ERIN TOKARZ ZEPHRA, a Dublin Bay 24 designed by Alfred Mylne in 1938, is being completely rebuilt at The Apprenticeshop in Rockland, Maine. Little of the original boat remains. At 38′ LOA, she is the kind of project that continues longer than the two-year apprenticeship program, giving a succession of apprentices a chance to share in large-boat work. Walk through the back