NAV20
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787 Fuselage Bulge - The Full Story

Thu Jun 21, 2007 9:49 pm

Many issues raised on A. net remain mysteries for a long time - so I thought that it would be worthwhile posting Mike Bair's 'full and final' explanation of the mysterious 'gap.' Turns out that it wasn't bad design or bad workmanship - just a case of components for one section of the first airframe (essential to holding its shape) not turning up on time and being fitted before it was transported:-

"Bair explained in detail the fuselage-gap problem.

"He said the forward fuselage built by Spirit AeroSystems of Wichita, Kan., had sagged and bulged outward in one quadrant after some secondary parts were late and not put in position early enough to hold the shape.

"The distortion was corrected in Everett. Engineers disconnected the internal structure and "pushed the bulge back in," Bair said.

"He said the issue would have been much harder to fix if the plane were aluminum, which is less flexible than the 787's composite plastic."


I'm sure it was just one of the many 'glitches' that Boeing and its partners will have to surmount as they struggle not just to get the aeroplane flying, but to move on to producing large numbers of frames in preparation for EIS. My own business field was major building construction, not aviation - but I'll still always remember the 'mad rush' to get everything on site and then the strange feeling of 'calm' (almost anti-climax, "What the hell were we all losing sleep over?") when the very last bit came off the truck and slotted perfectly into place.......

Mike Bair had a little fun at the end, with a play on words - mentioning what could prove to be not just Boeing's, but the whole industry's problem for some months to come - the worldwide shortage of fasteners:-

"Alluding to the shortage of fasteners, which he said is "a struggle" but not a showstopper, Bair said that the airplane program is close to its climax.

"The fundamental big bets have gone better than we imagined," Bair said. "We're into nuts and bolts, no pun intended, the little stuff."


http://seattletimes.nwsource.com/htm...chnology/2003754761_airshow20.html
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
 
NYC777
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RE: 787 Fuselage Bulge - The Full Story

Thu Jun 21, 2007 10:03 pm

Yup and you can bet that when these fuselage sections start getting to final assembly pre-stuffed according to the plan then fit issues will be non existent.

The first 787 will be standing on it's own landing gear tomorrow (June 22nd) so it has come a very long way in short amount of time.
That which does not kill me makes me stronger.
 
halls120
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RE: 787 Fuselage Bulge - The Full Story

Thu Jun 21, 2007 10:06 pm

Quoting NAV20 (Thread starter):
Many issues raised on A. net remain mysteries for a long time - so I thought that it would be worthwhile posting Mike Bair's 'full and final' explanation of the mysterious 'gap.' Turns out that it wasn't bad design or bad workmanship - just a case of components for one section of the first airframe (essential to holding its shape) not turning up on time and being fitted before it was transported:-

"Bair explained in detail the fuselage-gap problem.

"He said the forward fuselage built by Spirit AeroSystems of Wichita, Kan., had sagged and bulged outward in one quadrant after some secondary parts were late and not put in position early enough to hold the shape.

"The distortion was corrected in Everett. Engineers disconnected the internal structure and "pushed the bulge back in," Bair said.

"He said the issue would have been much harder to fix if the plane were aluminum, which is less flexible than the 787's composite plastic."

While I suspect many of the B haters will continue to insist that there is a B cover-up, or that B is ignoring icebergs looming in their future, it is refreshing to hear about an issue fully and frankly from the leadership of Boeing. Bair's statements are consistent with the "if we had a gap this small with an aluminum airplane, we'd have a party" statements attributed to unnamed B mechanics.
"Suppose you were an idiot. And suppose you were a member of Congress. But I repeat myself." Mark Twain, a Biography
 
Poitin
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RE: 787 Fuselage Bulge - The Full Story

Thu Jun 21, 2007 10:11 pm

Quoting NYC777 (Reply 1):
The first 787 will be standing on it's own landing gear tomorrow (June 22nd) so it has come a very long way in short amount of time.

Get a picture if you can. Sort of like baby's first step.
Now so, have ye time fer a pint?
 
bringiton
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RE: 787 Fuselage Bulge - The Full Story

Thu Jun 21, 2007 10:17 pm

Quoting NAV20 (Thread starter):
The distortion was corrected in Everett. Engineers disconnected the internal structure and "pushed the bulge back in," Bair said.

