moment coefficient is due to the moment of the induced drag distribution b12 J

Moment coefficient is due to the moment of the

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moment coefficient is due to the moment of the induced-drag distribution ,_b12 = ! J " .... °. °L_._. Cni Sb_ 18o y dy -b/2 A _ _i :_ b Z-8_ d i r-i k,, /c_c : Om 18o (2l)
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20 NACA TN No. 1269 The induced-yawing-moment coefficient for an antisymmetrical lift distribution is equal to zero and has little meaning inasmuch as the lift coefficient is also zero. The induced-yawing-moment coefficient is a f'_nction of the lift and rolllng-_T_oment coefficients and must be found for asymmetrical lift distributions. ?rofile-yawing-moment coefficient.- The profile-yawing- moment coefficient is due to the moment of the profile-drag distribution, 1 ,[ b/2 = -- CdoCY dy Cno St U-b/2 r-i _--- (CdoC) )-- --T,m m=! APPLICATION OF METHOD USING NONLINEAR SECTION LIFT DATA FOR SYMMETRICAL LIFT DISTRIBUTIONS (22) The method described is applied herein to a wing, the geometric characteristics of which arm given in table IV. Only symmetrical lift distributions are considered hereinafter inasmuch as these are believed to be sufficient for illustrating the method of calculation. The lift, profile-drag, and pltching-moment coefficients for the various wing sections along the span were derived from unpublished airfoil data obtained in the Langley two-dimensional low-turbulence pressure tunnel. The original a_rfoil data were cross-plotted against Reynolds number and thickness ratio inasmuch as both varied along the span of the wing. Sample curves are given in figures 1 and 2. From these plots the section characteristics at the various spanwise stations were determined and plotted in the conventional manner. (See fig. 3.) The edge-velocity factor E, derived in reference 9 for an elliptic wing, has been applied to the section angle of attaok for each value of section lift coefficient as follows:
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NACA TN No. 1269 21 c% = E(C_o-_tQl+ °'_o,, lift Distribution Computation of the lift distribution at an angle of attack of 3° is shown in table V. This table is designed to be used wl_ere the multiplication is done by means of a slide rule or simple calculating machine° _lere calculating machines capable of performing accumulative multiplication are available, the si_aces for the individual products in cohnnns (6) to (15) may be omitted and tl_ table made smaller. (See tables VII and VIII.) The mechanics of computing are explained in the table; however, the method for approximating the lift coefficient distribution requires some explanation. The initially assm,_ed lift-coefficlent distribution (column (3) of first division) can be taken as the d_stributlon given by the geometric angles of attack but it is best determined by some simple method which will give a close approxiy._atlon to the actual distribution. The initial distribution given in table V was approximated by ! t cz = A l- cZ( ) A + 1.8 2 _c where c_(_) is the lift coefficient read from the section curves for the geometric angles of attack. This equation weights the lift dlstrib_tion according to the average of the chord distribution of the wing under consideretlon and thst of an elliptical wing of the same aspect ratio and s_an. _.._enthe lift distributions at several angles
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