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Aviation History
1936
1936 - 1115.PDF
SUPPLEMENT TO FLIGHT 462/ THE AIRCRAFT ENGINEER APRIL 30, 1936 representing as regards length along the span, the front and rear spars respectively. 3. Measuring from the rear spar line plot the values of " R " as ratios of the distance between the lines repre senting the spars. 4. Proceed now to obtain the flexural line exactly as when the spars were parallel. 5. If points on the fiexural line so obtained are now treated as ratios of the distances between the spars and so plotted, being measured from the rear spar, the true flexural line for the loading considered is obtained. If this procedure is followed the flexural line for any loading and non-parallel spars is found quite easily. Example As a final summary, an example in full will be given, which includes the various points considered, and from a perusal of this, and the previous descriptions given it should be possible to obtain quickly and easily a flexural line for any wing likely to be met with in practice. The above method has been checked against values obtained by calculation by the method of R. and M. 1617, and the agreements was remarkably close, whilst the gain in time was considerable. The final example is as follows :—" R " line straight, Spars not parallel. (Reference Fig. 6, a, b, c, and d.) x/s Tip .1 .2 •3 -4 •5 .6 •7 .8 •9 Root IF 1-57 1.78 2.0 2.2 2.41 2.62 2.68 2-73 2.76 2.84 2.88 IR I-7 1.68 1.66 1.64 1.62 1.6 i-73 1.86 1.99 2.12 2-25 I j.- COS3dF i-5 i-7 1-9 2.1 2-3 2-5 2-55 2.6 2.65 2.7 2-75 IF co'.-3 OF IK cos3 ar^lRCOS3aR -47 .496 •535 .02 .586 .'11 •595 •5.8.3 •57r -56 •55 x/s Tip .1 .2 •3 •4 •5 - .6 •7 .8 •9 - Root Ratio Uniform Load. •47 • 554 .636 •72 .804 .89 •524 •5 •48 •454 •43 Ratio Taper Load. •47 •53 •58 .636 .69 •75 •5(> •544 .526 •51 •49 Spar Centres. 3-2 3 38 3^55 3-73 3-9 4.08 427 4-45 4.b2 4-8 5 r Uniform. 1.5 1.87 2.2O 2.68 3.12 363 2.24 2.22 2.2 2.18 215 r Taper. 1-5 1 79 2.06 2.36 2,68 3.06 2-39 2.42 2.42 2.44 2-45 aF = 100 aR = Q° Cos3aF = Cos3aR Q-955 : I x/s Tip .1 • 2 •3 •4 •5 .6 •7 .8 • 9 Root MF — — — 2.5 4.6 7-f>5 11 *4-7 19 2.3-5 28.9 • IF 1-57 1.78 2.0 2.2 2.41 2.62 2.68 2-73 2.76 2.84 2.88 MF IF •— — — 1.14 1.91 2.92 4-1 538 b.Q 8.28 IO MR -— — — 1.88 3-14 4-7 7.0 9.8 U3 2 17.1 21 5 IR i-7 1.OS 1.66 1.64 1.62 1.6 x-73 1.86 1-99 2.12 2.25 M. TR~ — — — 1.14 1.93 2-93 4°5 5-2S 6.7 b.i -9.6 It will be seen from the above that if the values of M T are plotted for the two spars, and as deflections are pro- M portional to — the two spars would deflect equally along the axis X X. This therefore is the check that the flexural line derived is the line on which the load has to be applied to give no twist to the wing. EXAMPLE. DIAGRAM OF PATIOS Kah'o. uniform load Ratio leper load R LINE. 1 1 1— . ] . MB*' . .»—- FIG. 6 b. J 1 1 1 , ROOT 9 -8 I ZT PROPORTION OF LOAD OH S0MS u/'• Loadon rving 1 1 ..-. J— • 1 W.I 0 \^^ FIG.6c ROOT -9 -8-7 •I TIP ROOT •» -8
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