This thread will detail several of the interwar battleship and battlecruiser designs which led ultimately to the Nelson Class.
Following the end of the First World War, the Admiralty began studies for a new generation of capital ships that could withstand 18in or 15in gunfire. The series would be numbered from J upwards for battleships and J downwards for battlecruisers.
The number 2 or 3 denoted the number of barrels the turrets had.
Design L Twin June 1920
Design L Triple June 1920
The first two baseline designs were drawn up in June 1920 and pre-dated the numbering system and were L Twin and L Triple. Later these designs would become the modified L2 and L3 with transom sterns. The design was based on the U4 of 1914 with all the turrets on the same level, probably to lower the centre of gravity and adequate stability. The stern was modelled on that of Hood. L Twin was 850 (wl) x 106 x 31ft and displaced 50,750 tons with 70,000shp for a speed of 25kts. Armament was 4x2 18in, 8x2 6in, 4x1 4.7in HA and two underwater 24.5in torpedo tubes. L Triple was 850 (wl) x 106 x 30.5ft and displaced 49,100 tons with 70,000shp for a speed of 26kts. Armament was 3x3 18in, 8x2 6in and 4x1 4.7in HA. In both designs, the 18in thick main belt was mounted internally at an angle of 10 degrees. The belt was 495ft long and the deck armour was 8.25in thick, the edges being 13in thick sloping down to the top of the belt. This formed the top section of an integral blister while the forecastle deck was flared outboard. The anti-torpedo bulkhead system was 12ft thick and 12ft deep with an air-filled outer and liquid-filled inner voids. The double bottom was 7ft thick.
Design L2 1920
The 'L Twin' was further refined to become the L2. The major change was the introduction of the transom stern. Possibly D'Encourt himself suggested that since the long stern was only kissing the water, that there might not be a severe penalty if they were cut off square. Already in March 1920, Haslar had tested models with transoms for the 'AR' battlecruiser design. Four alternatives were tried; the stern cut off at 30ft abaft the aft perpendicular (the rudder stock), that at 15ft abaft, 7ft 6in abaft and finally at the rudder. The resistance curves for all but the last configuration were identical to the original. The loss of efficiency at moderate speeds was noted however. Superintendent S. Payne began introducing transoms and the Ls benefited from this. The broad transom aided stability in damaged condition and gave the performance of a hull form some 20ft longer.
L2 was 860ft (oa) (850ft wl) x 106 x 33.5ft and displaced 52,100tons with 70,000shp for a speed of 25kts. Armament was 4x2 18in, 8x2 6in, 6x1 4.7in HA, 4x10 2pdr and two underwater 24.5in torpedo tubes. The 15in thick main belt was mounted internally at an angle of 25 degrees, it was 470ft long and all the armour weighed 18,850 tons (37.1% of the displacement). This thinner belt was probably as effective as the 18in thick belt inclined at 10 degrees of the original design.
Design L3 1920
The L3 was the same length as the L2 but was around 1,000 tons lighter. Armament was 3x3 18in, 8x2 6in, 6x1 4.7in HA, 4x10 2pdr and two underwater 24.5in torpedo tubes. The 15in thick main belt was mounted internally at an angle of 25 degrees, it was 445ft long and the armour weighed 17,800 tons (36.3% of the displacement!).
Design M2 1920
Following on from the L2 and L3 designs came M2 and M3. M2 was 805 (wl) x 106 x 33ft and displaced 48,750 tons with 56,000shp for a speed of 23kts. Armament was 4x2 18in, 8x2 6in, 5x1 4.7in HA, 4x10 2pdr and two underwater 24.5in torpedo tubes. The 15in thick main belt was mounted internally at an angle of 25 degrees. The belt was 440ft long and the deck armour was 8-9in thick. The armour's total weight was 17,310 tons. The M designs introduced a novel layout, the aft engine layout reduced the length of the citadel to save weight (1,540 tons saved over the L2 for the belt alone). The engine rooms were ahead of the boiler rooms to reduce the rake of the shafts and possibly because the gearing would not have fitted aft. The firing arcs of the rear turrets were restricted to 60 degrees off the bow to 75 degrees forward of the stern. The blast effects from the 18in guns were expected to be severe. The unarmoured ends also posed problems as if they were riddled with gunfire the loss of stability would be severe. Both M2 and M3 were submitted in December 1920, but it would be M3 with triple turrets that would be selected for further design work to become the N3.
