Clydebank Battlecruisers. Ian Johnston

office work reveals that most of the structural work for the hull went to Armstrong Whitworth, with most of the work associated with the armour going to Fairfield.

      With orders now formally placed, in January, Fairfield wrote to the Controller requesting information on the ship’s scheme of complement as ‘so much depends on this’. Admiralty response was to provide Fairfield with a full list of the ships complement.

      Once drawing office work began, drawings could be made available to the mould loft to enable the ship’s lines to be laid off in full size. Wooden templates taken from these lines were then transferred to the platers’ shed where the first steel plates could be prepared for keel laying. At the same time, the building berth was made ready by ship-wrights, who carefully and accurately aligned massive baulks of pitch pine to the correct declivity ready to receive the keel plates. Inflexible was the first of the class to be laid down. The laying-down dates of the three ships were:

Inflexible	5 February 1906
Indomitable	1 March 1906
Invincible	2 April 1906

      A detailed month-by-month account of progress based on reports made at Clydebank is given at the end of this section. However, the following notes, covering some of the more salient issues, give a fuller view of activity in the yard and elsewhere.

      Throughout the building period, there was a constant flow of information, usually by letter, from the shipbuilder to the Admiralty and vice versa. When the matter was urgent, communication was by telegram. The following examples provide some indication of the traffic that passed between the Admiralty, shipbuilder and other contractors. In January 1906 it was agreed that Fairfield should be allowed, at their request, to use 24ft-long steel plates for the forecastle. In November, Armstrongs and Vickers, the main armament manufacturers, were advised that henceforth main armament wing turrets were to be referred to as ‘P’ and ‘Q’, as gun trials on Dreadnought had proved that ‘B’ and ‘C’, as they were originally named, caused confusion because of the similar sound these letters made. In December 1906, when a mock-up of the anchor and hawse pipe arrangement on Indomitable gave cause for concern under trial, a better solution was observed on the Cunard liner Lusitania, then fitting-out at Clydebank. It was agreed by the Admiralty overseers that this arrangement should be used on Inflexible and Indomitable. In February 1907, Engineer Commander F D Thomsett RN, was ‘directed to inspect during the fitting on board, the machinery and boilers of HMS Invincible at the works of Sir W G Armstrong Whitworth & Co Ltd, Newcastle on Tyne. Mr W Vick, Boiler Overseer, to assist in connection with the boilers’.

      The three Invincible class ships were launched (in chronological order):

Indomitable	16 March 1907
Invincible	13 April 1907
Inflexible	26 June 1907

      On 25 March 1907, the Hull Overseer at Fairfield observed the water testing of No 1 boiler room on Indomitable noting that, ‘When flooded to 5 feet above the load water line, one stay in the starboard wing bunker bent under compression and others showed indications of bending. The transverse bulkheads at [stations] 55 and 81 deflected very little under the full head of water. The water was not out of the compartment on Saturday to enable a complete record to be made of the permanent deflections, but as far as could be judged, it is anticipated that they will be insignificant.’ The solution was to change the flanged plate method of connection to that used in Inflexible, i.e., plate and angle brackets, as no failure was observed in a similar test on board that ship.

      On 5 July 1907, an inclining experiment, conducted to calculate the ship’s centre of gravity and thus her stability, was carried out on Indomitable in the fitting-out basin at the Fairfield Works. To do this, the ship was held by two hawsers, one at the bow and one at the stern. One hundred tons of ballast was ‘spread over 70 feet’ and two 15ft-long pendulums were positioned one forward and one aft. ‘During the reading, the men on board were stationed at the middle line. The ship was free of water but a considerable amount of lumber and plant was on board.’

      The main armament mountings for Invincible (electric) and Indomitable (hydraulic) were both manufactured by Armstrongs at Elswick. In late July, the first of Inflexible’s main armament mountings arrived at Clydebank by ship from Vickers ordnance works at Barrow. These complex and heavy components were carefully lifted out of the specially-prepared coaster and placed on the quay of the fitting-out basin. With a maximum lift of 150 tons available at the fitting-out basin, manufacturers such as Vickers and Armstrong had to plan for this while these mountings were under construction.

      Inflexible’s hydraulic gun trials, where the mechanisms were operated but the guns not fired, took place on 14 May 1908 in the shipbuilder’s fitting-out basin and were found to be generally satisfactory. Full gun trials were carried out on 18 June 1908 off the Isle of Wight under the supervision of the Shore Establishment HMS Excellent. Despite finding the trials to be generally satisfactory, criticism was levelled at Vickers as the excerpt from the first page of the report indicates.

      The following were incomplete and could therefore not be tested at Gun Trials. It is important that these should be completed before the Final Gunnery Inspection takes place, and when possible in future before Gun Trials.

      Fire control installation

      Kilroy’s Bias and Danger Signals

      Alternative wash out system for turrets (shipbuilder’s part)

      Blast screens for 4-inch guns crews on A and X turrets.

      It must be remarked that the erection and care and maintenance since erection, of the 12-inch mountings, as in the case of the Agamemnon, compares unfavourably with mountings erected by Messrs Armstrong, as for instance in Indomitable. Many simple adjustments, among others, some which were pointed out to Messrs Vickers’ representatives at the preliminary hydraulic trials on the 12 May were still incorrect at Gun Drills and Trials, such as run out cut off, fouling of sights against the armour, etc, and it is considered that more attention in this respect should be paid by Messrs Vickers.

      A marked feature of the trials was the poor training control. The creep is not at all good; the movement is jerky; the turrets do not start or stop with precision, the reversal of direction of training is erratic.

      Invincible’s full power trials were carried out on the Polperro measured course on 7 November 1908 and returned 46,500shp at 295 revolutions for a speed of 26.64 knots and her gun trials on 30 October 1908.

      In October 1908, the DNC wrote to the E-in-C to advise him on the differences between Babcock & Wilcox boilers fitted in Indomitable and the Yarrow type in Inflexible. The total weight of the machinery installation for Indomitable was 3166 tons and 3047 for Inflexible a difference of 151 tons in favour of Yarrow which, the DNC noted, was greater than had been anticipated. The Ship’s Cover quotes the estimated original and actual costs of the three ships as follows:

      Another pre-launch view of Inflexible showing the forward poppet on the starboard bow. This is one of four poppets that will keep the hull upright during the launching run. Drag chains have been neatly arranged on the ground beside the hull to slow the ship once in the water. Notice the starboard underwater torpedo tubes visible immediately behind the poppet. In the right foreground the launching platform has been erected and the area fenced off in preparation for the thousands who will come to witness the launch.

      (NRS UCS1-118-374-11)

      A detail of Inflexible’s stern showing rudders, propellers, shafts and cast steel shaft brackets.

      (NRS UCS1-118-374-15)