Why just one 10th of an inch at the trailing edge could give 20% more lift.

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Why just one 10th of an inch at the trailing edge could give 20% more lift.

Postby uplink » Mon Mar 11, 2019 1:16 am

Dan Gurney, in the 1970s, improved the downforce on racing cars by the application of a tiny strip projecting up from the cars wing.

It introduced almost no extra drag but benefited the downforce by about 20% to 30%.

This device became known as the Gerney Flap and has gone on to find uses in improving aircraft aerodynamics.

The size of the flap is extremely small, being typically about 1.25% of the cord (width) dimension of the wing - so on an 8inch wing cord

it would be just 8 x 0.0125 ie 1/10th of an inch high - so achievable with a narrow strip of 3/32 balsa (which is 0.09375 inch thick)

or with 2.5mm thick balsa.

Here is a fairly basic look at aerodynamics and a look at the Gurney Flap in some detail.

Of course in the video we see its use for giving negative lift or downforce, as used on cars, to push the tyres hard onto the tarmac.

For use on aircraft, to give greater lift, the Gurney Flap would be located, not on the top - as shown here for cars - but located

along the bottom of the wing's trailing edge.


Now THAT'S a thermal.

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