MODERN SHIPBUILDING.
CHAPTER I.
RECENT PROGRESS IN STEAMSHIP CONSTRUCTION.
The achievements in shipbuilding and marine engineering within recent years may be said to borrow lustre from one particular feat of past times. The Great Eastern undoubtedly furnished, in large measure, the experience that has recently been causing so great a change in the tonnage of our mercantile marine. Commercially, as is well known, that huge vessel—“Brunel’s grand audacity,” she has been called—has all along proved a lamentable failure. It has been stated on good authority that between 1853—the year in which the contract for her was entered into—and the year 1869, no less than one million sterling had been lost upon her by the various proprietors attempting to work her. Financially, indeed, she may be said to have proved the “Devastation” of the mercantile marine. Although at various times in her long life-time she has unquestionably done most useful service in sub-marine cable-laying—service, indeed, which, but for her, could not well have been accomplished—these times of usefulness have been far outbalanced by her long periods of inactivity.
Apart from commercial considerations, however, this premier leviathan still stands out as a wonder and pattern of naval construction. In her admirably-conceived and splendidly-wrought structural arrangements—due to the joint labours of the late Mr I. K. Brunel and Mr J. Scott Russell—she possesses as successful an embodiment of the dual quality of “strength-with-lightness” as can be found in any subsequent ocean-going merchant ship. She was, if not the first, certainly the greatest embodiment of the longitudinal system of construction, and in virtue of this, as well as of her phenomenal proportions, she represents, alone, more of the intrepidity and skill essential to thorough progress, than are exhibited by combined hosts of the “departures” of recent times.
Despite the far-reaching views of the eminent designer, those changes which have since taken place in the essential conditions for successful ocean navigation eluded his vision. Owing to the opening of coal mines in almost all parts of the world, it is now no longer necessary nor desirable that a steamer should be capable of carrying coals for a return voyage, either from India or Australia—this being the dominant and regulating condition in the Great Eastern’s design. Further, the improvements in marine engineering, represented by the greater possible economies in coal consumption and the fuller utilization of steam, which have since been effected, have rendered the great ship inefficient and obsolete. In short, Brunel and his financial supporters were ahead of their time, and failed to appreciate the law of progress, now better understood—“invention must wait on experience.”
The urgent demands of our broader civilisation, improvements in navigation, the spread of population in new colonies and over wider continents, and, above all, the fresh accessions of experience and invention, are forces which now impel shipowners to increase the dimensions of their vessels, and shipbuilders to carry out the work. Each year the contrasts as to dimensions between the first leviathan and her later sister grow less and less. The completion within the past few years of such monster merchant ships as the Servia, the City of Rome, the Alaska, and the Oregon, and the forward state of the Etruria and Umbria, two remarkable steamships, building on the Clyde for the Cunard Company, constitute an epoch in the history of our mercantile marine, and give colourable justification to the belief sometimes expressed, that the proportions of the Great Eastern will in time be surpassed.
The feasibility—in a scientific sense—of ships growing in proportions commensurate with the growth of commerce and traffic, has often been commented upon. The whole tendency of our time is towards the aggregation of effort: the massing of capital and labour. A vessel of five thousand tons can be built cheaper than five vessels of one thousand tons. In the manning and working of ships there is a still more striking economy, e.g., one captain instead of five, and so on throughout the staff of officers, engineers, stewards, and crew. Not only so, but long ships can be propelled at greater speeds than short ones, the whole conditions of construction, engines, and propellers being considered. Mr Robert Duncan, in his presidential address before the Society of Engineers and Shipbuilders in Glasgow in 1872, declared:—“Looking forward one generation, and measuring the future by the past, I think it is not problematical that we shall see steamers of eight hundred feet long the ferryboats of two oceans, with America for their central station, and Europe and Asia for their working termini.” Even since that was uttered, eleven years ago, we have approached, in solid practice, the limit thus laid down, by 150 feet at least. Three years previous to Mr Duncan’s address, vessels exceeding four hundred feet were not afloat, with the notable exception already referred to; now, there are few merchant fleets of any pretensions engaged in ocean traffic which do not include vessels over or approaching four hundred feet, and it is even no great boast that vessels close on six hundred feet are afloat and in active service.
As better illustrating the growth in dimensions of merchant steamships, the Figs. on the following page may prove interesting. They show, all to the same scale, a number of representative steam vessels from the Comet downwards.
“Comet,” 1812.
“Elizabeth,” 1813.
“Industry,” 1814.
“Caledonia,” 1815.
“Rob Roy,” 1818.
“James Watt,” 1822.
“Sirius,” 1837.
“Great Britain,” 1843.
“City of Glasgow,” 1850.
“Great Eastern,” 1857.
“Scotia,” 1861.
“Columba,” 1878.
“Arizona,” 1876.
“Servia,” 1881.
“City of Rome,” 1881.
