Britannia Waives the Rules
Few believed that it would be possible to fit a combination of a useful armament, a high speed and any level of adequate armour onto a 23,000-ton ship, but they reckoned without Charles Coles, the Deputy Director of Naval Construction. He had come up through the design office during the Fisher years and had seen the successes and failures of war. He also came from a family of engineers and could perhaps see a little more widely than many of his colleagues what was and wasn’t possible, both mechanically and industrially.
The concept of a light battleship had met with extreme scepticism at the Admiralty, but Coles’ persistence and the specifications of the ships he ultimately presented assisted in changing their minds. The fact that the RN could sustain its numerical advantage by building five ‘light battleships’ using just two years’ Treaty allocation was also attractive.
When they saw that each of these new ships was quite capable of menacing a ‘proper battleship’, and that Coles had practically re-invented the battlecruiser, their minds were soon made up.
Even so, there were still hurdles in the way.
It proved impossible to fit nine guns in three identical turrets. A reduction in calibre, either to 13.5” or 14” was considered, and alternatively, an outline design featuring six heavy guns in twin turrets was prepared, permitting an increase in both speed and armour. However, mounting a lighter armament meant these expensive ships might not be able to challenge the latest battleships, while long-standing preferences and fire-control considerations suggested a minimum of eight guns.
It was therefore decided to fit eight, by using one twin turret in place of a triple. The largest weight savings could be made by fitting this in ‘B’ position, reducing the diameter of the longest barbette and giving the greatest benefit to topweight.
By the spring of 1925, Coles and his designers had a ship of 728’, with a transom stern and a beam of 93’ 6”, and they were optimistic that it could meet the tonnage limit. However, design calculations at that time showed an estimated Standard Displacement of 24,640 tons.
Further savings had to be made, and the most radical piece of redesign was a decision to fit the outer part of the bulge and the torpedo bulkhead after construction was completed (and therefore justifying these weights as a separate, legitimate increase in torpedo protection). After some allowances, this removed 1,100 tons from the Standard Displacement and transferred it to the additional 3,000 tons that were allowable under the Treaty. A further 210 tons was transferred by arranging to fit the rotating disk of armour deck inside the barbettes at the same time as the turret roofs.
Subdivision of unarmoured spaces and the machinery was to be as extensive as possible, as underwater protection was necessarily limited. Unlike the more capable torpedo protection systems of the latest battleships, the objective of the system was to try to ensure the survival of the ship, but not necessarily its survival as an effective fighting unit.
Even with the ‘outer bulge’ fitted, the system would never be more than 13’ deep, and in most places, it was just 10-11’. The boilers sat three-abreast and the rooms ran out to the torpedo bulkhead, leaving no room for a coffer dam behind. This reduced the effectiveness of the torpedo protection, and so Coles did his best to compensate by putting each set of three boilers in a separate room, making four boiler rooms. These would be further split up by using a machinery space and the secondary magazine to separate two pairs of rooms, making it highly unlikely that a single torpedo hit could disable all the boilers.
Above decks, the twin turret would be a cut-down version of the triple, with the centre gun removed. In addition to improvements elsewhere in the ship, the weight saved helped to allow a 36’ rangefinder and an auxiliary fire-control position to be fitted into the rear of B-turret.
Just 40 rounds-per-gun would be included in the legend, as it was found that no RN Captain would hesitate to engage with such a level of ammunition available. However, even when the magazines were full, they could only contain 68-rpg for the aft guns, and 81-rpg for the forward guns; another sacrifice in such a compact ship.
As built, the ships would have just four secondary guns, each of 4” calibre. A further eight 4” anti-aircraft guns and a director system would be fitted after completion, with all the guns in new twin mounts that would be capable of both high and low angle fire. A dozen 1-pdr machine cannons would complete the AA fit.
Barbettes stayed at 5” and 3” inside the hull, but were reduced to 3” and 2” over the innermost 90-degree arc where they were shielded by the hull and superstructure. A few tons were saved by thinning engine room bulkheads in favour of deck armour, and the lower deck over the steering gear was reduced to 3”. Thanks to more detailed calculations, 50 tons could be taken out of the hull, allowing splinter protection to be added to the aft DCT. The forward unit had 6” armour protection for both itself and its communication tube down to the armour deck, and all other communication lines were duplicated.
By the beginning of June 1925, designers had reached a Standard displacement of 22,895 tons, permitting a modest Board Margin of 100 tons. Heavier-than-expected turret machinery and the appropriation of 12 tons for splinter protection around the bridge used up half of this within weeks.
Approximately 2,440 tons was scheduled to be added at the ships’ first refit, which would nominally happen after the first sea trials.
This including the additional 5.5” armour for the turrets roofs, 1.5” blast-proof plating for the foc’sle deck around the guns, and teak deck planking amidships (all justified as providing additional protection against air attack). A 1½” torpedo bulkhead would be added inboard of the double hull as the bulge was being fitted, as the armour plates could be fitted through the gaps in the hull that would be available during the process of fitting the outer bulge.
With these and the additions in ammunition and other equipment, true Standard Displacement was 25,865 tons, and Deep Load was 30,905 tons.
-o-
The 10th February 1927 was an icy day, but in Portsmouth and on the Clyde, two handover ceremonies took place. HMS
Fisher and
Indomitable were formally delivered to the Navy, and within another three months, their sisters
Invincible, Indefatigable and
Anson were handed over.
Their eight 16” Mk.2* guns could challenge anything afloat, and their armour would keep enemy 16” shells out of the magazines at longer battle ranges. With a design speed of 32 knots at normal load, they could catch almost anything afloat.
Anson’s performance was typical of the group; on trials she achieved 31.99 knots at 29,310 tons, with 134,600shp. The only ship that was pushed was
Invincible, making 32.82 knots on trial, but at just 27,850 tons, and by forcing the machinery up to 140,600 shp.
Just as importantly, they could reach 30 knots, even when close to Deep Load and a few months out of dock.
The Admiralty knew they would be tricky ships for any foreign power to counter. On that cold winter’s day, there were more than a few who wondered, with a wry smile, whether ships such as
Fisher would supplant the battleship, just as Admiral Fisher himself had once predicted.
HMS
Fisher as refitted in 1928.