I was flying my Avistar and noticed that when I did a high speed dive, there was a weird sound that could only be described as a vibration over a hollow area. To me, it sounded like the covering was vibrating. There was a small hole in the wing, I'm wondering if the air is passing over the opening and creating this sound. My friend, who has more experience, thought it may have been a prop overspeed. My only doubt on this is that half way through the dive i cut the power but the sound continued. Any thoughts?

I had a Das Ugly Stick do that to me a long time ago and it was aileron flutter. I powered it with a K&B .61 and the flutter would occur when operated at full throtle. I substituted an O.S. 46 for it and the flutter stopped due to the decreased top airspeed.

Go around your plane and check all the surfaces for slop. If there is none, it's probably just the air whistling through the cowl/other blunt parts. Though, no Avistar I've ever flown has made such a noise, so I'm betting you have flutter.

it could be many things.

if it's a buzzing sound it could be flutter. Flutter can rip planes apart fast, so be cautious when doing this until you can determine what that sound is.

I used to have a 100" polyhedral glider (Gemini MTS I think) with a thick sheeted wing that I would slope fly. It would make a really loud howling noise in a dive. Most enjoyable and powerfull sound.

If it a purely howling noise I'd say you're OK, but not if there's buzzing along with it.

If it "sounds like vibration over a hollow area" as you say, then the odds are that is exactly what it is, vibration...or FLUTTER. Check everything over as other have already described here.

I'll second (third? fourth?) the flutter deal, probably on the ailerons. The torquerod holes in my Avistar wing have gotten a little "widened" out by the rod and there is some pretty decent play in there, might be the same as yours. Are your aileron hinge-gaps sealed? Easy to do: Run a 1-inch wide string of white monocote all along the hinge gap on the bottom (have the aileron full up when you put it on to make sure you dont cause binding). Adds a little damping and safety to the ailerons.

It's best to get into the habit early of chopping the throttle whenever the nose is pointed down. Throttle management is a big part of R/C flying. Too much throttle on your down-lines can tear apart most airframes rather quickly unless it's built for all out speed.

you guys (gals) remember those nerf howler foot balls? remember how they worked? i think you are right, patchup the covering and (check surfaces too just to be safe) and take her up and see if this helps. i personaly dont believe that the sound you described would come from flutter but i could very well be wrong. but im still going with the monokote acting like a kazoo (little kids instrument that used to come in crackerjack boxes and such)...

-edit-

spelling corrections, thats enough
wow gramar goes to pot at 3 am doesent it?

it may also be the prop, my cloud dancer.. given the right wind speed, throttle setting and plane attitude will made what could be described as "full size" sound
on a .53 irvine on a cloud dacner with a 11 x7 Scimitar