Myths have long shadowed the design history of the class. These cutters were to have been much larger ships, and two theories persist as to why they were shortened. The first is that they were built to replace the ships supplied to Great Britain under lend-lease, and Congress stipulated that the Coast Guard had to build these replacement cutters to the same size and character as those provided to the British. The second is that their length was determined by the maximum length that could pass through the locks of the Welland Canal from the Great Lakes to the St. Lawrence River. The Great Lakesshipbuilding industry brought pressure on Congress to ensure that it had the potential to bid on the contract. The first theory seems to be correct, but the second cannot be ruled out. The Coast Guard had prepared a design for a cutter that was to have been an austere 327. This design was cut down into the ship. To accomplish this, everything was squeezed down and automated to a degree not before achieved in a turbo-electric-driven ship.
Machinery
The machinery design of the 255s was compact and innovative, but overly complex. It had pilothouse control, variable-rate burners, and automatic synchronizing between the turbogenerator and the motor. Westinghouse engineers developed a system of synchronization and a variable-frequency drive for main-propulsion auxiliary equipment, which kept the pumps and other items at about two-thirds the power required for constant-frequency operation. The combined boiler room/engine room was a break with tradition. The turbo-alternators for ship-service power exhausted at 20 psigauge pressure instead of into a condenser. This steam was used all over the ship before finally going to a condenser. Space heating, galley, cooking, laundry, freshwater evaporation, fuel, and feed-water heating were all taken from the 20 psi back-pressure line.
Icegoing design features
The class was an ice-going design. Ice operations had been assigned to the Coast Guard early in the war, and almost all new construction was either ice-going or ice-breaking. The hull was designed with constant flare at the waterline for ice-going. The structure was longitudinally framed with heavy web frames and an ice belt of heavy plating, and it had extra transverse framing above and below the design waterline. An enormous amount of weight was saved utilizing the technique of electric welding. The cutters' weights were used for estimating purposes. Tapered bulkhead stiffeners cut from 12" I-beams went from the main deck to the bottom. As weight was cut out of the hull structure, electronics and ordnance were increased, but at much greater heights. This top weight required ballasting the fuel tanks with seawater to maintain stability both for wind and damaged conditions. The superstructure of the 255s was originally divided into two islands in order to accommodate an aircraft amidships, but this requirement was dropped before any of the units became operational. Following completion of the preliminary design by the Coast Guard, the work was assigned to George G, Sharp of New York to prepare the contract design.
Number
The number of ships in the class – thirteen in total – had an interesting origin. Three were to have been replacements for over-aged cutters, the Ossipee, Tallapoosa and Unalaga, and ten units were to be replacements for the class transferred to Great Britain under lend-lease. For economy, all thirteen units were built to the same design.
Service
The class was initially heavily armed with World War II service in mind, but much of this armament was deemed unnecessary for peacetime and was removed in the postwar period. Construction of the class received a low priority, and consequently none of the cutters were commissioned in time to see action in WWII, but a number eventually saw combat in the Vietnam war. They were all however to provide many years of peacetime service in regular Coast Guard roles such as law enforcement, ocean station, and search and rescue operations. Iroquois suffered major damage in a maritime incident in the 1950s and was cannibalized for parts for the other cutters before being scrapped in 1965. The remainder of the class was scrapped in 1974.
