Sounds like flutter....looking for opinions  
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Sounds like flutter....looking for opinions - 2/20/2004 3:30:32 AM   
ZeppelinIII


 

Posts: 104
Joined: 7/23/2003
From: brookline, NH, USA
Status: offline 		Took out my nice shinny new Sig Kavelier today and unfortunately only got in two laps. Took off, came around, trimmed it out on the down leg (was pretty close to start with) and then brought it back around.....as I got about back to myself (and about 1 mistake high or so) I heard it start to hum.....it only lasted for a few seconds and seemed to me to stop before i throttled down, but that could have been an illusion. I've heard/seen flutter in person once before and am looking for some ideas. My ailerons are completely sealed but the elevator and rudder are not, but they have very small gaps (i have had bigger gaps on other planes)....one other note is that the wing looked normal while it happened(one time i saw it the wing was almost flapping like a bird).....

Plane itself is fine....have an OS 46FX on it, and was turning an APC 11x7

looking for thoughts/comments/suggestions...


Thanks,
Zep
       Post #: 1

RE: Sounds like flutter....looking for opinions - 2/20/2004 4:28:12 AM   
swooper



Posts: 251
Joined: 11/25/2003
From: Victor, ID, USA
Status: offline 		Have you checked all the control surfaces for slop and "soft" action? I like to do it with the radio on so the servos resist being moved off center. With your fingers, gently move each control surface both directions. Slop is free play, like a loosely fitting clevis pin in a control horn. It doesn't take much to allow the surface to vibrate during flight. By "soft" action I mean the kind of movement allowed by control linkage that can bend or twist, allowing the surface to move off center without moving the servo arm. Unbraced wooden pushrods to the tail surfaces and too long and light gauge aileron torque rods are common examples. While sealing the hinge lines is always a good idea, it won't prevent flutter if other problems exist.
best wishes!

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Paul Brabenec
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(in reply to ZeppelinIII)
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RE: Sounds like flutter....looking for opinions - 2/20/2004 4:46:47 AM   
ZeppelinIII


 

Posts: 104
Joined: 7/23/2003
From: brookline, NH, USA
Status: offline 		Definately checked for that before hand....slop is one of those things that I'm nitpicky over....but will check again and see....thanks for the advice

Zep

(in reply to swooper)
       Post #: 3

RE: Sounds like flutter....looking for opinions - 2/20/2004 6:16:34 AM   
FHHuber



Posts: 4931
Joined: 1/1/2003
From: gone, , USA
Status: offline 		There are all kinds of places that can help flutter get started...

I'd start by looking at the elevator on the Kavalier. If you rounded the TE of the elevator... you invited flutter. Also.. seal that hinge line just as you did the ailerons (do the rudder while you are at it.) You may even need to mass balance the elevator.

My first experience with flutter... i didn't have a clue what that neat buzzing sound was... so I added throttle to make it louder Lost the rear half of the airplane.

(in reply to ZeppelinIII)
       Post #: 4

RE: Sounds like flutter....looking for opinions - 2/20/2004 7:04:32 PM   
ZeppelinIII


 

Posts: 104
Joined: 7/23/2003
From: brookline, NH, USA
Status: offline 		The TE is not rounded at all....

my thoughts were to go down to an 11x6 prop, seal up the hinges, check for any slope, double check the stiffness of the elevator and rudder and then try flying again...

(in reply to FHHuber)
       Post #: 5

RE: Sounds like flutter....looking for opinions - 2/20/2004 8:20:40 PM   
FLYBOY



Posts: 8691
Joined: 1/7/2002
From: Missoula, MT, USA
Status: offline 		Is the covering tight? I have seen covering slap and sound like flutter that wasn't tight.

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Fly it till the wings come off.

(in reply to ZeppelinIII)
       Post #: 6

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