Clayton Ewing, 70, a longtime resident of Talbot county, on Maryland's Eastern Shore, who was active in community affairs and international yachting circles and who had served on the America's Cup Committee since 1968, died Thursday in Queen Annes County, Md., of arteriosclerotic cardio-vascular disease.

Mr. Ewing owned and operated the Oconto Falls pulp and paper mill and hospital in his native Wisconsin before moving to Talbot County in 1961. He was a member of the board and chairman of the finance committee of the Easton (Md.) Memorial Hospital and a member of the Navy War College Foundation. At the time of his death, he was serving as secretary of the board of the Maryland Agricultural Society for the Eastern Shore. He also served as president of the board of governors of the Chesapeake Bay Maritime Museum in St. Michaels, Md.

A past commander of the Cruising Club of America, he also was a member of other yachting clubs in this country and in Europe and had competed in five transatlantic races and numerous Newport-to-Bermuda races, as well as contests on the Great Lakes and Chesapeake Bay.

Survivors include his wife, Janet Lawton Ewing, and a son, Mark C., both of Trappe, Md.; a daughter, Mrs. Howard Tuthill of Grand Rapids, Mich; two brothers; a sister, and eight grandchildren.