With courage, determination and grace he lived his life and faced death. Dave Keast, 86, of Westford St., Carlisle passed away peacefully from complications of a neurodegenerative disorder on May 22, 2017 at his home surrounded by his loving family. He was the devoted husband of almost 62 years (on June 18) of Estelle (Karukas) Keast. Born on January 8, 1931 in Pittsburgh, PA, he was the son of the late David S. Keast and Nora Lewis Harlan. He was predeceased by his eldest son Jeffrey David in 2011. He graduated from Northfield Mount Herman School, and earned a BA at Amherst College in 1952 and a BS and MS degrees in Electrical Engineering from MIT in 1953. He soon began a rewarding and successful career as an acoustical engineer. He was elected to Sigma Xi and was the author of Measurements in Mechanical Dynamics (McGraw-Hill) and over 100 technical papers and reports. He spent 34 years with Bolt Beranek & Newman, MFE Corporation and HMM Associates, and was self-employed as a consultant in acoustics from 1988 -2002. He married Estelle in Stamford, Connecticut and soon moved to southern California in 1957 where they raised their 4 children. In 1971, he moved to Carlisle and lived here ever since. He served on the original Carlisle Bike/Foot Path Committee, the Finance Committee and was the first to digitize the town's property records as a volunteer assessor for 12 years. His home and family were the center of his life and he enjoyed spending many hours puttering inside and outside his home and back-packing and hiking with his family and friends. His intellect and energy were inexhaustible. For many years, he piloted his private plane to and from work in southern California, in the High Sierra and in New England. Whether hiking the John Muir Trail or climbing all 48 of the New Hampshire 4,000 Footers in his late 70's he always was ready for a challenge. He was a member of the Sierra Club and the AMC. He and Estelle were also world travelers visiting over 60 countries on six continents. Along with his wife he is survived by his daughter-in law Mrs Jeffrey Keast of Natick; his children, Craig Lewis Keast and his wife Barbara of Groton; Diane Nager of North Salem, NY and James Keast and his wife Suzanne of Holliston. He is also survived by his devoted 13 grandchildren and his brother W. Scott Harlan and his partner William Cavanaugh of New York City. The Keast family extends their heartfelt thanks to the Carlisle COA, Police & Fire Departments and EMT's for all their caring and support. Family & friends will gather to honor and remember David on Saturday, June 17 at 3:00 pm at the First Religious Society in Carlisle. Private burial was at Green Cemetery in Carlisle. In lieu of flowers, donations in his memory may be made to Emerson Hospital, 133 Old Road to Nine Acre Corner, Concord, MA 01742 or CareDimensions (Hospice and Palliative Care), 75 Sylvan St., Danvers,MA 01923. Arrangements are under the care of the Dee Funeral Home of Concord.