Owasco-class cutter

Myths have long shadowed the design history of the 255-foot (78 m) 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 Lakes shipbuilding 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 316-foot (96 m) cutter that was to have been an austere 327. This design was cut down into the 255-foot (78 m) ship. To accomplish this, everything was squeezed down and automated to a degree not before achieved in a turbo-electric-driven ship.

The machinery design of the 255s was compact and innovative, but overly complex. It had pilothouse control, variable-rate (10 to 1) 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 psi gauge 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.

USCGC Pontchartrain (WPG-70).

The 255-foot (78 m) 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 250-foot (76 m) cutters' weights were used for estimating purposes. Tapered bulkhead stiffeners cut from 12" I-beams went from the main deck (4' depth of web) to the bottom (8" depth of web). 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.