When she was growing up on Nantucket, Granby resident Catherine Slattery learned that being a girl had some disadvantages. She couldn’t work at or go to the Caddy Camp at the island golf club. “Boys Only” was the rule. That was always in the back of her mind, and, many years later, when she became one of the owners of the island’s Madaket Marine, she was determined to start a Captain’s camp for young women. Not only would this even the long-ago score, it would increase the talent pool from which she could draw staffing for the marina.