gurney flap

[kestrel2003]

Does anyone know if a gurney flap ( as used in F-1 car racing) would work on a model plane to increase lift?
Comments,ideas.,Raynoldnumbers? drag increase?

[Ollie]

Yes, properly sized gurney flaps will increase lift. If properly sized not to exceed the thickness of the boundary layer, gurney flaps will increase lift appreciably at the cost of some increase in drag. The lift to drag ratio is seldom improved and if the flap is too big, the L/D will be seriously degraded.

Windtunnel test data and discussion of gurney flaps can be found in Summary of Low-Speed Airfoil Data, Vol. 2 by Michael S. Selig etal., available from Carstens Publications. See:
http://www.carstens-publications.com/
Look under soaring books.

[kestrel2003]

Thanks a lot for the help. Do you happen to know if the flaps are used often?

[Ollie]

I've been involved in R/C model sailplanes for 34 years. I've attended national and international competition. In all that time I've never seen an R/C model sailplane flown, reported in the model press or advertized for sale that used gurney flaps. I have to conclude that their use is extremely rare or, close to nonexistent.

[kestrel2003]

Any new developments with the gurney flap?

[Sparky Paul]

I've used a couple to trim out serious warps on wings which had no ailerons.
Depending on the direction of the warp, they're on the top or the bottom.
A simple easily checked change.

[nauga]

I have to conclude that their use is extremely rare or, close to nonexistent. Sounds like that's definitely the case in modeling, where the problem may be one of scale (they're not exactly huge in proportion to the size of the model) but they're not uncommon in full-scale fixed wing (some DC-10/MD-11's) and helicopters. I distinctly recall seeing them on at least one general aviation airplane as well but would get it wrong if I said what I thought it was so I'll refrain :D

Nauga,
still flapping

[HELModels]

The AMA Cub rubber powered pos uses a Gurney Flap by virtue of using a stick trailing edge and a tissue covered upper surface.

[biber]

I have worked on some inflight measurements of gurney flaps and so called mini flaps on a fullsize DG1000.
The flaps' size was around 2% chord and seem to give about an increase of around 15-20% in the maximum lift coefficient.
But also the drag is increased significantly.
The mini flaps were basically the same size but with less deflection, 60° 45° 30° and 15°
and thus gurney flap wouldn't have been a correct name for that (as they are allways 90°).
The 60° flap seems to have about the same positve effects on the lift with less drag penalty.
Note that the Cm is increased by such devices a big deal and not every airplane design will like that feature too much.
But if only max lift is needed and the wing surface area is limited, gurneys can be a sensible measure.
In formula one racing there are rules that limit the size of spoilers and often the better grip at the costs of some additional drag is a good deal.
And another good thing with them is, they are not to hard to build and yet effective.

http://www.fva.rwth-aachen.de/gallery2/main.php?g2_view=core.ShowItem&g2_itemId=704&g2_GALLERYSID=0595a9d024763da80ec58de7d4f9a859

biber

[shaneyee]

This looks like a great device to put on a model serving as flaps but requiring a much smaller servo than conventional flaps.

Shane