Journalist and historical researcher Kevin P.Duffus has unraveled some of the most puzzling mysteries of the North Carolina coast. Duffus argues that the popular image of the 18th-century pirate bears little resemblance to the historical figure. As the fourth in Disney’s “Pirates of the Caribbean” franchise, “On Stranger Tides,” debuts this weekend in theaters across the country featuring a Blackbeard character, played by Ian McShan, Duffus will present new findings about pirate culture at a conference in Washington, N.C. called “Pirate Parley on the Pamlico.”