Editor's Note: This article was originally published in Ships and the Sea magazine, Fall 1957. The language, spelling and grammar of the article reflects the time period when it was written. Learn more about Liberty Ships here.
What could be done with the outmoded Liberty ships in the event of an emergency? The Maritime Administration is proving they can be turned into assets.
During World War II, pressed by the dire need of the national emergency, U.S. shipyards produced thousands of merchant ships. During this era, even the most lubberly of land-lubbers came to hear of that famous-type ship, the Liberty. Shipyards on all coasts of this nation made headlines with the fantastic speed with which these large oceangoing vessels were constructed. The average time for the completion of a Liberty was an amazing 62 days!
By the time the building program had been completed, some 2600 standard Liberty ships had splashed into the water and taken up their vital task of delivering war material overseas. This tremendous fleet had a carrying capacity of almost 30 million tons.
But what has happened to this vast fleet of Libertys in the postwar era? Have their bluff-bowed and full-bellied forms, and their 2500-horsepower reciprocating engines which produced speeds of only 11 knots, managed to survive the competition of cargo vessels with speeds up to 20 knots? The best answer to that may be a blunt statistic – some 1400 Liberty ships are tied up in the U.S. Maritime Administration's reserve fleet sites in rivers and bays around our coastline.
This figure, taken in conjunction with the fact that several hundred Libertys were lost due to enemy action and other causes, and that several hundred others have been converted to such speck-purpose vessels as colliers, oil tankers, troop transports, hospital ships, ammunition ships and training vessels, leaves us with but one conclusion – the Liberty is too slow and inefficient for modern shipping needs. Some Libertys, of course, are in operation, but these are mostly doing tramping duty under foreign flags or carrying bulk cargoes like grain, ore and coal.
However, it is not the economic aspect of the outmoded Liberty which concerns the Defense Department and the Maritime Administration. Those 1400 Liberty ships in the reserve fleet are supposed to represent security in any future national emergency. In the last few years the conviction has been growing among these military experts that the Liberty ship in its present design does not really represent insurance in case of need.
Can the Liberty, for example, keep up with the speeds of future convoys? Can the Liberty hope to elude atomic-powered, snorkel-type submarines with speeds under the water of, say, 20 knots? The answer is clearly "No." Even in the limited Korean emergency, very few Liberty ships were taken out of the reserve fleet in spite of the need. The faster (16-knot) Victory and C-type ships were taken out first. Then the Defense Department had to charter privately owned vessels.
With these dismal facts confronting it, the Maritime Administration has now embarked upon and completed an experimental Liberty conversion program which proves that those 1400 ships still represent an enormous national asset. The program, using four ships, had as its objective the upgrading of the ships with regard not only to speed but also to over-all efficiency.
Increasing the speed of the Liberty may sound, on paper, like an easy matter. Why not increase the horsepower and efficiency of the engines and build new streamlined bows to replace the bluff "ugly-duckling" bows? To be sure, this can be and has been done. The problems confronting the Maritime Administration, however, were not simple in deciding upon the extent of the alterations which should be made. It must be remembered, first, that to upgrade hundreds of Liberty ships quickly in case of emergency would require vast dry-docking facilities, a call for quantities of scarce steel, and a need for new and more efficient engineering equipment.
There were other equally pressing problems of design. Could the war-built ships stand the pounding in heavy weather which the higher speeds would cause? The Liberty ships, as a matter of fact, have been quite prone to cracking, even at the lower speeds. It was apparent that the altered ships would have to be heavily strapped. Also, there were the problems of propeller vibration at higher revolutions per minute, greater stresses on the rudder, and the like.
Defense authorities had indicated a desire for 18 knots for the upgraded Libertys, but were willing to settle for 15 knots as a minimum. The latter speed was finally selected in view of the numerous problems involved, although technically it is possible to obtain an 18-knot speed with an appropriately lengthened, strengthened, finer and more powerful ship.
