The science of sections
 

I recently read up on the design of airfoils for the DR 109 and the caps 232.

They're not exactly what I thought they would be, namely the DR 109 having a roughly elliptical forward section and a straight trailing edge, and has been shown to have considerably less drag at low velocity (uplines) and increased drag at high velocity (downlines), and a clean preditcable stall.

I've noticed that on the whole we still tend to steer towards the NACA style airfoils, is there any reason for this? Has there been any development in the design of pattern airfoils in the last few years that I'm not aware of?

RE: The science of sections
 

I'm not so sure about the cap, but I think the DR109 section was designed for home builders, with the section being a compromise b/n ease of construction and performance.

Performance wise how this compares with the NACA sections I have no idea.

RE: The science of sections
 

---Sometimes you can't win though----at a recent comp. one of the judges thought my uplines were too fast,and the downlines too slow......

RE: The science of sections
 

Constant speed:)

That's where it's at.

RE: The science of sections
 

I did a bit more research into the sections that are currently being used, and it's pretty interesting.

John Roncz designed the airfoils that are used in the Zviko Edge 540 and show a similar design to the DR 109. This elliptical leading edge, and a thickness point well forward of 30%. I have to admit that I noticed something similar on Extra 300's for a while now. Take a look at a real one where the root of the wing is and it looks really odd (well compared to a NACA airfoil) it just looks fat.

Is there any reasoning for pattern to stay with the NACA airfoil? Benefits? Drawbacks?

Discuss.

RE: The science of sections
 

I agree, some of those home full sized acrobats have very strange looking airfoils. Some of them remind me of the old Coke can airfoil we made years ago for our funflys.
No science involved in those babies.

There seems to be a great deal of different approaches when to come down to pattern, some like them fat, others like 'em thin. There are even those that like them fat at the center cord and thin at the tip or even fat at the tip. Look at CPLR's original Synergy wing and it has a very thick airfoil at the tip. Just about everyone I know has had their own Synergy wings cut using a thiner tip airfoil! Obviously it suited him!!!
Some years back Chip Hyde experimented with a double convex airfoil. After the fanfare of trumpets had died away, seems to have decided to kick it in the head and get back to basics.
The fact that there are so many different approaches and personal preferences indicates one thing... You can get away with just about anything! One could could even start to question the actual contribution the airfoil selection make to the overall performance of today, super light, super powered pattern planes. My indoor flat foamies "fly" superbly and don't have an airfoil... not even a sharpen leading edge.
I put the word fly in inverted commers because thats not what they're really doing and it's it's exactly that what's separating our light weight, low wing loading, super powered models from full size aeroplanes.