File:Cassier's magazine (1911) (14760945021).jpg

Identifier: cassiersmagaz401911newy (find matches)
Title: Cassier's magazine
Year: 1891 (1890s)
Authors:
Subjects: Engineering
Publisher: New York Cassier Magazine Co.
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Smithsonian Libraries

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the necessity for securing the neces-sary trim by the stern when loaded.The oil space proper terminates about65 feet from the collision bulkhead,leaving a small hold, which, however,is seldom used for carrying cargo. THE HULL STRUCTURE It is in the design and combina-tion of the materials forming thestructure of the vessel that the de-signer meets with his most difficultproblems, and this is so because ofthe many conflicting conditions whichhave to be considered. Look, fora moment, in this connection atthe nature of the cargo he is dealingwith. Unlike the majority of car-goes carried in merchant steamers, itrests directly upon the shell platingof the ship instead of upon the in-ternal floors and frames, and thussevere stresses are induced on therivets connecting the plating to thesegirders. This effect is greatly in-creased by the inertia of the fluidcargo when the vessel is pitching orrolling in a seaway. It is to be no-ticed also that both plating and rivet- OIL-CARRYING VESSELS 74i
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FIGS. 6 AND 7. STRUCTURE OF OIL-TANK STEAMSHIP ing are subject to fluctuating stresseswhich cannot be insignificant eitherin rate or range. We are becomingincreasingly aware of the fatigue in-duced in materials under such con-ditions. It is now known that, underconditions of repetitive stress, resist-ance to rupture depends not so muchon the maximum stress of one kindor the other as upon the algebraicdifference of the stresses; that frac-ture may take place for a stressmuch less than the elastic limit ofthe material if repetition takes placea certain number of times; and thereappears reason for believing thatmany cases of structural damage in oilvessels may be explained by some suchconsiderations as these. Again, itis to be remembered that each tankmust be oiltight, and must bedemonstrated to be so by a watertest of considerable severity, andthat in many cases the arrangementof riveting sometimes necessary tosecure oiltight work is not the beststructural arrangement. When onetakes int

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