Gurney Flap

[dusty IV]

I've been messing around with a .40 size 3D design. Nothing really exceptional except with the newer electric motors and batteries some higher power is now available for larger planes.

Has anyone played around with a Gurney Flap? This looks like it might have an application in a model airplane. Maybe not 3D due to inverted flight but not sure of this.

[Bobber Bob]

Hi Dusty...

If you mean the Gurney flap that we played around with at M'Douglas for the DC=10/MD-11...

Your right, it is a camber increasing divice, and therefore would not improve 3D performance, where you want everything to act symetrically.

But I have observed "Gurney Flaps" that extended the same amount above and below the wing's trailing edge. And the intended use seemed to be nothing more then as a brake, but operating aft of the CofG to give some stabilizing effect.

As a wind tunnel model maker with all the major American airframe manufactures, I got to play with a lot of different design configurations, and some of them got pretty wild !!!

With all of these flat 3D foamies around, it does not seem that it would be very complecated, or expensive, to tape something on, and just give it a go....

Bob Reynolds
. "ComeUpHere"

[biber]

Such a double sided Gurney flap might be used to remove the dead band effect off the Cl vs alpha curve.
At least on the rudder of the Mu 30 Schlacro that's the case.
http://www.airliners.net/photo/Akaflieg-München/München-Mü-30/0273978/L/

biber

[MarkusN]

Such a double sided Gurney flap might be used to remove the dead band effect off the Cl vs alpha curve. Huh?!!?? If anything I'd have expected the opposite (The fow not being able to decide which side of the flap to conform to). Fluiddynamics never cease to astound me.

[macboffin]

So what about hingeing the gurney flap so it can go up or down? Could use it inverted then.Don't know what the h*** for though!

[BMatthews]

So what about hingeing the gurney flap so it can go up or down? Could use it inverted then.Don't know what the h*** for though!

So it would lay flat at neutral and then flip when the surface is deflected? Sounds interesting but with the flat foamies already using 30% chord widths and up over 45 degrees of throw in many cases I'm not sure there's much to be gained by having this small "compound Gurney flap" being added to the trailing edge.