It would seem that the more this post continues "how many hinges thang" 4 -5 -6 etc...AH
Neva nuff hinges...huh? NOT NECESSARLY SOOOO, SAYS THE STUNT BIBLE!
Although hinge failure happens...but usually with our stunt machines....it is not the hinges themselves. The majority of flap elevator hinge failures on our stunt models boils down to just one often consistant over-looked item.
FUEL RESIDUE-MOISTURE RESIDUE finding its way to the bare-boned naked balsa (or wood) joints which then swells and breaks down the balsa around the glue joints---then throw in the constant wing-flap hinge loads...etc.
SEAL THOSE HINGE LINES!!
Usually it isn't a matter of "HOW MANY HINGES!" EVEN A FULL LENGTH PIANO TYPE HINGE would also fail....if those parts are not protected from all outside foreign moisture,and exhaust etc. Amazing how much crappola' thrown up by that whirling prop can find its way into the hinge lines.
BOTTOM LINE!!!
TAKE AS MUCH CARE IN SEALING THOSE HINGE JOINTS AS POSSIBLE!
From my experience from my daze watching old flutter model movies, it never ceased to amaze me just how many forces work on a wing hinge fittings.....usually boiling down to one simple thing thang....actually quite rare indeed...was the fatigue of the hinge part "usually metal fatigue of the pin itself"
Lets just keep in mind on most stunt models it is that ol' fuel residue, cleaners...moisture...etc that finds it way into the smallest unprotected bare wood parts...AND NOT FATIGUE OF THE HINGE
Then again...my old trumpet playin friend...Ray Klein, Boeing's noted principle acoustical engineer also suggested how sound or harmonics...could also play a part in inducing flutter into a flap or elevator on our stunt models (after seeing one of Joe Dill's flaps start fluttering and explode into many little pieces after one tip of his cut down 13.6 prop parted off the front of his model from that unbalanced prop.)
Ray laughed...and replied "DUMB QUESTION SHULTZIE...VIBRATION CAN START ANY STRUTURE PART TO SET UP HARMONICS, RESULTANT OVER TONES..ETC...THAT CAN INDUCE FAILURE...OR EVEN INDUCE VIBRATION.....and as far as that balsa flap exploding into pieces... BOTTOME LINE:pure and simple was the force induced by the UNBALANCE PROP ITSELF!
Gads...forgive the rant..n' drivel! JUST SEAL THOSE HINGE POINTS. n~ n~ :-X y1