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#11
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Can Washout Cause Flutter??
"cavelamb himself" wrote in message link.net... DonMorrisey wrote: WERE (because it's probably a moot point now) the hinges and alieron actuation mechanism TIGHT (or maybe a little sloppy)? Well, I actually never saw the airplane. My firiend says they were tight but who knows, he also didn't realize the bolts in the brackets were too far down from the bend in the spar flange, so I can't really say. He was surprised that the aileron and nothing associated with it had any damage. That's what led him to his conclusion that the washout had something to do with it. Don... As another poster pointed out, we don't know anything about the design or construction of this plane. But you _may_ have just answered your own question. If the aileron brackets were supported by nothing more than the web of the rear spar I wouldn't be surprised it it encountered flutter. It's an Aero-Elastic phenomenon, remember? If it can flex, it fer sure will... Glad nobody was hurt. A wing being built here at the moment has three steel channel aileron hinge brackets supported by the rear spar. They are attached to the web by AN 5-5 bolts. They are also attached to the false spar, though. That must make all the difference in the world. Here's something interesting, to me anyways. C. G. Taylor did some interesting things when he broke away from Bill Piper and tooled up for the Taylorcraft. He made extensive use of magnesium alloy, in the wheels, yokes, and aileron hinge brackets. It's light and strong, but woe unto you when it starts to corrode. On my Taylorcraft I noticed that the false spar was tight against the hinge brackets. I should have looked more closely. When the aircraft was built in the '40's, the false spar holes for the magnesium hinge brackets were hand-cut, and some of them allowed the aluminum false sp ar to rub up against the hinge brackets. From the constant faying one of the magnesium brackets developed a crack over decades of use, and one day it broke. I noticed the aileron response was mushy. Thankfully a friend preflighted the aircraft before I flew it again. |
#12
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Can Washout Cause Flutter??
"DonMorrisey" wrote in message ups.com... : : WERE (because it's probably a moot point now) the hinges and alieron : actuation mechanism TIGHT (or maybe a little sloppy)? : : Well, I actually never saw the airplane. My firiend says they were : tight but who knows, he also didn't realize the bolts in the brackets : were too far down from the bend in the spar flange, so I can't really : say. : : He was surprised that the aileron and nothing associated with it had : any damage. That's what led him to his conclusion that the washout had : something to do with it. : : Don... : the aileron & linkage could be stout and break the wing without any damage visible. |
#13
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Can Washout Cause Flutter??
Yeah washout has nothing to do with it.
Flutter is equivalent to when you boost yourself on a park swing to go higher. Your body is the aileron, and the swing chains are the wing structure, and you move the CG of your body in a harmonic relationship to the swing to excite and then amplify its movements. The aileron is doing the same thing if its CG is aft of its hinge line. By balancing the aileron and putting its CG on the hinge line the aileron is incapable of adding to the energy in the vibrating wing structure so stiffness is less critical. Its like laying out horizontal on the park swing so if someone moves the swing your body just goes along and can't amplify its motion. John |
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