Hi Guys,
Just finishing my Profile Edge 540 and waiting for my Aeron to arrive and wondered what other peoples findings are with regard to trailing edge profiles. I've had a number of other aircraft use square trailing eges and wondered if they would be OK on the Edge and Aeron?
I've also heard that they're supposed to reduce the risk of flutter. What do you think?

Thanks,
Tony.

on the trailing edges of the control surfaces you need them square. If they are rounded they have a high potential for flutter.

I disagree with the square trailing edges. You should always at least bevel or round the trailing edges to maintain the laminar airflow coming off of the wing, other wise you will create "eddies". Eddies are turbulant airflow, which can and will cause flutter. I've seen this effect in wing tunnels, more than once (low speed wind tunnel tests).

This subject has been beat to death in the formus. The general concensus is that square trailing edges are less likely to cause flutter. This opinion can be found in numerous written articles. However, due to the small size of our models, I gather that the effect is very small and that you can pretty much do as you wish with trailing edges. For the racers, sharp trailing edges do reduce drag. Much more important in reducing flutter are strong control surfaces, rigid control mechanisms from the servo and keeping the center of gravity of the control surface as close as possible to the hinge line. I always taper the control surface from the hinge line to the trailing edge and have only had one flutter problem on 25 models, including many lightweight fun fly types. The flutter problem was on a stick where the ailerons got wider towards the wing tip and extended all the way to the wing tips. It was easy to fix.

I'm on the side of the square TE's, it causes the disruptive airflow to occur farther past the TE than a rounded one will. I heard a rumor once that if flag poles were square the flag wouldn't ripple in the wind. If you can find Ed Mormons web page, he has some really good info on this subject of TE's. If anything, I would taper it to a sharp point if it were a faster plane, but leave them square for a fun-fly type plane.

I've always round my trailing edges, never had a problem.

I think a sealed hing line wound be more important.


Don

I think I will stick with my actual test data. I put more faith in that over opinions. Though I do agree with the comment that it is more important to seal the seams than worrying about the configuration of the trailing edge, rounded VS square.

There's nothing better than the tried and beaten path, if you know it works, go with it.

Maybe this would help? After test flying a full scale exp.
it was found the plane was dropping the left wing.
A call the the kit mfg. got this fix. (On the aileron of the wing
that is dropping the TE is most likly to sharp to maintain contact
in the slip stream. To fix it hold a 3' section of 2X4 on the TE
of the aileron and give it a few good hits with a hammer.
The idea is to remove the sharp TE and give it some thickness
to maintain contact in the slip stream.)
The owner tried it and it really worked.

I'd never thought of that one.

Seems opinion is split on this one. I have over the years flown models with both types and have never experienced any flutter what so ever. Mind you, I do make sure my hinge gaps are minimal and ensure all linkages are nice and solid and slop free, maybe that's the real secret?
On the subject of hinge gaps, it always makes me cringe to see some of the models in magazines that you can see daylight through the hinge line - yeeuuck!

Thanks for the input though. To sand or not to sand, that's the question ;-)

Tony

Well this one is interesting and has been brought up a lot over the years. Let's see now, I have been building these little planes going on 48 years and the last 25 have been R/C. I have always rounded the edges on the control surfaces and have yet to get any flutter, is it the right way??? heck who knows? I guess you just go with what works for you.

I guess you just go with what works for you.

That's it ina nut shell. It's not a problem till its a problem.
We've glued tri stock to the rudder TE on some TOC planes
to get rid of the dead band and a bit of flutter and that's
with 4 110oz servos with steel cable pull pull.
It fixed the problem but it WAS ugly.

To throw another tid bit in... during a discussion of flutter on 200mph+ Diamond Dusts we were talking that the thickness of the leading edge should be thicker than the trailing edge of the wing to stop high speed flutter.....