That just sounds funny!!! remind me please who gets this aircraft so if i fly i will make sure i get seats that are farther back  Smile
 
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Stitch
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RE: 787 Fuselage Bulge - The Full Story

Thu Jun 21, 2007 10:32 pm

Quoting Bringiton (Reply 4):
That just sounds funny!!! remind me please who gets this aircraft so if i fly i will make sure i get seats that are farther back.  Wink

Personally, I hope they fly LN1 to The Museum of Flight when done with the flight test regimen and put her in the airpark with a nice futuristic interior.
 
TeamAmerica
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RE: 787 Fuselage Bulge - The Full Story

Thu Jun 21, 2007 10:33 pm

Quoting NAV20 (Thread starter):
"He said the forward fuselage built by Spirit AeroSystems of Wichita, Kan., had sagged and bulged outward in one quadrant after some secondary parts were late and not put in position early enough to hold the shape."

Elastic deformation...just as I (and others) said in several overheated threads on this subject.
The problem was in the assembly procedure, not the parts. thumbsup 
Failure is not an option; it's an outcome.
 
bbobbo
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RE: 787 Fuselage Bulge - The Full Story

Thu Jun 21, 2007 11:06 pm

Quoting Bringiton (Reply 4):
Quoting NAV20 (Thread starter):
The distortion was corrected in Everett. Engineers disconnected the internal structure and "pushed the bulge back in," Bair said.

That just sounds funny!!! remind me please who gets this aircraft so if i fly i will make sure i get seats that are farther back Smile

Sounds like the 787 had a hernia.

By the way, if you Google "hernia", be prepared to cover your eyes.  crazy 
 
Poitin
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RE: 787 Fuselage Bulge - The Full Story

Thu Jun 21, 2007 11:35 pm

Quoting Bringiton (Reply 4):
Quoting NAV20 (Thread starter):
The distortion was corrected in Everett. Engineers disconnected the internal structure and "pushed the bulge back in," Bair said.

That just sounds funny!!! remind me please who gets this aircraft so if i fly i will make sure i get seats that are farther back Smile

Maybe they used a heat gun and shrunk fit the barrel  Big grin
Now so, have ye time fer a pint?
 
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Stitch
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 2:09 am

Quoting Poitin (Reply 8):
Maybe they used a heat gun and shrunk fit the barrel  Big grin

Thought I saw an A340 depart PAE the other day. Perhaps they flew her in to back her up next to the 787 and let the four hair dryers hanging offer her wings warm it up a bit.  duck 
 
ikramerica
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 2:25 am

Quoting Bringiton (Reply 4):
That just sounds funny!!! remind me please who gets this aircraft so if i fly i will make sure i get seats that are farther back

"Not hyena! Hernia! Hernia!"
Of all the things to worry about... the Wookie has no pants.
 
Rheinbote
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 4:25 am

"He said the forward fuselage built by Spirit AeroSystems of Wichita, Kan., had sagged and bulged outward in one quadrant after some secondary parts were late and not put in position early enough to hold the shape.

"The distortion was corrected in Everett. Engineers disconnected the internal structure and "pushed the bulge back in," Bair said.

"He said the issue would have been much harder to fix if the plane were aluminum, which is less flexible than the 787's composite plastic."[/quote]

I am seriously puzzled that nobody here challenges this lousy explanation.

1. A composite barrel cannot 'bulge in one quadrant' once cured. It may ovalize as a whole in case it is not (yet) properly stiffened. But 'bulge'? Local elastic deformation in one quadrant only?

2. "Aluminum is less flexible than CFRP"...what???

3. If there really was a bulge,e.g from a curing or mold defect, you can't just 'push it back in' with brute force (use of hydraulic press reported). That would leave the barrel joint non-uniformly pre-loaded and would severely limit the useful life of that part of the structure.

Maybe they just tried to find an explanation that is comprehensible for the layman. But this explanation given by Mike Bair is hogwash.

