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777way
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787 Engines Paint Work Issue

Wed Aug 01, 2007 1:41 am

Is there a reason for not having coloured them in shades of blue as on other aircraft in Boeing house colours? will other airlienes have to drop coloured engines too.
 
ikramerica
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 1:49 am

Quoting 777way (Thread starter):
Is there a reason for not having coloured them in shades of blue as on other aircraft in Boeing house colours? will other airlienes have to drop coloured engines too.

Yes. They determined that one color is better for economy. So on the test frames, they will be white or grey. But that won't stop carriers from putting on various paints. They will just have to sign something saying they know it will hurt performance ever so slightly. Really stupid, in my opinion, but these are the days we live in...  Wink
Of all the things to worry about... the Wookie has no pants.
 
grantcv
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 1:56 am

I don't understand why the color makes a difference. I can see how patterns or decals might create surface irregularities that might make a small difference, but what does color have to do with it?
 
justloveplanes
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 1:58 am

This is a wild guess, but maybe the pigment in the white/grey is smoother or works better with the engine nacelles.
 
777way
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 2:01 am

Virgin have painted their engines light grey and dropped red for the 787.
 
FriendlySkies
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 2:18 am

Quoting 777way (Reply 4):
Virgin have painted their engines light grey and dropped red for the 787.

All of the promo images from Boeing feature the grey engines...doesn't mean those airlines will paint the engines grey.
 
ikramerica
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 2:20 am

I expect QF to put on the red triangle roo logo, for example. Maybe JQ will leave them grey...
Of all the things to worry about... the Wookie has no pants.
 
vapar8
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 2:23 am

I think if they are painted all one color it was ok, but when they are painted more then one color the ridge increased fuel burn by a little. CRAZY
 
777way
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 2:23 am

FriendlySkies I doubt Branson would allow that for Virgin promo's.

[Edited 2007-07-31 19:29:31]
 
dl757md
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 3:03 am

Quoting 777way (Thread starter):
Is there a reason for not having coloured them in shades of blue as on other aircraft in Boeing house colours?



Quoting Grantcv (Reply 2):
I don't understand why the color makes a difference.



Quoting Justloveplanes (Reply 3):
This is a wild guess, but maybe the pigment in the white/grey is smoother or works better with the engine nacelles.

I don't know the answer for sure but in my experience dark colored carbon fiber engine cowlings develop cracks in the upper layers of the composite that propagate out into the paint layers leaving a surface similar to a dried out muddy lake bed. It's not smooth at all and does have an effect on aerodynamic efficiency. The same cowls painted in lighter colors don't have the same problem. Now you may be wondering, why only the cowls and not the whole airplane as it is also mostly carbon fiber? Well, again I don't know for sure but it may have to do with the higher vibration and heat the cowls are subjected to, along with their different structural design. OK, so why does color matter? Light colors reflect heat...dark colors absorb heat....the resins in carbon composites don't withstand heat well. Light colors reduce the amount of heat retained in the cowling and therefor reduce the chances of the dried up muddy lake bed phenomenon occurring.

Quoting Ikramerica (Reply 1):
They will just have to sign something saying they know it will hurt performance ever so slightly. Really stupid, in my opinion, but these are the days we live in...

Again, I'm not pretending to have the answer rather an educated guess as to why Boeing is requiring this acknowledgment from the 787 customers. I do know, however, that they must have a good technical reason for it, not just some CYA legal crap.

DL757Md
757 Most beautiful airliner in the sky!
 
tdscanuck
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 3:17 am

Quoting 777way (Thread starter):
Is there a reason for not having coloured them in shades of blue as on other aircraft in Boeing house colours? will other airlienes have to drop coloured engines too.

Early Boeing promo materials had the nacelles in standard Boeing livery (white + shades of blue). That was before they decided to switch to a laminar flow nacelle.

Once they went laminar flow, they went to all grey. You could do all white too, I'm sure, but you're basically stuck with a single light shade of whatever...no ridges between paint layers, no dark colours.

No ridges because that would mess up the laminar flow. No dark colours because the CFRP doesn't like it, as posted above. You'll notice that no 787 liveries have dark coloured upper fuselages.

Tom.
 
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vzlet
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 3:20 am

As explained by Boeing last year:

SEATTLE, July 10, 2006 -- The Boeing [NYSE: BA] 787 program has made a subtle but important change to the airplane's livery to enhance airplane performance. By developing a method for maintaining a smooth flow of air -- called laminar flow -- over more area on the 787 nacelle inlet, Boeing is able to reduce aircraft drag and fuel consumption.

The 787 nacelle has a tightly controlled smooth surface to preserve laminar flow over a greater distance than that on a standard design. "Aircraft drag is reduced because laminar flow has much lower skin friction drag than turbulent flow," said Ron Hinderberger, propulsion leader for the 787 program.

