It is proposed to confine this paper entirely to the point of view of the propeller constructor.

More than 90 per cent, of the propellers now in use are constructed by shaping from a block formed by the glueing together of hardwood laminations. This type is cheap to produce either individually or in quantity, and has been proved by experience to be satisfactory for all types of aircraft, for tip speeds up to 1,000 feet per second, diameters up to 19 feet and for engines developing over 1,000 b.h.p., without showing any signs of having reached a structural limit.

This construction was standardised for production purposes by the Air Ministry during the War, and the official Handbook of Instructions is a most complete guide to the method of manufacture.

Other forms of construction are, to a certain extent, still in the experimental stage and will be considered chiefly by comparison with the standard type.