Interesting arrival yesterday - RC Groups
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Mar 01, 2009, 09:09 AM
Sloping off....
leccyflyer's Avatar

Interesting arrival yesterday

For the second time in succession one of my models on a revamped power train has suffered a fluttery problem in the air. Both survived relatively unscathed but this second event was a bit more alarming than the first.

A while back I bought a second hand Esprit Supra-E aerobatic model (pictured below, many years ago) and after some experimentation arrived at a power train of AXI 2820/12, 4s1p4400mah lipos and 11x7 APC-E. That draws about 46 amps and sets the model sprinting across the strip and into the air very nicely.

Anyway, after a few circuits, sufficient to see that the model was going well, the air was rent by that loud Thhhhhhhhhhrrrrrrrrrrrrppppppppppp sound that usually indicates a fluttery control surface. In this case however there was a great swathe of covering flapping against the model. A couple of circuits to lose height and the model dropped in just off the field. If I'd given her a blip more power she'd have cleared the threshold so that was my fault.

On recovering the otherwise undamaged model practically the entire film covering on the underside of one wing, together with the aileron servo cover, linkage and even the servo itself had peeled back, leaving me with one functioning aileron.

She'll need no more than a recovering job on the wings, but this time the overlap will face AWAY from the airflow, with the bottom of the wing covered first
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Mar 01, 2009, 10:28 AM
Registered User
Andy W's Avatar
Many of these 25-40 sized models were designed in the days when 500W (16 round cells and 30A) was a SERIOUS power system. Now we're regularly doubling that or more. I wonder if that played a roll here?
Mar 01, 2009, 10:34 AM
Sloping off....
leccyflyer's Avatar
Hiya Andy

That was certainly true in the other case with the upgraded Zagi, and you're probably right, but this time I really wasn't going that fast. I'd put a lot of it down to the age of the model - she must be at least 7 years old and the old adhesive just let go - must have been just too much for the old girl.
Mar 01, 2009, 01:47 PM
Registered User
Were dis-similar covering materials used in covering the wing?
Sometimes the adhesive on dis-similar coverings doesnT adhere well to each other. Also I have experience problems with old covering but that was rare.

Mar 01, 2009, 05:20 PM
turn, turn, turn.
Glad to see you got it back safely.

That was some serious flutter!
Mar 02, 2009, 06:44 AM
Registered User
Andy W's Avatar
Hey, Brian.
Sorry, thought the covering came off due to the flutter, not the other way around.
Mar 04, 2009, 03:55 AM
Sloping off....
leccyflyer's Avatar
I couldn't say whether the aileron fluttered and brought to covering off, or the other way round. I hope it was the latter, as that's an easy cure. The covering material looks like a Solarfilm clone -Easycote or similar- directly onto sheet balsa.

I'll recover with Pro-Film (Oracover) and replace the aileron servo mounts with pukka Robbe ones in which the servoes are retained with mouldings and the cover screwed on.
Mar 04, 2009, 12:48 PM
SB-28 UK Display Pilot
GeeW's Avatar
I was wondering if the horrible rubbery type glue they use in ARTFs was a possible factor here? As well as age deterioration....also UV deterioration?? I know POR is truely dreadfull when exposed to UV ...even though we get bu^^er all sunshine!