Where can it possible to find pictures or drawings of "endplate"? (for "winglet" is much easier, but not endplate)
I'm asking what's written above, after I read the following text from Raymer and I need a better comprehension of it.
The wing aspect ratio "$A$" is the geometric aspect ratio of the complete reference planform. the effective aspect ratio will be increased by wing endplates or winglets
Endplate: $A_{effective} = A(1+1.9\frac{h}{b})$ - (12.10) where $h$ = endplate height
Winglet: $A_{effective} = \approx 1.2A$ - (12.11)
These effective aspect ratios should also be used in the induced drag calculations below. note that Eq. (12.11) for winglets is a crude approximation based upon limited data for wings of moderate aspect ratio
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The extra drag due to non-elliptical lift distribution and the flow separation can be accounted for using e, the "Oswald span efficiency factor". This effectively reduces the aspect ratio, producing the following equation for $K$
$K=\frac{1}{πAe}$ (12.48)
If the wing has end-plates or winglets, the effective aspect ratio from Eq. (12.10) or (12.11) should be used in Eq. (12.48)
(Source: Daniel P. Raymer "Aircraft design . A conceptual approach" , Chapter 12 Aerodynamics)