Quoting Stitch (Reply 5):
Personally, I hope they fly LN1 to The Museum of Flight when done with the flight test regimen and put her in the airpark

If they really did what Bair described, then LN1 will end up there very quickly.
 
ikramerica
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 4:29 am

Quoting Rheinbote (Reply 11):
I am seriously puzzled that nobody here challenges this lousy explanation.

It's not lousy, it's layman. Know your audience, know the difference.

What he describes is quite plausible and logical, and just because you don't see it or you want highly technical terms to be used, doesn't make it less so.
Of all the things to worry about... the Wookie has no pants.
 
astuteman
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 4:40 am

Quoting NAV20 (Thread starter):
"He said the issue would have been much harder to fix if the plane were aluminum, which is less flexible than the 787's composite plastic."

This will be the same CFRP that's so rigid it doesn't need frames, presumably..........

Quoting Rheinbote (Reply 11):
"Aluminum is less flexible than CFRP"...what???

Colour me confused.  Smile

Regards
 
Byrdluvs747
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 4:44 am

Quoting Rheinbote (Reply 11):
I am seriously puzzled that nobody here challenges this lousy explanation.

 Yeah sure

Here we go.
The 747: The hands who designed it were guided by god.
 
TeamAmerica
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 5:01 am

Quoting Rheinbote (Reply 11):
A composite barrel cannot 'bulge in one quadrant' once cured. It may ovalize as a whole in case it is not (yet) properly stiffened. But 'bulge'? Local elastic deformation in one quadrant only?

Yes, when the remainder of the structure is restrained this is possible. Find a flexible ring of some sort and cup it in your hand, applying gentle pressure. Suppose that the portion held by your hand is the "desired shape"...leaving a bulge only in the portion not in contact with your hand. Add a rigid support to hold the ring in that shape, and you have an analog to what happened with the 787 fuselage.
Failure is not an option; it's an outcome.
 
khobar
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 5:17 am

Quoting Rheinbote (Reply 11):
3. If there really was a bulge,e.g from a curing or mold defect,

Since there was no bulge from a curing or mold defect, nothing to worry about.  Wink
 
IAD787
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 5:20 am

All the original pictures of the problem are on my site about 3/4 down the page where it has the fuselage status section.

http://flightblogger.blogspot.com/2007/05/building-dreamliner.html

Enjoy.
Former FlightBlogger turned Wall Street Journal Aerospace Beat Reporter
 
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Devilfish
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 6:06 am

Quoting Stitch (Reply 5):
and put her in the airpark with a nice futuristic interior.

The "James Bond" scheme by BMW comes to mind. idea  Although that may not be futuristic enough.

Quoting Rheinbote (Reply 11):
I am seriously puzzled that nobody here challenges this lousy explanation.

Maybe people here are confident that someone from over there could be relied upon to do it?  Wink
"Everyone is entitled to my opinion." - Garfield
 
col
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 6:13 am

Anybody concerned should fly on line number 2 and later units  Smile
 
Jerald01
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 6:15 am

Take any large-diameter (10 feet diameter or larger) ring-shaped object, whether it be made of aluminum or composite, load it onto a transport device (truck trailer, sled, pallet, etc.) horizontally, restrain it on that device, then ship it half a continent. Unless that ring-shaped object has some kind of internal bracing it will, to some degree or another, sag (I believe it was a Mr. Newton who "discovered" gravity, which is the culprit in this case.) Measure the diameter horizontally and then measure it vertically and see what you get.... two different diameters, right?

Large-diameter composite rings flex considerably if they are stood on their side. How do you get them back into a "round" shape if they are on their side? Opposing hydraulic presses work just fine, and they don't get in the way of whatever it is you are trying to mate the ring to (another fuselage section???). If done properly ther is no compromising of structural integrity of the ring or the composite material it is made of.
"There may be old pilots, and there may be bold pilots, but there are darn few green cows"
 
Airlinemodeler
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 8:01 am

I doubt seriously that using brute force would be a technique used because the stress load in the area that the pressure was applied would have a serious compromised integral strength issue.
Tom from Hot KLAS
 
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Stitch
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 10:32 am

Man, listening to some of the folks here you'd think Boeing connected 5X's 744F to the 787 fuselage section with chains and then went to max take-off power to yank the part into position.

