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planation for the serious troubles ex- perienced in so many of these steam- ers at the bracket attachments to the transverse bulkheads. The _ in- vestigation points to the necessity of further increasing the depth of the web frames in ordinary oil-carrying vessels, and also of fitting double- riveted attachments to the shell plat- ing as prescribed by the rules of Bureau Veritas. 7 is Of interest to notée,- im the new rules of the British Corporation Registry for oil carrying vessels, that this society has the courage to pro- vide for "deep frame" construction in this type of vessel. Close investiga- tion shows this to be distinctly pref- erable to the web framed arrange- ments generally adopted; and this is confirmed by the experience gained in steamers having deep frames in deep water ballast tanks. In the system of framing under consideration, it is a simple matter to single out and determine the stresses on all parts of the structure under test conditions. Under these conditions the rivets attaching the brackets to the transverse bulkheads are subject to stresses in no case ex- ceeding 354 tons per square inch, which is only a fraction of that to which the _ stringer attachments in ordinary vessels are subject when considered under the same conditions. The strength of the rivet attachments in all parts of the structure in the new system have also been carefully investigated. The transverses are connected to the shell plating with double angles, having the rivets spaced about four and half diameters apart. The rivets attaching the longi- tudinals to the shell plating are Spaced: six diameters apart, except in the vicinity of the transverses. The Shearing stresses at these parts being at a maximum, a closer spacing has been adopted, viz., from three and a half diameters to four and a_ half diameters, except at the uppermost longitudinals, where a uniform spac- ing of six diameters has been adopted. It is a debatable point whether direct attachments of the longitudinals to the transverses are necessary, or whether the shell plating itself does 'hot provide a gusset binding the two Parts of the structure efficiently to- Sether. It would appear that if both longitudinals and transverses are ef- ficiently riveted to the plating in the manner previously described no indi- _Vidual movement could take place. In this oil-carrying steamer, how- 'ver, and having in view the testing four rivets and the upper ones "'TAE MARINE REVIEW of tanks before the vessel is launched, it was decided to attach the bottom longitudinals to the transverses with vertical lugs having six rivets in each flange, the lower bulb angles with with rivets. These attachments, whether structurally necessary or oth- erwise, were expected to facilitate the erection of the steamer, but in actual practice they proved of little import- ance. The transverses, where con- nected to the middle line bulkhead, are attached to the plating with single angles double riveted, and, as at the skin plating, the rivets are closer spaced in the horizontals in the vi- cinity of the transverses. The deep web plates on transverse bulkheads are attached with single angles having the rivets four and a half diameters apart and a uniform spacing of five diameters is adopted for the lower horizontals and six diameters for the upper ones. The comparative longitudinal stresses calculated under the usually accepted loaded" conditions, -viz., by assuming the vesel on a wave of her own length and the bending moment D Xs two asc . show the tension at the 35 bridge gunwale amidships to be 18% per cent less in the vessel built on the new system, the results being as fol- lows: New Systent.....7 2. 6.7. tons per sq. in. Ordinary system....8.22 tons per sq. in. In making the comparison at the bridge ends, the bending moment was DX on account of these assumed 45 parts being some distance from 20 anuidships. (Whether the factor 45 is correct or otherwise is unimportant since it would not materially alter the comparison.) Under these condi- tions the comparative stress at top of trunk is 10.8 per cent less in the new system, the results being as fol- lows: Dew... systemis.w... ts 6.61 tons per sq. in. Ordinary system....7.41 tons per sq. in. The comparative transverse and deck stresses on the bases previously described are shown in the _ table. Although this comparison of stresses shows the structuré...to-< be: of generally increased strength, yet there is a saving in weight of mate- rial estimated at 275 tons. _ The saving is due to the redistribution of mate- rial, which admits of dispensing with a large number of transverse con- nections. The vessel, in consequence, could carry 275 tons more deadweight on the same draught, with the same model and with 'the same consump- tion of fuel, thus considerably in- creasing the earning power of the steamer. A few remarks as to the erection of the ship may be of interest. The keel plate was laid and middle line keelson fitted as usual. The after peak is framed with the usual trans- verse frames, and the erection up to the peak bulkhead was the same as in ordinary vessels. The peak bulkhead and the two transversé bulkheads forming the two short compartments ait were then put together on the ground, erected and secured in posi- tion, middle line bulkhead fitted, and longitudinals placed in position. The two transverses in the next compartment were erected on _ the port side of the ship, circular tunnel OIL TANK SHIP." Transverse System. Tons per sq. in. Deep frames us tanks) 356 beeen ences Decne ences Web frames (increased as is usual in i S321 Oil steamers) <5 2.6%. ccs ole bee Deck beams (in bridge).......+..- +. 5.04 Deck beams (clear of bridge, and in- creased as usual in oil steamers)... 4.32 Maximum shearing _ stresses on I bo rivets attaching deep frames to shell plating OIL TANK 'SHIP. "Isherwood" System. Tons per sq. in. Transverses-- Siders: Bunt oh he eee eas 3.76 Bottom. vous ws ee eee a eee 3.67 DICCK Se Pie ee eee sk wees Os kee 0520 Deck Longitudinals-- An PHASE oe ac eos ae es 3.8 Clear of "bridges. 3 oe ret ees 2525 ( ( Tea7 Nos. 1 ss 2°34 ; % 25 : Pe 4.49 Bn S41 ol 4 36 Be, : 5 4.65 ss} as Pa 4.92 Bas | 5.46 2 "9 é 5.89 mole cee @ 4.02 gi) ik es a Bh 4,68 14 © 3°31 2 "e 15 io . Le ee Ay Maximum _ shearing' stresses on rivets attaching strong _ trans- 4.94 verses to shell plating.... 75 22. stresses on } to ; 1 to5 ' ee Maximum > shearing rivets attaching longitudinals shell plating