A headfoil is a streamlined moulding, usually made of plastic or aluminum—that fits over a sailboat's forestay, featuring a groove on its aft side that allows a headsail's luff to slide up and down. It serves as a more aerodynamic and efficient alternative to using hanks to attach the jib to the forestay.

Key Aspects of a Headfoil:
Purpose: It acts as a track for the headsail luff (forward edge), providing consistent, continuous support for the sail.

Performance Enhancement: It improves the aerodynamic efficiency of the headsail by reducing drag compared to hanks.

System Types: It is commonly used with "Tuff Luff" systems for racing—which can feature double grooves for fast sail changes (zipping on a new sail before taking down the old one)—or simply as part of a permanent racing or cruising setup.

Installation: Headfoils are usually installed in segments over the forestay wire.