The Development of Navies During the Last Half-Century/Chapter 7
ARMOUR — LATER TURRET SHIPS
Early Iron Plates—Increased Thickness—Competition of Guns and Armour—Steel and Compound Plates supersede Iron—Deck and Coal Protection—Progress of Turret Ships 'Nile,' 'Trafalgar' and 'Hood,' 'Victoria' and 'Sanspareil'—Second-Class Battle Ships Early Types—Latest Development—'Centurion' and 'Barfleur.'
In describing the 'Inflexible' I have stated that her turrets were protected with compound armour instead of the wrought-iron plates which up to that time had been employed. As the struggle between steel and compound plates has for some years been almost as keen as that between guns and armour, a brief history of this portion of our subject seems here desirable.
I have read that about thirty years ago the present Sir John Brown happened to be at Toulon and saw the new French ironclad 'La Gloire.' Her plates were 5 ft. long, 2 ft. wide, and 4½ in. thick. They had been hammered to these dimensions, as were all the plates of the early American monitors. Mr Brown—as he then was—came to the conclusion that such plates could be rolled, and on his return to England instituted a series of experiments which fully bore out this view. When it was decided to put 4½ in. of iron on the 'Warrior,' rolled plates of this thickness were manufactured without difficulty. In 1861 a target representing a section of the 'Warrior,' and consisting of a 4½-in. iron plate, with 18 in. of teak backing, and an inner iron skin ¾ in. thick, was fired at with a Whitworth rifled gun throwing a flat-headed steel bolt of 80 lbs. The target was indented and cracked, but not perforated.
In 1862 Mr Brown was able to roll at his works at Sheffield, in the presence of Lord Palmerston, an iron plate 18 ft. long, 4 ft. wide, and 5½ in. thick. The following year, when the Lords of the Admiralty visited his works, at the opening of a new rolling mill, the energetic manufacturer showed that plates up to a thickness of 12 in. could be produced.
From that time there was no difficulty in supplying the increased protection demanded for the new ironclad navy, till in the 'Dreadnought' we placed on the hull and turrets plates 14 in. thick. Though the water line amidships of the 'Inflexible' has 24 in. of iron, it is not in one but two plates, each 12 in. thick, with a layer of wood between them.
But already there were indications that no increase in the thickness of wrought-iron plates would suffice to resist the growing energy of the gun. As early as 1869 a Krupp gun of 11 in. calibre had perforated 12 in. of iron and 36 in. of wood. Our own 38-ton gun pierced 19 in. of iron in 1876, and the following year the 80-ton gun sent its projectile through three 8-in. iron plates. In the meantime Mr Schneider had been developing at Creusot, in France, the manufacture of steel plates, and some experiments at Spezzia, in Italy, showed the softness of wrought-iron as compared with steel. The latter resisted penetration to a much greater extent, though it had a tendency to break up when attacked by numerous comparatively light projectiles. From this moment plates composed entirely of wrought-iron were doomed. The manufacturers of them in this country—Messrs Brown and Messrs Cammell—then proposed compound armour. In Cammell's method—which is according to Wilson's patent—a wrought-iron plate is put into a box, placed in a vertical position, and liquid steel poured in between one side of the plate and the side of the box. The composite plate thus made is then rolled, by which process the steel face is hardened and made to adhere rigidly to the wrought-iron foundation. In Brown's method—which is according to Ellis's patent—instead of a box, a thin steel plate is placed at the required distance from the iron plate and the melted steel poured in between the two, making the whole a solid mass. It is then reheated and passed through the rolling mill. In both systems the steel face is about one-third the total thickness. In 1877 experiments with compound armour plates showed their superiority to wrought-iron, and consequently it was decided to place them on the 'Inflexible's' turrets. In 1880 a compound plate made by Messrs Cammell, in which the steel face was 5 in. and the wrought-iron back 13 in. thick, was fired at by the 38-ton gun, with a Palliser chilled shot, the result being that the projectile broke up on impact with the plate, and effected no damage beyond slight indentation and surface cracking. It was then evident that steel projectiles would henceforth be necessary to attack hard armour.
From that time up to the present the competition has been between the compound plates and all-steel plates. The latter resist perforation better, while the harder surface of the former is more effective in breaking projectiles, and causing them to glance off if struck at an angle. For very thick armour we have therefore adhered to compound plates, employing steel plates where only a few inches are required. France has hitherto produced the best all-steel plates, but a demand for such an article could no doubt be met by our own manufacturers. Already Messrs Vickers have made steel plates which have behaved most satisfactorily under severe tests. Steel is continually being improved, and its resistance to perforation increased by the admixture of small quantities of nickel, manganese, or other substance. The original object of armour being to keep out projectiles, I believe we shall soon adopt that material which shows a marked superiority in this respect, and steel plates appear to me to be winning the day. If the projectiles hold together—and those of modern steel make appear to stand impact well—it stands to reason that the medium they have to pass through should, from front to rear, offer a strenuous resistance. When the face of a compound plate is pierced, the remainder is no great obstacle to an uninjured projectile having a considerable amount of unexpended energy.
