Planform and Dihedral Considerations Figure1 compars the span eﬃciencyof wings with three types of taperand nowashout twist. Theadditional benefitof goingfrom asingle tapertodouble taperis verymodest, and has to be weighed againstgreaterstructural complexity. e = 0.960 e = 0.989 e = 0.997 constant chord double taper Γ ΓΓ λ=0.6 λ=0.6single taper Figure1:Spaneﬃciencyofthree differentplanform untwistedwings. Dashedlines are ellipticalloadingswiththe same lift.A meaningfulwaytodefine the taperratioλ foramulti-taperwingis interms ofthe rootchord cr andaverage chordc.2c cr = cλ = 2−11+λcr Thisλ definitionreducestothe usual definitionλ = ct/cr forastraight-taperwing. Because theroot chordcr dominatesthe structural bendingproperties of awing, any twowings with the same area,span,andλvalueswill likely have
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