Abstract: The present invention relates to a hydrofoil system of a sailing-trimaran having a central hull and two outriggers. Inclined, retractable foils are placed in a head of each outrigger, forward of the center of area of a sail and from the center of gravity of the trimaran. Two additional hydrofoils are arranged each on the stern of an outrigger so that each is clear of the water if the side wind pressure effecting the sail is low. A third additional hydrofoil is arranged on a rudder in the stern of the central hull.