Twenty years ago we commenced experiments against iron plates 1½ in. thick on 6 in, of wood. The target thus formed was placed at a small angle from the horizontal, and fired at with a 9-inch projectile. The protection was insufficient, but succeeding experiments have led to decks of steel 3 in. thick being placed over the submerged portions of vessels. The sides of this armoured deck usually slope down to a short distance below the water line, and are given an additional thickness. This portion of the armoured deck of the 'Blake' and 'Blenheim' is 6 in. thick. Advocates of internal armour urge that, for a given weight, more complete protection can be afforded if disposed in this way than if placed externally on the hull.
Later on experiments were instituted to ascertain what effect masses of coal would have in stopping projectiles, and if it could be ignited by shell. It was found that 20 ft. of coal would stop a 6-in. shot at a short range, and 30 ft. an 8-in. shot, but this would hardly hold good with later guns and steel projectiles. The explosion of common shell did not set the coal on fire.
But this latter result only applies to coal in confined spaces. If placed between decks, it will be more readily ignited. I believe at the battle of Lissa the 'Palestro' was destroyed in this way. Her captain, impressed with the necessity of not running short of fuel, had placed a quantity of coal outside the battery. During the action with the Austrian Squadron a shell exploded in the heap and set it on fire. The occurrence appears to have been unheeded at the time, or the crew were too busy with their guns to be called off. When they did endeavour to extinguish the fire, it had gone too far, and while they were thus employed the ship blew up. Few of the crew escaped, but I have been told by an officer, who took part in the action in another ship, that this mass of coal was over a magazine, and it is believed that the intervening deck was burnt through until suddenly a flaming mass of coal fell into the magazine. This seems a reasonable explanation, as the explosion was unexpected, or preparation would have been made to abandon the ship. This occurrence shows the danger of carrying extra coal about the decks. It appears to me unwise, also, to place reliance on protection from coal when stowed in its proper place. If it is not to be used, why employ it in preference to armour? When consumed in the legitimate way, which circumstances may render necessary, a vulnerable part of the ship may be exposed to an enemy whom this fuel has assisted the ship to overtake, or from whom it has not sufficed to make escape possible.
The disposition of armour and armament adopted in the 'Inflexible' was followed in only four other vessels, the 'Ajax,' 'Agamemnon,' 'Colossus,' and 'Edinburgh.' It was considered that smaller battle ships on the same design would be useful additions to the fleet. The first two named have a displacement of 8700 tons, and carry in each turret two 38-ton guns, while the maximum thickness of their armour is 18 in. Being only 280 ft. long, with a beam of 66 ft, their speed is moderate, and for a long time difficulty was experienced in steering them. The 'Colossus' and 'Edinburgh' were great improvements. By increasing the length to 325 ft., and the displacement to 9500 tons, a speed of over 15 knots was obtained. Their turrets are armed with 45-ton breech-loaders instead of the old guns, and steel instead of iron is mostly used in the construction of the ships.
But naval officers did not approve the departure from the 'Dreadnought' type. The advantages of placing the turrets en echelon were more fanciful than real, and consequently, when after a lapse of some years there was a return to double-turret ships, an improved 'Dreadnought' design was decided upon. The 'Trafalgar' and 'Nile' represent this reaction, and as they have not long been completed it is evident the interval was considerable.
These ships are approximately the same size as the 'Inflexible,' viz., 12,000 tons at load draught. They have a central citadel, containing the two turrets, placed on the middle line, as in the 'Dreadnought' Each turret contains two 67-ton guns. Between the turrets, and above the citadel, are mounted eight 45-pounder guns in a battery, thus giving an auxiliary armament which had not been provided in the earlier turret ships. The length of the 'Nile' and 'Trafalgar' is 340 ft., of which 230 ft. is protected at the water line with compound armour, varying in thickness from 16 to 20 in. The turrets are covered with similar armour, 18 in. thick. Machinery of 12,000 horse power gives these vessels a speed of 16 knots. Compared with the 'Inflexible,' they represent a considerable advance in every detail, and are powerful fighting ships. Their only defect, to my mind—independent of the size and cost—is that the guns are not carried sufficiently high above the water, and for this reason I have always preferred the barbette system. The turret ship 'Hood,' now building, is more than 2000 tons larger than the 'Trafalgar,' and represents what appears to be the final development of this system, which originated in the cupola ship of Captain Coles. The 'Hood' is of similar dimensions to the seven first-class barbette ships of the 'Royal Sovereign' type, and only differs in having her heavy guns mounted in turrets instead of en barbette. It remains to be seen which of the two plans will be followed in future designs.
