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Old 08-16-2017, 04:42 AM
Steve Melton's Avatar
Steve Melton Steve Melton is offline
Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 1,328

what if someone would model the elevator using finite element analysis and apply a gust load to determine the failure points? I don't have the time now but maybe over the Winter. seems like it would be a good project.

may also want to look at the dynamic response.
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 600+ for all

Simplicity is the art in design.

Last edited by Steve Melton : 08-16-2017 at 05:02 AM.
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Old 08-16-2017, 02:41 PM
John G John G is offline
Join Date: Dec 2007
Location: Raleigh, NC
Posts: 15
Default A possible theory

I referred back to my builders manual to check this. Part of the process to construct the elevators is to squeeze the trailing edge to the required radius.

The elevator trailing edge is essentially the "rear spar" of the elevator. It takes the bending loads across the rear of the elevator due to control application, vibration, and aerodynamic buffeting. If during construction the trailing edge radius is squeezed down too much, or if it is repeatedly squeezed and opened up again to get the right radius, it may be weakened or even cracked. If that has occurred, it seems possible that the weakest spot along the trailing edge will eventually fail locally. If that happens, bending along the trailing edge will be focused at that point, resulting in rapid longitudinal cracking of the upper and lower elevator surfaces and associated increasing bending deflection from further weakening. This looks like it might fit what is seen in the video.

Stripping the paint off of the trailing edge area of the elevator to get a look at the metal may help in understanding whether or not this is actually the case.
John Gerber
RV-8 FB empennage done, working on QB fuselage, QB wings here
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Old 08-16-2017, 07:57 PM
bret's Avatar
bret bret is offline
Join Date: Feb 2010
Location: Gardnerville Nv.
Posts: 2,656

did the 1/8" welding rod in the bend radius trick on mine.
7A Slider, EFII Angle 360, CS, SJ.
2017 gladly supported
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