FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1929
1929 - 1337.PDF
.lune 27, 192t Supplement to FLIGHT ENGINEERING Edited by C. M. POULSEN June 27, 1929 CONTENTS Cantilever Wings. By F. Duncanson, B.Sc, Wh.Ex.... Air-Cooled High-Speed Seaplanes. By W. G. Carter, M.B.E. The Hydrodynamical Efficiency of Flying-Boat Hulls and Seaplane Floats. By J. H. Lower, A.F.R.Ae.S., A.M.I.N.A. The Tail Plane Area to Give. Longitudinal Stability. By W. R. Andrews, Higher National Diploma (Hons.) ... Technical Literature PAGE 45 47 49 50 .52 EDITORIAL VIEWS. The subject of single-spar cantilever wings is one which is well to the fore just at the present time, due largely to the recent introduction of the Stieger mono-spar form of wing construction. As is so often the case when a strikingly new departure is brought forward, opinions are divided as to the merits or otherwise of such a form of structure, some seeing in the new wing an enormous step forward in aircraft structural efficiency, while others hold that the gain to be expected may be a good deal less than is now apparent; at least the system is untried, and has not yet had an oppor- tunity to prove itself. It is certainly of interest to examine the possibilities of the single-spar wing, and in the present issue we publish an article by Mr. F. Duncanson, of the Technical Staff of the Gloster Aircraft Co., dealing with a method of calculating the wing torsion, size of torque member and angular distortion to be expected in a cantilever wing in which the loading occurred at a centre of pressure position somewhat remote from the main spar. It will be seen that Mr. Duncanson has taken for his subject a single spar composed of an I-beam to take the bending loads, and that he has surrounded this I-beam with a tubular tapering torque member. Thus, structurally, Mr. Duncanson's wing differs materially in detail from the Stieger wing, although results of a comparable order are obtained as regards wing weight. One outstanding result of Mr. Duncanson's examination of the subject is that the intensity of stress in the torque member is low because the amount of material to be put into the torque member is decided mainly by the requirements of stiffness. He finds that this does not neces- sarily mean a heavy torque member, as a conical circular- section tube is a very efficient transmitter of torque. With the Schneider Trophy Contest approaching, con- querable interest naturally attaches to the design of racing seaplanes, and this month Mr. Carter returns to the subject ^tk an article on a tandem air-cooled engine design. Mr. Carter arrive0 at the result that, although the tandem engine "laohine is naturally not as efficient as the single-engined, we use of existing power plants in tandem may be expected to give a gain in speed of about 17 per cent. CANTILEVER WINGS An Investigation of Torsional Strength and Stiffness By F. DTJNCANSON, B.SC., Wh.Ex. In the AIRCRAFT ENGINEER of March 28, 1929, a method of" estimating the amount of material necessary to resist the bending moments and shear forces imposed normally to the' chord of a cantilever wing was proposed and in order to confine the problem to one of pure bending, the case of a wing with a stationary C.P. was chosen. In any case, adequate torsional stiffness must be provided. to guard against wing flutter and to avoid undue distortion under the loads imposed by full use of the ailerons. It is also desirable to legislate for wing sections which have- definite C.P. movements under varying conditions of flight. The object of the present article is to consider a method of calculating the wing torsion, size of torque member and angular distortion that would occur in the ease of a cantilever wing subjected to loading at a C.P. position remote from the main spar. The form of torque member that lends itself best to simple mathematical treatment is of circular cross section and of small thickness /diameter ratio. We will consider a torque member of this form, inserted in the wing section at ite maximum thickness—about 0-3 chord—and as the wing under consideration is of tapered formation, of constant thickness/chord ratio, the shape of the torque member will be conical, the diameter at any point along the wing span being defined by a simple mathematical expression, as was the case with the spar depth in the previous investigation. Fig. 1 illustrates a section through the wing, in which is combined the conical torque member above described and the spar considered in the previous article, both at or in the neigh- bourhood of the maximum thickness of the wing. The combination thus arrived at constitutes a single spar arrangement which in practice has been found to give very satisfactory results. There are, naturally, many different ways in which the scheme could be carried out in detail, but at the present stage we are not concerned so much with details of construction as with a method of ascertaining the amount of material necessary to resist the torque imposed on the wing. It is inevitable that the torque member will be subjected to the general bending strain of the wing and will therefore have combined direct and shearing forces imposed on its material, but it will also take a certain share of the bending moment and thus relieve the main spar. As will be seen later, the criterion of the quantity of material required to be put into the torque member is dependent more on the 522«
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
