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Aviation History
1933
1933 - 1329.PDF
DECEMBER 28. 1933 yi THE AIRCRAFT ENGINEER SUPPLEMENT TO FLIGHT •04-8 046 044 052 OS dKL doc •048 •046 044 SYMMETRICAL AEROFOILS SERIES 00 LAW TO CURVE dKo/doc - -0512-6-2 ts •002 •004 006 002 •004 t3 -006 •008 •008 01, •052 •OS 048 046 044 TIG.2r + 5» ***N*£ + SERIES 43-65 © SERIES 43 + SERIES 63 • LAW TO CURVE dKL/doC - 0512 - 53 tJ •01 ^05 LAW TO CURVE dKi/doc - 0505 - 60 t5 •002 •004 006 008 01 The second group comprises sections with maximum camber at 0.4 and 0.5 of the chord has a fall off of 0.42 t\ Taking the cambered sections, it would seem that the fall off in slope of the moment curve could be repre sented by Fig. 18. How reliable this curve is can only be found by comparison with future test results. The variation may be partly due to the choice of centreline shape, and any other shape having the maximum camber at the«same point would not necessarily give the same fall off in slope as shown on the graph. In the interim it is probable that a Variation of the form 1^0-25-0-4/* (12) d KL y ' will give results sufficiently close for practical purposes. After all, the change in the estimated C.P. position due to neglecting the effect of thickness, is not likely to be serious. There is no evidence to show at what camber the extrapolated value of dKm/dKi for t =. o departs from 0.25 for the present cambered sections and tends towards that of 0.243 for the svmmetrical sections. The question of maximum lift has been dealt with in Ref. 1, which covered only the 43, 63 and 45, 65 series. A new set of curves has been made to show the varia tions covering the 44 and 64 series as well. The results are given m Fig. 19 for values of KMU of 0, —0.02 and -0.04. It appears safe to draw the following general con clusion from these results. (1) To obtain the highest maximum lift, the point of maximum camber must move forward as the section is thinned and conversely moved backward as thicker sections are used. (2) There is a definite increase in maximum lift as the no-lift moment increases at all positions of the maximum rise of centreline and constant thickness. For example, by moving the point of maximum camber from 0.3 to 0.5 of the chord at 19 per cent, thickness the same maximum lift is obtained with a no-lift moment of —0.02 as was previously obtained with Km„ = —0.04. If it is safe to extrapolate these results, it would seem that for sections in the region of 20 per cent, the point of maximum rise could be moved further back than 0.5 of the chord to obtain maximum lift possible for the particular thickness ratio. This important conclusion, •30 •20 X o 10 0 -•1 / KLopt fbr 43-*5 SERIES / / / / , V\ / 'A r / '/ / / / / / // / • / * ^ / r / / FIG. 22 J 01 02 03 f 04 05 06 07 30 •20 •10 0 1 / KLopt for 44-63 SERIES / // y\^ '// ^ v / 'A / / s* / / /% <v FIG.23 ) 01 02 03 y 04 05 06 07 1310g
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