Hello,

I am embarking on the design of a competition funfly model which departs from the classic approach to this class of models design.

I am particularly interested in building a model with excellent glide characteristics - so will be increasing the aspect ratio to something like 6 - or even 7 to win gains on the climb and glide area of the competition.

However, I still want to have good high alpha (high Angle of attack) performance.

So there are some competing design objectives - like all interesting design problems!

I was wondering if anyone had some ideas for an airfoil with the following attributes:-

wide or reasonably wide drag bucket
low drag
high angle of attack before stall
docile - smooth stall characteristics - I don't want a sharp cut off at high AofA

I am not concerned with roll rate or high lift co-efficients as I have some interesting (and top secret!) ideas for how to get rapid roll, and high drag and high lift with various devices, but I am interested in a good symmetrical section for low drag.

Have any of you experience of Selig's Low speed symmetricals e.g.

Selig/Donovan SD8020 (http://www.nasg.com/afdb/show-airfoil-e.phtml?id=1085)

or Eppler's aerobatic airfoils:_

Eppler 474 http://www.nasg.com/afdb/show-airfoil-e.phtml?id=182

The eppler airfoils look to me to be designed for full size, though it is interesting that they employ a thickest point well ahead of traditional symmetricals like NACA 0012 for example. And I have seen "drawn round a boot" sections on plenty of funfly models with a thickest point well forward.

I know the leading edge radius will have a big impact on Aof A at stall as will the aspect ratio, but I want a shallow glide too!

Another approach would be to go for a slippery section and employ leading edge slots as mentioned by the likes of Andy Lennon in RC Airplane Design. But I'd need them to pop out automatically at high angles, and then pop back in
and I'm not sure I can build them that well that they would always work without being really heavy. Other option would be servo operating leading edge flaps or slots - but again weight becomes a problem....

If you have a section in mind which you really like in this kind of class of model then I'd be really interested to hear from you.

thanks