Part 8

The success of the locomotive was very questionable until the exhaust steam was turned into the chimney so as to create a rapid draught, and the steam-blast to-day enables the locomotive to travel at its great speed by causing the comparatively small boiler to generate such a large amount of steam. When this form of boiler was tried on board ship its power would have been very much crippled had not some other means been adopted for forcing the draught, as the steam could not in this case be allowed to escape through the funnel, but must be condensed into water for the use of the boiler. By closing the stoke-hole and forcing into it by mechanical means a plentiful supply of air, this boiler was made to be as efficient for a torpedo boat as for a locomotive. This forced draught has now been adopted on large ships, and to-day the very high speed of naval vessels, and of many mercantile steamers, is due to it. Consequently, with the same weight of machinery, higher powers are developed with a corresponding increase in speed, and the cruiser Piemonte, constructed by Sir William Armstrong & Co., of which an illustration is shown on p. 91, had her speed increased by means of forced draught from 20 knots to 22.3 knots, at which speed she was going when the picture was taken.

Mr. James Howden patented a forced draught process by which the incoming air is warmed by the heat (which would otherwise be wasted) in the uptakes and funnels, and then conducted direct to the furnaces; and he claims by this to be able to do with still smaller boilers, besides avoiding the danger to the tubes now sometimes experienced in war ships with closed stoke-holes.

But there still remains the problem of how to feed the furnaces by mechanical methods, so as to save the very large staff now required in the boiler-room of our large steamships. So far all means hitherto adopted with success on shore have proved failures at sea, and at present there is no reason to suppose that any one of them can be so adapted as to prove generally efficient for service. It is necessary for such a purpose that the gear can go continuously for many days, and the coal be small and tolerably uniform, and the supply regular. Such coal is not convenient for passenger ships, and if the demand for the present supply of small coal were increased the price would preclude its use. Some success, however, has been achieved in saving labor in the stoke-hole, and the most noticeable invention to this end is that of Mr. Thomas Henderson, whose now well-known self-cleaning fire-bars do away with the necessity for the firemen raking the fires out to remove the clinkers which adhere to the grates and obstruct the air-passages. By means of this apparatus, the alternate bars having a very slight movement, the coal gradually travels to the back end of the grate together with the clinker, which latter is eventually deposited behind the bridges. Thus not only is considerable labor saved, but the fires are always in such good condition that the full pressure of steam is maintained, and so a better speed kept up by the vessel herself.

On shore the tendency is to substitute gas for solid fuel, or to use the coke resulting from gas manufacture. That something of the same kind might be done on shipboard is possible, although not at present probable. The higher efficiency of the coal when treated in this way would enable still more power to be obtained from a pound of it, and there would be savings in other ways of a beneficial nature.

Then, again, if petroleum, or other liquid of a similar nature, could be obtained at a fairly low price, it might be used on shipboard; and as it has a heating power twenty-five per cent. higher than the best coal, and fifty per cent. higher than some of the commonest kinds weight for weight, the substitution of it would be a means of obtaining better speed. But it is always a question of _cui bono_, and when it is taken into consideration that the voyage between Sandy Hook and Queenstown is now done in 140 hours, and to do the distance in 5 days would require a speed of nearly 23-1/2 knots, with an increase in power of sixty-two per cent., and in fuel consumption of thirty-eight per cent., the cry must be regarded as a very far one at present. At the same time it is not desirable to believe that there is now finality in the speed of steamships, although by analogy with railway trains that conclusion might be arrived at.

Footnotes:

[10] This, however, is not an absolute test of the fineness of the _water-lines_ of a vessel, and it can only be used as such on the assumption that the midship sections of ships are of similar form. The best test of the fineness of water-lines is made by taking the displacement as a percentage of the prism whose length is that of the ship and whose section is the same as the midship section of a ship, assuming, however, that the midship section of all ships is approximately that found in general practice to-day; in speaking of coefficients it will mean the percentage of the rectangular block above named.

[11] More than thirty years ago this matter had been observed by the officers of the British navy, and experiments were ordered to be tried with H. B. M. S. Flying Fish, a 1,100-ton cruiser, her length being 200 feet, breadth 30 feet 4 inches, and her draft of water 10 feet 6 inches forward and 13 feet aft. With 1,290 I. H.-P. her speed was only 11.64 knots, whereas with 577 I. H.-P. it was 9.923 knots, and a speed of 11.201 was obtained with but 878 I. H.-P. A false bow 18 feet long was then fitted, so as to give finer lines forward, or, as sailors describe it, “a better entrance,” when it was found that with 1,285 I. H.-P. a speed of 12-1/2 knots was attained, and with 1,345 very nearly 12-3/4 knots. There is also every reason to suppose that could the stern have been altered in a similar way, the speed would have been still higher, in spite of the ship being larger and with a consequent increase of immersed surface to cause resistance. It has, besides, been observed on many occasions that when steamers have been cut in two and lengthened there has been no diminution of the speed, but, on the contrary, in some cases there has actually been a gain; so that in these two instances there is an apparent anomaly, viz., that with the same power the larger ship is propelled at a quicker speed.

