68 NOTES ON RIVETS AND SPACING OF RIVETS FOR OIL-TIGHT WORK. 
transverse to longitudinal bulkhead and five-diameter spacing in bar connecting 
to the shell. No gunning was used and no special effort made to have the box 
absolutely tight on the first test. 
A similar tank was also recently tested at the New York Navy Yard to dem- 
onstrate the efficiency of a six-diameter spacing for T-bar stiffeners and for bound- 
ing 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 endurance test with oil 
at the same pressure. Then the pressure head was increased to 93 feet, which 
pressure was maintained for four hours without leaks. 
The results of the tests appeared to indicate that in fairly heavy plating, 
where the members are not under the influence of other stresses than those due to 
head, six diameters are suitable. The thickness of angle bars, it was suggested, 
should preferably be not less than three-eighths of an inch. 
It is understood that further 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 construction. A description of these tests in greater detail would be inter- 
esting, 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 bulkhead stiffeners if caulked 
oil-tight. This is a closer spacing than is required for water-tight work. Experi- 
ence 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 not prepared to make the spacings the same, a com- 
promise has been made allowing a somewhat greater spacing than called for by 
the navy rules for oil-tight work. For single riveting three and one-half diameters 
are retained, 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 result of mathematical analysis, has sug- 
gested the following spacing as permissible, provided that considerations other 
than oil-tightness did not determine the spacing :— 
Diameter of rivet Thickness of plating Spacing in diameters 
3/4" 5/16” 3-6 
3/4” 3/8" 4.2 
7/8" 12m 4.9 
1” eae! 5.6 
1/4 Ty 6.3 
Maly AM 1 yas 7.0 
The above spacings were based on the supposition that three and one-half inch 
diameters were satisfactory for a 10-pound plate using five-eighths-inch rivets, and 
