothing' concept of protection was embraced. The latest type of protection was to be used, namely an inclined internal armour belt and internal 'bulges' against torpedoes.     For the first time a triple turret was adopted to concentrate armament. The secondary armament was mounted in twin turrets. Various designs were drawn up, but all had in common a concentration of heavy armour over the vitals, with turrets grouped together to permit the maximum thickness of armour. They represented a big a step forward in fighting power as the Dreadnought had 17 years earlier, and they showed how much the size of capital ships had increased in little more than a decade.     After lengthy consideration, design 'G 3' (out of an alphabetical series) was accepted in February 1921, the final legend being approved in August 1921. Orders followed on 26 October - one each from Beardmore, John Brown, Fairfield and Swan Hunter (the last with machinery sub-contracted to Parsons) - but the orders were suspended on 18 November by Cabinet order. The threat of these ships being built was used as a bargaining counter during the Washington Conference, but it was quite clear by the end of 1921 that Britain was in a deepening financial crisis, and the Cabinet would not have permitted the programme to go ahead, even if the Americans and Japanese had refused to negotiate reductions in their fleets. Although the ships had not started construction the details of the design were sufficiently developed to provide a basis for Nelson and Rodney, truncated versions carrying the same armament and scale of protection, but 8-9kts slower. Under the terms of the Treaty the four 'G 3's were cancelled on 13 February 1922. Names were never allocated, and the two sets of names often quoted are merely speculative: St. George, St. Andrew, St. David and St. Patrick; or Invincible, Inflexible, Indomitable and Indefatigable.


  Main 356mm belt with 4.2m depth would protect main magazines, abreast machinery its thickness would be 305mm, the belt would be inclined at 18° inside. Main belt would be closed by 305mm and 127mm fore and 254mm and 102mm aft bulkheads, aft part of the belt abreast secondary turrets was tapered to 229mm at upper and 152mm at lower edges. TT compartment was protected by shallow 152mm belt extended between citadel and stem and 152mm deck and 152mm bulkhead. Turrets would have 431mm faces, 330mm sides and rears and 203mm roofs. Barbettes would be protected by 356mm armour over the main deck from the sides and by 305-279mm armour near the centreline. CT would have 356mm face, 254mm sides, 102mm rear and floor and 203mm roof, communication tube would been protected by 203mm armour. Funnel uptakes would have 44-19mm armour. There would be 4 protected decks: 25mm forecastle deck, upper deck: 203mm over main magazines, 102-76mm over machinery and 178mm over secondary magazines, 25mm main deck and medium deck with 152mm armour fwd from citadel and 127-76mm armour aft from citadel. Steering gear compartment would been protected by 127mm deck and 114mm bulkhead.

Underwater protection could resist the explosion of 343kg TNT and included 44mm longitudinal bulkhead, its deep would be 4.3m.

Many thanks to Borys Estrin for granted additional information