foam wing aerodynamics

[windywestflyer]

I recently bought a hobbyzone super cub and looked at it. It flies well but has a few weird characteristics. The trailing edge of the wing is blunt, i have never seen an airfoil like that. I would assume it is a poor airfoil because of it. But is it really? I don't know enough about aerodynamics to figure that out.
I have a bit of background in rubber band powered airplane flight and like to build more than fly. I was wondering if it is a good idea to design a new wing or would that put the plane out of porportion and cause poor flight characteristics?

[DT56]

If it flys well, then it's a good airfoil for that model. :)

The thick trailing edge is probably a compromise to add durability to the model. You may have noted from your experience with rubber powered models, that at the lower reynolds numbers, simple undercambered sheet wings work better than thicker built-up designs. An elegant solution is not always the most efficient answer to aerodynamic problems.

But, since you say you like to build, try a few new wings and see what you think!

[Brandano]

Add to that the fact that the airflow is unlikely to be laminar at the trailing edge. For the cost a little added drag having a trailing edge that is less likely to break is a good thing in an ARF design.

[eflightray]

There are a lot of models that have flat sheet wings, (such as 6mm depron sheet), most will get the leading edge 'rounded', but most will leave the trailing edge square, (6mm thick), none will have what could be called a recognized 'airfoil'.
One of my 'experimental' models is made from flat sheet, with what is referred to as a Kline-Fogalman wing section, the crude version with just a double sheeted leading edge and square T.E.
I was amazed at how well it flew, even with power off.

As long as you don't tell the model, "you can't fly like that....", they usually just go ahead and fly, also don't let the model read this forum either. ;)

I used to build free flight rubber many years ago and probably would stick to the 'correct' airfoil if I ever got back into it again, but for RC..........anything goes, and usually quite well.

[nmasters]

A blunt TE is not all that bad as long as it's thin and square. If it's rounded it'll make more drag and may increase the likelihood of aileron flutter. You can see a drawing of a TE squaring sanding block here: http://www.rcgroups.com/forums/showthread.php?p=8792126#post8792126

--Norm

[DT56]

Here's a link to an article about flat airfoils that might surprise you.

http://www.twitt.org/Bixel_WIG.html#top