DREADNOUGHT
Outboard and inboard profiles, 1906
A note concerning the reduction of the armour protection on the turrets is worthy of mention. Captain Jellicoe told the Committee that, although a thickness of 11in or 12in was quite sufficient to keep shells out, it had never been tested to see whether or not the actual turret mechanism could withstand the shock of a direct hit; he felt there was little need to increase the thicknesses, but suggested that an all-round reduction could be made.
The torpedo net defence was devised by Captain Bacon, and was the most elaborate and complete system fitted to a warship to that date, yet needed only two or three minutes to drop the nets from a stowed position. The net defence ran for three-quarters of the length of the ship along the upper deck level.
Machinery
The original proposals for the new ship was that she be fitted with reciprocating engines, although the obvious advantages in efficiency and economy of turbines were well known, but whether or not it was practicable to fit them to such a large vessel was debatable. It was estimated that with reciprocating engines and earlier hull forms of equal fullness, about 20,000 tons displacement and 30,000 SHP would have been required for the 21 knots asked for in the initial design. The first four designs all had reciprocating engines, turbines appearing in designs after this, with comparisons of both turbines and reciprocating machinery in the same basic layouts. The main difficulty in fitting turbines to the new vessel was her size, and it was debated whether or not she would have adequate stopping, turning and astern power for rapid manoeuvring under all conditions.
In January and February 1905, comparative trials were carried out between the Gem-class cruisers Amethyst (turbines) and Sapphire (reciprocating), and the River-class destroyers Eden (turbines) and Waveney (reciprocating). Throughout the trials it was seen that the most satisfactory results came from the ships with turbine propulsion, and it was found that to secure the requisite stopping and astern power one turbine needed to be fitted to each shaft, which afforded greater astern power than in any previous machinery.
The principal advantages of having turbines fitted in Dreadnought were:
1. Substantial saving in weight, space and cost compared with reciprocating plant.
2. Smoother running, easier operation and reduced engine room complement.
3. Economy in fuel at high powers.
4. Reduced risk of damage in action because of machinery being fitted lower in the hull.
5. Increase in ship’s handiness because of using four propellers instead of two; the wing shafts being farther off the centreline.
DREADNOUGHT: STEAM TRIALS 1906
Preliminary steam speed trials were held off the Isle of Wight 1–9 October 1906. Winds of Force 3–4 and Strength 2 seas prevailed throughout. The ship had left dock after hull inspection on 28 September, so her bottom was clean.
Draught: 25ft 6in forward, 27ft 1½in aft
Steam pressure: 241 psi boilers, 221psi engine room
Shaft revolutions: 321 starboard outer, 337 starboard inner, 321 port outer, 333 port inner
Mean revolutions: 328.4 on all shafts
Pitch of propellers: 8ft 4½in
During the 8-hour full power trials, 12,225shp was developed by starboard engines, 12,487shp by port. A total of 24,712shp gave a mean speed of 21.05 knots
A total of 134 tons of best, handpicked Welsh coal was used throughout
Feedwater temperature: 70°F starboard, 66°F port Various speeds were achieved on the measured mile runs, the following figures being logged: 21.78; 21.45; 21.78; 21.39 knots.
Dreadnought coaling on a Saturday afternoon late in 1906, just outside Portsmouth Harbour.
The installation in Dreadnought was: the high pressure (HP) turbines were fitted on the wing shafts, the low pressure (LP) on the inner shafts. These inner shafts were also fitted with cruising turbines. There was one HP ahead and one HP astern on each wing shaft, plus one LP ahead and one LP astern on the inner shaft. The steam for low power was passed from the boiler into the cruising turbines and thence to the HP wing turbines, before returning to the LP turbines and finally into the condensers.
On trials of the completed ship it was seen that the continuous seagoing speed was greater than that of Lord Nelson, but at low speeds Dreadnought’s radius was less. This was because at speeds of 10–12 knots, Dreadnought was using her cruising turbines which proved troublesome, a feature which could not have been foreseen; fuel consumption of the cruising turbines was extremely high and after Dreadnought they were not fitted. In all other respects, the turbines fulfilled expectations; there was much less vibration in the ship and noise was considerably reduced. As the first turbine-driven battleship completed for any navy (the Japanese Aki, begun seven months before Dreadnought, was the first turbine-engined battleship laid down, but was not completed until 1911), Dreadnought proved a successful innovation in design and, together with improved hull lines, gave a speed of more than three knots higher than preceding classes without excessive rise of displacement or cost.
Other Features
The rig details, fire control and boat arrangements were worked out by Captains Bacon, Jackson and Jellicoe. The problem of reducing vibration to a minimum for fire-control purposes received particular attention. Nine alternative proposals for cranes or gallows for boats were submitted, one of which embodied a mast, of light girder construction, which did not require stays. The final proposal, which was accepted, was for a tripod mast, this being considered safe, strong and easy to construct. The tripod mast had first appeared in the Royal Navy in the 1860s in the rigged turret ships Wyvern and Captain, as a means of eliminating shrouds which had always considerably restricted arcs of fire. It was reintroduced in Lord Nelson in 1904, although only on the mainmast which needed adequate support for the main derrick. The position for the tripod mast in Dreadnought, close abaft the fore funnel, was selected in the belief that smoke and fumes would be carried away from the control top, but this did not prove to be the case and was one of the design’s weak points.
The reversed forward rake of the tripod legs was so designed to enable the boat derrick to swing well outboard without hindrance. The alternative possibility of a tripod mainmast with derrick does not seem to have been considered at that date. No mainmast was originally proposed for Dreadnought, although subsequently it was considered necessary to have some kind of after control top which could also be used as a spreader for the wireless aerials. The small baby tripod, finally fitted in Dreadnought, was greatly criticized in service as being too low and of little use for anything except perhaps the W/T lines. It was never repeated after Dreadnought.
The design of the superstructure, which was broken up by the amidships turret, was entrusted to the same three Captains. Boat stowage was located between the funnels, and the main derrick handled the heavy steam launches and larger pinnaces. There was also a pair of long topping davits fitted on each side of the forward superstructure for the smaller