A friend of mine is building a Focke-Wulf 190 profile plane and the manual says to round the trailing edges of the control surfaces. I thought I read somewhere that it is not advisable to round these edges, on any plane, because it helps to promote flutter. Any comments helpful.
Thanks,
Richard

[8D]I can only tell you that from building/flying experience, I have built many model
aircraft from kits which indicated that the trailing edges should be rounded. I have
never experienced any flight performance problems due to the trailing edges on my
aircraft being rounded. Beyond that, I cannot offer any pros or cons of a particular
trailing edge configuration due to my lack of formal aeronautical engineering
schooling/training.

Well there was a big discussion about this and after a lot of debate I'm sure if a concensus was ever arrived at. I do know that I have been building these planes for close to 50 years and have rounded the edges with no ill effect and I have left them the other way and saw no difference. I'm sure someone will come up with a lot of reasons for not rounding them but like I said, been doing it for a long time and no problem.

I have done it both ways without issues.....HOWEVER the word is that a rounded main wing trailing edge causes TURBULANCE and it is this turbulance that can cause the elevators to flutter.....THIS IS ONLY WHAT I HAVE HEARD from someone that SHOULD know. I can also tell you that since this person told me that, I no longer round the trailing edges of the wings. As a custom builder, there is too much liability involved.

I have viewed many plans, and almost evryone of them called for the trailing edges to be rounded. By rounding the trailing edge, it seems to me the chance of flutter would be reduced instead of increased, due to the fact you are making it more aerodynamic and reducing the wind resistance. Just my opinion.

Thanks guys for the feed back. I quess if the manufacturer says to round the trailing edges then maybe it is OK.

Richard

RCS:

It's all in the boundary layer separation from the trailing edge. The hard corners are less drag, and the turbulence is isolated from the surface.

If you are building an airplane intended for high speeds then use the hard corners. With a fun flier you'll probably never tell the difference.

Bill.

I've done it both ways- depends on the plane. I custom build as well and I haven't hadn't any problems rounding the TE's when called for. Ailerons do, however, demand even rounding. If there is a thicker or shallower area left on the TE it can cause turbulance and different lift characteristics between the wing halves.

In theory not rounding the edges may be better with regard to flutter, but I have never seen or heard of anyone around here having a problem with rounded trailing edges. And they look a whole lot better.

I think taking care of other factors (no big gap in hinge line or loose servo horn/control arm connections, etc.) are a whole lot more important to preventing flutter than the shape of the trailing edge.

If you are just building something to throw around and don't care how it looks then leave them square. Otherwise I would round them as the plans describe and don't worry about it.

I square off my trailing edges. For two reasons, one I had also heard that rounded edges is less aerodynamically stable and increases drag, and secondly I find square edges are easier to do and cover.