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23 shipbuilders in the design and con- struction of tankers intended to be classed at Lloyd's. Within a comparatively short time after this, Bureau Veritas, apparently profiting by this paper, published rules for tankers, and the American Bureau of Shipping published their first rules in 1902. The first rules of Lloyd's did not appear for general use until 1909. Both Bureau Veritas and the Amer- ican Bureau recommended three and one-half diameters at the start, while Lloyd's specified one more rivet in a frame space than required for water- tight spacing resulting approximiately in three and one-half diameters. Ac- cording to the recollection of the writer there was a_ period when Lloyd's practically decided not to class any more converted vessels, but both workmanship and details of con- struction must have improved, as many converted vessels have since been classed and have given good service. - Evolution was a slow process, and no doubt in numerous cases the true cause for failure was not recognized. Mr. Martell realized this when he wrote his paper and _ provided for tanks not over 24 feet in length, in- creased stiffeners and brackets, as well as closer spacing of rivets. Had the earlier tankers been better de- signed as regard tanks, _ stiffeners, brackets and compensation, where. needed, the question of rivets and spac- ing of rivets for oil-tight work possi- bly might 'have received somewhat less attention during those troublous times. This appears to be a reason- able inference from the fact so many converted tankers since have given long and satisfactory service. Double and Single Riveting Rivets in the shells of the early tankers were continually getting loose and leaky, while it is very rare that the shell rivets spaced for water- tight work of later converted vessels, where the interior details of construc- tion were in accord with Mr. Martell's recommendations or classification rules, showed leaks. The compara- tively slight variation in the spacing of shell rivets would not account for this great difference and must be at- tributed somewhat to improved de- tails of construction and, in a meas- ure, superior workmanship. That oil-tight work should be dou- ble riveted was an accepted rule. This is still the general requirement, but single riveting now is permitted in the seams of double bottoms intended ir eartvirg fuel oil. This concession was not made until after many vessels in commission had been converted to THE MARINE REVIEW carry fuel oil in their double bottoms with single-riveted seams and _ their class continued. The writer recalls a large vessel on, the stocks with tank top required to be double riveted to carry fuel oil, while at the same time an old vessel lying in a wet slip along- side was being fitted to carry fuel oil in the double bottom where the tank top was single riveted. Both new and old single-riveted tank tops, where fuel oil is carried in dou- ble bottoms, have proved a success. Why should there be any greater risk in single-riveting the seams for decks and trunks of tankers, which are subject to less test head and deflec- tion, especially where the spacing is made closer for oil-tight work? This is a parallel case to double bottoms above noted, for both Lloyd's and the American Bureau have vessels on their books, which have been fitted with deep tanks for fuel oil, retaining the original single-riveted decking. This point has been discussed with. repre- sentatives of both the above societies and one of the largest shipowning oil companies. They agreed that there would be no real objection with crude oil. Just how far. this argument could be carried for tankers intended or lia- ble to carry bulk gasoline or. other light distillates is an open question. If single-riveted seams are tight for crude oil, would they be as tight or rust up tighter with gasoline? Lloyd's do not permit gasoline to be carried in single-riveted double bottoms, but it is not known whether or not it would be permitted even with double- riveted seams with dry cargo above. The writer was closely associated with the conversion of three passen- ger steamers to carry about 18,000 bar- rels of fuel oil in deep tanks forward of the fire room. The vessels had double bottoms, which were opened so as to form part of the deep tanks, but the water-tight divisions in the double bottom did not coincide with the tank bulkheads and a portion of the double bottom under each tank form- ed a part of an adjoining deep tank. In other words, the transverse bulk- heads extended, so to speak, under the next tank to the first double-bottom division and then down to the keel, the new part above double bottom be- ing double riveted and the horizontal part, or what was the original double bottom, being single riveted. The af- ter tank extended in this way under the forward fire room. These vessels have given excellent service, notwith- standing they were built during a strike where the best work could not be expected. It is not concluded from this that it would be advisable to single-rivet January, 1921 transverse bulkheads in tankers, but, with a view to eliminating possible un- necessary expense, it might be well worth considering whether or not there would be serious objection to sin- gle-riveting the longitudinal seams of center-line bulkheads with the excep- tion of the lower seam. A cargo is sometimes made up of more than one kind of oil, therefore it is important transverse bulkheads be _ absolutely tight. Different kinds of oil have sel- dom been carried on opposite sides of the center-line. So it would appear a single-riveted longitudinal bulkhead would fulfil every function the trade demands. Specified Three Diameters As noted above, Lloyd's in their first announcement, more or less offi- cial, recommended three diameters for all oil-tight spacing. This was, "in some cases, applied literally. Two ves- sels were converted in the vicinity of New York to carry o1 in bulk, on which a spacing of three diameters was required in both rows of rivets in the flanges of single 5 inches by 5 inches 'bulkhead bounding bars. This both crowded the rivets and unneces- sarily impaired the strength of the shell plating. Classification societies now allow a spacing of five diameters connecting bulkhead bounding bars to shell. Lloyd's formerly recommended sin- gle double-riveted bulkhead bounding bars, but later gave the builder the option of using double single-riveted bars. The general practice now is to use double single-riveted bars with countersunk heads and _ points and bars caulked on both flanges on each side. The writer is inclined to favor single double-riveted bounding bars and pan-head rivets in standing flange with caulking on one side, because it is believed this lends itself to cheap- er and better workmanship and would insure the parts being drawn up more closely. Countersunk heads are, of course, unavoidable in the shell flange. On the Clyde, bulkhead bounding bars frequently are hydraulically riveted on the ground, using pan-head rivets and firtishing with snap heads and points. Similar practice universally is followed in this country in the case of locomo- tive oil tenders and tank cars. Snap rivets driven by hand also are satis- factorily used in the construction of oil storage tanks. There are two vessels now building for the same owner in different yards with double -- single-riveted bulkhead bounding 'bars with countersunk head rivets, where in one case every rivet is required to be caulked head and point before testing, while in the other case