Method for constructing a rotor blade intended for a rotorcraft, blade and rotorcraft

A method for manufacturing a blade for a rotor of a rotorcraft, the blade extending in a longitudinal direction spanwise from a first end intended to be connected to a hub of the rotor towards a second free end, and in a transverse direction from a leading edge towards a trailing edge, the blade comprising a blade root including the first end, a profiled zone having (i) a central part and (ii) an outer part including the second free end, and a blade neck situated between the blade root and the central part of the profiled zone, the blade root, the blade neck, and the profiled zone comprising a series of aerodynamic profiles;

• wherein the method comprises the following steps:
• determining a leading edge section of each aerodynamic profile for the blade root, the blade neck, the central part of the profiled zone, and the outer part of the profiled zone;
• determining a trailing edge section of each aerodynamic profile for the blade root, the blade neck, and the central part of the profiled zone by axial symmetry of the leading edge section along an axis of symmetry perpendicular to a segment connecting the leading edge to the trailing edge and positioned in the middle of the segment whereby for each aerodynamic profile for the blade root, the blade neck, and the central part of the profiled zone the trailing edge section is axially symmetrical to the leading edge section;
• determining a trailing edge section of each aerodynamic profile for the outer part of the profiled zone that is tapered relative to the leading edge section of the aerodynamic profile whereby for each aerodynamic profile for the outer part of the profiled zone the trailing edge section is not symmetric to the leading edge section;
• determining an intermediate upper surface section of each aerodynamic profile connecting the leading edge section and the trailing edge section of the aerodynamic profile;
• determining an intermediate lower surface section of each aerodynamic profile connecting the leading edge section and the trailing edge section of the aerodynamic profile;
• and
• manufacturing the blade according to the aerodynamic profiles by forming for each aerodynamic profile (i) an upper surface of the aerodynamic profile comprised of the intermediate upper surface section of the aerodynamic profile connecting the leading edge section and the trailing edge section of the aerodynamic profile and (ii) a lower surface of the aerodynamic profile comprised of the intermediate lower surface section of the aerodynamic profile connecting the leading edge section and the trailing edge section of the aerodynamic profile.