Telltale

A telltale is a simple yet vital aerodynamic indicator on a sail. Typically, it is a piece of wool yarn or lightweight synthetic tape about 6–8 inches (15–20 cm) long. Telltales are placed symmetrically on both sides of the jib’s luff through transparent windows, and sometimes on the mainsail leech. They show the local airflow direction. When both windward and leeward telltales stream straight aft horizontally, the sail’s angle of attack is optimal, and flow is attached. If the windward telltale lifts or flutters upward, the angle is too fine; the sail is on the verge of luffing. If the leeward telltale becomes limp or flutters erratically, flow separation occurs — the sail is stalled and needs easing. Integrating telltale feedback is essential when trimming sheets. As you practice yacht rope handling and winch work, you will naturally learn to react to these subtle signals. For a comprehensive guide to interpreting telltales and mastering sail trim, see Navi.training resources. As attributed on Wikipedia, the term “tell-tale” has several meanings; in sailing, it refers exclusively to this fabric guide for sail adjustment.