Airfoils

[Entropist]

Having flown my Leadfeather Yak 55 profile foamie into well past the "best before" date, I'm thinking about remaking it, and toying with cutting an aerodynamic wing. I've got the parts for the hot-wire cutter, but need to select a profile. I found this site with what looks like some good basic advice:

https://www.flyingfoam.com/content/what ... ld-i-use-0

I saw a reference elsewhere to the Eppler169, any of you out there with some advice. I don't know what's on the real Yak, but, given an order of magnitude divergence in the Reynold's number anyway, not going to worry about being scale. I'd like to see some comments in the thread about glider profiles, too. If I'm going to set up for cutting one type of wing, I'll probably tackle a flying wing and something for slope soaring eventually as well.

BTW, the site I reference above has a lot of other neat stuff to offer. If anyone's into putting in a foam order, let me know.

J

[JohnOSullivan]

Symmetrical Airfoils are best for aerobatic models. Typically in the 13 to 16% thick range. Thinner for faster and thicker for slow flying.
Don't be uptight about sticking to a particular airfoil, as for these type of models, airfoils are not critical as long as the nose radius is not too small. This can induce stalls. Any of the NASA sylletrical sections in the 13-16% thick range will work well and the Eppler sections are good too.
I have coordinates for 1500 + sections so if you need some I can provide.
You really only have to get picky when you are pushing glide performance or in the case of pylon racing, where low drag is important.
Aerobatic models are typically flying at moderate to low speeds and a conservative section works well.
As for Reynolds numbers, don't worry about that, as at the wing chord and airspeed range of aerobatic models, most airfoils will be well within the optimum Reynolds Number range.

[saboo]

If you want to mess with airfoils here are some sites.

http://www.profili2.com/

http://www.profoil.org

http://www.soartech-aero.com/ This site has links to Dr. Michael Selig's work at U. Illinois as well, which is sort of the Holy Grail of low speed airfoil research.

http://www.mh-aerotools.de/

At low speeds Reynolds numbers get low regardless of the airfoil. Increasing chord makes a bigger impact on performance than airfoil shape on planes such as LeadFeathers EPP planes.

Jim