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® 14 MARINE REVIEW. [June 7, THE PRACTICAL RESULTS OF SOME INNOVATIONS IN MODERN SHIP BUILDING. BY HENRY B. WORTLEY, MEMBER INSTITUTION OF NAVAL ARCHITECTS.* It may be of interest to the members of this institution to lay before them the results of sothe departures from ordinary merchant ship building practice, which have been embodied in eleven steamers owned by the Ocean Steamship Co. and managed by Mr. Alfred Holt. These vessels. like all their predecessors in the line, are unclassed. Their moulded dimensions are 440 feet by 52% feet. They carry 8,200 tons of dead weight ona draught of 25% feet, the freeboard having been assigned by the Brit- ish corporation for the survey and registry of shipping. The profile is shown in Fig. 1, where it will be observed that the upper deck has no sheer; though, for the sake of eye sweetness, a slight sheer has been given to the bulwark rail. The engines in normal condition indicate 3,600 H. P., giving a continuous sea speed of 13 knots. Three of these vessels have now made two round voyages from this country to China and Japan, each covering a total distance of about 50,000 miles, and two of them have started on a similar maiden voyage of about 25.000 miles. Amongst the innovations are the following: External--A rudder so hung that no stern frame has been required, and allowing the atter dead- wood to be cut away. Internal--The substitution in the main hold of two pillars in place of the usual numerous stanchions; a 3-foot frame spacing; the disuse of cement on the ship's bottom inside the ballast tanks. The stern frame of a merchant steamer is a feature which still retains to a large degree its primitive form and section. It has varied but little since its patible with the weight involved. 'Whether considered as a girder or pil- lar the section is most primitive, and the number of broken stern posts constantly seen do not justify them as being simple things to manufac- ture, or fitting contrivances for ending the after body lines. When broken no other part of a ship of equal weight is so costly to repair, or requires so long a period for renewal. The form renders it incapable of being in- corporated with the framing of the ship at reasonable cost, excepting at the transom, and at the upper portion of the inner or propeller post. Its whole weight is therefore sandwiched between the comparatively thin end plates of the. shell, to which it is attached by a multitude of long rivets of a large diameter. The number of slack rivets observed in the after deadwood and the number of stern frames broken just below the boss, clearly show that a considerable deflection takes place in thin deadwood during the ordinary working of the ship. The deadwood of the sailing ship has definite reasons to justify its existence, but it is difficult to find an excuse for deadwood in steamers. Its weight is generally greater than its buoyancy, it probably interferes with the efficiency of the propeller to an appreciable extent, and it certainly tends to prevent rapid man- euvering. Most ship owners have experienced in greater or less degree the foregoing disadvantages of the ordinary forged or cast steel stern frame and rudder; and many agree that the present type of stern is "found Fig. 1. . : ' CourLINe s a ; { l a4 | 1 i ie al Oacn (ye tH tron ae & 3 | ~ adh hownityoms 9 1 | WATERTIGSR TE CLAY ess 0 PLATS lA ; Arnwartsnie SECTIONS Fig. 2. introduction into iron ship building, and probably it had more arguments to justify its inception than can be claimed for its retention today. When introduced it was small in weight, size and section, easy to forge, and formed a convenient method for finishing the run of a small ship. Since then the sizes of ships have gradually increased, and the stern frame has steadily advanced in weight, size and section, until at the present time it is quite common to have stern posts of 20 tons weight and 13 inches by 8 inches of rectangular section. It is needless to say that these posts are very clumsy to handle, even though scarphs have been introduced, and, despite the care bestowed in the manufacture, the results are not always satisfactory. The commendable action taken by Lloyd's in the early eighties, in appointing specialists to survey forgings during the process of manufacture, and the circular issued in 1886 requiring all sections above 40 square inches to be welded under the steam hammer have done much to minimize the evil; but it is not yet cured. Cast steel was intro- duced for stern frames and rudder in the hope of cvercoming bad welds, but a reaction has taken place against the use of this material, as many ship owners have had unfortunate experiences of contraction flaws, neces- sitating the removal either of partial to complete stern frames and rudders. The rectangular section of stern frame is most commonly used, although in some few of the largest vessels--especially twin-screw steamers--a U-shaped section of cast steel has been adopted for the inner post, while oo ee portion of the outer post has been retained of rectangular ction. Now the strength of a stern frame of rectangular section is incom- _*Read at last annual meeting of Institution of Naval Architects, London. wanting." With a view to overcoming these difficulties the following guid- ing principles were laid down for designing a stern and rudder for vessels of the Ocean Steamship Co.'s fleet: That there be no useless after dead- wood; that a support at the heel of the rudder is not essential; that forg- ings and castings be reduced to a minimum; that the frame terminating the run of the vessel be compatible with the adjacent scantling; that the frame be thoroughly incorporated with the ship's structure; that the rudder be of the balanced type. Several designs were made to meet these requirements, but the one illustrated in Fig. 2 was finally chosen. It will be noted in the diagram that the after end of the rudder was 8 inches thick, and forms the termination of the water lines above the propeller arch. This gives a much longer and cleaner run to the vessel than is possible when the lines terminate upon the ordinary stern post. The greatest ad- vantage, however, lies in the increased thwartship width that these lines give to the stern, as it enables the requisite strength to be obtained from material of much less weight than the ordinary form of stern frame. The increased space also gives easy access to every rivet in the structure. In this case the stern post is made of a wrought iron tube of 21 inches exter- nal diameter and 1 inch thick, with an internal liner at the lower part of the same thickness. The lower part of this tube forms the bottom pintle for the rudder. The propeller arch is made of a Siemens-Martin steel plate 1 inch thick, of U-shaped section. The after part of it is riveted to the sides and also the front part of the stern tube; and the forward part is carried down to the boss and riveted thereto. The boss is a steel casting --the size of which has been reduced as much as possible. It has one palm on the top riveted to the extension of a water-tight flat, and another at the fore end of its lower part riveted to the after-peak bulkhead. It will