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Can endplates be used to reduce chord length by up to 14%?

I understand large endplates can change the lift distribution from an elliptical one to a uniform one, making the wing more efficient by increasing lift near the wing tips.

This increases the effective aerodynamic span by up to 16% ( see pic below ).

pic: Effect of large endplates on a short span wing, Source: Zenith

Effect of Endplates

Can this be used to shorten the chord?

eg.

16' span, 2' chord, total wing area: 32 sq ft rectangular wing.

Use large end plate, h/b=20%.

revised effective aerodynamic wing span: 16' x 1.16= 18.5'

Revised chord: 32 sq ft / 18.5 = 1.7' chord.

Is this correct thinking?

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  • $\begingroup$ I read somewhere many years ago that endplates have to extend about a full chord length beyond the airfoil profile to do much good, at least a net benefit over their own drag. Which is why you rarely see them. The ones you sometimes see on STOL modded airplanes that stick up a couple inches are useless. $\endgroup$ – John K Apr 21 '20 at 19:21
  • $\begingroup$ Why would chord be any different? Just because the effective span is increased, doesn't mean the physical area has increased. $\endgroup$ – JZYL Apr 22 '20 at 15:47
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It would be possible to do as you suggest.

However the short-chord wing would have to be either thinner and therefore heavier, or less streamlined and therefore less efficient causing higher form drag. Both effects increase induced drag.

The endplate would need to be roughly square in proportion, which would add drag of its own. Also its mass and side area would complicate the aircraft behaviour.

It is generally better to add a small winglet rather than a big flat plate and use it to reduce the wing tip vortex. But even there, a bit extra wing span with suitable washout is just as good.

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  • $\begingroup$ But can one use the longer aerodynamic span instead of shorter physical span for chord calculations? $\endgroup$ – Fred Apr 22 '20 at 15:19
  • $\begingroup$ I would not muck about with correction factors, they are really only advisable for sanity checks. Large endplates will allow a greater total lift because it does not taper off, so the flatter lift profile will allow a higher mean wing loading. Once you decide on the weight, span and wing loading then the area and mean chord will fall out of that. $\endgroup$ – Guy Inchbald Apr 22 '20 at 16:26

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