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Wing skin oil canning in flight

The skin appears to be rippling in multiple adjacent bays. I wonder if the rivets are all tight? How does it appear on the ground if you press down gently on the skins in that area.
 
Ripple effect on wing skins....

ronrapp said:
On a flight the other day, I noticed that the top skin on the left wing and left aileron were oil canning in a rhythmic fashion. I don't recall seeing this before. Here's a video:
https://share.icloud.com/photos/089ZfwDr-ei_C2H8u3ZeKQgxw
Is this a concern? --Ron
Click to expand...

This pattern seems to be diagonally across the wing emanating from the tip, inwards, perhaps. :confused: Is that a wing-tip locker access panel on your wing tip? I wonder if that is causing enough burble that it is affecting the skins of the wing. I wonder what would happen if you taped over that access panel and see if the problem is still there. I agree: it does appear excessive but may be from disturbed airflow. Has it always been there or a recent development? What did the Mother Ship have to offer?
 
Is this video actually a good representative of what you're seeing with your eyeballs in flight? Sometimes video scan effects can apparently magnify cyclic things like this.

Just want to make sure everyone is seeing the correct data...
 
Roadjunkie1 said:
This pattern seems to be diagonally across the wing emanating from the tip, inwards, perhaps. :confused: Is that a wing-tip locker access panel on your wing tip? I wonder if that is causing enough burble that it is affecting the skins of the wing. I wonder what would happen if you taped over that access panel and see if the problem is still there. I agree: it does appear excessive but may be from disturbed airflow. Has it always been there or a recent development? What did the Mother Ship have to offer?
Click to expand...

The access panel is for a wingtip fuel tank. It's easy enough to tape over; I'll give that a try. The access panel on the right side doesn't ride up the way the one on the left slightly does.

I don't recall seeing this before, but did notice it throughout the day's flying.

I haven't talked to Van's yet.

--Ron
 
RV7A Flyer said:
Is this video actually a good representative of what you're seeing with your eyeballs in flight? Sometimes video scan effects can apparently magnify cyclic things like this.

Just want to make sure everyone is seeing the correct data...
Click to expand...

Good observation. I think it was worse on video than in person, but I'll have to make a test flight and compare the two, just to be sure.

I searched the web and found other aircraft with similar action. For example, here's a video of it happening on a Cherokee:

https://www.youtube.com/watch?v=9oGngg-374Y

--Ron
 
PaulvS said:
The skin appears to be rippling in multiple adjacent bays. I wonder if the rivets are all tight? How does it appear on the ground if you press down gently on the skins in that area.
Click to expand...

So I went by the hangar today. Wasn't able to fly my own plane since I was airborne with someone else's. But I checked the skins and rivets on both wings to compare, and didn't notice any difference between them.

While there is some "give" when I press down my finger in the middle of a bay, it's minimal and reacts the same way on both wings. I did not notice any loose or smoking rivets.

--Ron
 
Is it possible that the poor fit of the aux filler is causing the wing to pressurize in flight?
 
Jpm757 said:
Is it possible that the poor fit of the aux filler is causing the wing to pressurize in flight?
Click to expand...

I don't think so. The auxiliary fuel tank is self-contained within the wingtip.

The access panel skin riding up a little bit might be causing some turbulence airflow, however. I might tape it down on my next flight and see if anything changes.

--Ron
 
I got an email response from Van's support. Tony Kirk replied and said "It's normal and nothing to worry about". So I guess I won't!

--Ron
 
ronrapp said:
I got an email response from Van's support. Tony Kirk replied and said "It's normal and nothing to worry about". So I guess I won't!

--Ron
Click to expand...

I was kind of guessing that it was OK, but certainly wanted you to get Van’s judgement on it - I’d have just been guessin’…. someday I’ll have to take a picture of the oil canning on our eXenos wing - those long metal things with thin skins are downright heart-stopping when you pull more than a G and a half…. But the engineering is sound, so I just have to tell myself that if I don’t like it, don’t look at it!
 
I'd be interested to see that! You've certainly flown a lot of unique and fascinating airplanes. :)
 
Different design philosophies in metal semi-monocoque construction.

Some designs use a strong internal frame (spars, ribs, bulkheads, stringers, etc.) and thin skins which are basically just a covering that takes minimal loads, and are meant to buckle (i.e., 'oil can') under normal flight loads. The Schweizer 1-26D & E model sailplanes comes to mind; its wing oil cans a lot and you can sometimes hear it in the cockpit.

On the other side of the spectrum are designs that use thick skins that don't buckle under normal flight loads, combined with a weaker internal frame. The Blanik L-13 and L-23 sailplanes come to mind.

The extreme case is fully monocoque construction where the skin takes all the loads, with no load-carrying internal frame.

Most designs are somewhere in between with more load sharing between the skins and the frame, like the Van's designs.
 
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slight thread drift...
I suggest someone installs a cam on the wing, goes out, and pulls some Gs. Say around 5, and let's have a look.

Whilst building the first RV-4 in Switzerland, we had to static load it to satisfy the authorities. Installed on the canopy rails upside down on a supporting jig, the noise and canning observed were interesting to say the least...

And yes, the wings held alright :D
 
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