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30 longitudinal bulkhead and _ five-diam- eter spacing in bar connecting to the shell. No gunning was used and no special effort made to have the box ab- solutely tight on the first test. A similar tank recently was tested at the New York navy yard also to dem- onstrate the efficiency of six diameter spacing for T-bar stiffeners and for bounding bars to bulkheads. The tank was first subjected to a test head of 65 feet of water and found to be tight; then to a twenty-four hour en- durance test with oil at the same pres- sure. Then the pressure head was in- creased to 93 feet, which pressure was maintained for four hours without leaks. The results of the tests appear ed to indicate that in fairly heavy plating, where the members are not under the influence of other stresses than those due to lead, six diameters are suitable. The thickness of angle bars, it was suggested, should prefer- ably be not less than three-eighths of an inch. It is understood that fur- TAES MARINE sRE VIEW not prepared to make the spacings the same, a compromise has been made al- lowing a somewhat greater . spacing than called for by the navy rules for oil-tight work. For _ single-riveting three and one-half diameters are re- tained, but four and four and one-half diameters, depending on the thickness of the plates are now accepted; five diameters are used in bounding bars of oil-tight floors. One of the larger builders, as a re- sult of mathematical analysis, has sug- gested the following spacing as _ per- missible, provided considérations other than oil-tightness did not determine the spacing :-- Thickness Spacing Diameter of rivet, of plating, in diameters, inches inches inches 34 ts 3.6 34 ¥ 4.2 % ¥% 4.9 1 % 5.6 1% 1 6.3 1% 14 7.0 The above spacings were based on the supposition three and_ one-half January, 192] diameters; 35-pound plate, 5.6 diam- eters. The above were deduced with. out reference to strength of joint and, it was pointed out, this consideration might be more important than questions of tightness. For five-eighths-inch rivets in 10-pound plating it was shown that approximately 0.006 inch is the deflec- tion or amount of seam that can be caulked off without exceeding the elastic limit of the material. The stresg on the rivet for such caulking was found to be very moderate. The analysis used in deriving the above tables of rivet spacing for oil- tight work was made to confirm a theory that every unnecessary rivet is a possible source of leakage and for heavy plating wider spacing is permissible, For thin plating, where large rivets in relation to thickness are used, the diameter is based more nearly upon theoretical considerations. But if the same considerations were followed in determining the diameters for thicker plates, the rivets would exceed the NEW TANKER ARGON OF THE STANDARD OIL CO. WEIGHT TONNAGE OF 10,000. 42-GALLON BARRELS ther tests were directed to be made on experimental tanks at navy yards, as the navy contemplated revising its rules for oil-tight riveting due to the very considerable increase in amount of oil-tight work involved by new con- struction. A description of these tests in greater detail would be interesting, but, unfortunately, full particulars are not at hand. It has been the practice in naval work to use a spacing of three and one-half diameters for oil-tight work in seams and straps, four diameters in angles to plates including staples, and four and one-half diameters on bulk- head stiffeners if caulked oil-tight. This is a closer spacing than is required for water-tight work. Experience in the construction of oil tanks in double bottoms seems to indicate that, with ordinary good workmanship, water- tight spacing will be satisfactory for oil. While the naval authorities are HER TANK CAPACITY IS 75,000 SHE HAS A DEAD- STEAMSHIP FAIRFIELD CONDEMNED AFTER ONE YEAR SERVICE. KEEL AND UNDERBODY WERE BADLY BATTERED ON HER THE ROCKS OF MARTHA'S VINEYARD inch diameters were satisfactory for a 10-pound plate using five-eighths-inch rivets, and assuming the deflection of the plate edge caused by caulk'ng probably varies as the ratio of the fourth power of the distance between rivets to the fourth power of the thickness of the plating, and that the extension of the rivet varies as the ratio of the distance between rivets to the area of the rivet. In order to make prac- tical use of the above it was suggested water-tight spacing be used for rivets in oil-tight work on naval vessels. A naval constructor stationed at the same yard carried the investigation further by considering the deflection caused by caulking and by the amount of general deflection of plating due to water pressure, and suggested the fol- lowing spacing would be satisfactory: --l5-pound plate, 4 diameters; 20- pound plate, 4.5 diameters; 25-pound plate, 5 diameters; 30-pound plate, 5.3 limit practicable to drive, and spacing based even on using the same number of diameters would at some point be- come greater than indicated in the tables. Thick plates, however, are used where greater strength is required, and as the rivets used are much smalfer in relation to thickness a greater num- ber is necessary to develop __ the strength of the plating. The uniform spacing in diameters adopted in prac- tice, substantially, for all thicknesscs of plating is a great convenience, ani it is only necessary to increase the number of rows of rivets where grea*- er efficiency of joint is desired. If the spacing suggested in the above tables is suitable for oil-tight work, it might be necessary to increase the number of rows to. insure proper strength and friction of the joint, in which event there would be an_ in- crease in weight and the attempt to reduce the number of rivets defeated.