Lifting Power of Air Propellers, being Experiments with Propellers 30 ft. in Diameter

Extract

These experiments were carried out during the latter part of 1899, with the expert and financial assistance of Mr. Patrick Y. Alexandsr, of Experimental Works, Bath.

Experimental Apparatus. Five propellers 30 feet in diameter were tried, lettered A., B., C, D., E., the skeleton structure of the blades was also tested, the different propellers were formed by altering the canvas stretched on the skeleton blades. The skeleton propeller was made as light as possible, and for reasons of strength and lightness, a Mangin type of propeller was used of four blades, the blades b3- ing fixed one behind the other, and connected together by diagonal struts and ties; the blades were 3 feet 1½ inches apart. A pair of blades are thus, from a structural point of view, similar to a “warren” or lattice girder supported at one end, the respective blades cf one pair constituting the upper and lower flanges of the girder; therefore, when the propeller is exerting a thrust, the members of one blade will be in compression, and the other in tension.