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cptcolo
cptcolo is offline
#6
Dec11-11, 01:19 AM
P: 1
Ken,
Spanwise lift coefficient is what you multiply the local CL by. An elliptical wing is 1 across the entire semi-span (root end to tip). Most wings have taper and are defined by a taper ratio (tip end cord length/root end cord length).

For most straight wings the spanwise lift coefficient is given as a function of the fractional semi-span distance (x):
1. Taper Ratio = 1
From x= 0 to 0.86
= -1.3474x3 + 0.8774x2 - 0.2469x + 1.1736
From x=0.86 to 1
= -36.7776x2 + 63.5583x - 26.7419

2. Taper Ratio = 0.5
From x= 0 to 0.65
= -0.43567x2 + 0.39804x + 0.97582
From x=0.65 to 1
= -5.51768x3 + 7.29061x2 - 2.31958x + 0.97582

Please note for both of these the real life spanwise lift coefficient does not really ever drop below 0.6. You will have to make that adjustment when x gets high (for an approx sol you can ignore this)