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Aviation History
1935
1935 - 0689.PDF
MARCH 28, 1933 19 THE AIRCRAFT ENGINEER SUPPLEMENT TO FLIGHT 33^ Fuselage Intersection of Fitters nith fuselage Intersection of fillets with wing surface. 0 I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 67&8 FIG. I lower edge of fuselage VIEW LOOKING TORWWIO (Seal* rwitt profile) FIGHT Rad af3 Topsurfcce TYPICAL WING ROOT FILLET F1G.JT PROFILE FIG.Iff 8 9 10 II IZ WING FILLET DIA.G. BODY PLAN surface. A certain rate of expansion can be tolerated, but if the surfaces diverge from one another too rapidly the flow of air detaches itself from them, and a region of tur bulence is set up which leads to loss of lift and an increase of drag. Hence the surface of the wing-root fillets should conform to the cone of a venturi tube if the flow of air is to follow the surface without breaking away. (Ref. 2.) On the underside of the wing the pressure gradient is of the opposite sign, and so will, to some extent, assist the flow of air to adhere to the surface. From certain experiments carried out at the N.P.L. a fillet of radius only one-sixteenth of the wing chord increased the lift by more than 100 per cent, and reduced the drag 20 per cent. This radius is assumed to be placed at the deepest section of the wing and to increase in radii towards the trailing edge (Ref. 3), and decrease towards the L.E. In setting out a wing-root fillet one must lay out the standard wing profile for the centre section in its relative position to the datum of the machine, then proceed to mark off a number of stations from the L.E. of the wing to a distance beyond the T.E. (Fig. 4). Next proceed to draw in the half '' body plan'' and indicate the stations in section (these are circular in the illustration, for simplicity). Having drawn in a few sections, project the centres of spars and indicate the top and bottom surface of the wing at deepest section (Station 3 in illustration). We can now draw in our radius equal to one-sixteenth chord, joining the fop surface with the body at that section. The bottom surface is purely a matter of fairing-in, and depends on the vertical position of wing root intersection with body. Proceeding, we draw a line intersecting the fillet at any given distance from the centre line of the machine as at 0.0." The number will depend on the scale and size °i fillet, and, naturally, the larger number of intersections *e make will add to the accuracy of our resultant shape. ^3 in Fig. 4 indicates the point of intersection of the ver- "cal with the radius, and should be projected back on jj° the profile at Station 3. This point is indicated at " e." Measure the distance between the point " e" and the top surface of the wing at Station 3, and proceed to mark off this height at all other stations between the L.E. and 1 ;E. of the wing. Draw a line through these points which *lu be parallel to the wing surface at a given height above ]• Project these points back on to line '' 0-0'' on the °°dy plan, giving us a third point to draw our radii in for 3,1 Nations between the L.E. and T.E. We can now proceed to draw radii passing through these points and tangential to the body and top surface corre sponding to each station, giving us a series of radii increas ing towards the T.E. Reference to Fig. 2 will illustrate how the trailing edge is continued on into the body from Station 8 to 12 (Fig. 4), as obviously it would be impos sible to stop the fillets abruptly at the T.E. of the wing as indicated by heavy line at T.E. (Fig. 2). A plan view will have to be projected from the profile, and the wing T.E. proper carried on in a curve to meet the body and given a reflex curve in profile. The inter section of the reflex T.E. with the Stations 8 to 12 will have to be projected on to the body plan and faired into the body at each station. A typical example is shown in Fig. 3. The main feature to bear in mind is that you are trying to fit a form of venturi tube at the junction of the wing with the body. Ref. 1. Report No. 482, Wing-Fuselage Interference, etc. By J. A. White and M. J. Hood. Ref. 2. Effect of Fillets on Wing-Fuselage Interference. By A. L. Kleen. Ref. 3. Interference. By E. Ower. Journal R.A.E.S. Vol. XXXVI, July, 1932. The Institute of Metals The 27th annual general meeting of the Institute of Metals was held in London on March 6 and 7 last. Twelve papers were presented for discussion, of which two were of direct interest to aeronautical engineers. "Corrosion-Fatigue Pro perties of Duralumin with and without Protective Coatings '' was the title of a paper presented by Mr. I.J. Gerard and Mr. H. Sutton, both of the Royal Aircraft Establishment, Farn- borough. Tests were made in air and in salt-spray after protecting the surface in various ways. In air the untreated material gave a fatigue limit of stress of ± 9.1 tons per sq. in. at 107 cycles, and the anodized material ± 11.1 tons per sq. in. In a salt-spray lanolin coating and cadmium plating afforded little protection, but zinc plating gave a substantial im provement. The best results were obtained with a coating oi synthetic resin varnish and stoving for 2 hours at 150 deg. C. Metal so treated gave a fatigue limit stress of ± 12.2 tons per sq. in. at io' cycles. " Alloys of Magnesium " was the title of a paper presented by Mr. W. E. Prytherch, of the N.P.L. It described investi gations into the mechanical and rolling properties of some magnesium alloys. No magnesium alloys have yet been made with the satisfactory heat treatment characteristics of alu minium alloys.
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