NEW 20,000-TON TANKERS. 
By H. F. Norton, Eso., MEMBER. 
[Read at the twenty-eighth general meeting of the Society of Naval Architects and Marine Engineers, held in New 
York, November 11 and 12, 1920.] 
The vessels designed by the Newport News Shipbuilding & Dry Dock Com- 
pany for the Standard Oil Company of New Jersey will be of interest to the Society 
on account of being, so far as we are aware, the largest tankers yet built, and of 
several unique features in design, especially in connection with the structural 
work. 
They are two twin-screw ships 550 feet between perpendiculars, 75 feet beam, 
43 feet 3 inches depth to shelter deck, and about 20,300 tons deadweight on a 
draught of 30 feet. The vessels are designed with straight stem and elliptical 
stern and rigged with three pole masts. They are of the shelter-deck type with 
complete steel shelter and upper decks, except that the upper deck is omitted in 
the expansion trunk in way of the oil tanks. The vessels are being built under the 
special survey of the American Bureau of Shipping to the highest class. 
The propelling machinery is located in the stern and consists of two triple- 
expansion engines set side by side in the same engine-room. The engines are 
designed for 3,800 indicated horse-power total at 200 pounds working boiler pressure 
and a piston speed of 585 feet per minute. The cylinders are 23-inch, 39-inch and 
68-inch diameter respectively with a 45-inch stroke. The high-pressure and inter- 
mediate pressure valves are of the piston type, and the low-pressure valve is flat 
and double ported. The crank and thrust shafts are 13 inches in diameter, the 
line shafts 1214 inches and the propeller shafts 141% inches. 
One condenser is fitted outboard of each engine, with an attached air pump on 
each engine, and attached bilge and sanitary pumps on the starboard engine only. 
The starting platform is at the level of the top of the engine bed plates, and located 
between the two engines. There are two centrifugal circulating pumps with 
engines. The propellers are to turn outboard, one a left-hand and one a right- 
hand screw, each with cast-iron hub and three manganese bronze blades. 
There are three single-ended Scotch boilers, placed side by side, with their 
backs toward the engines and fired from the forward end. They are four-furnace 
boilers 17 feet inside diameter by 12 feet long, and designed for 200 pounds steam 
pressure. So far as we are aware these are the largest Scotch boilers yet built 
in this country except those for three ships for the same owners built by the Harlan 
and Hollingsworth Co. in 1916, each of which had two boilers 18 feet in diameter 
by 11 feet 7 inches long, and which are said to have given excellent service. There 
is also a cylindrical two-furnace, single-ended, return-tube donkey boiler 10 feet 
