Marcy Consalvo was 9 when his parents gave him a boat-building kit. More than 70 years later, he is still building boats, from clipper ships to Gloucester schooners, and for 20 years he’s been helping others with the hobby at the Peabody senior center.

Meeting twice a week, up to 20 people — including a retired ship’s captain, a doctor, and engineers like himself — work on their own projects, from kits and from scratch.

One works exclusively with paper the thickness of business cards. After designing the pieces with a computer program, “he cuts it out, glues it together, and it becomes a battleship,’’ said Consalvo, who can explain how to rig a sailing ship, plank a hull, or build a frame. The center has a woodworking shop with a band saw, drill press, and lathe. And if everyone is stumped on a design, the class has its own library on the history of ships.

“It helps me keep my manual dexterity,’’ Consalvo said, adding that model building flexes the mind as well. “I’m fully convinced that part of the war on dementia is to keep using your brain. There’s always a problem to be solved. That’s why a lot of these guys are going past the age of 90.’’