Abstract: A propeller has a hub 1 with a pair of blades 3 extending therefrom. Each blade 3 has a root, a tip, a first blade portion 10a extending between the root and tip and a second blade portion 10b extending between the root and tip adjacent and substantially parallel to said first blade portion 10a. The first and second blade portions 10a, 10b each have an arcuate concave face 11a, 11b, the radius of curvature of the concave face 11a of said first blade section 10a being greater than the radius of curvature of the concave face 11b of the second blade section 10b. The concave faces of said first and second portions 10a, 10b facing in substantially opposite directions such that, in use, said concave face 11a of said first blade portion 10a faces rearwards and said concave face 11b of the second blade portion 10b faces forwards.

Abstract: A propeller has a hub 1 with a pair of blades 3 extending therefrom. Each blade 3 has a root, a tip, a first blade portion 10a extending between the root and tip and a second blade portion 10b extending between the root and tip adjacent and substantially parallel to said first blade portion 10a. The first and second blade portions 10a, 10b each have an arcuate concave face 11a, 11b, the radius of curvature of the concave face 11a of said first blade section 10a being greater than the radius of curvature of the concave face 11b of the second blade section 10b. The concave faces of said first and second portions 10a, 10b facing in substantially opposite directions such that, in use, said concave face 11a of said first blade portion 10a faces rearwards and said concave face 11b of the second blade portion 10b faces forwards.