It was decided that one of the four ships, the Benjamin Chew, would have its speed increased to 15 knots merely by the expedient of installing 6000-horsepower steam turbines with no change in hull form. This was undertaken with some misgiving as to the seakeeping qualities of such a blunt form driven at a 15-knot speed. But the savings in steel and dry-docking capacity in an emergency dictated that the attempt be made.
Early experience with the ship has, in fact, confirmed these misgivings to some extent since the ship has had difficulty in maintaining 15 knots in heavy weather. The rate of fuel oil consumption has also been relatively high. However, it has been proved that, if necessary, the Liberty in its original form can be driven at significantly higher speeds with a minimum of alterations.
The second of the ships, the Thomas Nelson, has been given geared diesel engines with 6000 horsepower as well as a lengthened and finer bow. As expected, 15-knot speeds have been easily maintained with a very low rate of fuel consumption. It would appear that if time and facilities permit, this type of alteration is to be preferred over that of the Benjamin Chew.
The third and fourth ships, in addition to having lengthened and finer bows, are also being used to pioneer a new type of prime mover for ships – the gas turbine. The John Sergeant is the first all-gas-turbine merchant ship in the world, although a few vessels have been fitted with gas-turbine engines combined with other types of power plants. A controllable pitch propeller, another innovation for large U.S. ships, is used in conjunction with the gas turbine. This enables the pitch of the propeller blades to be controlled from the navigating bridge.
For those of our readers who are not acquainted with the principles by which a gas turbine operates, a brief description might be helpful. A gas turbine operates by first compressing air, then heating it before sending it to a combustion chamber where fuel is mixed with the air and burned. The resulting gas is expanded through turbine nozzles, thus providing the power to turn the propeller shaft. The gas turbine is claimed to produce high thermal efficiency with reduced size and weight of machinery. Low-cost bunker "C" fuel oil may be burned. The gas turbine will probably be most efficient in the 7500- to 15,000-horse-power range.
The William Patterson, the last of the four conversions, went into service in mid-1957. She is equipped with a gas turbine, too, but it is of a somewhat different type from the Sergeant's. The latter has what is known as an "open-cycle" gas turbine, while the Patterson has a "free-piston" type. (in the free-piston machinery, the pistons are not connected to crank-shafts as is customary in other internal combustion engines. Instead, the air-fuel mixture is burned between opposed pistons which then spring apart, compressing air at both ends of a cylinder. The compressed air causes the pistons to bounce back, thus forcing the gas into the turbine.)
The marine industry is watching with great interest to find, first, whether the gas turbine will produce a more efficient prime mover than the steam turbine or diesel drive and, second, to find which type of gas turbine is better from an over-all point of view.
Another aspect of the Liberty ship conversion program deserves comment. The Maritime Administration is using the program to experiment with different types of cargo-handling equipment, the theory being that increased speed at sea is only part of the picture of more efficient utilization of ships, the time spent in port loading and discharging cargo being of equal importance. So we find that the Thomas Nelson, for example, is equipped with radically new cargo cranes of two different types. The Benjamin Chew has a conventional set of cargo booms but of an improved type. She also has a removable 'tween deck in No. 2 compartment.
All in all, these four Liberty ships are vastly improved vessels from their 1400 sisters still resting in the reserve fleet. They are being operated on the North Atlantic run by the same operator, the United States Lines. This will ensure, as nearly as possible, the same weather and port conditions, so that the many differences among the ships can be evaluated to arrive at valid conclusions as to what the ultimate form of the converted Liberty prototype should be. Although the program has primarily been aimed at the objective of upgrading the reserve fleet of Liberty ships in time of national emergency, it is also proving of great value to U.S. ship operator.
The new look in Liberty ships appears to be not only new but also very pleasing.
This article, written by John La Dage, appeared in the Fall 1957 issue of Ships and the Sea magazine.
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