64 NOTES ON RIVETS AND SPACING OF RIVETS FOR OIL-TIGHT WORK. 
converted vessels, where the interior details of construction were in accord with 
Mr. Martell’s recommendations or classification rules, showed leaks. The com- 
paratively slight variation in the spacing of shell rivets would not account for this 
great difference and must be attributed somewhat to improved details of con- 
struction and, in a measure, superior workmanship. 
That oil-tight work should be double riveted was an accepted rule. This is 
still the general requirement, but single riveting is now permitted in the seams of 
double bottoms intended for carrying fuel oil. This concession was not made until 
after many vessels in commission had been converted to 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 alongside 
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 double 
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 deflection, 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 representatives of both the above societies and one of the 
largest shipowning oil companies who agreed that there would be no real objection 
with crude oil. 
Just how far this argument could be carried for tankers intended or liable 
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 passenger 
steamers to carry about 18,000 barrels 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 formed a part of an adjoining deep tank. In other words, the transverse 
bulkheads 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 being 
double riveted and the horizontal part, or what was the original double bottom, 
being single riveted. The after tank extended in this way under the forward fire 
room. These vessels have given excellent service, notwithstanding 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 trans- 
verse bulkheads in tankers, but, with a view to eliminating possible unnecessary 
