Weight B should equal weight E.
Weight C should equal weight D.
There is no standard practice as to the degree of error permissible, but if there are any appreciable differences the propeller is unfit for use.
5. Surface Area.—The surface area of the blades should be equal. Test with calipers thus:
The distance A–B should equal K–L.
The distance C–D should equal I–J.
The distance E–F should equal G–H.
The points between which the distances are taken must, of course, be at the same distance from the centre in the case of each blade.