Design M3 1920
M3 was 765 (wl) x 106 x 33ft and displaced 46,000 tons with 56,000shp for a speed of 23.5kts. Armament was 3x3 18in, 8x2 6in, 5x1 4.7in HA, 4x10 2pdr and two underwater 24.5in torpedo tubes. The 15in thick main belt was mounted internally at an angle of 25 degrees. The belt was 401ft long and the deck armour was 8-9in thick. The armour's total weight was 16,060 tons The engines aft design had saved roughly 1,500-1,800 tons of armour over the L3 design. Both M2 and M3 were submitted in December 1920, but it was M3 which was selected for further design work to become the N3. Following experience with this design, it was planned to improve ammunition supply to the 6in guns (triple turrets were considered) and the slope on the citadel armoured end bulkheads would be eliminated.
Design N3 November 1921
The M3 design was further refined as the N3 at the end of 1921. N3 was 815 (wl) 820 (oa) x 106 x 33ft and displaced 48,500 tons with 56,000shp for a speed of 23kts. Armament was 3x3 18in, 8x2 6in, 6x1 4.7in HA, 4x10 2pdr and two underwater 24.5in torpedo tubes. Two aircraft would also be carried (I’ve left off the turret ramps as they would have been outdated when these ships completed and the blast issues would wreak havoc with them!). The new 18in guns were a new 45cal model, firing a 2,837lb shell at a MV of 2,837fps. The main belt was mounted internally at an angle of 18 degrees. It was 15in thick around the magazines and 13.5in around the machinery spaces. The citadel had 14in forward and 6in aft bulkheads. The upper deck was 8in thick, the lower deck 8in forward and 6in aft. The torpedo bulkheads were 2in thick. The barbettes were 15in thick while the turrets had 18in fronts, 14in sides and back and an 8in roof. The conning tower had 15in walls and 8in roof , 6in floor and 8in tube. The director hood had 6in armour and protective plating 1in thick was fitted to the 6in working spaces, bridges and DCTs. The Admiralty hoped to lay down four of these vessels during 1922 but financial pressures and the Washington Treaty prevented this from happening and the ships remained at the early design stage.
As stated in the introduction, the series of designs ran in reverse alphabet from K to G.
Design K2 1920
The K2 and K3 were battlecruiser versions of the L2 and L3. K2 was 875 (wl) x 106 x 33.5ft and displaced 53,100 tons with 144,000shp for a speed of 30kts. Armament was 4x2 18in, 8x2 6in, 4x1 4.7in HA 4x10 2pdr and two underwater 24.5in torpedo tubes. The 12in thick main belt was mounted internally at an angle of 25 degrees and the deck armour was 7-6in thick. The combined weight of armour and machinery was equal to the heavier armour but much smaller machinery fit of the L2. Machinery occupied 250ft of the hull length compared with 152ft in the L2. The 'Ks', like the 'Ls' were unsatisfactory, they were too big (indeed K2 has the greatest displacement and is the second longest of all the series) and it was felt they needed more protection and a 33kt speed to match the Lexingtons.
Design K3 1920
The K3 was the battlecruiser version of L3. K2 was 875 (wl) x 106 x 33ft and displaced 52,00 tons with 144,000shp for a speed of 30kts. Armament was 3x3 18in, 8x2 6in, 4x1 4.7in HA 4x10 2pdr and two underwater 24.5in torpedo tubes. The 12in thick main belt was mounted internally at an angle of 25 degrees and the deck armour was 7-6in thick.
Design J3 November 1920
The J3 was an attempt to develop a design comparable in size to Hood. J3 was 860 (oa) x 104 x 29ft and displaced 43,100 tons with 151,000shp for 32kts. Armament was 3x3 15in, 6x2 6in, 6x1 4.7in HA, 4x 2pdr pom-pom mounts and two underwater 24.5in torpedo tubes. J3 was the only design of this series to have an external belt, 12in thick and still inclined at 25 degrees and a single flat armoured deck of 4in. This was the last of the non-transom hull designs. The design was not successful, the 15in gun was considered too small, it was still 1-1.5kts slower than Lexington and the armour was only proof against 15in fire and the deck armour was poor.
Design I3 December 1920
The I3 was the battlecruiser version of M3. I3 was 925 (oa) x 108 x 33ft and displaced 51,750 tons with 180,000shp for 32.5kts.
