At 12:59 PM 2/25/2000 +0000, Tord wrote: >I mentioned this need for balancing surfaces chordwise to avoid flutter >a while back here and you, Chuck, mentioned that you had been involved in >the Piper Cherokee design, with it's all-flying stabilator, which is pivoted >far beind the regular 25% mean chord. Sorry but I was never involved in Piper design. My only experience with the Cherokee was a couple of hours flying time about 25 years ago. I wasn't overly impressed with the airplane. In face, the last Piper airplane I really enjoyed was the Cub. That includes everything from the J3 I first soloed 50 years ago to the last Super Cub I flew. >What I wonder is: We (Zagi-flyers) have all experienced severe flutter >at max speed, as the weight of the elevons are far behind the torsional >centre of the wing. I have tried to fix it by adding a rear CF spar, but >maybe a steel wire embedded in the EPP leading edge is better? At least >outboard, where the flutter starts? or should one opt for something softer, >as the steel rod surely will move both the chord-wise centre of weight >forward and the torsional centre forward?! > Flutter is not my field but I suspect what you are experiencing may be initiated by aileron flutter. I haven't flown a Zagi very much but have experienced flutter when launching from a winch. I launched it flat as if in a catapult launch and accelerated in level flight until reaching maximum speed before pulling up sharply. I tried this twice and got severe flutter both times during the pull up before giving up for the day. I suspected the wing flutter was excited by the unbalanced ailerons going into flutter coupled with the weak torsional stiffness of the wing. If so, then mass balancing the ailerons should increase the flutter speed sufficiently to move it above my normal flying speeds. But then I had a better idea. I removed the receiver from the Zagi and hung it on my shop wall where it remains to this day. :-) The reverse taper of the Zagi ailerons certainly doesn't help flutter resistance and mass balancing is not a practical solution for combat models. If combat flying wings are your thing, then the most practical thing is probably just plan on frequently replacing the servo gears and living with the problem. I was under the impression that combat models didn't have a long life expectancy anyway. :-) Chuck Anderson RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
