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.