I doubt the stresses were anywhere near as fierce as people believe or if they were, well Boeing just proved how robust a 787 fuselage barrel is and as such I would not be surprised to see the first controlled flight into terrain end with a huge trench being dug by the fuselage with everyone inside still sipping the champers in utter oblivion they'd just landed the hard way... (sarcasm smiley)
 
pygmalion
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 12:25 pm

Think about a ring that is on the order of 58 Feet in circumference and on the order of a eighth of an inch thick from the photos. It would be very flexible if it was not supported.

Does anyone really expect a barrel to stay round if unsupported?? The stringers run longitudinally not circumferentially. The frames and floors must be installed to have the barrel hold its shape. Bairs explanation makes perfect sense.

And if you wanted to apply load carefully and slowly.. what would you use? A pry bar? Two guys named Guido and Bubba? Or a calibrated load cell with a hydraulic jack? Hydraulics are really nice in that they are very controllable and stable. Perfect for this.

Just because you can get one that will lift your car... doesnt mean that Boeing used a car jack. Anyone else ever use a Porta-power ram??
 
NAV20
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 12:40 pm

Quoting Stitch (Reply 22):
I doubt the stresses were anywhere near as fierce as people believe

Agree - it's not as if any force was 'captive,' any pressure applied would not have been borne solely by the section being reformed, it would be evenly-absorbed by the whole 'ring' - that's the whole point of making fuselages tubular.

One shouldn't forget that all airliner fuselages have (HAVE to have) incredible strength - since they're going to have routinely to resist forces of around six pounds per square inch all day every day from pressurisation once they're in service.

[Edited 2007-06-22 05:41:54]
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
 
474218
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 12:41 pm

Quoting Pygmalion (Reply 23):
Anyone else ever use a Porta-power ram??

How else are you going the remove the trunnion pins from the landing gear?
 
XT6Wagon
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 12:44 pm

Quoting 474218 (Reply 25):
How else are you going the remove the trunnion pins from the landing gear?

dynamite works I'm sure.... not to servicable after, but the pin would not be in your way anymore.
 
WestJetYQQ
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 1:53 pm

Quoting Bbobbo (Reply 7):
Sounds like the 787 had a hernia.

 rotfl 

About the Bulge; I've seen the 787 skin material up close. The composite material is very thin and strong, but i would be quite easy to make such a correction, as the Boeing employees did in this situation.

Cheers
Carson
Will You Try to Change Things? Use the Power that you have, the Power of a Million new Ideas.
 
aminobwana
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 2:07 pm

Quoting Bringiton (Reply 4):
That just sounds funny!!! remind me please who gets this aircraft so if i fly i will make sure i get seats that are farther back



Quoting Col (Reply 19):
Anybody concerned should fly on line number 2 and later units

I really am concerned by these insinuations. As I noted in the thread regarding the rumor of a crack in the A380 wing, such will not die if the manufacturer clarifies thoroughly the sitation, but here, even if this clarification is done with the outmost detail, some A-netters know much better how to build a plane as the manufacturer !!
I hope you realize that if Boeing make these statements, they know more than well their liability if these were incorrect, a problem the Forum aircraft builders fortunately (for them) do not have regarding the captioned insinuations.

aminobwana
 
Maersk737
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 2:35 pm

Quoting Aminobwana (Reply 28):
I really am concerned by these insinuations. As I noted in the thread regarding the rumor of a crack in the A380 wing, such will not die if the manufacturer clarifies thoroughly the sitation, but here, even if this clarification is done with the outmost detail, some A-netters know much better how to build a plane as the manufacturer !!
I hope you realize that if Boeing make these statements, they know more than well their liability if these were incorrect, a problem the Forum aircraft builders fortunately (for them) do not have regarding the captioned insinuations.

aminobwana

You really are amazing Big grin

Peter
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bringiton
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 2:41 pm

Quoting Aminobwana (Reply 28):
some A-netters know much better how to build a plane as the manufacturer !!

On my part it was a joke ! Obviously any airframe put into testing would go through a rigourous testing regime and would be approved before acceptance by the airlines.
 
