I have had my Acromaster for about 5 or 6 years. 100's of flights. About a month ago, I was doing some very low inverted passes and lost it...flat on its back. The only damage was some slight scratches (which you don't notice because after all it is an old foamy
) and the prop ripped off (APC 11x5.5 EE). Anyway, I put it all back together, remounted the motor and a new prop. Even did some crude balancing.
On the first flight after the crash the thing vibrated so bad that the canopy came off. I mean it sounded like all hell was breaking loose at about 50% throttle. I thought it was going to shake the airframe apart
I went back and took everything apart made sure it was okay. Re-installed, tightened everything down big time and no change at all....It was so bad at one point I think the thing said "eat mor chicken"...LOL
The most terrible vibration noise you ever heard.
After the second or third attempt to get rid of the mad cow, I finally just cut out a full round firewall and placed it in the front, glued it all the way around with epoxy on front and back and then added several braces across (like the stock mount only much beefier). Then coated the inside of the cowl with epoxy top and sides and mounted the motor again. Now it is quieter than it was the day I got it
. It took me a week of Sunday's to fix but it flies really nice again...If the new firewall would not have worked, the airframe would have been put in the dumpster!!