Robert Taggart, 64, a naval architect and marine engineer who founded a research and development company and who was an authority on underwater acoustics and methods for maneuvering ships, died of cancer July 15 at Commonwealth Hospital in Fairfax.

Mr. Taggart was a principal designer of a control and propulsion system to keep ships in precise positions on the surface of the sea. The system was used on the Mole Hole project, which was undertaken about 25 years ago to drill a hole through the earth's crust. The system later was used on drilling ships exploring for undersea oil.

Mr. Taggart, a resident of Falls Church, was born in Montclair, N.J. He graduated from the Webb Institute of Naval Architecture in 1942 and moved to Washington to work for the Maritime Commission. During the remainder of World War II, he was a Navy officer.

After the war, he worked for the Naval Research Laboratory here, for the Army Transportation Corps in Brooklyn, N.Y., and then for the Bureau of Ships in the Navy Department in Washington. In 1954, he became director of the experimental test division of Reed Research Inc.

In 1958, Mr. Taggart founded his firm, Robert Taggart Inc. He remained president of it until his death.

Mr. Taggart was a past president of the American Society of Naval Engineers, a fellow and former vice president of the Society of Naval Architects and Marine Engineers, and a member of the U.S. Naval Institute, the Acoustical Society of America and other professional groups. He was the author of a book on marine propulsion and contributed about 200 papers to professional journals.

In private life, he was a past president of the alumni association of the Webb Institute, a scoutmaster for Fairfax Troop 875, a member of the Fairfax City School Board and a member of the Fairfax Rotary Club.

His marriage to Emmi Taggart ended in divorce.

Survivors include his wife, Bettie, of Falls Church; two children by his first marriage, Karen Hamilton of Fairfax, and Robert Taggart III of Alexandria; a stepson, Kurt Frankl of Syracuse, N.Y., and three grandchildren.