Along with the change or evolution in the sizes and types of merchant vessels, important modifications in their structural arrangement have of late years been effected, and it is to the constant progress being made in these matters—to the skill and intrepidity which are brought to bear on their execution, and to the readiness with which our shipowners recognise their importance and value—that the maintenance of our mercantile supremacy is largely owing. An American journal, writing a few years ago on this subject—perhaps with more of taunt for the conceit and self-sufficiency evinced by its own country than of adulation for the ability and enterprise displayed by ours—said:—
“In the whole world there is no place whatever that can in any degree compare with the Clyde for either extent or quality of steamship building; and at this moment an indisputable verification can be adduced, for between American and European ports there are at the present time something like a score of steam navigation companies, doing an immense passenger and carrying trade, with vessels of great power and magnificence, and notwithstanding the variety of trade nationalities, at least two-thirds of the vessels employed were built and equipped on the Clyde; and more—unless there has very recently been a change, there is not an American steam company in the whole Atlantic trade. With a run of about fifty years to try it, and after many unsuccessful attempts, the Americans have utterly failed to sustain permanent competition. All the British companies have prospered beyond any probable anticipation clothed with reason. The Cunard Company, starting with four vessels some forty years ago, have now twenty times that number. What is this something which enables Europeans to so far outstrip the Americans in a competitive traffic so as to exclude them from the merest show in the largest steam trade in the world? A baneful, overweening, and ignorantly selfish conceit invariably leads to disastrous results, and a nation given over to the fulmination of concentrated boast cannot fail to be suffocated with foolery of its own making.”
This is doubtless the outcome of a vicious antipathy—natural in the circumstances—to those stringent and over-reaching laws which forbid that ships built away from America shall sail under the American flag, or enjoy the pertaining privileges. American shipbuilders thus secured from the encroaches of foreign competition, have enjoyed their own pace, but at too great a sacrifice. Preferring to take the material most at hand, the manipulation of which they well understood, they have allowed their wood age to be dove-tailed thirty years into our iron one, with the other result that America now occupies as unimportant a place in the traffic of the sea, as the above quotation indicates.
Evidences are not wanting, however, to show that America is at least endeavouring, in some respects, to be abreast of the times, and that she has brought herself to acknowledge and follow the lead of this country. In this connection, the four new vessels presently being constructed for the U.S. Navy may be shortly referred to. The vessels comprise three cruisers and one despatch boat, all of which are being built by Mr John Roach, of Chester, Pa., the material employed in their construction being mild steel of American manufacture. Twin screws will be employed for the propulsion of the largest vessel—the Chicago—which is to be 315 feet long between perpendiculars, 48 feet beam, and 34 feet 9 inches moulded depth to spar deck. The other vessels are the Boston and the Atalanta, single screw cruisers of 270 feet length; and the Dolphin, single screw despatch boat, of 250 feet length and high speed.
In almost every feature except machinery these new American naval vessels strongly resemble Government vessels of recent British build, a circumstance for which there is little difficulty in accounting, as it is well known the naval authorities in the States have within recent times been recruited by young American naval architects educated in our Naval College at Greenwich, and consequently steeped in British naval practice. This and other facts, such as the visit of a technical commissioner of the States’ navy, two years ago, to our naval and mercantile shipyards—upon which he has since fully reported—leave one in no doubt as to the source of coincidence in design and structure.
| Length, | 500 ft. 0 in. | Depth, | 40 ft. 0 in. |
| Breadth, | 57 ft. 0 in. | Tonnage (Gross), | 7,718 tons. |
| Built by Messrs Elder & Co., 1884. | |||
The subject of America’s position as a shipbuilding and shipowning country has involved reference to wood shipbuilding, but to revert at any length to this topic in a work dealing with modern progress in British shipbuilding, the bulk of which is written of and for industrial and commercial centres where wood shipbuilding has been long entirely tabooed, is quite unnecessary. Doubtless, however, the amount of wood and composite building still carried on in the minor seaports of the United Kingdom, and in several of the British possessions, is of sufficient importance to demand some reference. As the present position of affairs in this connection is briefly and forcibly illustrated by statistics compiled and issued by the British Iron Trade Association, two tables taken from this source may be given, the subject thereafter being finally departed from:—
Tonnage of Vessels constructed and registered in the United Kingdom of Iron, Steel, and Wood respectively, in each of the years 1879 to 1883, with Percentage of Total Tonnage constructed in Iron and Steel.
| Year. | Gross Tonnage of Vessels built of | ||
|---|---|---|---|
| Iron and Steel. | Wood. | Excess Tonnage in Iron and Steel. |
|
| 1879 | 484,636 | 26,186 | 458,450 |
| 1880 | 525,568 | 19,938 | 505,630 |
| 1881 | 730,686 | 18,107 | 712,579 |
| 1882 | 913,519 | 14,850 | 898,669 |
| 1883 | 1,012,735 | 15,202 | 997,533 |
| Totals, | 3,667,144 | 94,283 | 3,572,861 |
Tonnage of Wooden Vessels registered in the United Kingdom which were Lost, Broken up, &c., during each of the years 1879 to 1883, with Tonnage of Wooden Vessels built and registered in the United Kingdom during the same period.
