How Does a Hydrofoil Boat Work?

A hydrofoil boat has wing-like structures (foils) mounted below the hull on struts. As the boat accelerates, water flows over and under the foils just as air flows over an aircraft wing, generating hydrodynamic lift. At a certain speed (typically 15–25 knots), the lift is sufficient to raise the hull entirely clear of the water — a state called "foilborne." With only the thin foils and struts in contact with water, drag drops by up to 80%, allowing much higher speeds and better fuel efficiency. Modern hydrofoils use actively controlled surfaces with sensors and computers to adjust foil angles in real time, maintaining smooth flight even in choppy seas.