The late Dr. Froude investigated this matter some years ago, and showed that such results were quite possible, independently of any fining of the lines, owing to the effect on the ship of the waves set up when in motion. One very curious illustration of how such waves may seriously affect a vessel is in that of a yacht built many years ago by an eminent firm on the Clyde, which failed to come anywhere near the performances guaranteed owing to the fact that as the speed increased the hollow following the wave formed at the bow increased and approached nearer and nearer to the paddle-wheels, until the water dropped below the floats and allowed the wheels to spin in the air; the propelling effect was thus entirely lost until the vessel slowed down sufficiently for the water to rise again to the level of the paddle-wheels. Such a thing could scarcely happen with a screw steamer; but the very bad steering qualities of certain naval ships is due to the fact that the inrush of water at the stern causes currents to flow _with_ the ship, and therefore to produce quite different results with the rudder from those which generally obtain.

[12] A nautical mile is 6,080 feet, the land mile being 5,280 feet. The knot is a measure of _rate_ of speed per hour. A vessel makes 20 knots when she is travelling at the rate of 20 nautical miles per hour.

[13] The dimensions, speed, etc., of the steamers here referred to, as well as other representative steamers from 1836 to 1890, are shown in the table on page 78.

[14] In the case of river steamers of moderate size there is not the same restriction on the position of the wheel, and as a matter of fact, as in the case of stern-wheelers, it is altogether at one end.

[15] It is now claimed for the twin-screw ship that she is not only capable of entering shallower harbors, but that she is in every way much safer, and it is most unfortunate that, owing to an act of carelessness, this was not conclusively shown in the recent accident to the City of Paris. But there is safety in the twin-screw beyond that which is rendered possible, as in the cases of the City of Paris and Majestic, by the division of the engine-rooms, viz., the fact that if one engine breaks down it is improbable that the other would do so at the same time, and that the vessel, although somewhat crippled in speed, would still be able to pursue her voyage; also, that in the event of accident to the steering apparatus the passage could be continued and the direction of the ship guided by regulating with one or both of the engines. Each of these features is pronounced, and the advantages have been proved on many occasions.

THE BUILDING OF AN “OCEAN GREYHOUND.”

BY WILLIAM H. RIDEING.

THE COST OF AN OCEAN RACER—INTRICATE “FINANCING” OF SUCH AN UNDERTAKING—THE CONTRACT WITH THE SHIP-BUILDERS—THE UNCERTAIN ELEMENT IN DESIGNING—GREAT SHIP YARDS ALONG THE CLYDE—THE PLANS OF A STEAMER ON PAPER—ENLARGEMENT OF PLANS IN THE “MOULD LOFT”—WHAT IS MEANT BY “FAIRING THE SHIP”—THE “SCRIVE BOARD”—LAYING DOWN THE KEEL—MAKING THE HUGE RIBS—WHEN A SHIP IS “IN FRAME”—SHAPING AND TRIMMING THE PLATES—RIVETING AND CAULKING—READY FOR LAUNCHING—THE GREAT “PLANT” WHICH IS NECESSARY FOR THE BUILDING OF A SHIP—DESCRIPTION OF A TYPICAL YARD—WORKS COVERING SEVENTY-FOUR ACRES—WHERE THE SHAFT IS FORGED—THE LATHES AT WORK—THE ADJUSTMENT OF PARTS—SEVEN THOUSAND WORKMEN.

I.

As often as the “record is broken,” and the Atlantic voyage is reduced by some unprecedentedly fast passage, we may be sure that there is a flutter in the offices of the rival lines which have thus been left behind. Between the Cunard, the Guion, the Inman, and the White Star lines there has been a constant race for supremacy, now one, and then the other, taking the first place. No ship has been allowed to keep the lead for more than a year or two. When sixteen knots have been developed by one line, seventeen knots have been aimed at by another, and the ship of that speed is no longer a wonder. So when we read in the newspapers of the “fastest passage” we may take it for granted that it is no sooner heard of in Liverpool than the managers of the lines momentarily surpassed are preparing to beat it. If the triumph belongs to the Cunard line, at the very next meeting of the directors of the White Star and Inman lines it will be discussed, and though an order for another ship may not be given there and then, it is sure to follow.