Rheinbote
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 3:20 pm

Guys, I'm neither sensationalist nor stupid. I am familiar with the concept of ovalizing. It is also pretty clear that a leightweight structure like S41 will 'sag' if not yet completely stiffened. That's plausible and logical, right. It is also appropriate to keep explanations comprehensible for the layman audience.

But I don't buy 'a bulge in one quadrant', an explanation that is not supported by the pictures. And I don't buy that 'this issue would have been much harder to repair with aluminum, which is less flexible than CFRP'. This is factually wrong.

The use of 'brute force' is an exaggeration of my part and I hope it is factually wrong as well.  wave 
 
JoeCanuck
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 3:38 pm

Quoting Rheinbote (Reply 31):

It's not factually wrong...in fact, it's factually correct. If you compare how CFRP and AL pieces of the same thickness bend, you'll find that the AL piece will reach the point of permanent damage much sooner than the composite. That means the CFRP piece is more flexible.

Almost any plastic is more flexible than Al. Flexibility is really not one of Al's strengths.
What the...?
 
NAV20
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 4:01 pm

Quoting Rheinbote (Reply 31):
It is also appropriate to keep explanations comprehensible for the layman audience.

I think that's the key, Rheinbote. As you imply, logic suggests that if there is a bulge in one sector (given that the circumference was correct, otherwise the parts would not have mated at all) the bulge would have to have been compensated for by contractions elsewhere. But if those contractions were spread evenly round the 60-foot circumference, they would likely have been microscopic at any one point - and in any case one would expect that they would automatically have been corrected by pressure being applied to the bulge.

I don't myself blame Mike Bair for not going to that (unnecessary) level of detail when addressing a lay audience.

Quoting Rheinbote (Reply 31):
And I don't buy that 'this issue would have been much harder to repair with aluminum, which is less flexible than CFRP'.

Don't know enough to comment much on that - but one thing I do know is that sheet aluminium, like any metal, is easy to dent. It may well be that it is the elasticity of CFRP, rather than its 'flexibility,' that made the repair easier than doing the same with aluminium. That is to say, the engineers could be more certain that pressure applied at one point would be evenly absorbed around the circumference, rather than just producing yet another local deformation. Sheet metal also stretches pretty readily if treated harshly, as any amateur (like me) who has tried to hammer out a dent in their car's wing will know!

PS Crossed with your post, JoeCanuck - but you put the point in a shorter and more elegant form than I did!  Smile

[Edited 2007-06-22 09:10:22]
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
 
Rheinbote
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 6:41 pm

Quoting JoeCanuck (Reply 32):
If you compare how CFRP and AL pieces of the same thickness bend, you'll find that the AL piece will reach the point of permanent damage much sooner than the composite.

We are comparing aluminum and CFRP skins designed to similar requirements, not pieces of similar thickness. Aluminum skin on commercial aircraft is down to 0.016in in thickness, ~1/60th. The skin of the 787 is about 1/8th of an inch (Pygmalion's etimate). In layman terms, a piece of skin cut from a Coke can is much more flexible than the CFRP ruler I have on my desk, made by Beechcraft and about 1/8th on an inch in thickness.  wave 

Even assuming that aluminum skin is beefed up around joints, it is safe to assume CFRP would still be at least 2-3 times more in thickness.
 
SailorOrion
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 8:18 pm

What is "flexibility"? It's a term that is not really defined in material science.

There's the modulus of elasticity, which basically tells you how much deformation you get under stress.
There's tensile strength, with the 3 main components for Al-like materials:
Ultimate strength, yield strength, breaking or rupture strength...

"Flexibility" is a property of a structure, not of a material. To give you a very very very primitive example, if you put 4 bars of steel together to a square, you have a very flexible structure. If you add a bar diagonally, the structure becomes stiff.

SailorOrion
 
NAV20
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RE: 787 Fuselage Bulge - The Full Story

Fri Jun 22, 2007 11:52 pm

Quoting Rheinbote (Reply 34):
In layman terms, a piece of skin cut from a Coke can is much more flexible than the CFRP ruler I have on my desk

Speaking as a fellow layman, Rheinbote - if you bend the piece of Coke can, it will stay bent and probably stretch and be permanently deformed. If you bend the ruler it will spring back to its previous form when you stop, and suffer no permanent deformation.

