Flutter - How to find the cause??
01-19-2015, 04:19 AM
#62
Its very easy to ascertain which surfaces are experiencing flutter. All it takes is one small hole. As I have noted repeatedly 'After all else fails' AJ try the simple mass balance.
To arbitrarily dismiss mass balance as makeshift and even ignoring its usefulness as a diagnostic tool to identify which surfaces are affected as well as the only tool we normally have avalible to us is head in the sand thinking. Despite what some would have you think there are occasions when all the normal cures that is under discussion here do not work. This is the ideal candidate for mass balance.
There have been some more modern airplanes, typical scale aerobats or near scale that have had history of flutter. For some of these that I have assembled (arfs) for the fellows it was a very easy matter to insert a small ball of lead into the aerodynamic balance area of all the surfaces which thereby allows these portions of the surfaces that is forward of hingeline to also acts as internal mass balance in addition to aerodynamic balance area. In these cases none that I ever put together experienced flutter on any surface.
So AJ and agine your airplane is at risk for aileron flutter, so what are you gonna do?
John
To arbitrarily dismiss mass balance as makeshift and even ignoring its usefulness as a diagnostic tool to identify which surfaces are affected as well as the only tool we normally have avalible to us is head in the sand thinking. Despite what some would have you think there are occasions when all the normal cures that is under discussion here do not work. This is the ideal candidate for mass balance.
There have been some more modern airplanes, typical scale aerobats or near scale that have had history of flutter. For some of these that I have assembled (arfs) for the fellows it was a very easy matter to insert a small ball of lead into the aerodynamic balance area of all the surfaces which thereby allows these portions of the surfaces that is forward of hingeline to also acts as internal mass balance in addition to aerodynamic balance area. In these cases none that I ever put together experienced flutter on any surface.
So AJ and agine your airplane is at risk for aileron flutter, so what are you gonna do?
John
01-19-2015, 07:11 AM
#64
Thread Starter
While taking photos I looked things over close again. The ailerons and elevator are pretty solid, as good as any
other planes I have built. The rudder has some play in the hinge probably more than it should have. I have the idea
to disconnect the rudder control and pin the rudder so it can't move then fly. Maybe if the rudder is fluttering that's why
I haven't seen the flutter and it hasn't destroyed itself. I have had smaller planes with just aileron
and elevator control but have never seen or heard of a plane of this size with only aileron and elevator control. Does anyone see
any problems with trying this.
other planes I have built. The rudder has some play in the hinge probably more than it should have. I have the idea
to disconnect the rudder control and pin the rudder so it can't move then fly. Maybe if the rudder is fluttering that's why
I haven't seen the flutter and it hasn't destroyed itself. I have had smaller planes with just aileron
and elevator control but have never seen or heard of a plane of this size with only aileron and elevator control. Does anyone see
any problems with trying this.
01-19-2015, 08:11 AM
#66
It is certainly possible to prevent flutter using all these methods.
Reference: http://en.wikipedia.org/wiki/Aileron...alance_weights
To prevent control surface flutter (aeroelastic flutter), the center of lift of the control surface should be behind the center of gravity of that surface. To achieve this, lead weights may be added to the front of the aileron. In some aircraft the aileron construction may be too heavy to allow this system to work without huge weight increases. In this case, the weight may be added to a lever arm to move the weight well out in front to the aileron body. These balance weights are tear drop shaped (to reduce drag), which make them appear quite different from spades, although both project forward and below the aileron. In addition to reducing flutter, mass balances also reduce the stick forces required to move the control surface in flight.
01-19-2015, 02:28 PM
#68
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This 3D model is one two identical models that I fly and it had aileron flutter when flying into the wind. The addition of balance weights to the large ailerons cured the problem. The other model has no flutter at all.
The model has flat wing tips that allowed me to easily glue balance weights to the ends of the ailerons. The lead weights are embedded and epoxy’d in cutouts in the light plywood that extends forward of the leading edge of the ailerons.
When the ailerons are neutralized for transportation there are no long protrusions sticking out to hook into anything else in the car.
The model has flat wing tips that allowed me to easily glue balance weights to the ends of the ailerons. The lead weights are embedded and epoxy’d in cutouts in the light plywood that extends forward of the leading edge of the ailerons.
When the ailerons are neutralized for transportation there are no long protrusions sticking out to hook into anything else in the car.
01-19-2015, 04:14 PM
#69
This is a good example of information overload! This Tauri model is not a 3D model, with gynormous surfaces. It also has no leading edge control surface exposed to the airstream. So adding ballast may we be a solution, but I am telling you, if you clip those ailerons back, it will most likely stop.
01-19-2015, 05:00 PM
#70
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Ahh, yess, I knew Ed Kazmirski's Tauri very well. I’ve kept this souvenir of mine from the 1960’s. Six channel reeds and scratch built home made servos. Shot down by citizens band voice.
03-15-2015, 06:20 AM
#73
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Hi guys. I had a model that flew great until I cut out a new wing and installed it. It had much the same problem, I got flutter in a high spead dive. I repaired the crash damage, looked for problems, nothing loose, no hinge gaps. I sealed the hinge surfaces. I crashed again. I consulted my club members, and found the wing airfoil was just a little bit thicker than the old wing. The consensus was I was flying too fast for the airfoil, causing the air to seperate from the surface. That creates turbulance that reaches the control surfaces and causes flutter. There is no fix other than to slow down, or build a wing with a thinner profile. Its called overflying your wing ! I just put a bigger diameter prop with less pitch on. The model flew better manuvers and landed slower. I was a happy man. Speed is not everything. I looked at the pics of your plane and it looks like a pretty thick airfoil. The engines that were around when that plane was designed, didnt put out the power that the modern day engines do. You might consider the prop fix. Happy flying!
Last edited by kenworthbob; 03-15-2015 at 06:24 AM. Reason: spelling
03-16-2015, 06:33 AM
#74
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Hi!
You have aileron flutter!
It's a no no to have the ailerons going all the way to the wing tip! Cut off the last 10-15cm part of the ailerions and glue them to the trailing edge of the wing and you will see that the flutter disapears
You have aileron flutter!
It's a no no to have the ailerons going all the way to the wing tip! Cut off the last 10-15cm part of the ailerions and glue them to the trailing edge of the wing and you will see that the flutter disapears
Last edited by jaka; 03-16-2015 at 07:34 AM.
09-18-2015, 01:51 PM
#75
Thread Starter
I believe I have found where the flutter is coming from. It's the ailerons. The guys at the field though the rudder had a lot of slop on the hinge. They suggested taking the monokote hinge off and replace it with mylar hinges. So I did that. Still had flutter with the new hinges. Then I put a 6 to 8in piece of cellorphane tape on the end of each aileron. Still had so flutter but the sound had changed. Then added another piece to the bottom. All the flutter then was gone. I could fly fast as I wanted and dive as hard I wanted with no flutter.
Last edited by A. J. Clark; 09-18-2015 at 02:12 PM.