# Drooped down wingtip or the drooped up wingtip better for an RC plane?

Hi,

Can someone pls help me out in telling me whether the drooped down wingtip or the drooped up wingtip is better for an RC plane? I have read that the drooped down wingtip is better but none of the planes in production(commercial airliners) use it. They use the drooped up wingtip! Also, is an angle of approx. 120 degrees to the wing surface alright for the positioning of a new wingtip?

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Wingtips

Hi,

If I need to design a wingtip for an exisitng wing then what size must the wingtip be relative to the wing. If someone can help out by providing links or any info, I will really appreciate it!

berkeman
Mentor

What you call a drooping down is known as dihedral configuration, it enhances roll stability. It is so in almost all of the commercial planes. Drooping down is the anhedral configuration, & it gives more maneuverability, hence observed in few military & cargo planes.

You can easily prove the point by making a free body diagram of both configuration. In dihedral, lift(perpendicular to wing surface) produces a restoring moment while rolling. Try explaining to yourself why anhedral are high mounted wings(must have observed this on cargo planes)

Hi,

I think there seems to be some confusion.Pls take a look at this http://ojas.ucok.edu/96/T96/Jdavis.htm#Abs [Broken]. I'm talking about the ends of the wings (wingtips). The second option in the link seems to be better than the third. However it is not used in any commercial airline.

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russ_watters
Mentor

For a middle-school kid, that's a pretty good article, but generally what you describe are called "winglets".

http://en.wikipedia.org/wiki/Winglets

Often (see the bottom of the article), if they go both above and below the wing, they are called a "wingtip fence".

grant9076

Hi,

Can someone pls help me out in telling me whether the drooped down wingtip or the drooped up wingtip is better for an RC plane? I have read that the drooped down wingtip is better but none of the planes in production(commercial airliners) use it. They use the drooped up wingtip! Also, is an angle of approx. 120 degrees to the wing surface alright for the positioning of a new wingtip?
A drooped down winglet (depending on size) will contact the runway at a noticably lower angle of bank than a turned up winglet. This will drastically lower the landing crosswind limit of the aircraft and will adversely affect airline operations.

For a middle-school kid, that's a pretty good article, but generally what you describe are called "winglets".

http://en.wikipedia.org/wiki/Winglets

Often (see the bottom of the article), if they go both above and below the wing, they are called a "wingtip fence".
damn, go middle school kid. I think someone was helping him big time :rofl:

A drooped down winglet (depending on size) will contact the runway at a noticably lower angle of bank than a turned up winglet. This will drastically lower the landing crosswind limit of the aircraft and will adversely affect airline operations.
Haah. DUHHH...! Good observation, never thought about that!