. Principles and design of aëroplanes . cale. There are three types of machine for * Bleriot, Esnault-Pelterie, Ferber, Vaija, Gastambide-Mangin, Roe. performing mechanical flight, each de-pending on a different principle : (1) The gyroplane, or helicoptere,which uses vertical lifting-screws. (2) The ornithoptere, which has flap-ping wings like a bird. (3) The aeroplane, kite, or glider,which is a surface pulled or pushedthrough the air. Although the first two types are verypromising, yet it is the last which hasdone definite work, and it is with thisvariety I propose principally to deal. It w
. Principles and design of aëroplanes . cale. There are three types of machine for * Bleriot, Esnault-Pelterie, Ferber, Vaija, Gastambide-Mangin, Roe. performing mechanical flight, each de-pending on a different principle : (1) The gyroplane, or helicoptere,which uses vertical lifting-screws. (2) The ornithoptere, which has flap-ping wings like a bird. (3) The aeroplane, kite, or glider,which is a surface pulled or pushedthrough the air. Although the first two types are verypromising, yet it is the last which hasdone definite work, and it is with thisvariety I propose principally to deal. It will be noticed that the title kiteis also applied to this type, and, as amatter of feet, in its esse: tial principlesthe aeroplane is merely a large varietyof kite. It therefore behooves to study brieflythe action of the ordinary kite and thenconsider in what manner the kite maybe modified to act as a flying-machine. Taking the very simplest type of kite as shown in sketch, we notice three fea-tures : TWISTING EFFECT _ BALANCED BY TAIL. Fig. 1. KITE (1) A more or less rigid surface. (2) A cord tying this surface to theearth. (3) A continuous motion of airagainst the surface. It follows from the simplest mechani- 8 cal principles that there are threeforces in this case, the wind pressure onkite, the pull in the cord, and theweight of the kite. These three are inequilibrium if the kite is stationary. Ifthe kite ascends then the vertical com-ponent of the wind pressure exceeds theweight and downward component of thecord pull. This vertical force is termed lift. If the kite travels with the windthe component of the wind in the direc-tion of the cord exceeds the pull in thecord. This lateral force is called driftor waftage. Since the air is almost frictionless thepressure of the kite is practically nor-mal to • its surface, and this surface, ifthere is any lifting force, must be in-clined to the horizontal, and if the windis horizontal the surface must thereforebe inclined to the
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