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Aviation History
1920
1920 - 0232.PDF
Each upper plane contains 10 spars of duralumin tube,without counting the aileron tube. Fig. 3 gives a section drawn to scale, showing the disposition of these spars, andthe lower half of the diagram gives all dimensions, including SECTION OF LOWZJL PL WE ATx/U/S/CT/(yv WITH CENTRE SECTIOM. ,*:... . _ /a' —4— £5%— SEcno\ OF LXSV/EQ. PLANE. 3 FT. FQJDM TIP. Fig. 3a.—Sections to scale of Junker lower wing the diameters and gauges of the tubes. The tubular sparsare braced to each other by means of smaller tubes, also of duralumin. The exact system employed is shown very clearly FEBRUARY 26, 1920 JJ steel collars Examples of these joints are given in Figs. 4,5 and 8. The constructional methods already described as being'found in the upper planes are followed throughout both wings and centre sections except that towards the tipsjtheplace of the bracing tubes is taken by strips of duralumin " longitudinally grooved to resist bending strains. Fig. 8 (7)shows this, and also makes it clear that the steel collars to which the bracing tubes are riveted are not found wherestrips are employed. The finish of the tubular bracing and commencement of strip bracing is illustrated in Fig. 6.Some of the wing spars are spliced, a tube of larger diameter being joined to one of smaller diameter by being pressedinto a square section as shown in Fig. 19, and riveted in place. The lower drawing of Fig. 19 shows how two portions o£equal-sized tube are joined by means of a steel collar. The way in which the wings are joined to the centre sectionsis simple and effective. Reference to Figs. 8 (No. 8) and 16 (No. 9) (which are not necessarily drawn to scale), shows that each ofthe spars is fitted with a steel sleeve which fits inside the duralumin tube and is riveted in place. One sleeve carries athreaded collar bevelled as shown. The opposite spar has a similar internal liner of steel, riveted in place, and a looseinternally threaded steel collar. The end of the liner is bevelled to take the bevel of the opposite spar. Thus, when the bevelaare fitted together, and the collar screwed on to the male thread (tommy holes can be seen in the sketch), a firm and Fig. 5. rigid joint is made. When it is remembered that all thenumerous tubes are joined in this manner, it is evident that the junction of wing to centre section is of great strength.Indeed, the designer has trusted solely to these joints to take all lift, drag, and landing strains, for there are no otherattachments of any sort between wings and centre sections. The sheet duralumin covering is .015 in. thick (roughly28 S.W.G.). It is corrugated so that a section cut parallel to the trailing edge is waved and the pitch of the wave is :'.•:£:.• Fig. 4. . -, :._.. .-.y:'-.^ in the photograph (Fig. 7) and the sketch (Fig. 8 (1 and 2)).It will be noticed that steel sleeve3 are riveted at intervals along the spars, and that the bracing tubes are flattened outa t the ends and riveted to small flat plates welded on to the if ins., the depth being J in. The sheets are riveted togetherby aluminium rivets spaced at intervals of 1.8 in. The sheet weighs 3.65 oz. per sq. ft. of area, not allowing for lapin riveting. (It may be remarked that an approximate 232
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