76 NOTES ON RIVETS AND SPACING OF RIVETS FOR OIL-TIGHT WORK. 
riveted, I think the risk would be too great, particularly in view of many disasters that 
have taken place, due to accumulation of gas with low-flash oil. 
With reference to the single riveting of the seams of the center-line bulkheads, I 
might say that in vessels designed for carrying heavy oil the seams of the center-line 
bulkheads have in some special cases been allowed to be single riveted. If, as Mr. Frear 
seems to think, the same grade of oil is always carried on the opposite sides of the center- 
line bulkhead, and if the owner would agree to guarantee the same, I think the classifi- 
cation societies might be willing to consider single-riveted seams. In what was known 
as the ‘“‘heavy oiler class,’’ built during the war, and which has proved successful, quite a 
large amount of the work, such as the seams of the center-line bulkhead and some of 
the transverse bulkheads, the decks, and the tank top were all single riveted. 
With regard to the caulking of rivets, I consider this should only be done where 
necessary, to save trouble in awkward corners. If care is taken by subpunching and 
close bolting, the caulking of rivets would be reduced to a minimum and need generally 
only be resorted to after testing. 
I have observed men.caulking rivets and undoubtedly making them worse, because 
where the point is unusually full and spreads over the surface, they very often caulk 
the plate away from the rivet, the result being a tendency to loosen the rivet. 
I might say here that the practice which is very often adopted, of double-hammering 
the rivet, appears to me to be very good, and, if flat-headed hammers were always used, 
this would ensure the rivet filling the hole thoroughly, and caulking would be cut down 
to the minimum. Further, I agree with Mr. Frear that a good panheaded rivet should 
never require caulking before testing. 
There is no doubt that the T bars are a boon to good oil-tight work, and it is a pity 
that there is not a slightly larger section available. It has occurred to me that a 7 inch 
by 7 inch angle, if rolled, would be very suitable and would take the place of the T bar, 
by fitting the plate in the bosom of the bar. I also agree with Mr. Frear that a 5 inch 
by 5 inch gunwale bar is unsatisfactory for oil-tight work and that a 6 inch by 6 inch bar 
is more suitable. 
With reference to the spacing of rivets for oil-tight work, the unanimity of the 
requirements of the classification societies goes to show that, unless the work could be 
ensured by subpunching, etc., their tables appear to be reasonable. If the spacing 
should be modified in future, the thickness of the plates will be an important factor, as 
there is no doubt that in way of thicker plating (providing strength considerations allow 
for the change) wider spacing could be adopted, particularly starting above % inch thick. 
Thought should be given to the riveting in the ends of stiffeners, and these should 
receive very special consideration, as experience shows that this is where trouble usually 
develops. This is featured in the Isherwood system by the close spacing at bulkheads 
and transverses, and Lloyd’s rules require the riveting to be closed up to four diameters 
for 15 per cent at each end of unbracketed vertical stiffeners. 
Rivet points should be maintained full and raised above the surface of the plating 
about %inch. On the other hand, there is a tendency in so doing to make the points 
unnecessarily full, which is a bad feature, as the rivet spreads over the plate and does 
not ensure good workmanship. Although it may look satisfactory, if the hole is not 
entirely filled, when any working takes place the rivet may become slack, where origi- 
nally, to all appearances, the rivet looked good. 
