George H. Main, 51, director of Navy Department cost estimates for shipbuilding since 1957, died Saturday of an infection following abdominal surgery at Sibley Memorial Hospital.

Mr. Main joined the old Bureau of Ships as a civilian supervisor of naval architects and general engineer in 1952.

In 1957, he became head of cost estimating analysis for naval shipbuilding and in 1976 was named director of the naval ship construction cost estimating and analysis division of the Naval Sea Systems Command.

He received several superior performance awards from the Navy.

Mr. Main was born in Baltimore, and moved here in the early 1950s. A graduate of the U.S. Merchant Marine Academy, he served for a short time in both the U.S. Merchant Marine and the Navy. He later earned a law degree at George Washington University.

He was a member of the American Association of Cost Engineers and the American Association of Naval Engineers.

Mr. Main was a past president of the North Bethesda PTA and had been a member of Emmanuel Lutheran Church of Bethesda, where he taught Sunday school for 10 years.

He is survived by his wife, Joan M., & son, Charles R., and a daughter, Barbara Ann, all of the home in Bethesda: his mother, Mabel W. Main, two sisters, Mabel Wilson and Charlotte Monaghan, and a brother, John, all of Baltimore.