Stepped wing leading edge.
 

I notice several of the latest pattern models have a step in the leading edge of the wing. Assume there must be some aerodynamic reasoning behind this. What's the deal?

Aero Marketing? ;-)

What do you mean by "STEP"? IF I understand correctly, you may mean a wing LE that is either curved/bent ala Spitfire (elliptical) to the rear, or the wing's outer 1/3 or so that is actually smaller in chord.

In either case, the designer reduced tip chord for two reasons: it becomes elementary to reduce LE radius at the tip. It becomes elementary to reduce wing area at the tip. Both conditions allow a simpler set-up for snaps and spins that doesn't take more than 11-12 degrees of elevator to be effective.

My wing solution (that I've used the past 15 years or so) is simpler, just as effective if not more so, and is far easier to actually build. I simply choose to use a root chord to tip chord ratio that is fairly high by Pattern standards. Ratios of 3+ (18" root,6" tip) work very well in Pattern plus they bring the MAC closer to the fuse CL. (One current wing I'm using actually is closer to 21" root to 6" tip, or a 3 1/2 : 1 ratio). This wing type is bothered less by crosswind turbulence to boot, eventhough span is a full 2 meters.

Hi Matt,
Dick Hanson was a firm believer in higher root to tip chord ratios to improve snaps, too.
Do you have plans of any sort available for your latest pattern creation? Scanned files would be great!
If yes, I will PM my email address.
Thanks,
Will Bartlett

I think for the most part it's about spin and snap entries. Aerodynamically a wing like that gets treated as if it were two separate wings. What happens at the 'blend' is an unending aerodynamic conversation - a good way to clear out a room at a party, for sure.

BJ Craft wrote a little about his in his blog for at least one of his airplanes. Basically you get the benefits of each different type of wing design (inner and outer).

Often there is a change in sweep - sometimes just in the angle of the wing ribs. The angle that the air passes over the wing impacts the Reynolds number as the chord length of the wing section changes with that angle. That explanation might be lacking a little, but if you take a rectangular wing with perpendicular flow, the air sees the least amount of wing chord possible. If you flow air over the rectangular wing from an angle (simulating a swept wing), the air sees essentially a wing with more chord. That is why high speed jets have swept wings - it is a trick in that you get to used a smaller wing for less drag, but maintain a low enough relative velocity over the top of the wing. If the air speed over the wing exceeds the speed of sound you get a shock wave which is bad and everything changes.

So you can tune the wing based on expected air velocity, which in this case is driven by aircraft attitude and air speed. Note that as an airplane turns, the inboard root of the wing and the wing tip are likely seeing different air velocities. If you were designing for something as simple as an airplane turning, a simple tapered chord would work just fine. If you are designing for a supersonic fighter jet, or an F3A airplane during a spin or snap, the design could get much more complex.

So there's a long answer for "An attempt at improving maneuvers like spins and snaps while having minimal impact on the rest of the flight envelope."

No plans Willy,

The only email conversation I have ever had with Dick has been on gasoline engine efficacy. His early experiments with the ZDZ40cc inspired me to give gasoline a go 5 years ago. MY ZDZ didn't go quite like his (to put it mildly), but my other gasoline experiments have been terrific.

It's interesting to me that he came to the same conclusions RE: high chord ratios on wings. Don't know how high he went on his ratios. There are so many benefits it amazes me that so many (practically every one else, I should say) have not jumped on that simple fix for current schedules. I would love to see the result in the hands of a highly calibrated pilot....that's not me....LOL!

Big thanks all for the comprehensive replies. Starting to understand things a little better now. Not much info on the web around this subject relating to RC models.