| Year. | Tonnage of Wooden Vessels. | Excess of Vessels lost over those built. |
|
|---|---|---|---|
| Lost. | Built. | ||
| 1879 | 149,828 | 26,186 | 123,642 |
| 1880 | 173,065 | 19,938 | 153,127 |
| 1881 | 170,283 | 18,107 | 152,176 |
| 1882 | 166,809 | 14,850 | 151,959 |
| 1883 | 144,138 | 15,202 | 128,936 |
| Totals, | 804,123 | 94,283 | 709,840 |
Whence it appears that while 709,840 tons of the 1,779,112 tons of ships removed from the register during the last five years were wooden vessels, only 94,283 tons of the 3,667,144 tons built and registered in the United Kingdom during the same period were constructed of that material. In other words, wooden ships represent 45 per cent. of the total losses, while they only represent 2·5 per cent. of the total tonnage built and added to the register during the five years in question.
Just as the introduction or general adoption of the compound engine marked an epoch in the history of shipbuilding and marine propulsion, so now the introduction of “mild steel” or “ingot iron” as a material for shipbuilding, together with the more extended adoption of water ballast, and the rapid development of the continuous-cellular system of construction, may be said to constitute a fresh starting point in the history of the industry.
Although the introduction of steel as a material for shipbuilding dates at least as far back as 1860, its use has been but partial or occasional until within very recent times. The uncertainty as to quality, the frequent great disparity between pieces cut from the same plate, and the special care needed in the manipulation, prevented its general adoption. With the highly-improved “mild steel,” however, first manufactured in France, and applied to shipbuilding purposes there about nine years ago, and subsequently introduced into this country, began the more extended adoption of steel, which every day, or with every accession to experience, is displacing iron.
The facts relating to the introduction into this country of mild steel for shipbuilding purposes, may be briefly recounted. In the latter end of 1874, Admiral Sir W. Houston Stewart, Controller of the British Navy, and Mr N. Barnaby, Director of Naval Construction, availed themselves of the opportunity to observe and study the use of steel in the French dockyards of Lorient and Brest, where three first-class armour-plated vessels were then being built of steel throughout, supplied from the works at Creusot and Terrenoire. Mr Barnaby, at the meetings of the Institution of Naval Architects in March following, gave an account of his observations during this visit, and pointed out clearly and precisely to the steel-makers of Great Britain all the indispensable conditions which would have to be met and satisfied by steel for shipbuilding, so that it could be used with confidence in the construction of the largest vessels. Before the end of 1875, the Landore-Siemens Company was enabled to fulfil these conditions, and the Admiralty contracted with them to supply the plates and angles necessary for the construction of two cruisers of high speed—the Iris and the Mercury. The material involved in this contract was steel obtained by the Siemens-Martin process. Shortly after this the Bolton Steel Company was in its turn able to produce by the Bessemer process plates and angles, satisfying all the requisite conditions. The Steel Company of Scotland, Butterly Company, and other important works, also entered into the same business, and operations are still going on in various parts of the country connected with the formation of new works, and the perfecting of other processes.
The steel furnished by these different works, subjected as it has been to systematic and severe tests continually applied, is now possessed of the qualities of ductility, malleability, and homogeneity, which render its employment in shipbuilding not only permissible but highly desirable. Its good and reliable qualities have been admitted by the Constructors of the Navy, the Officers of the Board of Trade, of Lloyd’s, and of the Liverpool Registries, as well as by all the most competent authorities. The experience of all who have practical dealings with the material in the shipyard is that it entirely satisfies—even more than iron—all the requirements of easy manipulation. The confidence with which it can be relied on, as to its certain and uniform qualities, places it on a much higher level than the steel formerly manufactured; and its superiority over the best wrought-iron as regards strength and ductility renders it a highly preferable material.
While doubt exists, however, as to the adoption of steel for shipbuilding being commercially advantageous; there must be hesitancy on the part of shipowners and others concerned. Although, since its introduction, mild steel has been greatly reduced in price, the first cost of a steel ship is still somewhat over that of an iron one, even after the reduction in weight of material is made, which the superiority of steel permits of. It has been shown that, about two years ago, a spar-decked steamer, of 4,000 tons gross, built in steel, as against a similar vessel built in iron, entailed an excess in cost of £3,570. The advantages, however, which accrue from the change, both immediate and in the long run, make the gain clear and considerable. Steel ships have been built with scantlings reduced one-fourth or one-third, and in some early cases even one-half, from what would have been considered requisite had iron been employed. Some authorities, not unnaturally, questioned the wisdom of accrediting steel with all the qualities which make such sweeping reductions justifiable. Except in vessels for river or passenger service, however, this is much in advance of the reductions obtained in ordinary modern practice.
