golftango
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What Exactly Causes And/or Are These Bubbles?

Sat Jul 29, 2006 7:15 am

Right in front of the speed brakes? Just air under the panels?



[Edited 2006-07-29 00:17:48]
 
474218
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RE: What Exactly Causes And/or Are These Bubbles?

Sat Jul 29, 2006 11:40 am

Those are bonded honeycomb panels, honeycomb core with the upper and lower skins bonded to the core. The bubbles are delaminations, of areas where the skin has come un-bonded from the core. There are limits to the amount of delamination allowed before it must be fixed.
 
meister808
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RE: What Exactly Causes And/or Are These Bubbles?

Sat Jul 29, 2006 2:07 pm

In addition, these somewhat loose pieces of skin will bulge a little bit during flight due to aerodynamic forces.

-Meister
Twin Cessna 812 Victor, Minneapolis Center, we observe your operation in the immediate vicinity of extreme precipitation
 
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HAWK21M
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RE: What Exactly Causes And/or Are These Bubbles?

Sat Jul 29, 2006 4:18 pm

Looks like Delamination to the Honeycomb Panels.
The Coin tap test is the best method to check this.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
kaddyuk
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RE: What Exactly Causes And/or Are These Bubbles?

Sun Jul 30, 2006 11:07 pm

Quoting HAWK21M (Reply 3):
The Coin tap test is the best method to check this.

According to the CAA, the reccomended taps per second is 4. Which i think is stupidly high...
Whoever said "laughter is the best medicine" never had Gonorrhea
 
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zeke
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RE: What Exactly Causes And/or Are These Bubbles?

Sun Jul 30, 2006 11:34 pm

Its called postbuckling, its due to the panel being in compression, its efficient structural design.

Its not an aerodynamic effect, nor does it have anything to do with the composites or delamination.

If you every get to fly a PA28/PA38, or some other low wing trainer, have a look at the wing in a steep turn you will see the same thing happen, when you roll wings level it goes away.
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Buzz
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RE: What Exactly Causes And/or Are These Bubbles?

Tue Aug 01, 2006 1:10 pm

Hi Golftango, Buzz here. Zeke has it about right, the (relatively) thin panels are in compression right now, and the have bowed upwards a little. Take a look at the panels forward of the outboard aileron... not much distortion, but visible due to the sun angle. And if we could see a front view of the airplane, I wonder how many feet of flex those wingtips have? Is that a 747-400?

If there were that many square inches of panel delamination, there would be a flutter problem and it could lose pieces of upper skin.

g'day
 
meister808
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RE: What Exactly Causes And/or Are These Bubbles?

Tue Aug 01, 2006 1:36 pm

Quoting Zeke (Reply 5):
Its called postbuckling, its due to the panel being in compression, its efficient structural design.

Its not an aerodynamic effect, nor does it have anything to do with the composites or delamination.

Hm. I, officially, am an idiot.

Good call.

-Meister
Twin Cessna 812 Victor, Minneapolis Center, we observe your operation in the immediate vicinity of extreme precipitation
 
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HAWK21M
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RE: What Exactly Causes And/or Are These Bubbles?

Tue Aug 01, 2006 4:44 pm

Quoting Buzz (Reply 6):
Is that a 747-400


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regds
MEL
I may not win often, but I damn well never lose!!! ;)

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