An order for a new ship of the class required to compete in the modern passenger service of the Atlantic is not by any means a matter to be determined on without grave consideration. Speed is costly, and as you increase it it is generally necessary to also increase the tonnage. Thus if the problem before you is to beat the record of a seven-thousand-ton ship, which has developed eighteen knots with engines of twelve thousand five hundred horse-power, you must (principally for economic reasons) have a larger hull as well as more powerful engines for your competing vessel. This forces upon your consideration tides, channels, harbor-bars, and dock accommodations, all of which impose limitations upon you. And then the cost of the ship herself is not a matter which even the wealthiest of corporations can provide for at a moment’s notice: it is not one hundred thousand dollars, or five hundred thousand dollars that the work calls for, but about five times the latter sum, for it is safe to say that a vessel superior to the City of New York or the Etruria could not be built for less than two million and a half of dollars.

The “financing” of such an undertaking requires time: there are long consultations between the directors, bankers, and ship-builders. If we could follow the steps of the gentleman to whom these negotiations are intrusted, we might see him flying off from Liverpool for Euston: closeted in a private office down in Lombard Street or Cornhill with some capitalists who are expected to contribute to the necessary funds; again, after dinner, engaged in argument with these same capitalists in a West End mansion to which they have adjourned, and then racing off in the precarious hansom cab to catch the night train from King’s Cross for Glasgow.

Sometimes the ship-builders are willing to become part owners of the projected vessel; sometimes they take as part payment for the work some older vessels of the line, which they refit, re-engine, modernize, and sell again. The ability of the builders to make an arrangement of this kind, of course, influences the placing of the contract, in a measure, but they must also be able to give certain guarantees. They must enter into an engagement that the projected ship shall be able to carry so many passengers and so many tons of cargo, and to attain a specified speed on a given consumption of coal per day. Let us say, for instance, that the stipulations are these: Accommodations for 600 saloon passengers, 150 intermediate passengers, and 1,500 steerage passengers; registered tonnage, 6,000, speed, 19 knots on a consumption of 300 tons per day. If the ship fails to fulfil these conditions the builders agree to forfeit a part of the amount they would otherwise receive for her, or they may be compelled to take her back altogether. This was the case with the City of Rome, which was built for the Inman line by the Barrow Ship-building Company. A beautiful ship in every way; of exquisite model; fitted with a degree of luxury unsurpassed at the time she was launched, she proved to have neither the speed nor the carrying capacity which had been guaranteed, and the Inman line refused to accept her. In a very few instances only are such guarantees omitted from the contract.

Now, ship-building is not an exact science, and the closest calculations are often upset in the result by unforeseen and inexplicable causes. It can never be said with absolute certainty just what speed a ship will attain, or exactly what quantity of cargo she will carry. The most ingenious and patient of experiments have not yet succeeded in eliminating the mysterious variability of result which the ship-builder finds, however closely he repeats his well-defined formulas. Two ships, like the Umbria and the Etruria, may be built side by side, of identical materials, lines, and dimensions; engines, boilers, and propellers may be the same, yet one will turn out to be a knot or two faster than the other, and neither the designer nor the builder is able to say why.

It is apparent, then, that in guaranteeing an exceptionally high rate of speed the builder assumes no little risk. The designing of a fast ship is indeed more of an art than a science, and each designer proceeds on a theory more or less his own. If the reader has an opportunity to compare models of the Servia, the Alaska, and the City of Rome, three ships built at the same time, each intended to rival the others, he will see by the varying proportions of length or breadth, and by other contrasts, how the opinions of the architects have differed as to the best lines for obtaining speed. True, it is not possible to ignore formulas altogether, but the designer’s intuitions or inspirations are not less serviceable to him than his technical knowledge.

We will suppose, however, that the designer sees his way to build such a ship as the specifications submitted to him call for, and that the contract is awarded to him, or to the firm he represents. The ship is now tentatively on paper, though her essential features are well defined, and the next step takes us to Glasgow and the Clyde.

II.

If in crossing the Atlantic for the first time you choose Glasgow for your port of disembarkation, the sail up the Firth of the Clyde and the river is likely to be full of agreeable and memorable surprises. The beauties of that route are not advertised, and one hears so little of them in advance that they gain impressiveness from the absence of expectation. The Firth itself is like a great Fjord, a land-locked bay hollowed between hills and crags, among which vapory clouds are always shifting, and its deep salt waters are ploughed by fleets of vessels of every class, and especially by yachts, sea-going steamers, and the most rakish-looking excursion boats in the world; it is not unlike the Hudson above Peekskill, though much wider; the rounded hills have the same soft and civilized outlines, and the same appearance of reclamation for man’s use and delectation; modern villas crown their heights and watering-places cluster at their feet.