The reductions allowed in vessels built to Lloyd’s requirements—and it cannot be urged that this society is too reckless in concessions of this nature—are 20 per cent. in scantling, and 18 per cent. in weight. As it is impossible to adjust the scantlings of material to take the full advantage of these reductions, and further, as allowance has to be made for extra weight due to the continued use of iron in vessels of steel—for purposes not essential to structural character—the average weight-saving effected in practice is about 13 to 14 per cent. This represents, in the finished vessel, a clear increase of at least 13 per cent. in dead-weight carrying power. The gain obtained in general practice has been otherwise stated on good authority as 7 to 7½ per cent. of the gross tonnage.
In trades where there is constancy of dead-weight cargoes, this increase in dead-weight carrying power should speedily recoup the owners for extra first cost, and in the life-time of vessels generally, a clear pecuniary gain should result. In trades, however, where the cargo consists of measurement goods, the advantages are not so decided, for it may sometimes happen that before vessels have been loaded to their maximum draught the limits of stowage will have been reached. Even here, however, the steel vessel has the advantage of her iron rival; her hull is 13 per cent. lighter, and consequently may be propelled at a given speed with much less expenditure of power, and has the further advantage—often a very important one—of a shallower draught. This latter consideration alone, in a service where every iota of such saving counts, has influenced many shipowners to adopt the steel.
As the manufacture of mild steel progresses and extends, the assimilation of the rival materials as to cost is sure to follow. Already very great advances have been made towards this end, the fact being abundantly evidenced by the greatly increased number of steel ships on hand, and by the establishment of new works, and transformation of old, for the better production of the new material. In 1877 mild steel was about twice as costly as the iron in common use. The sources of supply, however, were then comparatively few, and the thorough and severe testing to which the new material had to be subjected, necessarily increased the cost relatively to iron, which has never been subjected to the same rigorous ordeal. In 1880, owing to the increased sources of supply and the progress in manufacture, the cost of steel had been reduced, relatively to iron, by about 50 per cent. At the time of writing (March, 1884), the price of steel for a good-sized vessel is—overhead—about seven pounds, seven shillings and sixpence per ton; while the corresponding figure for iron is about five pounds, five shillings, or a difference of only about twenty-nine per cent. in favour of the older material.
Doubts were at first expressed by not a few, regarding the durability of steel ships compared with those of iron, such misgivings being aggravated by the thinness of the steel plating. This fear is being gradually lessened by the results of laboratory experiments and bona fide experience—the broad deduction from which is, that the deterioration of steel, under the action of sea water, is no greater than that of iron, and that, if the same care and constancy in cleaning and painting, common to ships of the latter material, be extended to ships of the former, their durability will be equal.
Several large shipowning companies were not slow to place faith in the new material. In the early part of 1879, the “Allan Line” Company entrusted to Messrs Denny & Brothers, of Dumbarton, the order for a huge vessel, which the intrepid confidence of the principal partners in both the owning and the building firms determined should be of mild steel, be bound with steel rivets, and have her boilers of the same material. This was the large steamer Buenos Ayrean, the first transatlantic steamer built with the new material. She was finished early in 1880, and had not been over nine months in the water when the order for a second and still larger steel vessel—the Parisian—had been given by the same owners to Clyde builders. The Union Steamship Company of New Zealand, the Pacific Steam Navigation Company, Messrs Donald Currie & Co., and several smaller companies, ordered vessels of steel almost simultaneously, while yet the new material was in the early stage of trial. Amongst the orders for steel vessels which were subsequently given, the Servia and Catalonia, for the Cunard Company; the Clyde and Thames and Shannon for the Peninsular and Oriental Company; the India, for the British India Company; the Arabic and Coptic, for the Oceanic Steam Navigation Company, and the four twin screw steamers of the “Hill” Line, represent the principals. The companies who then adopted the new material have mostly continued to have their new ships built of steel, and to name the vessels since built and now building in which this material is employed, would simply be to enumerate three-fourths the fleet of high-class modern merchant ships. There were 21,000 tons of steel shipping built throughout the United Kingdom in 1879; 36,000 in 1880; 55,000 in 1881; 126,000 in 1882; and over 244,000 in 1883. It is computed that at the present time the amount of steel shipbuilding going on throughout the kingdom is not less than 175,000 tons, or the largest amount on hand at any one time since its introduction.
The modification in the structural arrangement of ocean trading vessels, already spoken of as the continuous-cellular system, although only within very recent times receiving extended adoption in the mercantile marine, possesses in some of its essential features the prestige of years. So long ago as 1854, Mr Scott Russell strongly advocated the principle of longitudinal construction, and applied it in practice to ships of the mercantile marine, to the success of which, in a scientific sense, the Great Eastern is surely overwhelming testimony. The principle met with much scientific favour from many besides Mr Russell, but it did not take root in solid practice. Pecuniary and other kinds of considerations interposed to prevent its general adoption. The urgency for increase in the size of vessels was not such as to make longitudinal strength (the special advantage claimed for the new principle) a great desideratum; and there was perhaps reluctance on the part of shipbuilders to relinquish time-tried and familiar methods. The system presently under notice—although, as has already been said, the same, in its main principles, as the system then advocated—by its descent through the Admiralty Dockyards, by its application to merchant vessels—first of East Coast, and then of Clyde build—and by its close association with water ballast, has undergone many modifications which almost constitute it a creation of recent times.