So you might have to buy a new can of Coke - but you won't need to buy a new ruler. Or, by all accounts, a new 787 fuselage.......
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
 
Rheinbote
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RE: 787 Fuselage Bulge - The Full Story

Sat Jun 23, 2007 12:04 am

Nice analogy, NAV20, but you're comparing plastic deformation ('stays bent') with elastic deformation ('springs back'). That's apples with grapes. But while we are at it, you don't want to try plastic deformation with CFRP: The resin matrix would break and the carbon fiber plies would delaminate - meaning loss of structural integrity.
 
NAV20
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RE: 787 Fuselage Bulge - The Full Story

Sat Jun 23, 2007 12:25 am

Please refer to #33 above, Rheinbote, I was the one who suggested that 'elasticity' was possibly a better term than 'flexibility.'

As far as I can see, the fuselage section 'sagged' (not by much, by one inch at one point in its 60-foot circumference) because a component which should have kept it to its proper shape was missing. Boeing engineers decided that a) it was feasible, by applying controlled pressure, to ease the section back to its proper curvature, and b) that neither the original problem nor the remedial procedure would result in the part being weakened and requiring replacement.

So what are you saying? That Boeing are wrong (criminally wrong, there's no other word for it), the part was in fact fatally weakened, and should have been scrapped?

Or just that Mike Bair should have said 'elastic' rather than 'flexible?'  Smile
"Once you have flown, you will walk the earth with your eyes turned skywards.." - Leonardo da Vinci
 
khobar
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RE: 787 Fuselage Bulge - The Full Story

Sat Jun 23, 2007 12:56 am

Quoting Rheinbote (Reply 31):
But I don't buy 'a bulge in one quadrant', an explanation that is not supported by the pictures. And I don't buy that 'this issue would have been much harder to repair with aluminum, which is less flexible than CFRP'. This is factually wrong.

Perhaps when dealing with coke cans (one piece); perhaps not when dealing with aircraft skins made up of many pieces of aluminum riveted together?

Quoting Rheinbote (Reply 34):
We are comparing aluminum and CFRP skins designed to similar requirements, not pieces of similar thickness. Aluminum skin on commercial aircraft is down to 0.016in in thickness, ~1/60th. The skin of the 787 is about 1/8th of an inch (Pygmalion's etimate). In layman terms, a piece of skin cut from a Coke can is much more flexible than the CFRP ruler I have on my desk, made by Beechcraft and about 1/8th on an inch in thickness. wave

AYK, an aluminum plane skin is in many pieces, so you can't simply unbolt the skin from the interior frame. You'd have to undo the many, many rivets - a PITA I would imagine, and then hope all the rivet holes still lined up. I can see how a 58' circumference one-piece ring would be more flexible than a 58' circumference conglomeration of pieces all bolted to a rigid support ring. Maybe here the word "flexible" doesn't pertain to the capability of being flexed but rather it's capability to adapt to new, different, or changing requirements?
 
Ceph
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RE: 787 Fuselage Bulge - The Full Story

Sat Jun 23, 2007 11:47 pm

Lets hope the plane doesn't blow up during pressure testing or after being subjected to many pressure cycles like the Aloha Airways 737 that lost a roof
 
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Stitch
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RE: 787 Fuselage Bulge - The Full Story

Sun Jun 24, 2007 3:34 am

Quoting Rheinbote (Reply 37):
But while we are at it, you don't want to try plastic deformation with CFRP: The resin matrix would break and the carbon fiber plies would delaminate - meaning loss of structural integrity.

Not necessarily true. I was watching "How It's Made" on the Science Channel last night and they were showing how CFRP light-poles (for streets) were made. They used steam heat to "loosen up" a CFRP pole to bend it into the proper shape and the "memory" of that shape to keep it in the new shape once it was cooled again.

I admittedly have no clue how this relates to the CFRP used in the 787, but evidently Boeing was able to re-shape the piece into a new form because the sections fit now.
 
