Gavin Sheehan holds his father’s 1958 Gibson at his workshop in Biddeford. A gift from his grandfather to his dad, it was the first guitar Gavin ever played. Years later, he cleaned away the corrosion and got it playing again. Photo by Cy Cyr A portrait of Earth 3, a guitar Gavin Sheehan built by hand. Its fretboard inlays trace the moon’s orbit around Earth, with an eclipse at the octave in a nod to Sun Ra. Before Gavin Sheehan could play a guitar, he knew what it felt like