I have a UCD 46 size with a Saito 100 turning 15x4W

My wings are making a loud vibration noise from the coating - I can't seem to stop it. It seems that because the spars are so far apart this gives it room to vibrate and it is LOUD.
Any thoughts on how to stop this?

Dan

Is this during run up on the ground,or while you fly it.The engine at a certain rpm may resonate in sync with the airframe.Is it during a specific throttle setting? Is the engine hardmounted or did you use softmounts of anykind?

It does both on the ground and in flight - it's the stock mount. It starts about a 1/4 throttle and up.

Did the stock mount need carving to fit the 100? does the crankcase easily clear the motormount beams? no tight fit?What prop did you use and did you carefully balance the prop? are you running a spinner? Exhaust is not touching firewall,and is secure? is engine evenly snug on mount?

I noticed this on mine today, too. But only after I switched to a 14x4W prop. I had a 14x6 MA on it and don't remember it being that bad. (I have a Saito .91) Other than sounding weird, it doesn't hurt anything. I think you may be right on the reason, though....

I was able to use the stock mount without any problem. The carb intake does slightly touch one of the mount bolts. The muffler is well clear. No spinner. Prop is balanced 15x4w.

no touching allowed

welcome to the world of thick wing, wide rib spacing, and a hard hitting 4 stroke.

Ed M.

after i fiberglassed my gear (the fiberglass went half way down the wing plate) it tightened my wing up and doesn't do it as bad. it use to sould like someone was play the snare drum while the plane was at idle. anyways just a thought.

I did a couple of things that helped on my UCD 46. I reshrank the covering on the wing with heatgun and used wing seating tape I made from bulb shaped weather stripping - glued on with medium ca. I was goning to use well-mounts in the firewall for the engine mount bolts but just live with the noise like bentgear above.