G3 was promising, but needed many modifications.
1. Disposition of secondary guns.
Numbers of guns were OK, but disposition far from perfect. Forward 6” turrets were OK, but rest not. They were too close, and all 3 of one site could be put out of action by one (un)lucky hit. More important – they were put under the deck. Deck was needed for space for boats and other equipment. But it was fear, that if could collapse, when hit, and block turrets under.
Something different was needed
2. Belt armour
Upper part of belt armour was ~3-4 feet inside hull. And stepped 25 degrees. It moved torpedo bulkhead far away from external plate. It gives extra protection, both torpedo and shell, but there were fear of stability. What good is to have intact citadel, if ship will capsize?
So armour was a bit more vertical. Still inclined, but now 18 degree, not 25. The same time forward and aft bulkheads become vertical. In all previous designs were inclined 25 degrees.
Thickness were retained the same, so protection was some way lower.
3. Deck armour.
Most important was to improve deck over machinery. Generally it was thickened by 1” in all areas over machinery. It generated increase of mass 1125 tons. To compensate
1. Removed 2 turrets with 6” guns. ( later restored )
2. Height of belt armour reduced by 1 feet
3. Reduced forward and belt armour of main turrets by 2”
4. Small alternation of deck armour over magazines.
All were 425 tons of savings. Rest 700 could not be compensated that way, so rising of displacement was accepted.
Deck over machinery was still only 3” thick. It was thickened to 4”. Somewhere that time ( I don’t know exact when ) slopes of deck armour was removed, and deck placed just over belt amour, but with small slope – say 2 degree from centerline to belt.
Max power was removed from 180 000 SHP to 160 000 SHP, interesting that original 18 boilers were switched to 20 new, but smaller ones.
Alternation of after part of the hull – to gain room for gearings – resulted increase in resistance. Later again improved, but still resistance was a bit larger in final design compared to original.
Mass was still increasing, so as weight savings, main guns were reduced from 16.5 to 16”.
Thanks to that change it was possible to restore original 16 guns 6”, and add one 4.7” AA gun
Armour again was changed. 1” was added to turrets forward and belt ( first 18” forward 14” belt, than thinned to 16” and 12”, in final configuration 17” forward and 13” belt )
Original height of belt was restored.
Some protection against diving shells were added ( only over magazines )
As a result, ship become 3 meters shorter, but displacement reach 48 000 tons.
In 1921 for short time, restoration of power to original 180 000 SHP was considered, but ruled out. Expected increase of displacement was 200 tons, more important length by 8 meters ( 24 feet ). With such a length there will be problems with docking in Porthsmouth. Machinery spaces had to be widened. Total beam of ship could not be increased, as it was at the limit of translate through Panama canal, so torpedo protection will be compromised. Expected extra cost was 350 000 pounds. And running cost will be more due to higher burning rate, and need of some extra crew. Expected increase of speed by 0.5 knots was considered not worth all those costs.
At first max speed 31-32 knots was considered too low, as it was 1-2 knots lower than Lexingtons, but soon that fear was ruled out. G3 was so much better armoured that this 1-2 knots difference should not be a problem.
Final version of G3
Belt was internal and inclined 18 degree. Upper part was 4 feet inside hull. In normal displacement ~1.4 meter was under waterline, and 3 meters over. Over magazines 14”, over machinery 12”. Forward boiler room had 14”. Magazines had to be protected against racing fire.
Deck over magazines: 8”
Over machinery more complicated. Forward boiler room 8”, than next boiler room 6”, rest, and turbines 4”. After magazines, and half of after turbines 7” deck ( racked fire ).
Aft of the citadel was deck armour more or less on waterline. Forward only over torpedo rooms. Lack of deck armour forward was considered flaw by British, but there were no other choice due to weight restrictions ( for Americans it was not a problem, they do not use that armour, Japanese on Yamato did not use either ).
Designed to protect against 750 lbs of TNT. More or less on waterline there were crushing tubes. It was expected that they will give some stability in riddled condition, and possibly could decapp come shells.
SPS to work needed over 2000 tons of water to be in place. Special system of blowing out that water by compressed air ( similar to that used in submarines ) was designed, to allow quick restoration to even keel in case of asymetrical damage.
Double bottom was 7 feet ( 2 meters ) high under magazines and boilers, 5 feet on rest.
Main guns 9x16”
Turrets ordered for first 2 were reordered for Nelsons, but were extensively modified compared to original design. They become lighter, put on smaller barbettes, and fire/flash protection was increased. It resulted those initial problems.
16x6” Turrets with original 40 degree elevation. They were put on Nelsons, but later elevation increased to 60 degree
AA guns as in AA committee recommendation.
3 September 1921 invitation was send to Breadmore, John Brown, Cammel Raid, Vickers, Fairfield, Armstrongs, Harland and Wolf and Swan, Hunter. Accepted oferts:
- Breadmore, cost 3 786 332 Ł
- John Brown, cost 3 879 000 Ł
- Fairfield, cost 3 900 000 Ł
- Swan, Hunter, cost 3 977 175 Ł
Cost for hull and machinery. Artillery, armour and fire control were ordered, and paid separately.
Hard limit for construction since sighting contract and “ship ready to tests” 30 months. ( or 36 I’m not sure now )
Not single one was laid down when WNT was signed and all program scrapped. But ~0.5 million was spend for various tests, designs, weapons systems and so one. What could be used, was used on Nelsons.
Even some sums was paid for builders, as they started assembly of various things, before all was canceled ( yes some work was started before they were laid down, after contract was signed )
All modifications incorporated to G3, were included to battleship design. Instead of adding something to M3 point after point, all was included, and new design was named N3.
Some things were not set when program was canceled. Numbers of boilers for example was not decided, nor exact configuration of protection of funnel uptakes and air intakes. It was time to decide it later, before ships were ordered.
Basically compared to M3. Sloped were omitted, sec guns rearranged, ship lengthened ( to reduce resistance, so power of machinery could be lower ). Configuration of machinery with turbines forward of boilers were retained.
Belt over some of machinery were thinned to 13.5”
That time all was canceled due to WNT.
Friedman in it’s “British battleships” put some info about O3 – some improved N3 with a bit better armour, and more displacement. I don’t remember details, but how serious that design was, is visible, as name O3 was attached to one of preliminaries of Nelson. Much different and smaller design.
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