Though the general opinion in the navy has been always in favour of double turrets, especially in vessels of large dimensions, sufficient success in the production of single-turreted ironclads, as exemplified in the 'Rupert' and 'Conqueror,' led to a further extension of this principle in two later ironclads, the 'Victoria' and 'Sanspareil,' now complete. The former was built by Sir William Armstrong's firm at Elswick, and perhaps is the only instance of a first-class battle ship being supplied with the whole of her equipment from a private yard. She has a length of 340 ft., a breadth of 70 ft., and displaces 10,500 tons. In a single turret forward, protected with 18 in. of compound armour, she carries two 110-ton guns. In order to supply the deficiency of stern fire, which the single turret forward entails, the 'Victoria' and her sister have a 29-ton gun mounted aft, working behind a barbette shield. The protection afforded by this arrangement is not great, but considerations of weight doubtless prevented more being done in this respect. To make up for this restriction of the principal armament to three heavy guns, she carries amidships a battery of twelve 6-in. guns and numerous machine guns. Machinery of 14,000 horse power gives these vessels a speed of 16 knots, so that in every respect they show a marked superiority to the 'Conqueror' and 'Hero.' They are the only British ships in which a pair of 110-ton guns are mounted side by side; in the 'Benbow' one of these monsters is placed at each end. The first-class battle ships of to-day thus indicate a variety of ideas concerning offensive and defensive capacity, and a conflict of opinions as to the best disposition of armour and armament. We seem, however, to be approaching the time when experience with these divergent types will enable us to select the best points in each, and combine them in some type which shall finally fill the place of the old three-decker. Whether it will prove equally durable, he who deals with the development of navies half a century hence can alone record.The two-decker also had her counterpart in the small ironclads built or converted between 1860 and 1870. Those of about 6000 tons and under were usually termed second class. For a country which has important interests in every part of the world, useful service can always be found for vessels of these dimensions.
There were six ships of the same type which for many years carried our flag in the China and Pacific seas. These were the 'Audacious,' 'Invincible,' 'Iron Duke,' 'Swiftsure,' 'Triumph,' and 'Vanguard.' The career of the latter was cut short by sinking, after collision with a consort, in the Irish Channel. None of them exceeded 6500 tons displacement, but they carried a powerful battery of guns and 8 in. of armour at the water line. They were, besides, roomy and comfortable vessels, so that, until left behind by the wonderful advance in engines and armament after their completion, they proved admirably adapted for foreign service. They were succeeded by the armoured cruiser in this duty, and therefore the demand for ironclad battle ships of moderate size diminished.
But under the Naval Defence Act two so-called battle ships of the second class are being constructed, to be named 'Centurion' and 'Barfleur.' The length to which we have gone in adding to the size of all classes is strikingly illustrated in this pair. Their displacement is to be no less than 10,600 tons, which will enable them to combine four 29-ton guns—a pair en barbette at each end—ten 45-pounder quick firers, side armour 12 in. thick, and a speed of 18 knots. A certain number of torpedo tubes will also be provided. The 29-ton gun is one that can be worked without the aid of machinery, and hence is not so easily disabled as the larger patterns dependent on hydraulic loading. Its power is about double that of the old 38-ton muzzle-loader, which at one time we considered such an effective weapon. The 45-pounders are to be on the broadside in two tiers, for greater distribution, and to prevent a single shell from disabling two or three of these guns. They will furthermore be screened by stout steel shields. Many are disposed to think that high speed, though essential for a cruiser, is not so requisite in a battle ship. But as vessels like the 'Centurion' and 'Barfleur' will probably take the place, and do the duty, of armoured cruisers, they would be of little value if unable to proceed rapidly from point to point, or to compete in speed with vessels of their own class. For home waters, including the Mediterranean, a moderate speed that can be sustained will suffice.
After dealing with so many ships clad in mail 18 in. thick it may seem that a protection limited to 12 in. is insufficient, but that amount of hard armour will exclude all but the heaviest projectiles, and something must be left to chance. When wrought-iron was succeeded by a less easily perforated substance we might well have retraced some of the steps which culminated in 2 ft. of armour. I should be disposed to say that we should never exceed a maximum thickness of 12 or 14 in., but should offer a high premium on improvements in quality by which greater resistance to projectiles may be attained.In the 'Centurion' and 'Barfleur' we have a type which will, I believe, be highly commended by naval officers. All the attributes necessary for an efficient fighting ship are present, and the instrument is in due proportion to the human faculty which has to wield it. There must be a point at which this ratio is disturbed. Mechanical science, pushed on by the exertions and talents of a few, may outstrip the capacity of ordinary intelligence, and what is successful experimentally when no disturbing element comes into play may fail under the more searching conditions of war. We, in common with all nations, appear to have gone too far in the production of monster ships and guns, and I trust the reaction that must always follow such excesses will lead to a great increase in the numbers of what, for the moment, we term second-class battle ships.
- In the compound plate, owing to the support afforded by the iron back, a harder steel can be used for the face. Unsupported in this way, a steel plate of the same manufacture would be liable to break up under heavy blows, and hence steel armour is made of somewhat softer—or less brittle—though tougher material.