Flat air foil Vs. Symmetrical air foil

[chris8105]

Wondering how much the flight characteristics change, if they do, from flat air foil and symmetrical air foil.

Thanks

[azkeith]

The airfoil shape plays a major role in the performance of the aircraft. Airfoil is dependent on the job design of the aircraft.

[Charleyh]

Flat bottom airfoils provide lift on their own lift while moving through air while level.
Symetrical airfoils do no create this lift and must have an "angle of attack" or tilt to create lift.

They do fly differently (especially inverted) but feel similar once you get used to it.

[BJAZ]

C&P

Airfoil: If you face the wing tip of the plane and cut it from front to back, the cross section exposed would be the wing's airfoil. The Flat-Bottom Airfoil will develop the most lift at low speeds and helps return the model to upright when tilted. This is ideal for trainers and first-time pilots. A Symmetrical Airfoil's top and bottom have the same shape, allowing it to produce lift equally whether right side up or upside down and to transition between the two smoothly. This is recommended for advanced pilots. Lastly, a Semi-Symmetrical Airfoil is a combination of the other two and favored by intermediate and sport pilots.

[foamflyer]

chris8105,

I assume from the posted answers you mean flat-bottom airfoil? When I first read this I thought you meant "Flat Plat" airfoil, which, technically, is symmetrical. A good flat-bottom airfoil is the Clark Y and it's derivations.

[Pinecone]

A flat airfoil (foamie) is a very low percentage symmetrical airfoil. And thus flies in a similar manner. It requires a positive angle of attck to produce lift and flies upside down the same as it does upright.

[chris8105]

I shoulda clarified it a little better. The reason behind thisd question is I was looking at 3D planes on the north east sailplanes web site, and I noticed that some of them was symmetrical and others were flat. So I was just wondering if one would fly better than the other or if the flight characteristics were any different.

[jgleigh]

AFAIK, the relative performance of a flat plate airfoil vs. a symmetrical airfoil (well, I guess a flat plate is also symmetrical but you know what I mean) depends on the Reynold's number - flat plates get relatively better in terms of L/D at low Rn. At very low Rn (insect size) they are actually better, IIRC.

[jrb]

Here’s a thread/posting of interest: http://www.rcgroups.com/forums/showpost.php?p=3256251&postcount=36