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I would like to know what airfoils are used for the Boeing 737 winglets.

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Aviation Partners Boeing, a joint venture between the two companies, developed the winglets for 737NG, 757 and 767 aircraft. They are offered in two varieties, a "blended" version, which is where the wingtip is upturned to near vertical and a newer, "split scimitar" version which adds a downward pointing tip as well. They are made of a composite material with aluminium leading and trailing edges.

Their purpose is not to generate lift, but rather, prevent wingtip vortices (which generate a significant amount of induced drag) from spilling onto the top of the wing.

The design characteristics of the blended winglet are described in US Patent 5,348,253.

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    $\begingroup$ They actually do generate lift by increasing the pressure differential at the wingtip. But they do not prevent those mythical "wingtip vortices", and the reason for induced drag is lift creation. All they do is to spread out lift creation over a slightly greater air mass, and the reduction in drag is easily lost with a little sideslip. If you add the additional friction drag, their drag reduction is marginal at best. $\endgroup$ – Peter Kämpf Jul 2 '14 at 19:16
  • $\begingroup$ You're right, it is impossible to prevent wingtip vortices. Winglets produce a forward thrust inside the circulation field of the vortices to reduce their strength. This, in turn, reduces the amount of induced drag. Airlines using winglets experience fuel burn reductions of up to 5%, hardly a trivial amount. $\endgroup$ – newmanth Jul 2 '14 at 21:27
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    $\begingroup$ @Flanker for continuity they keep using the same airfoils as in the wing. $\endgroup$ – Trebia Project. Feb 9 '15 at 6:55
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    $\begingroup$ @PeterKämpf Airbus was able to get 3.5-4% fuel burn netly (including airframe structure weight increase) when retrofitting the A320 airinsight.com/2012/11/27/… $\endgroup$ – Trebia Project. Feb 9 '15 at 6:57
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    $\begingroup$ a joint venture between the two companies which companies? $\endgroup$ – Federico Feb 25 '15 at 8:49

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