PROPELLER

摘要

A propeller has a frustro-conical hub (1) which, in use, is configured to taper inwardly towards the front of the craft to which it is attached, a pair of propeller blades (3) being attached to and extending substantially perpendicularly to the outer conical surface (5) of the hub (1) so as, in use, to provide a forward rake angle. Each propeller blade (3) is composed of a first and a second blade portions (3a, 3b), each of which has an arcuate cross section and is in the form of a longitudinal segment of a hollow truncated cone (20) defined between two planes (21a, 22a) which extend longitudinally of the cone (20), are inclined to each other and which each intersect each other along the longitudinal axis (23) of the cone (20). The two blade portions (3a, 3b) are connected together along their neighbouring longitudinal edges with one portion (3b) being rotated through 180 degrees relative to the other such that the blade has a sigmoid cross section.