Fairing for stepped hull boat with cambered planing surfaces

A planing boat with its vertical longitudinal center plane and a hull featuring a stepped bottom with at least one step provided with a cambered planing surface as a bottom surface of this step, so that edges of said step represent trailing edges of said cambered planing surface, which boat is provided with at least one movable relative the hull fairing located aft of said trailing edges and having a leading edge, while said leading edge of the fairing in its lower operational position, corresponding to low-speed displacement and transitional modes of the boat, is predominantly shaped to conform to, abuts upon and fits flush with said trailing edges at least along some length of said trailing edges,

• wherein, within said length of the trailing edges and along the line of abutment of said leading and trailing edges, in sections by vertical longitudinal planes, at the points of abutment of the outer contours of the cambered planing surface of boat bottom and the surface of fairing, the angles of inclination of tangents to the outer contours of the surface of fairing are positive and substantially equal to the angles of inclination of tangents to the outer contours of the cambered planing surface of boat bottom, that is, at said points of abutment, the tangents are turned counterclockwise relative to the horizon at an angle less than 90 degrees when viewed from the starboard side of the boat,
• while, when moving aft along at least the forward part of said contours of the fairing outer surface, the angles of inclination of the tangents to the contours gradually decrease and, at some distance aft from the leading edge, the tangents come to the zero-angle horizontal position, and then the angles of inclination of the tangents become negative, while their absolute values increase when moving along the contours of the fairing further aft,
• so that, when moving aft along at least the forward part of the contours of the fairing outer surface, the tangents to the contours of the fairing outer surface rotate clockwise, when viewed from the starboard side of the boat, at angles greater than the initial angles of inclination of the tangents to the horizon at the point corresponding to the abutment of the outer contours of the cambered planing surface and the fairing, forming convexities of the outer contours of the fairing and a bulge of the fairing arranged substantially along the trailing edges and protruding downwards below the trailing edges in projection onto the transverse plane,
• whereas, when the boat is in its main operational high-speed planing mode, the fairing is in its upper inactive position, in which the leading edge of the fairing, said bulge and the fairing as a whole, are located higher than the trailing edges of said cambered planing surface of boat bottom in projection onto the transverse plane.