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Aviation History
1910
1910 - 0464.PDF
I i (/LIGHT) JUNE I8, 1910. say much in detail, for the machine is a typical example of the substantial and high-class workmanship with which that firm have already made a name, and with which our readers are already familiar. At first glance the observer is impressed with the solidity of the machine, and 'although there is no doubt thai the weight could be considerably reduced in the commercial manufacture of duplicates, such robustness is by no means to be despised in an experimental ap paratus even if the desired cha racteristic of the machine itself does happen to be complete natural stability. The out standing feature of the Dunne biplane is the arrangement of the main planes, V fashion, as viewed from above. In plan the machine is like an arrow head, the main planes sloping sharply backwards from the centre where they join the body. Their extremities lie a little behind the rear end of the body, and thus the wings themselves constitute the greatest fore and aft dimension as well as the greatest span. The leading edge of each wing is straight, but the gap narrows a little along the leading edge towards the extremities, so as to give an expanding passage to the air. This is another of those details that have been evolved from experiment, and for which the precise reason, from an aerodynamic stand point, is not at present clear. The main planes are cambered in a very peculiar way, for the camber varies at every point from the centre to the tips. In order to understand what this camber is like, the only accurate procedure is to construct a simple paper model, which may be done in the following manner. In the first place, cut a strip of paper to represent one of the wings, then roll another sheet of paper into a cone after the fashion of a foolscap. The piece of paper that is cut to represent one of the wings must be a rhomboid instead of a rectangle in order to " Flight" Copyright. Diagrammatic sketch illustrating the varying curvature of the ribs in the wings of the Dunne biplane. The dotted line represents the line of contact with the imaginary cone upon which the •wings are drawn out. Aft of this line the wing surfaces are flat. allow for the slope back when one of the short edges is joined to the side of the body of the machine. Taking this strip of paper, it is laid on the cone so that its longest diameter is in contact with the surface of the cone from the apex to the base. The corner of the paper should coincide with the apex of the cone. The short edge of the sheet of the paper representing the wing, which is adjacent to the base, is then bent down to touch the surface of the cone, while the short edge adjoining the apex is allowed to stick out tangentially J, UNE. OF CONTACT WITH corse-- • pun—- "Flight" Copyright. Sketch illustrating the use of a paper model in order to explain the shape of the wings on the Dunne aeroplane. behind. Thus arranged, the sheet of paper represents one of the wings of the Dunne aeroplane, only the camber will, of course, be much exaggerated owing to the scale on which such a paper model would probably be constructed. It will be observed that the initial contact line with the cone runs diagonally from the leading edge where the wing joins the body to the trailing edge at the outer extremity. Near the body, therefore, the wings of the Dunne aeroplane are not much curved, whereas near the extremities they are curved for the greater part of the chord. At first sight this will suggest that the extremities are much more cambered than any other part of the wings, but it must be remembered that the radius of the curvature also increases towards the wing tip, for the centre from which it is. struck lies on the axis of a cone, and not on that of a cylinder. If, therefore, less of the rib is actually curved in the vicinity of the body, that part which is curved has a more abrupt and consequently relatively greater deflection. (To be concluded.') ® ® © ff> Another Aeronautical Classic. "THE ART OF FLYING," by Thomas Walker, first published exactly a century ago, is to be issued immediately in the series of "Aeronautical Classics'' edited by T. O'B. Hubbard and J. H. Ledeboer for the Aeronautical Society of Great Britain. The present reprint will include an introductory preface, all the original illustrations, while the additional matter appearing in the I83I edition will be reprinted here for the first time. 462
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