The recent trend toward industrialization in emerging nations notwithstanding, it is a fact that much of the world's oil exists in regions where its consumption happens to be small. Conversely, the greatest oil requirements are still to be found in such areas as Western Europe, where supplies are relatively low. And since an estimated half of the world's energy is derived from petroleum, the job of moving that oil from source to user takes an immense importance. Ever since someone discovered a practical way to make the hull of a ship double as a container for oil, tankers have largely dominated liquid fuel transportation-and their role in the field is becoming more vital all the time. On January 1, 1966, according to the British tanker brokerage house of John Jacobs & Company Limited, there were in the world 3,484 tankers of 2,000 deadweight tons and over. (Deadweight tonnage represents the weight of the cargo, stores, water bunkers, the fuel carried to drive the ship, which that ship can lift, expressed in tons of 2,240 lbs.) Only five years earlier, when tankers already were accounting for one-third of all merchant shipping in the world, the Economist's industrial editor, J.E. Hartshorn, placed total tanker tonnage at some 67 million, which even then was a three-fold increase over 1939's and 25 times that of 1914. On March 30 last year there were 227 tankers under construction in various parts of the world, representing 43 per cent of all ships being built everywhere. Hartshorn notes that "over the last generation in particular, tanker tonnage has been by far the most rapidly growing element in world shipping." Not only are tankers becoming more numerous, they are also getting bigger and faster, for, as one writer put it quite simply, "The general rule is that a large fast ship is more economical than a small slow one." During a long period ending in 1939 the size of tankers gradually rose to between 10,000 and 12,000 deadweight tons, and seemed to stay there. It took military hostilities on a global scaie, with an accompanying need for fuel, to break the tonnage "sound barrier." World War II brought the famed T-2's, rated at a standard 16,000 deadweight tons. In the last three years of the war American shipyards turned out, assembly-line fashion, 500 of them. The astonishing postwar demand for oil began to exert its influence. Europe and Japan went to work rebuilding their shattered economies and the momentum of U.S. business activity, already shoved into high gear by the war, accelerated. Oil fields in the Middle East went into full production. New refineries were located near markets rather than sources of the oil which feed them. Oilmen studied the economics of larger tankers to meet the need, and increase in size won out. Adopting the old boxing rule that a good big man can beat a good small man any time, the oil industry experimented with tankers of 28,000 - 32,000-deadweight-ton range and found, as expected, that they cost less per ton of capacity than smaller ones to build and operate. So swift was the growth of the supertanker that by 1959 more than 37 per cent of the world fleet consisted of ships over 25,000 deadweight tons and 16 per cent were rated at more than 35,000 tons-and the end was nowhere in sight. In 1964 one-fifth of the world's tankers had capacities of 30,000 deadweight tons and up. By the beginning of this year 1 5 tankers of at least 100,000 deadweight tons were plying the seas, according to John I. Jacobs & Company Limited and the Petroleum Press Service. In February of this year, the new 1,006-foot Tokyo Maru docked at Ras Tanura and took aboard more than a million barrels of crude oil. The Tokyo Maru with a capacity of 150,000 tons, will reign as the world's largest oil tanker only until six vessels of 165,000, five of 175,800, one of 191,300 and another, the Idemitsu Maru of a staggering 205,000 deadweight tons, all now on order, have been delivered. Pre-World War II tankers had operating speeds of 11-12 knots. The T-2 standard tanker of the early 1940's was able to push through the water at between 14 and 16 knots. Powerful 33,000-horsepower steam turbine engines will enable the 1,120-foot Idemitsu Maru to cruise at a service speed of 16½ knots, fast enough to get her from Japan to the Arabian Gulf and back eight times a year when she is commissioned some time in 1967. Photo : Burnett H. Moody/Saudi Aramco World/PADIA So the universal demand for petroleum is only part of the reason behind the ever-increasing size and speeds of oil tankers. A glance at a world map further explains these two trends: with oil requirements growing apace often far from major areas of production, tankers now have to travel longer distances to supply those demands. It makes good business sense for them to carry large loads between source and destination in the shortest possible time. Besides taking into account capacity, speed and areas of trade when figuring cost-earnings ratios, tanker men note that capital investments do not rise proportionally with each increase in vessel size. Hartshorn expresses the idea another way when he says, "It takes less labor, steel and shipyard design to build a tanker to carry 60,000 tons of crude oil than it does to build two to carry 30,000 tons each." The same principle applies to operating costs. Up to a point the expense for insurance per ton of cargo falls as size increases. Very few more officers and men are needed to run a large ship than a comparatively small one, and automation, now being fully applied to tanker operations, helps hold down the size of ships' complements. Modes of propulsion (motor vs. steam) and fuel types (diesel vs. fuel oil) are being carefully studied for economy's sake. And even though the new giant tankers' capacities are huge, their expensive in-port stays are constantly being reduced by improved pumping systems, which shorten loading and discharging periods. There will of course always be a need for the small and medium-sized tankers able to get into the smaller and out-of-the-way ports. Oil-carrying ships of more modest deadweight tonnage are especially useful for carrying petroleum products to destinations where the giant cargoes could not possibly be absorbed in one load ashore. Flexibility is another useful factor in oil transportation, but the overriding characteristic of the ships used for this vital work is still their enormous-and growing-capacities. Where will the size of tankers stop? At which point will their bigness no longer pay off in the highly competitive petroleum market place? No one really knows, of course, but one thing is certain: the growing numbers of large tankers is further complicating the already complex oil business. No tanker makes money unless it is working steadily, transporting a full load of crude or products to a customer, so the big ones must be routed with great care to make them pay. Linked to this challenge is the problem of loading and discharging facilities necessary to accommodate the new breed of giants. Revolutionary concepts in marine terminal design must be worked out on or near the world's shorelines if the growth of oil tankers continues at its present rate. The seagoing mammoths also need correspondingly big dry docks for necessary maintenance and repairs, and these, like the new terminals, will of necessity be very costly. It is apparent that the bigger future oil tankers become, the sharper will have to be the imaginations-and pencils- of the men who design them.