Method of fabricating a spar of a blade with the aid of tapes of composite materials, said spar comprising transversely at least one arrangement (10, 15), each arrangement (10, 15) being for winding around a root axis (AX1, AX2), characterised in that: - during a preparation step, a lower-surface mould (22, 32) and a upper-surface mould (21, 31) for each arrangement (10, 15) to be fabricated are defined, each mould (21, 22, 31, 32) comprising a base (23, 24, 33, 34) extending longitudinally according to the span of said spar and defining a laying surface including: ∘ a root zone provided with a root wall, said root wall forming two flanks, ∘ a connection zone having two inclined connection walls (64, 65) forming an inverted V and connected respectively to the two flanks, ∘ a running zone having two running walls (66, 67) extending respectively the two connection walls (64, 65), - during a fabrication step, each arrangement (10, 15) being subdivided into a lower-surface subassembly and a upper-surface subassembly, each comprising a hank, each hank comprising a plurality of U-shaped tape segments stacked on one another, each mould (21, 22, 35, 36) comprising at least one removable slide called "lateral slide" (25, 26, 35, 36) delimiting transversely the mould (21, 22, 31, 32) by extending vertically from the base (23, 24, 33, 34) and/or at least one removable slide called "longitudinal slide" (37, 38, 39, 40) delimiting longitudinally said mould by extending vertically from the base: ∘ each slide (25, 26, 35, 36, 37, 38, 39, 40) is removed from each mould (21, 22, 31, 32), ∘ said lower-surface subassembly and said upper-surface subassembly of an arrangement (10, 15) are respectively fabricated on said lower-surface mould (22, 32) and on said upper-surface mould (21, 31) corresponding to the arrangement, each subassembly being fabricated by stacking tape segments on the corresponding mould by a method of placing fibres with the aid of a placement head, said placement head laying said segment over the laying surface of said mould, ∘ each mould (21, 22, 31, 32) is closed by putting each slide (25, 26, 35, 36, 37, 38, 39, 40) of the mould (21, 22, 31, 32) into place, and said moulds (21, 22, 31, 32) are juxtaposed in order to form a closed enclosure in which the subassemblies are to be found, - during a finalising step, said spar within the juxtaposed moulds is heated. - during a preparation step, a lower-surface mould (22, 32) and a upper-surface mould (21, 31) for each arrangement (10, 15) to be fabricated are defined, each mould (21, 22, 31, 32) comprising a base (23, 24, 33, 34) extending longitudinally according to the span of said spar and defining a laying surface including: ∘ a root zone provided with a root wall, said root wall forming two flanks, ∘ a connection zone having two inclined connection walls (64, 65) forming an inverted V and connected respectively to the two flanks, ∘ a running zone having two running walls (66, 67) extending respectively the two connection walls (64, 65), ∘ a root zone provided with a root wall, said root wall forming two flanks, ∘ a connection zone having two inclined connection walls (64, 65) forming an inverted V and connected respectively to the two flanks, ∘ a running zone having two running walls (66, 67) extending respectively the two connection walls (64, 65), - during a fabrication step, each arrangement (10, 15) being subdivided into a lower-surface subassembly and a upper-surface subassembly, each comprising a hank, each hank comprising a plurality of U-shaped tape segments stacked on one another, each mould (21, 22, 35, 36) comprising at least one removable slide called "lateral slide" (25, 26, 35, 36) delimiting transversely the mould (21, 22, 31, 32) by extending vertically from the base (23, 24, 33, 34) and/or at least one removable slide called "longitudinal slide" (37, 38, 39, 40) delimiting longitudinally said mould by extending vertically from the base: ∘ each slide (25, 26, 35, 36, 37, 38, 39, 40) is removed from each mould (21, 22, 31, 32), ∘ said lower-surface subassembly and said upper-surface subassembly of an arrangement (10, 15) are respectively fabricated on said lower-surface mould (22, 32) and on said upper-surface mould (21, 31) corresponding to the arrangement, each subassembly being fabricated by stacking tape segments on the corresponding mould by a method of placing fibres with the aid of a placement head, said placement head laying said segment over the laying surface of said mould, ∘ each mould (21, 22, 31, 32) is closed by putting each slide (25, 26, 35, 36, 37, 38, 39, 40) of the mould (21, 22, 31, 32) into place, and said moulds (21, 22, 31, 32) are juxtaposed in order to form a closed enclosure in which the subassemblies are to be found, ∘ each slide (25, 26, 35, 36, 37, 38, 39, 40) is removed from each mould (21, 22, 31, 32), ∘ said lower-surface subassembly and said upper-surface subassembly of an arrangement (10, 15) are respectively fabricated on said lower-surface mould (22, 32) and on said upper-surface mould (21, 31) corresponding to the arrangement, each subassembly being fabricated by stacking tape segments on the corresponding mould by a method of placing fibres with the aid of a placement head, said placement head laying said segment over the laying surface of said mould, ∘ each mould (21, 22, 31, 32) is closed by putting each slide (25, 26, 35, 36, 37, 38, 39, 40) of the mould (21, 22, 31, 32) into place, and said moulds (21, 22, 31, 32) are juxtaposed in order to form a closed enclosure in which the subassemblies are to be found, - during a finalising step, said spar within the juxtaposed moulds is heated.