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  #21  
Old 05-11-2014, 08:28 PM
tracy tracy is offline
 
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Occurring with only a passenger, I would look at his headset cord. Is it noise cancellation? The control could be hitting something when negative. I'm assuming its a tandem. I now see its a 7, but it still could be the culprit.
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Last edited by tracy : 05-11-2014 at 08:32 PM.
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  #22  
Old 05-11-2014, 08:43 PM
BillL BillL is offline
 
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Are you actually going negative g's over the top? If so, that might trigger the return of the oil canning. My 7 oil canned when the engine was mounted and the tail came up. It took only a touch to trigger it. Not 7's all are this sensitive. I added some very light stiffeners, but not flying yet. I can post pictures if you are interested.
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  #23  
Old 05-11-2014, 09:01 PM
Norman CYYJ Norman CYYJ is offline
 
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No unfortunately it was not anything banging around in the cabin or baggage area, the plane was empty for doing acros. No I don't go negative, I hate cleaning the oil off of the belly. Learned that years ago. I have been doing acros in RV's now for about 12 years and have never had this happen before. There are no skins lose enough to oil can on the ground and I don't think that was it, it was positive G all the way around each time. Seat belt cables were tight.
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  #24  
Old 05-11-2014, 09:22 PM
F1R F1R is offline
 
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Any chance it is the pickup weight or end of the flop tube falling aft as you approach the top third or past vertical?
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  #25  
Old 05-11-2014, 09:44 PM
Norman CYYJ Norman CYYJ is offline
 
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No chance it was the pickup weight, both pickups are fixed. I am talking of a loud bang like a brick or large hammer hitting the tail.

Thanks for all of the suggestions. I'll just have to try and simulate it again in the near future. It may have been as Russ suggested just a tail stall, but usually when I have experienced that before it was just a bit of buffeting.
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  #26  
Old 05-11-2014, 10:32 PM
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RV7A Flyer RV7A Flyer is offline
 
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Can you mount a GoPro or similar camera underneath the tail and get some video (maybe use the tail tiedown if -A model, or mount it to the tailwheel fixture if it's a taildragger)?
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  #27  
Old 05-12-2014, 04:47 AM
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Capflyer Capflyer is offline
 
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You stalled going over the top and felt the buffet. You can stall in any attitude even going straight down. I've done this pulling too tight a loop. Sometimes it feels like an engine miss, sometimes it feels like a bump, sometimes it sounds like a bang, and other times any combo of these.
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  #28  
Old 05-12-2014, 08:32 AM
FLTENG FLTENG is online now
 
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Norm,
Any possibility it was your tax refund cheque falling out of your pocket?
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  #29  
Old 05-12-2014, 08:36 AM
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Mel Mel is offline
 
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Quote:
Originally Posted by BillL View Post
Are you actually going negative g's over the top? If so, that might trigger the return of the oil canning. My 7 oil canned when the engine was mounted and the tail came up. It took only a touch to trigger it. Not 7's all are this sensitive. I added some very light stiffeners, but not flying yet. I can post pictures if you are interested.
When adding skin stiffeners, be sure to tie them into the bulkheads at each end.
Otherwise you will get skin cracks near the ends of the stiffeners.
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  #30  
Old 05-12-2014, 09:50 AM
BillL BillL is offline
 
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Yes, Mel,
I read about this here extensively, and decided not to run them long ways. I ran them parallel to the bulkheads. There is one rivet on each end and the bottom is bonded with 3M windshield urethane to the skin. I think most stresses are longitudinal so hope that this will not generate a crack.

I made a perfect contour with card stock, make a 3/4" MDF buck and bent the flange over, fluted it to straighten and it matched perfectly. One in the center still allowed some dimpling, so added two.



These are not for all planes. Apparently very few actually dimple, and mine was extremely easy with downward force on the tail end.
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RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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