Comment by aredox

2 years ago

For an example of a flat-ish airfoil that performs well enough for model airplanes (and is easier to build than a NACA & co airfoil), see the KFm airfoil family:

https://en.wikipedia.org/wiki/Kline%E2%80%93Fogleman_airfoil

Very useful when making model airplanes out of foamboard.

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aredox

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kqr  2 years ago

Huh, odd. I was under the impression that for swept/delta winged paper airplanes one wants a smooth top surface to encourage attachment and any steps on the bottom to provide decalage. (I.e. the area ahead of the step acts as a canard-like surface.)

Is this an airfoil that works for tailed aircraft but not tailless ones, perhaps?

Edit: I just skimmed the book on paper planes by KF and indeed they are using the variation with the step on the bottom for their paper planes.

I'm actually even more surprised now. How on Earth did they manage to patent the idea of reflex on a delta wing to give a tailless plane stability? This seems like the thing that (a) was known since early human-carrying gliders, and (b) implicitly discovered by anyone that folds a lot of paper airplanes. I will definitely read their book in more detail.

  • skykooler  2 years ago

    Attachment isn't as much of an issue with paper planes since the small size and low speed give much more favorable Reynolds numbers.