Sir Edward J. Reed, when Chief Constructor of the Navy, introduced the bracket frame system of construction into iron-clad ships of war, and, as already indicated, it is largely owing to the experience of the system as applied and practised in such cases—conjointly, of course, with its successful introduction in the case of the Great Eastern—that in so short a time it has reached the present structural perfection, and received such wide extension in merchant steamships. That it has recently received such wide adoption in the mercantile marine is due not so much to its structural advantages—and these are great—as to the way in which it lends itself to the economical working of steamships in actual service. This will be more explicitly referred to after some description of the system as applied in merchant ships has been given.
It is somewhat away from the field this work is concerned with, to trace the system in its stages of development in ships of war, but it may be said, shortly, that the impulse which the system has received in the mercantile marine has in no sense been a transference of the activity which at all times since its introduction has characterised the application of the system to the vessels built in our naval yards.
In order to assist the non-technical reader in appreciating what follows regarding the system in merchant ships, a general idea of the cellular bottom principle of construction is afforded by Fig. 1.
This shows in section the bottom part of a vessel amidships, fitted with a double or inner skin, extending across the ship from bilge to bilge, and there connected in a watertight manner to the outer bottom plating. A series of longitudinal plates are worked, fore and aft; set vertically between the outer skin of the vessel and the plating of the inner bottom, and connected thereto by continuous angles. Between these “longitudinals,” and at every alternate transverse frame, deep plate floors, lightened with oval holes, are fitted, connected to outer skin by the angle frame, and to inner bottom plating by pieces of angles corresponding to the vessel’s “reverse frames.” These floor plates are, in addition, connected by vertical angles to the longitudinals. Intermediate between the deep plate floors simple angle bar transverse frames and reverse frames are fitted, to give support to the outer skin and to the inner bottom respectively. Until recently, the deep floors consisted of “gusset” or “bracket” plates, each division being fitted in four separate pieces, the whole taking the form as shown in dotted outline. This practice is still most largely followed, but in those yards which are equipped with large hydraulic punching machines for piercing holes such as are shown in Fig. 1, the solid floors have superseded the bracket or four-piece floors, the change effecting a simplification of work and decided structural advantages.
With the employment of water as a substitute for dry or rubble ballast, the structural movement under notice may be said primarily to have begun. This movement has resulted in the present approved system, which, at the same time that it has regard to water-ballast with all its attendant advantages, most happily combines the important qualities of increased strength and security. The need for ballast in vessels whose service generally comprises “light” as well as “loaded” runs (as in the coal trade between Newcastle and London), or in trades where the full complement can only be obtained by shifting from port to port, is obviously great. It is doubtless to needs such as these, more than to any demand for increased structural strength, that the introduction and extended application of the longitudinal and bracket-plate principle is owing.
The screw-steamer Sentinel, built in 1860 by Messrs Palmer of Jarrow, Newcastle-on-Tyne, is mentioned by some authorities as embodying some of the main features of the longitudinal and cellular bottom system, and the screw-steamers Scio and Assyria, of 1440 tons, built in 1874 by Messrs Westerman, near Genoa, have been noticed in a similar connection. The next vessel, in point of time, which contained features answering to the system now in vogue, and from the date of whose production the movement has been almost constantly progressive, was the screw-steamer Fenton, built by Messrs Austin & Hunter, of Sunderland, in 1876.
Clyde builders were not slow to recognise the value of the system in its application to water-ballast steamers, and almost immediately some of the more intrepid of their number began to advocate its adoption, but with some modifications, in vessels then being contracted for. Mr John Inglis, jun., of Messrs A. & J. Inglis, Pointhouse, Glasgow, submitted to Lloyd’s Registry in March, 1878, the scantling section of some cellular bottom vessels, then in project, which contained several of the improvements introduced in subsequent practice. Messrs William Denny & Brothers, of Dumbarton, at the same time took up the principle, and have since actively applied it to steamers of every character in which water-ballast is a desideratum. Adopting it, five years ago, in four sister vessels for the British India Steam Navigation Coy., they subsequently raised the important issue with the Board of Trade regarding the tonnage measurement of these vessels. This august body insisted on computing the register tonnage—the figure upon which the tonnage dues are levied—not to the top of the inner bottom, but to an imaginary line half-way down the cellular space—in fact, to where the line of floor would have been if constructed in the ordinary fashion. Messrs Denny maintained, in effect, that as the register tonnage was meant to be a measure of the space available for cargo, the top of the ceiling on the inner bottom was the only equitable line of measurement. The principal reason for the Board seeking to pursue this course seems to have lain in the supposition that owners would endeavour to use the double bottom for cargo-carrying purposes. An ambiguity in the words of the Merchant Shipping Act, or their inapplicability to present day practice, were other possible elements in the case, but doubtless the red-tapeism and self-sufficiency characteristic of the Board had much to do with their action. This is borne out by the fact that although the Messrs Denny succeeded in their plea with respect to vessels having structural cellular bottoms, the absurd practice is still followed in cases where the bottom is fitted for water ballast on the girder principle, i.e.—the inner bottom fitted upon fore and aft runners or girders, erected on floors of the ordinary description, as shown in Fig. 2.
