Wing TE / flap LE

What is the best shape for the wing trailing edge/ flap leading edge?
Also, what about the elevator/stabilizer?
Most kits just call for the TE to be square and the flap/elev to be 45 degs.
Jerry

I use rounded TE on the wing and stab. The LE on the flaps and elevators are also rounded. Supposed to keep the airflow smooth during surface deflection. I think it also gives the model a "softer" look at the hingeline and helps blend them visually.

I have always made mine square with the movable surface rounded but after reading a few comments on this board I think I am going to start rounding the trailing edges.

I would love to see someone buy that little wind tunnel that was on eBay and do some experimenting with this and wingtips to see if it really makes any difference at the speeds we fly. I was thinking about it but already have too many projects..

After talking to some people recently it seems that maybe anything from the high point back may not be that critical, and that the leading edge is VERY critical. I looked at some T.O.C. or whatever that BIG RC Stunt contest is where they fly the extras and what not, Chris Hyde wins it a lot, anyway their wings are almost straight back from the high point of the wing with little taper.

I don't want to start controversy, just curious.

get a GNU copy of the XFOIL program by Mark Drela, spend a couple weeks learning how to use it, and you can get a pretty good idea of the airflow over your super zoot airfoil, including the hinge line.

http://raphael.mit.edu/xfoil/

I don't know how it handles the hinge line if it isn't sealed. Would be interesting to try.

I played around with a few combat airfoils. the most noticeable thing was that minor discontinuities in the airfoil, like from the spars on the surface, or D tube construction, can really play hob with the pressure distribution. Nice "smooth" airfoils, like a NACA 0015, do seem to fly better, esp. in tight, consecutive maneuvers.

>get a GNU copy of the XFOIL program by Mark Drela, spend a
>couple weeks learning how to use it, and you can get a
>pretty good idea of the airflow over your super zoot
>airfoil, including the hinge line.
>
>http://raphael.mit.edu/xfoil/
>

I appreciate the thought, but this is way too technical for me. Just wanted a general opinion as to what is considered the best, for flight characteristics and looks. The hinge lines will be sealed.
Not a designer, usually just build from kits. When I've strayed in the past have not had much success.

well, hopefully the guys designing the planes will do their homework and investigate what really works.

XFOIL is far from perfect. Folks who know tell me it misses some around the leading edge. The model used may not work well for details like the hinge line that are small fractions of the chord. Unfortunately, doing good ezperiments requires a lot more than one model a year.

Thus you'd think that stunt guys would use analytical tools more than combat guys, who build more airplanes and can experiment more easily.

Sounds like a job for used motor oil. Maybe some of the guys in places where it's still warm enough to fly could take some pictures and we can discuss them.

When you think about the pressure recovery happening at that area of the chord, it seems likely that the size of the hinge gap might be the most important parameter. Air leaking throught the hinge may have a greater effect on the entire wing circulation than a local disturbance at the hinge line. It will also greatly affect the drag if the air leaks through the hinge. It's also been shown that this leakage can have a great affect on control forces.

For this reason, I always use the square TE with a 45 deg flap (or elevator) leading edge, and recessed hinges. This gives me the tightest gap possible for my building skills. My logic is that in straight and level I'm not overly concerned with the flap or elevator efficiency, and in fact, a certain amount of "softening" of the controls while level might actually be a good thing (?). During hard deflections, however, the angled flap LE will provide even greater sealing, and hence better control response and lowered control force requirements.

Of course, the only part of this I have any data on is the control force. As for the efficiency, it's based on hueristics and not been tested - at least by me. YMMV. I'd love to test this out in the tunnel but it would take considerable effort. I'd have to build two sections (rounded and angled) and make several runs on each at different AoAs and control deflections. It could easily turn out that one is better at high deflections and low alphas while the other is good at high deflections and high alphas - which would open up a real can of worms! Or it may turn out that one is better for thick wingers ala Buso designs like the Cardinal, and the other better suited for traditional NACA four digit series airfoils.

Cool topic!

>>>which would open up a real can of worms<<<
will not, we seal gaps