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Bracketless System Improves Ship Construction LL who are conversant in the slightest degree with shipbuild- ing are aware of the rapid in- crease which has taken place in the number of ships built on the Isher- wood system of longitudinal framing, since its introduction in 1907. This increase has been most marked in vessels which have been constructed to carry oil in bulk, as the following figures will show. At present Isher- wood framed vessels number about 1492 and aggregate over 12,500,000 tons deadweight; of this number 696 vessels of about 6,750,000 tons dead- weight are vessels for carrying oil in bulk. The latter figures are most re- markable when it is recorded that, ex- cluding tankers of less than 1000 tons, the total tonnage of oil-carrying ves- sels recorded in Lloyd’s register book at July, 1925, was 5,384,290 gross tons. Until the introduction of the Isher- wood longitudinal system of framing the problem of carrying oil in bulk presented great difficulties. The earli- est method adopted was to convey the oil in barrels placed in the holds of ordinary cargo vessels. This was lat- er improved upon by substituting for wooden barrels a large number of small cases of iron. From these cases to large iron tanks, situated in the holds and ’tween decks, was a natural development which soon expanded into a double-skinned vessel, the inner skin Reprinted from Shipbuilding and Shipping Record. forming large rectangular tanks and becoming an integral part of the structure of the vessel. The latter type of vessel did service for some time until the idea was conceived to remove the inner skin and make the shell itself act as. the side of the tanks. Thus the modern form of tank- er with its large rectangular tanks was evolved by a series of progressive Bracketless System for New American Tanker It is understood that the large twin screw diesel tanker recently ordered by the Gulf Refining Co. from the Federal Shipbuilding & Dry Dock Co., Kearney, N. J., will be constructed on the new “bracketless system” of longi- tudinal framing described in this article. This tanker will be 543 feet 6 inches in length overall, 74 feet in beam, 40 feet 6 inches in depth and of 17,400 tons dead- weight, and it is expected will be completed ready for service late this year or early in 1927. steps, but it is significant that up to the birth of the first real tanker the designers’ energies appear to have been directed towards the develop- ments of what may be termed the oil containers, the construction of the hull proper being, seemingly, left to look after itself. As a consequence, aman gf Be tankers continued to be built with or- dinary transverse framing and heavy side stringers, the hull being divided and sub-divided by a series of oil- tight transverse bulkheads extending _to the shell of the ship and an oil tight center-line bulkhead. In view of the peculiar nature of liquid cargoes and the heavy local strains set up in the structure of a vessel when carrying such cargoes, a high standard of strength is essential, and despite all that was done to im- prove the structure in the light of past experience, the transverse sys- tem of framing was not particularly successful in meeting the exceptional demands made by the oil-carrying car- go vessel. In the old style of trans- verse construction there was continual trouble and leakage taking place in the bracket connections and the oil tank bulkheads in addition to the damage sustained in bad weather due to the deficiency in longitudinal stiffening and general longitudinal strength. The Isherwood system over- came the latter trouble and greatly minimized the former and at the same time provided, at less first cost, a considerable increase in deadweight carrying capacity. This system of construction is too well known to our readers to require description and they are doubtless aware that Lloyd’s reg- ister of shipping has adopted this system in the formulation of its rules (Continued on Page 38) FIG. 1—ORDINARY ISHERWOOD SYSTEM—AT LEFT, CAULKING SIDE OF BULKHEAD—AT RIGHT, STIFFENING SIDE OF BULKHEAD 16