This formed, and still forms in many places, a very common arrangement for water ballast steamers, although not so inherent a feature of the vessel’s structure as the continuous-cellular bottom. In most cases this system is fitted only for part of the length, and not, like the cellular system, applied throughout the whole length of the ship. If it was impossible for the Board of Trade to hold by the contention that cargo might be carried in bottoms of the structural cellular type, it is equally untenable in the case of bottoms such as are now referred to. The difference between the two kinds of ballast bottoms is one merely of construction, and if any one of the two lends itself to cargo-carrying purposes, it is certainly the cellular system. The anomaly is sufficiently striking to merit attention, and in certain districts where the girder system is largely adopted for medium-sized vessels, it is felt as nothing short of an injustice, both by shipowners and builders.
The concession or victory won by Messrs Denny removed a serious hindrance to the spread and general adoption of the water ballast cellular system. Other Clyde firms at the same time—or at least soon after the adoption of the system by the Messrs Denny—took the matter up and independently did much towards the popularisation of the cellular mode of construction. Speaking in the early part of 1880, Mr William John, of Lloyd’s Registry, now General Manager with the Barrow Shipbuilding Company, said:—“At the time Mr Martell read his paper on water-ballast steamers before the autumn meeting of this Institution (Naval Architects) at Glasgow, in 1877, there had been only two or three small steamers built (since Mr Scott Russell’s early ones) on the longitudinal principle. Now, it is within the mark to say there are one hundred steamers, built and building, whose bottoms are constructed on the longitudinal principle, or what is better described as the cellular system, amounting probably to 200,000 tons, and it is not outside the bounds of probability that a very few years will see the majority of merchant steamers constructed in this manner.” Mr John’s connection with Lloyd’s at the time, entitled his statements and opinions with regard to the prevalency and prospects of cellular construction to be accepted with every assurance, for it is in such Societies as Lloyd’s where the best consensus of information regarding the extent and tendencies of particular types of vessels can be obtained. In point of fact, the intervening period has witnessed, in great measure, a realisation of Mr John’s forecast. The advantages of a cellular bottom as regards safety, and for the purpose of ballasting and trimming vessels, also as meeting the greater need for longitudinal strength caused by the enormous growth in the size of vessels, have received that appreciation from shipowners and shipbuilders which is their due. The practice has accordingly spread, till now, it would not be rash to say, quite as many of the ocean-trading steamers being built are fitted with cellular bottoms as are without them.
The adaptation of water ballast to sailing vessels, as well as to steamers, has received consideration at the hands of both Tyne and Clyde builders. Previous to 1877, several small sailing ships were built on the Tyne, in which provision was made for water ballast in tanks entering into the structure of the bottom, but erected over the ordinary plate floors. About 150 tons of water ballast were carried by these vessels, the filling and discharge of the tanks being effected by Downton’s pumps, worked by the crew. The trade in which they were engaged—i.e.—carrying coal from the Tyne to Spanish ports, and back to this country with ore—was one in which the introduction of water ballast proved commercially and otherwise most advantageous. Two years subsequently Messrs A. M‘Millan & Son, Dumbarton, introduced water ballast into one of the largest class of sailing vessels then being built. Unlike previous sailing ships with provision for water ballast, however, the vessel was constructed on the structural cellular bottom principle, having bracket floors and continuous girders, as so generally approved in steamships. Capacity for water ballast, to the extent of over 300 tons was thus provided, the filling and discharge being effected by a special donkey engine, supplied with steam from a large donkey boiler. The boiler also furnished the motive power for cargo winches, off which, by crank gear, the manual labour pumps were also brought into requisition. Facilities for the expeditious management of ballast—the want of which, in sailing vessels, considerably hinders its adoption—were thus, in this case, efficiently provided. Several other sailing ships, built by Messrs A. M‘Millan & Son, and by other shipbuilding firms on the Clyde, have been fitted with this system, and the result of experience with these vessels in actual service, thoroughly encourages its more general adoption.
