THE STEAMER OF THE FUTURE

Otago Daily Times, Issue 6307, 29 April 1882, Page 6 (Supplement)

THE STEAMER OF THE FUTURE

Mr William Denny, the famous shipbuilder o£ Dumbarten, recantly delivered a lecture before the Greenock Philosophical Society upon " The Speed and Carrying of Screw Steamers." We make the following interesting extract from it:—

Steamers were increasing in size on the average at a much greater ratio than the ordinary world had any conception of, as was demonstrated by the table he exhibited showing the average tonnageof the steamers launched on the Clyde, Tyne, Wear, and Tees during the past three years. A glance at the table would sufficiently demonstrate that increase in average size was not confined to any one port, but was a universal fact. The increase in this respect was rather obscured in the Clyde district by the fact that so"many specialised small steamers and yachts, both steam and sailing, and barges and li^ht-draught steamers to be shipped in pieces, were built on the river, _ thereby reducing the average ; but in spite of that the average continued to increase, and if they wanted any further demonstration they might get it in the case of the City of Rome, the Servia, and the Alaska, although personally he did not think that either of these three steamers was the type of the future, either for speed or for cargo carrying. They would notice that of the tonnage launched on the Tyne, Wear, Tees, and Clyde for the three years, the latter river showed an incroasm* percentage year by year, a matter which should be of some comfort to any who might three years ago have been despondent about the fortunes of the Clyde. The lecturer then proceeded to speak upon the possibilities of the future. They had to ask themselves, he said, what could be done in the future in increasing speed upon the one hand, or deadweight capacity on the other, or both, subject to such economics as might render them financially possible. Financial considerations-must in all cases, and should at all times, influence the naval architect to his consideration of such important questions. They formed the necessity under which one was compelled to fulfil conditions, and the discipline by which redundancy of mere fancy or theory might be retained within proper limits. Now they knew that, provided the forffi and fineness "of the steamer were suitable, the speed could be enormously increased by the proper application of greatly increased power. That had been demonstrated in the case of even the comparatively small torpedo boats, where the application of great power had surmounted even the difficulties of driving a vessel of small dimensions. To apply mpre power to a vessel without abnormally increasing the weight of that vessel, or what came to the same thing, without increasing the weight of coal to be carried for a given distance to be run, was the problem before them. At the present moment there was proposed a method of diminishing the coal consumption required for a given development of power, and there was being fitted by Mr A. C. Kirk, in the screwsteamer Aberdeen, machinery from which it was hoped that a great economy. in coal consumption would be produced as compared with results obtained in practice from the present compound engine. The principle involved was that known as trip'o expansion— that was expansion through three cylinders successively, instead of through two as in the case of the compound engine. By the triple expansion the variation of temperature in each of the cylinders through which it passed on its way to the condenser was reduced. Should that further application of the principle of expansion be successful, and there seemed good reason for hoping that it would be so, they should be enabled to cross the Atlantic developing a given power continuously, and with a displacement reduced by the amount of coal which would be saved on the voyage. That was what might bo called an indirect method of saving weight; but two other direct methods of saving machinery weights were also attracting the attention of the technical world. Both of these were combined in the torpedo boats turned out by Messrs Yarrow and Thornycroft—one was, they saved weight directly by empleying only the strongest materials and in the smallest proportion in the construction of the engines; the other was by reducing the size and weight of the boiler by the employment of the forced blast—that wa's by employing a boiler of the locomotive type instead of the ordinary marine type. The former of those methods lias been exemplified upon a larger scale in the type of engines lately introduced into the Admiralty, and of which the first was designed by Mr A. C. Kirk. Those engines are fitted in the Nelson, and were, as compared with the engines of a sister ship, constructed by another engineering firm, which developed less power, 115 tons lighter. It would seem that in so far as they could hope for a combined economy, both in weight of machinery and in consumption of coal, they must confine themselves to such expectations as might be fulfilled by the employment of stronger materials and lighter design in the engines by the use of steel and a higher pressure in the boilers, and by a further development of the division of expansion now being attempted by Mr Kirk. ' Of course, in the use of steamers having only very short runs, where the weight of coal to be carried would'not be of great amount, the forced blast might be employod with decided advantage in reducing the weight of the machinery, and thereby reducing the total displacement to be driven. Granted, however, that they had. attained the maximum economy of weight of machinery and- the maximum economy in weight of coal to be carried, they had still to ask themselves what other conditions were involved in carrrying out such an improvement as there would be in placing fast express steamers on the Atlantic capable of crossing the ocean between the States and this country at an" a\acrage speed of of 20 knots an hour. That problem was the subject of much speculation and discussion at the present moment, but so far it had seemed to him that the speculation and discussion had only arrived at the preliminary stage. It had been said that the thing should be done and it had also been said that the thing was possible. -Both' these statements were, in his opinion, correct, and they had every reason to expect that at no distant date the problom would be solved. Before it was solved, however, if it was to be solved subject to -financial considerations likely to ensure success, a great deal more work would have to be done than in simply making probable statements. Having secured machinery of the highest possible practical weight for the power to be developad and at the same time of the highest possible present eebnomy, they had to secure a hull of such strength and rigidity as would sustain both the sea strain to which it must be subject and the vibration due to powerful machinery and propellers. They might decide at once that the material to be employed was steel, as being that from which they could obtain the greatest amount of strength and reliability with the least possible weight. They, must further decide upon the dimensions of the steamer to be employed, and while, m doing this, supplying a form of little resistance, they must if possible supply a form which would make the smallest calls upon them for weights of construction. He had already shown them that extreme actual length was unfavourable to the realisation of such wishes, He. was therefore oonvlnoed that the steamer which was to do this Atlantic work would be a vessel of what mMit be called at the present time moderate length— that was a vessel which would not only be shorter than the City of Rome, but shorter than the Sorvia, and shorter than the Alaska which of the throe steamers, as far as he could learn came nearest the type he had in view He believed the steamer to do this work would be under 500 feet in length between perpendiculars. What her° other dimensions would be would have to be nxed by experiment, and a very careful series of calculations and thought. The step he was going to recommend had been already taken by the Admiralty in special ship structures of providing in such for- the weight ot structure necessary to stand the strain of the sea, but in omitting the overweight of structure required for the purpose of providinglocal strength sufficient to allow of constant grounding and knocking-about. That might seem a good deal to ask of an owner, but its rejection meant that if he burdened the ship with the weight of structure to meet those requirements, he simply increased his first cost with the increased weight and size of the steamer, and^consequently his current expenses in drivirig her.' There was no reason why such a steamy should nqt be kept permanently afloat, excepting when sho required "to go into the dry dook, by her coal and stores and passengers and light packages being taken to and from her by tenders. If ho was not misinformed, this method of treating the larger Atlanticsteamers was at present either partially or completely in practice at Liverpool, and it was' he know, partially in practice on the Clyde' A complete development of it would permit of the conditions required, and this would be all the easier because for an express paasentrer •steamer the ownSr would have to, $acr.ifice~all idea of carrying cargo., This", among the various dißsqnsiQris. ancFremarks iipon this subjeoc, was, he was happy to see,, pretty well, understood Cargo carried in an express steamer would be one of the most expensive luxuries, one might say fancies, that any owner ever indulged m, because every ton of. it would be an increase, of tljo ctfspMcem'ent of the steamer consequently1" of the difficulty of drivmgher-of tier weight of construction, of tha weight of her machinery, and, finally of the amount of coal to be Qarn'pd. It was not possible for h.im within tl,Wimts at is dis pqs.ll fur.tl,or. tq deyelon tl,is quest U Nor m\th 4> ™S A° W o ™l^ '» "without a much, mqre J a b.QVJ O us consideration of it than 1)0 had yet been able to give the matter. Express boats might, however, bo used for other services than that of the Atlantic, wh. orft «" distances to be traversed wove, Wand to weather less temp^uous." Xfmg% Bowie's fed*!?, Ar lV 1g fl'.° m tll° «W« ihe^^w^ zT^S^ trebling tfft length of thfc, boat kecpL "the foi-m"uX" " 1<? T- c fcopor&^tgS «° «,m "•scU- Assumi"g that in tho event hnrt aU incrcil?° t'w> awnnrt of rotated orse-powor were, W proportional to the dis-pku-Qinenti and the weight of machinery per Wlloatod horse-power wcro no greater than in Mr \ arrow s torpedo boat, also that the weight of construction absorbed no greater percentage of displacement than in his boat, then a similSvessol 200 foot long by 2i\ feet nvtinmo rent 9 inches m draught of water, would have a displacement of 308 tons, and might bo oxpocted to attain a speed of about 27. knots per hour ; a similar vessel- 300; foet long, 37'feetiri oxtremo breadth, 33 feet breadth on wator-llno; M foot 8 inches dopth, and 8. feet 9 inches draught of watpr, with i\ displacement of 1040 tons, m^ht be. expected' to' attain a. spood of 31 SWt«: H° wa.B °.i'ly speaking qf" these as mat:

ters of speculation, but it wa3 impossible tc say that they might not be fulfilled, and they were within the bounds of possibility, provided engines could produce in the 200-feet boat about 800 indicated horse-power, and in the 300-feet boat about 16,000 indicated horse-power, as easily as Mr Yarrow produced G2O indicated horse-power in his 100-feet torpedo boat. The highest cf these developments of power was simply enormous, and fully 50 per cont. more tuaii the promised development of power in the three Atlantic liners lately built. They might thorefore assume that they were not likely soon to have the idea of the 300-fest boat developed, but it would be risky to say that something approaching to the 200-feet might not very soon be attempted. There were services and purposes for which such speed would ba very desirable, and the torpedo boat builders had worked so steadily up to the 100 feet in length that it seemed to "him not at all improbable they might go still further, while it was possible they might be met by the ordinary shipbuilders working down to meet them.—(Applause.) As to the prospects of increased dead-weight carrying, it was not dimcult to predict the probable line of its development. Experience showed that moderate proportions, low speed, and full form, combined with a draught having a great ratio to the beam, were the conditions of success in this class of steamers, and they might expect to see these conditions develop more and more. When they were so developed that the demand for draught pressed upon the facilities generally offered, as the want of draught was at present forcing the large Atlantic steamers into disadvantageous forms, and thereby pressing upon them, they would see the meaning attached to draught in this lecture forcibly and practically illustrated. Anyway, they might be sure that the differentiation between fast steamers and heavycarrying steamers would become greater every year, as neither could compete with the other mi • v n.° wn • s Pecialfcy ; and the trades in wnicn tins differentiation was going on would by its very operation make the cargo steamer more purely a cargo steamer, and the passenger and mail steamer more purely an express steamer day by day