Flutter or not?
 

I have a UCD 60 with an OS 91FX. I sealed all the hunges with clear monokote on both sides. I used the CA hinges also. It seems however that when I hover it gets to a certain point where I here like a buzzing sound when the plane pitches a certain way at a certain amount of throttle. It seems to happen almost everytime, but it only lasts a few seconds. Is this flutter and what can i do about it?

RE: Flutter or not?
 

Antman:
Flutter happens at higher speed. Sounds like something is resonatingwith the engine, as you say, at a certain rpm. maybe a pushrod hitting the side of a former, two pushrods hitting together, covering vibrating. See if you can duplicate it by having someone hold the plane at the same attitude, and open the engine up to what you think is the same RPM. If it does, go around and touch the surfaces and see if you can get it to stop.

RE: Flutter or not?
 

He's totally right. I was at an indoor fly-in yesterday when something simialr happened, but I was getting nterference. Try moving to new places!!! Its really weird though[&:][:@][:'(]

Dan[:-]

RE: Flutter or not?
 

Ant, an unballanced prop will make the plane vibrate. Did you balance and what were the results? Joe

RE: Flutter or not?
 

Antman, what you are hearing is not flutter. Most likely it's harmonics amplified by the big thck wing and wide rib placement. Causes could be many. Loose covering, crackd rib, loose glue joint, etc. or none of the above and nothing may be wrong. Have you ever heard the sound a pizazz makes when placed in a hover or you should hear my UCD46 with a Saito 100 rattle. Check it out for loose stuff, fix any you find, if all looks OK just go fly the thing and have a blast.

If you ever hear a plane fly over and flutter starts, you will hear it and most likely recognise it, you just won't hear it for long.....

Ed M.

RE: Flutter or not?
 

antman450,
The guys here have given you some good answers based on their experiences and you might like to examine all those possibilities.
The way you described the sound makes me think of another possibility. I've heard that sound while hovering also and it is a higher pitch than a rattle. The sound is coming from the prop and the reason you only hear it briefly is because the angle of the plane, the wind direction and engine RPM happen to be just right to make it audible at the location where your are standing. Its that same sound you hear coming from a helicopter rotor but it is a much higher frequency.

RE: Flutter or not?
 

Good one Rocketman_, forgot about prop cavitation...................................

Ed M.

RE: Flutter or not?
 

Thanks for the replies guys. i think it is prop cavitation. It does not seem to be flutter. I am all good, then.

RE: Flutter or not?
 

Awesome...lets see some pics now...=)

Dan

I flew a UCD with an OS91...what do you have in yours. THe OS had liek no POWER

O well goo dluck with it now

RE: Flutter or not?
 

And here I thought I was going to be the first one to suggest cavitation... really sounds like flutter but is actually just prop noise.

RE: Flutter or not?
 

Along the lines of loose stuff making the noise, I had a similar noise with my Funtana in a hover at a certain throttle setting. Turned out to be the top of my cowl on the flat fuse top... at the correct RPM the harmonics would make the top of the cowl slap the fuse and generate a loud "buzzing". Didnt do it in flight, I suspect that the air pressure pushing on it held it down at speed, but I duplicated it on the ground... feeling around the plane, put my finger on the top of the engine cowl and it disappeared. One screw on the top in the middle was the solution.

Brian