Many minor, yet aggregately important, structural features which are products of the progressive movement of recent years, or are simply revivals of old devices which were “untimely born,” still call for some notice. As a necessary consequence of the growth in dimensions and the change in relative proportions of vessels, greater regard has been paid to the systems of construction in which the longitudinal principle is involved. This, of course, is evidenced by what has been said of the cellular bottom system, but various minor structural features associated with the cellular bottom are also noteworthy in this connection. It is the practice, for instance, where large ships are concerned, to fit side stringers in the holds, throughout the entire length, made intercostal with regard to transverse plate or web-frames occurring at intervals of 16 or 20 feet, which extend from the bilge to the main deck. This arrangement—an outline of which may be found to the right of the section shown as Fig. 1—possesses many structural advantages, and finds additional favour with shipowners on account of its leaving a clearer hold for stowage by obviating the use of transverse hold beams.
Regard for transverse strength has increasingly evinced itself in the fitting of various kinds of plate side stiffeners or partial bulkheads. This is well exemplified in a very recent case—that of the National Company’s steamship America, built by Messrs J. & G. Thomson. This vessel, having been constructed independent of any special Registry Rules, embodies structural features not common amongst vessels in which such rules are undeviatingly conformed to. The system referred to, of plate frames or partial bulkheads, is one of the most conspicuous of these features. Throughout the length of the vessel, at intervals of about 18 feet, transverse plate stiffeners or frames, extending from the shell inwards about 4 feet, take the place of the ordinary angle frames, and are continuous from floors to upper deck, the stringers and other longitudinal features being scored through them. The surplus transverse strength resulting from this system is such as amply to compensate for uncommonly large breaches made in the deck beams and plating for light and air purposes in the saloons. This is a very special feature in the interior arrangement of the America, and will be referred to further on. The regard for transverse strength, again, conjointly with the increased attention to minute watertight sub-division, has led to the fitting of a greater number of complete watertight transverse bulkheads, relatively to the lengths of vessels.
In vessels of extreme proportions the method of forming shells two-ply, or of fitting all the shell plates edge to edge with outside covering-strakes over the fore-and-aft joints, has been recently revived and much improved. The system, although very expensive, has been adopted in vessels for the Anchor Line by Messrs D. & W. Henderson, Glasgow, and subsequently on even a more extensive scale by the Barrow Shipbuilding Company.
Affecting the structural character of modern ships very materially, but the result chiefly of an economy in labour, riveting by machine power has received a wonderfully extended application within recent years. Structurally, as well as commercially, the system has played a large part in the progressive movement under review. By its means the strength of united parts has been enhanced through the increase of their frictional resistance, and through the rigidity of joints, due to the more thorough filling of the rivet holes. The subject of hydraulic or machine power riveting will, however, receive fuller treatment in a subsequent chapter.
Within the past two or three years cast steel stems, stern-frames, and rudders, have been taking the place of forged iron work in ship construction. The practicability of manufacturing these of such strength and homogeneity as would meet the needs of ship construction even better than the ordinary forged work, had occurred some five or six years ago to several engaged in the steel trade. Mr J. F. Hall, of Messrs William Jessop & Sons, Limited, Sheffield, had the subject under consideration about that period, and actually made several small stern posts and rudders for steam yachts and launches. The advantages of solid and uniform steel castings over iron forgings—which, with their many weldings, so often prove inefficient when subject to any sudden shock—were even then rightly enough appreciated. It was only, however, after patents had been taken out by Messrs Cooke & Mylchreest, of Liverpool, for various devices connected with the actual fitting of such features to the ship’s structure—amongst other things the hanging of rudders without pintles or gudgeons—that the manufacture of cast steel stern-frames, rudders, &c., was seriously proceeded with.
In July, 1882, the Steel Company of Scotland (Limited), who are the manufacturers in Scotland of Messrs Cooke & Mylchreest’s patent form of rudders and stern-frames, successfully cast a stern-frame—the first of large size, it is believed, made for actual use in the construction of a steamer. In April of the same year, however, Messrs William Jessop & Sons (Limited), of Sheffield, had exhibited a crucible cast steel stern-frame and rudder of their manufacture, at the Naval and Sub-Marine Exhibition, held in London. These large castings, along with others, were subjected to a series of tests in the presence of Lloyd’s inspectors and other authorities, such as the forged frames and rudders ordinarily fitted would not have come through without severe damage, yet all of which the steel castings withstood most thoroughly.
Testimony to the efficiency of these new features in ship construction has already been furnished from the arena of actual experience, by the recent grounding of two steamers in which these features had been introduced. The screw-steamer Euripides, a Liverpool-owned vessel of about 1780 tons gross, completed in May, 1883, by Messrs Caird & Purdie, of Barrow, some time ago ran upon a reef of boulders, and remained thumping heavily for several hours. At the time she was laden with a full cargo of grain, which was afterwards delivered in perfect condition. The cast steel stem and stern-frame, which were manufactured by the Steel Company of Scotland, were practically without damage, notwithstanding that serious indentations were made in them. The stem, although receiving the full force of resistance, was not perceptibly altered in shape, and competent judges who inspected the damage in dock were of opinion that the stem, with its superior attachments, in all probability saved the vessel from total loss. The rudder on the Euripides is of solid cast steel, in one piece, and hung without pintles, and in a manner involving little or no riveting. In this, as in the other features, the immunity from serious damage testifies to the efficiency and durability of the steel castings. The second case of grounding referred to is that of the screw-steamer Strathnairn, of 400 tons, belonging to Messrs James Hay & Sons, of Glasgow; one of two vessels built by Messrs Burrell & Son, of Dumbarton, in which cast steel stern-frames and rudders were adopted. This vessel got aground while off Harrington, on the north-west coast of England, about the latter end of March of the present year. Her stern-frame sustained very considerable shock: such, indeed, as no ordinary forged work could possibly have undergone with like result. Subsequent docking showed that it would only be necessary to straighten the frame at the deflected portions in order to make it again structurally efficient. This was done, and the vessel is again actively engaged in service.
