I had just landed from my second flight on Sunday with my Mahers Pacer. It's a lovely model with great presence in the air and forgiving flight characteristics. Powered by a Moki 135 she is slightly overpowered for her type of airframe, but that means I fly with about 1/2 throttle most of the time, indeed, takeoff can be done on full throttle, but looks better on about 3/4. The engine vibrates quite a lot, and I have a perrenial problem with retaining cowl fixings, I usually lose one in a flying session.
I was just lifting her up to put her on my flight stand for refuelling, when I noticed that the cowl screw had gone awol, again, but more significantly there was a tapering gap below the fuselage from the trailing edge of the wing. On closer inspection it was clear that the vibration from the engine had loosened the steel M5 cap screws which hold the wing, and they were about 15mm undone. they are about 40mm long, so there was plenty of thread left to hold but even so it doesn't bear thinking about what would have happened if they let go. I clearly remember tightening them up when assembling the model at the field, so they must have undone in flight. I'd had two flights of about 10 minutes each with spirited aerobatics including spins loops and rolls and a fair bit of inverted flight.
Next time I commit her to the air I shall smear the bolts with thread locking compound before insertion. Perhaps nylon ones would be a better choice.