Rheinbote
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RE: 787 Fuselage Bulge - The Full Story

Sun Jun 24, 2007 3:48 am

Quoting Stitch (Reply 41):
They used steam heat to "loosen up" a CFRP pole to bend it into the proper shape and the "memory" of that shape to keep it in the new shape once it was cooled again.

I admittedly have no clue how this relates to the CFRP used in the 787, but evidently Boeing was able to re-shape the piece into a new form because the sections fit now.

The pole was probably made from thermoplastic material which 'gets soft when heated'. In contrats, most CFRP composites used for aircraft primary structures are thermoset material which means once it's cured it's 'set' and cannot be reshaped again.

787 fuselage skins are definitely thermoset composites, so re-shaping is not an option.
 
Poitin
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RE: 787 Fuselage Bulge - The Full Story

Sun Jun 24, 2007 7:30 am

Quoting Rheinbote (Reply 42):
787 fuselage skins are definitely thermoset composites, so re-shaping is not an option.

From what I heard, you are correct -- it is thermoset. However, it can be bent without deforming. All Boeing did was to remove some of the internal bits and pieces, corrected their shape and reinstalled them -- problem fixed.
Now so, have ye time fer a pint?
 
astuteman
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RE: 787 Fuselage Bulge - The Full Story

Sun Jun 24, 2007 3:59 pm

Quoting Poitin (Reply 43):
From what I heard, you are correct -- it is thermoset. However, it can be bent without deforming. All Boeing did was to remove some of the internal bits and pieces, corrected their shape and reinstalled them -- problem fixed.

 checkmark 

Provided the circumferential measurements were within spec, there should be absolutely no reason for this shape not to be correctable when unconstrained by internal structure.

Regards
 
Rheinbote
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RE: 787 Fuselage Bulge - The Full Story

Sun Jun 24, 2007 7:08 pm

Quoting Astuteman (Reply 44):
Provided the circumferential measurements were within spec, there should be absolutely no reason for this shape not to be correctable when unconstrained by internal structure.

 checkmark  exactly. If circumferential/diameter measurements would be confirmed as within spec, the issue would be closed. The pitctures do not seem to support this however, as there is only steps in one direction to various degree all around.
I agree that out-of-round is not necessarily a problem, as CFRP is elastic to a certain extent. But if the diameter would be off, it would be much harder to correct than with an aluminum structure, if at all possible without compromising long-term structural integrity. Boeing communication was misleading at least in this respect. I can't imagine though that Spirit would produce a barrel that would be off in diameter by 0.3in.
Whatever, in case aircraft #1 is put into airline service without the S41/43 joint being refurbished, this would be an indicator that indeed the diameter of S41 was within spec. Wait and see.
 
astuteman
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RE: 787 Fuselage Bulge - The Full Story

Sun Jun 24, 2007 9:11 pm

Quoting Rheinbote (Reply 45):
If circumferential/diameter measurements would be confirmed as within spec, the issue would be closed

If the circumferential measurements DO differ, you're well and truly screwed.
All you'll do is chase the difference round and round the join.

(My personal record is 2 complete revolutions round a Trafalgar Class Submarine circumferential join (10m dia) in the late '80's......  Smile )

Quoting Rheinbote (Reply 45):
I can't imagine though that Spirit would produce a barrel that would be off in diameter by 0.3in.

FWIW me neither.

Regards
 
aerodog
Posts: 114
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RE: 787 Fuselage Bulge - The Full Story

Tue Jun 26, 2007 5:54 am

Mike Bair said, "... the forward fuselage built by Spirit AeroSystems of Wichita, Kan., had sagged and bulged outward in one quadrant after some secondary parts were late and not put in position early enough to hold the shape."

I understand the secondary parts to be floor board ass'ys which would explain the out of contour condition. His use of the term bulge is probably misleading.
 
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Tugger
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RE: 787 Fuselage Bulge - The Full Story

Tue Jun 26, 2007 9:54 am

Interesting, it sounds like the 787 is to previous aircraft/airliner production what uni-body construction in cars is to the previous body-on-frame manufacturing. The entire unit is necessary for it to be properly structurally sound. To minimize weight and maximize the structural efficiency, everything contributes.

Tug

[Edited 2007-06-26 02:55:16]
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