The weldless stern-frames, rudders, and stems, as patented by Messrs Cooke & Mylchreest, Liverpool, and manufactured for them by the Steel Company of Scotland, Messrs Jessop & Sons, Sheffield, and Messrs John Spencer & Sons, Newcastle, have various advantageous features which may be noticed somewhat fully. One of these is the casting of flanges on the stern-posts, for attaching the shell plates to; by which arrangement much of the difficult and costly work in the riveting and fitting of the shell plates at these parts is done away with, while a considerable increase of strength is obtained. The solid rudder is a great improvement on the built rudder as usually fitted; the entire absence of rivets being an important desideratum. The rivets connecting the rudder-plates to the frame-forging are frequently a source of trouble and annoyance, through their being loosened by the constant vibration of the rudder, and the shocks it often receives. The heads of the rivets not unfrequently drop off, and the rivets themselves sometimes fall completely out. All this, of course, is entirely obviated in the solid rudder. By Messrs Cooke & Mylchreest’s improved method of fitting the rudder—a device which is only applicable in a casting—pintles are wholly dispensed with, and in their place a much stronger joint is substituted, with a considerably increased wearing surface. The rudder is also jointed at the top of the blade, by means of strong flanges bolted together; an obvious advantage of this arrangement being that it can be readily unshipped, even when afloat.
In addition to the stern-frames, stems, and rudders, there are, also being supplied, keels, garboard strakes, and centre keelsons in long lengths. It is claimed for these that as the keel, garboard strake, keelson, and brackets for connecting the floors, are all made in one piece, they are much stronger than as ordinarily constructed, and that a considerable saving in both labour and rivets is effected. As there are no angle irons to contend with, the limber-holes may be made close to the bottom plating, and a much thinner layer of cement will, consequently, be needed on the bottom; the saving in this respect, according to the patentees’ calculation, being 50 tons in a 2,000-ton vessel.
As the prices of these frames and rudders do not exceed those charged for frames of wrought-iron, and moreover, owing to the pieces which are cast on to them forming attachments for keels, decks, &c.—thus cheapening the work of construction in the shipyard—there appears to be no question of their great superiority. The presence of blow-holes, not unfrequently a source of misgiving in castings, is found from experience to be a constantly diminishing fault in these articles. The demand for them has steadily grown since their adoption in a few actual cases. It would seem, indeed, that the demand is only limited by the powers of production possessed at present by the four or five steel-making firms who have undertaken this class of work, and have satisfied the requirements of the registration and the insurance societies.
In addition to the frames and rudders for ordinary screw vessels, the Steel Company of Scotland have also supplied several sterns for war vessels, with rams and torpedo openings, which have proved very satisfactory. Other new adaptations are the casting of large brackets for shafts of twin screw vessels, of large crank shafts themselves, and of heavy anchors; the results of tests presently being made fully warranting the anticipation that the material will very largely be employed in the future for these important items in the outfit of merchant vessels.
The more important features of growth or change in ship construction which have made the past few years a noteworthy period in the history of mercantile shipbuilding have now been reviewed. Speed, and propulsive power of steamships, although absorbing very much of the progress for which the period has been so remarkable, have not been dealt with, but are reserved for the chapter following. The subjects named will also necessarily receive some attention in the chapter devoted to progress in the science of shipbuilding. In anticipation, however, apologies should be offered for the paucity of detailed references to the propulsive agents on board ship. Marine engineering, in all its recent developments, would require for its proper treatment considerably more space than can be devoted to it in the present work.
To meet the exigencies of the progressive movement, both practical skill, scientific knowledge, and commercial enterprise have been needed on the part of our shipbuilders. These have not been by any means wanting, as abundantly evidenced by the foregoing record of what has been achieved. With a continuance of that readiness displayed by shipbuilders and naval architects to modify, and even revolutionize if need be, types and methods which the times have outgrown, the lead in merchant shipbuilding will long be ours. With a maintenance also of the enterprise shown by our shipowners, Britain will still continue, as regards the number, size, and power of her merchant ships, supreme among the nations.
List of Papers and Lectures bearing on recent improvements in ship design and construction, to which readers desiring fuller acquaintance with the technique and details of the subjects are referred:—