I want to build a small glider (low speed) with very stable flight quality. Wing span less than 30in/75cm. Steering eventually with V-tail. Which airfoil would be the best? Are the wing area and the weight arbitrary increasable?
What are the maximum values for these?

Thanks for your help,
Tobias

One thing that you will note when you read back through the threads here and under Aerodynamics is that some of the more sophisticated airfoils require considerable accuracy when building to make them work right or to full potential.

The smaller the aircraft, the more difficult it becomes to meet the building and aerodynamic requirements of the SD and similar airfoils.

So, the answer is, go find a simple and fairly thick (I think that 9 to 10% has been suggested elsewhere, flat bottom airfoil and start with that.

Good luck. And if it don't work just remember that it might make a good freeflight chuckie if the radio is no good

We could probably use more info on how you'd like to use the plane...

Thick airfoils are not common on sailplanes because of the amount of drag they produce... thermal duration planes usually use a thin foil to be able to move fast through the areas between rising air... and slope planes use a thin airfoil to keep their speed up. As you suspected, a thin airfoil is not the answer to unlimited cargo lifting, but a thick airfoil is not the answer to prolonged gliding flight.

3/4 meter sialplanes were a real hot topic on the RC Sailing Exchange mailing list for a time, but I don't know whether they're still into that or not.... I know there were several designs around including the MAD Dragonette, which I'm pretty sure is still manufactured -- seeing what others use for foils, etc. is usually a good starting point. In the end, I wouldn't embark on a project that small unless you're already into sailplanes... because a plane that small won't have the wonderful flight characteristics that the big ones do.

See:
http://www.charlesriverrc.org/articl..._apogeehlg.htm
You probably can't do better than the Apogee airfoils. The lower the wing loading the better. Anything above 5 ounces per square foot wing loading in this size model will be a dog.