Armament was 3x3 18in, 8x2 6in, 5x1 4.7in HA, 4x 2pdr pom-pom mounts and two underwater 24.5in torpedo tubes. Armour was a 12in thick belt angled at 12.5 degrees and 7-8 inches of deck armour. The space between the internal belt and the hull side was filled with sealed steel tubes designed to retain buoyancy in the event of a torpedo hit and to serve as a de-capping layer for APC shells. This was a long ship and could not have docked at Portsmouth or Rosyth (in fact was she the longest ever considered official RN design?). Even though the design was a fast M3, her machinery layout differed in having the engine rooms behind the boiler rooms and of course in having four shafts. The design, not surprisingly, was abandoned as being too large.
Design H3a December 1920
I3 was too large so three smaller designs were prepared as the H Series. H3a was the smallest. H3a was 850 x 105 x 33ft and displaced 52,000 tons with 180,000shp for 33.5kts.
Armament was 2x3 18in, 8x2 6in, 5x1 4.7in HA, 4x 2pdr pom-pom mounts and two underwater 24.5in torpedo tubes. Armour was a 14in thick belt angled at 12.5 degrees and 8-9 inches of deck armour (total armour weight 13,250 tons). H3a was basically the I3 with the aft turret removed, which did not seriously lessen the ship's capabilities because the arcs for X turret had been poor anyway.
Design H3b December 1920
This variant of the H series had both turrets raised, but reverted to the fore and midships turret layout. H3b was around 500 tons heavier than H3a and had 13,600 tons of armour. Speed was slightly slower at 33.25kts.
Design H3c December 1920
Very similar to H3b, except the turrets were one deck lower. H3b was 750 tons lighter than H3a and had 12,800 tons of armour. Her speed was highest at 33.75kts.
The end result of the battlecruiser evolution was the G3 Class. These were the end product of this impressive series of designs, taking their layout from I3 but with 16in guns. Sadly, Washington Treaty negotiations and the poor financial health of Britain at the time prevented their construction. The G3s were perhaps the finest battlecruiser designs ever prepared.
Design G3 Initial Design 1921
Design G3 Final Design February 1921
The final design of the battlecruiser sequence, G3 was a development of the H3 series and the most impressive. A high metracentric height was designed in to allow G3 to remain stable with her spaces outside the citadel riddled with battle damage.
Displacement: 48,400 tons; dimensions 850ft (wl) length, 106ft beam, 32ft 6ins draught. Machinery 160,000shp for 32kts. Calculations showed 32kts just possible but the powerplant had been squeezed in the and the aft lines alerted causing a 7.5% performance penalty, later reduced to 4% from further Haslar tank tests, but 32kts might have been narrowly missed. Fitting a 180,000shp plant was briefly considered, it would have increased length by 25ft and only provided 0.5kt improvement.
Armament: three triple 16in turrets, eight twin 6in turrets, six single 4.7in HA, four multiple pom-pom mounts (10 or 8-barellled though the official plans show four 6-barelled experimental mounts), four 3pdr saluting guns, two submerged 24.5in torpedo tubes (6 torpedoes each, oxygen enrichment equipment would also be fitted). Each weapon system had director fire (two main director control towers, four 6in director control towers, one HA director control tower, one HA rangefinder, four pom-pom directors, two torpedo rangefinders and one conning tower rangefinder). The DNC wanted the torpedo tubes removed but was overruled. Two aircraft could have been carried on B and X turrets but no final decision was made.
Armour: main belt 14in inclined at 18 degrees (reduced from 25 degrees on the initial G3 design); 8-4in deck armour, 4in over machinery spaces (increased from 3in on the initial design), 8in with 9in slopes over the magazines and fwd and middle boiler rooms, 7in over aft 6in magazine and half of after engine room. The changes added 1,125 tons but savings elsewhere reduced the additional weight to 710 tons. The torpedo protection could withstand a 750lb charge, increasing the system to withstand 1,000lb would have increased the size of the ship too much.
The Legend was approved in August 1921 and four ships were ordered on 26 October from Beardmore, John Brown, Fairfield and Swan Hunter but almost immediately halted by a Cabinet order and then in February 1922 cancelled due to the Washington Treaty. It remains speculation if the order was serious or just a bargaining chip for the Washington talks, although it seems the Admiralty were keen to have them and still desired new battlecruisers though Britain was in a financial crisis and it seems unlikely they (or at least all) would have been completed. Names were never finalised and quoted names in several sources are speculative. From several viewpoints in term of armament and armour the G3 surpassed even later designs excepting the Yamato and even the Iowa (in terms of armour at least in this case). While the Japanese and Americans had developed the Amagi, Kii and Lexington to counter the Admirals, the RN had moved on further and the G3s made everything else under consideration at that time look obsolete. Their novel design was probably flawed given blast concerns with X turret given the experience of damage to Nelson and Rodney whenever they fired abaft of their beam with their forward turrets. However, in terms of fire control, turreted secondaries, extensive AA armament and their internal belt and torpedo protection systems they were far superior to any other design then under consideration. Anthony Preston Conway’s makes an interesting statement in comparing the development from Dreadnought to G3 in just over a decade.
