I got into a link at some post about what not to do
http://members.cox.net/moormanrc1/RC181DoNotRules.htm

http://members.cox.net/moormanrc1/RCUCatalog.htm

he says not to round the Trailing Edge of any control surface if its done it will flutter and who tells you to do this haven't flown his airplanes fast enough or overpower them.

As I look at the instructions of Goldberg chipmunk the elevator and the rudder TE's are rounded, in sig 4*60 all control surfaces TE's are rounded including ailerons.

then about Cool Power except for break in my engines most happy with green cool power.
who is wrong?

General consensus is that it is better to leave the trailing edges square. Rounding them has been shown to contribute to flutter but that does not mean rounding them will definitely cause them to flutter. There are many variables to take into consideration. However, I see no advantage to rounding them and do not do so on my airplanes. My .02 cents on the subject.

I have done it both ways depending on the plane. Some of them just look better rounded. For the most part I just leave them as is. That could just be how much I hate sanding??? Flutter depends on a lot more things then rounded TEs but it is one of the factors, I have just never seen it on any of my builds.

I have built a sig 1/5 scale cub and a .35 size monocupe in the recent years, both with rounded trailing edges on the rudder and elevator. They have been flying for about 3 plus years and I have not noticed any flutter at all.

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This is news to me....

Brian

I should restate that to read "rounding them has been suspected of contributing to flutter". I don't know as I've ever read anything conclusive, although I certainly have not done a great deal of research on the subject. A search of the RCU forums would provide more insight as it has been discussed here previously on many occasions.

I was leaving the TE's rounded because of laziness of sanding them and to avoid damages during transporting them.
Anyway my airplanes dont fly that fast so I'll keep doing them round or tapered to some extent.

I fine sanded the TE on my Sig Kadet's ailerons, elevators, and rudder to a nice taper, fairly long but not sharp due to the lack of experience at the time. Looked great. No flutter with a K&B .40 10x6 prop. Now I just round them on sport planes and leave the square on 3D models.

I have been shown those cute drawings showing how air turbulence goes over the surfaces and how it is supposed to create adverse turbulence if rounded and can cause flutter, I just never bought into it for RC planes. Whatever looks best. I just haven't ever built a plane with control flutter being a problem.

The only plane I ever owned where I experienced flutter was a Carl Goldberg Anniversary Cub. It had a full wing and strip ailerons. I had a Magnum .61 XL under the hood and it was FAST!!! I really miss that airplane. I sold it to a friend because I thought I had "moved on." I'd like to "move back" now. I didn't realize how much fun that airplane really was. It was my 2nd airplane build and I had the horizontal stab glued on with an angle, not glued on perpendicular to the airframe. It was repairable.

The trailing edge of the ailerons were squared.

It turned out, once I sealed the hinge gap- I never had flutter problems again.

Just a thought...

There have been quite a few studies on the effect of rounded, tapered and squared trailing edges surfaces. Some I've seen were quite well done in a scientific manner (wish I had kept the source) which, to me at least, pretty well proved that squared edges were best, sharply tapered next best and rounded the worst in so far as contributing to flutter onset. More important points than trailing edge shapes though are surface stiffness and making sure there is no slop or play in the servo to surface connections. Every surface will flutter under the right stimulus if it has any mass at all and gets the stimulus to start the flutter.).

I agree with the consensus that there are far more circumstances that contribute to control surface flutter than tapering or rounding trailing edges. It has never been an issue with me and I have built many planes both ways. I think the article is over stating the potential problem.

Vince

Round TE? Not Flutter but "Global Warming"

Full scale Piper Cubs have rouded trailing edges on the tail due to the tube construction covered with cloth. If you build a plane and power it with the engine it was designed for and install radio gear carefully, odds are you won't have trouble with flutter. Some designs just can't stand square T/E's. (EG. sportster, ugly stick, smith miniplane, any open cockpit plane for that matter)

For model planes, flutter is mostly going to be from uneven air over the control surface. Balancing the control surface *could* help prevent flutter in severe cases such as a stripped out servo. Loose linkage/shinges allow for flutter.We will probably get into it from uneven flow from ailerons, etc being installed crooked, and/or uneven gaps. Strip ailerons can get into flutter from wing tip vortices. The best prevention is to cover the gaps. I now cover mine with a single piece of covering when doing a wing, etc. The control response is much smoother, the gaps stay cleaner from gunk, and you have protection. I once had all of my Robart point hinges break loose but the covering held the big aileron of a pattern model on just fine.