To achieve laminar flow over the inlet it is necessary to maintain a very smooth, continuous surface without paint edges, which can occur when paint transitions from one color to another, or as paint details are added. The design parameter for the nacelles is based on thickness of the paint formulation for a single color; Boeing has chosen gray to complement the metallic appearance of the nacelle's inlet.

"If you interrupt the laminar flow by adding paint layers, which are common with airline liveries, you could increase fuel burn by 30,000 gallons per year per airplane," Hinderberger added. "An improvement like this -- especially with rising fuel prices -- can contribute positively to the bottom line for an airline."
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dl767captain
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 3:33 am

wasn't there a report about boeing using a less friction paint on the 787 or something? i seem to remember reading something on Boeing's website saying they were using a special paint that would help performance
 
dl757md
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 3:55 am

Quoting DL767captain (Reply 12):
wasn't there a report about boeing using a less friction paint on the 787 or something? i seem to remember reading something on Boeing's website saying they were using a special paint that would help performance

I can neither confirm nor deny that but what I can tell you is that color has absolutely nothing to do with the surface finish of the paint when new. Any special paint that may produce a certain finish that aides in laminar flow should do so as well in one color as the next. As I mentioned in my post above over time dark colors will cause the surface to deteriorate causing laminar flow degradation issues.

DL757Md
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iwok
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 1:29 pm

Quoting Vzlet (Reply 11):
By developing a method for maintaining a smooth flow of air -- called laminar flow -- over more area on the 787 nacelle inlet, Boeing is able to reduce aircraft drag and fuel consumption.

I still don't understand why they couldn't take the pocked golf ball approach.

Quoting Dl757md (Reply 13):
As I mentioned in my post above over time dark colors will cause the surface to deteriorate causing laminar flow degradation issues.

This is definitely a very interesting issue. I wonder if they patented this idea; i.e. using a lighter color to maintain surface finish for a longer period of time.

What about a nice silver finish. Now that would be sweet.  Smile

iwok
 
Bohlman
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 1:54 pm

Quoting Iwok (Reply 14):
I wonder if they patented this idea; i.e. using a lighter color to maintain surface finish for a longer period of time.

That would be akin to patenting "polishing a metal surface makes it smoother and therefore reduces drag".
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pygmalion
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 2:04 pm

how about patenting a special paint that flows out very very smooth and very thin, controlled in thickness of a few mils but lasts for ten years and is very stable in UV. You might be able to patent that.
 
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scbriml
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 4:11 pm

Quoting Pygmalion (Reply 16):
how about patenting a special paint that flows out very very smooth and very thin, controlled in thickness of a few mils but lasts for ten years and is very stable in UV. You might be able to patent that.

I should think you would be able to patent that. But you'd have to develop it first! Big grin
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tdscanuck
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 7:45 pm

Quoting Iwok (Reply 14):
Quoting Vzlet (Reply 11):
By developing a method for maintaining a smooth flow of air -- called laminar flow -- over more area on the 787 nacelle inlet, Boeing is able to reduce aircraft drag and fuel consumption.

I still don't understand why they couldn't take the pocked golf ball approach.

Because the golf ball approach only works over a narrow speed range for the specific aerodynamics of a golf ball.

For a sphere, and other similarly blunt shapes, there is a peak in the drag curve as you get near the top end of laminar flow because of flow separation on the backside. Tripping the boundary layer to turbulent flow reduces the drag for a little while because a turbulent boundary layer is more energized and will stay attached to the surface longer. If you keep speeding up, turbulent drag will surpass the maximum laminar drag. For golf ball size/speed, it happens that the turbulent solution is lower drag than the laminar solution...ergo dimples.

For an aircraft, the Reynolds number is *way* higher than a golf ball and the shapes are already nice and smooth so aircraft don't have the same flow separation problems as a sphere. We can wade into the nitty gritty calculations if we want to, but the short short version is that for aircraft shapes/sizes/speeds, laminar flow is lower drag than turbulent. Golf ball dimples on an aircraft would increase drag, not decrease it.

Tom.
 
CJAContinental
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 9:48 pm

Continental shouldn't have a problem here then.
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CO787EWR
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RE: 787 Engines Paint Work Issue

Wed Aug 01, 2007 10:29 pm

CJAContinental lol, yea CO should be fine
 
ebj1248650
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RE: 787 Engines Paint Work Issue

Thu Aug 02, 2007 12:06 am

Quoting Grantcv (Reply 2):
I don't understand why the color makes a difference. I can see how patterns or decals might create surface irregularities that might make a small difference, but what does color have to do with it?

I don't believe color makes a difference. You hit the nail on the head when you said patterns or decals might create surface irregularities. Those irregularities, apparently, make enough of a difference to degrade aircraft performance. My question would be just how much degradation would that be?
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