Design F2 November 1921
With the Washington Treaty imposing its 35,000 tons standard displacement cap, the Admiralty looked at two sets of new ships to meet this new limit, the F2 and F3 battlecruisers and the O3 battleship, which eventually became the Nelson Class. The two Fs had a new 15in/50 gun which freed weight to match the armour scheme of the O3 and attain a speed of 30kts. The F2 had three twin turrets.
F2 was 760 (oa) x 106 x 28ft 6ins and displaced 35,000 tons. The machinery was rated at 112,000shp for 30kts(light, 29.5kts deep).
Armament was 3x2 15in, 4x2 & 4x1 6in, 4x 2pdr pom-pom mounts and two underwater 24.5in torpedo tubes. The internal belt was 12in thick over machinery spaces and 13in over magazines belt angled at 72.5 degrees, deck armour 7in over magazines and 3.25 in over machinery spaces, barbettes 13in and turrets 16-7in. The armour totaled 10,210 tons.
Design F3 November 1921
F3 carried a heavier main battery with three triple turrets but sacrificed some secondary guns to reduce weight and some armour and speed to keep within the Treaty limit.
F3 was 740 (oa) x 106 x 28ft 6ins and displaced 35,000 tons. The machinery was rated at 96,000shp for 29kts(light, 28.5kts deep).
Armament was 3x2 15in, 4x2 6in, 4x 2pdr pom-pom mounts and two underwater 24.5in torpedo tubes. The internal belt was 12in thick over machinery spaces and 13in over magazines belt angled at 72.5 degrees, deck armour 7in over magazines and 3.25 in over machinery spaces, barbettes 13in and turrets 16-7in. The armour totaled 9,970 tons.
O3, P3, Q3 - Nelson Class Preliminaries
Mini-Nelsons - The Geneva Battleships
The ten year break in the Washington Treaty would end in 1931 and the four Iron Dukes would be scrapped in 1934 and replacements would be required. The accounts of Raven and Roberts and D.K. Brown among others state that no battleship designs appeared until 1927. However Smurf's research has found a requirement and a sketch design drawn up at the end of 1926, one which seems to have matured as the 1927 Battleship which was featured in Ravens and Robert's detailed account.
At the June 1927 Geneva Conference, the British delegation hoped to persuade the other nations to limit battleships to 28,500 tons displacement and 14in calibre guns. These thoughts came from the ideals to save costs by making smaller battleships.
28,000 Ton Design November 1926
The 1926 requirement called for a battleship armed with 4x212in turrets. No drawing has been found for this design, probably it was discarded in favour of the slightly more powerful 3x3 12in mini-Nelson design shown above. However, it is possible that just as the 1927 20,800 ton 14in design is an identical design, that the 29,200 ton 4x2 14in 1927 design had roots from this earlier 1926 ship. As far as I know, this design has never been published or drawn before.
The mini-Nelson design had an angled internal belt 13in thick over the magazines and 12in thick over the machinery spaces. Deck armour being 6.75in thick over the magazines and 6.25in over machinery spaces. Secondary armour was 6x2 6in, 8x1 4.7in and 2x pom-pom mounts plus 2x 24.5in torpedo tubes and 2 aircraft.
28,000 Ton Design January 1927
The 28,000 ton 1927 Battleship was almost identical, except the main armament was now a 14in gun (some documents state 13.5in but the calibre was always intended as 14in) and the forward 4.7in HA mounts moved aft and two extra pom-pom mounting fitted. The armour comprised an angled internal belt 12in thick over magazines and 10in over machinery, 6.5in thick deck over magazines tapering to 4.5in over the machinery spaces. Barbettes 12in and turrets 14-6.5in thick. The machinery produced 45,000hp for 23.25kts speed. Length 630 ft (wl) x 100 ft x 33 ft (deep), standard displacement 28,000 tons.
29,200 Ton Design June 1927
The 29,200 ton 1927 Battleship was identical in armament except for having 4x2 14in turrets, only 2 pom-poms and revised layout. All other specs were identical except for being 30ft longer and standard displacement of 29,200 tons.
34,800 ton Design 16A, 1928
Please see Charguizard's post for details: http://shipbucket.com/forums/viewtopic. ... 80#p179904
Many thanks to Smurf for research material to enable these to be drawn.