Whoops! Goodbye little Zagi!

[Ben B]

When I got back into flying R/C I decided to start with a Zagi 480si which I got from my LHS. It only had 90W (ish) from a brushed 400 but it flew (just!) on 8.4v nimh packs. Then I put a brushless / lipo combination in it and went to about 250W. Then I put a bigger motor in it and got 450W. Then it started fluttering.... the long and relatively flexible correx aerelons with a servo push rod just at one end was a recipe for flutter. I re-hinged them and that helped for a while but at the weekend it started again when going fast.Each time it started I throttle back and it settled down. I had a 4s set-up that pulled near 1kw put these flights were only done on 3s!! However on the last flight on one occasion the flutter seemed to stop spontaneously before I could throttle back, so the next high speed run I decided to see what would happen if I didn't throttle back. Answer= the whole wing flapped like a bird and disintergrated in the blink of an eye. I think the ply spar I had put in place gave up the ghost leading to total structual failure. Luckily one of the people was filming it so hopefully it will be on youtube soon! Until then it's visable on facebook under "Wormwood Scrubs rc".

Anyway, lesson learnt = don't mess with flutter!

[Ben B]

In retrospect I should have landed immediately when it started fluttering to investigate but because it had done it previously and survived I thought it would handle it again and I was interested in the self-terminating flutter that seemed to be occuring. Truth is, the ply spar was probably slowly fracturing with each flutter until it gave way completely. Oh well.... One to notch up to experience.... Still not sure why the flutter cured itself though!