Just below Greenock the passage narrows, and above that we enter the river, which, though not beautiful, is more of a surprise than even the Firth. It meanders through fields, and from the towering deck upon which we stand we look down upon ploughmen at work, cattle grazing, and snug farm-houses. So narrow is the stream, and so low are the banks, that the big steamer seems curiously out of place. How, one asks, has Glasgow ever prospered with so small a river as its only outlet to the sea? We have thought of the Clyde as a wide and capacious stream like the Mersey opposite Birkenhead, or the Hudson opposite New York; but, instead, it is scarcely as wide as the East River at Brooklyn, and there are reaches where two large vessels have no room to spare in passing each other.

Such as it is, all sorts of dredging operations are necessary to keep it open, and it has been said to be as much an artificial channel as the Suez Canal.

The first steamboat to navigate it was the Comet, in 1812, and though she drew but four feet of water she could leave Glasgow only on the flood tide. Even then she sometimes ran aground, and her passengers had to wade or swim ashore, or wait twelve hours for the next tide. Its depth is ample now, however, and it is the breadth that astonishes us: it seems as though a venturesome jumper might easily spring from the deck to either bank. The farms are alternated by shipyards in which the hulls of ships in various stages of construction loom up, with ant-like specks of humanity swarming upon them. Some of them are nearly twice as long as the river is wide, and it puzzles the stranger to say how they can be launched, until someone, wiser than he is, tells him that they slide into the stream obliquely and thus overcome the difficulty. Nearly all the steamers that have earned fame in the Atlantic trade have been built and engined at one or the other of these ship-yards, from the first Cunarder to the City of Paris; the Cunard, Inman, Guion, and North German Lloyd lines have come to this little river for their ships. And as we approach Glasgow, burrowing into the dark that envelops the town, it becomes narrower still, and within the limits of the port is nothing more than a long canal with ships huddled together along the banks.

The Clyde is, in fact, like one of those heroic personages who triumph over natural disadvantages which to the common mind are insuperable, and its inferiority in depth and breadth has been counterbalanced by excellences in other directions. In the first place Glasgow is the natural outlet of a great mineral field, so that after iron and steel became the principal materials of the ship-builder, he could find them on the banks of the little river unburdened by the increased price asked for them when it has been necessary to carry them long distances. In the second place the Clyde was the scene of the earliest attempts at steam navigation in Great Britain, by Miller, Symington, and Bell, and descending from them the genius of ship-building has become hereditary with the inhabitants of the town. “Practice makes perfect,” and the ship-builders of Glasgow have more practice than any people of their craft in the kingdom. In 1886 forty-five vessels were built at London, measuring 3,696 tons; sixteen vessels at Liverpool, measuring 18,268 tons, and on the Tyne, fifty vessels, measuring 49,641 tons. On the Clyde, during the same period, one hundred and fifty-one vessels were built, measuring 135,659 tons—nearly double the work done by all the other ship-yards combined. Thus, when after various conclaves and the discussion of ways and means, the directors decide to put a new vessel on their line, the order is pretty sure to go to Glasgow.

III.

We have assumed the work of the naval architect to be complete; all the specifications have been made out, and every part of the prospective ship has been drawn on paper. There are three plans: a “sheer plan,” showing all lines of length and height from stem to stern; a “half-breadth plan,” showing the lines of length and breadth, or, in other words, those lines which would be visible in looking down upon her decks from an elevation; and a “body plan,” which shows all lines of breadth and height, and represents the ship looked at “end on.” These are called the “construction drawings,” and with them in his hand the ship-builder can see in his mind’s eyes the vessel as she will appear when built. He does not work directly from these, however. They are carried up into the “mould loft,” the floor of which represents an enormous blackboard, and upon this they are reproduced to correspond with the exact dimensions of the ship. A foot is scaled down on the paper to a quarter of an inch, but in the mould loft a foot is a foot, and plate, girder, and rib are drawn to their full size. This enlargement leads to the detection of errors which are not apparent in the reduced drawings, and which must be eliminated. Straight lines are made with chalk by cords and rules, and curves by bending laths into the desired position and then tracing the sweep upon the floor. Every measurement has to be verified and checked, and “fairing the ship,” as this work is called, may take six or seven weeks. All errors having been corrected, still another drawing is made on a “scrive board,” and in this the lines, full-sized, are sunk in the wood so that they cannot be rubbed out. The “scrive board” is the plan from which the ship-builder works, and when it is complete the actual construction of the ship is begun.