Interesting!  I didn't know this was coming off the line until I read this article about Airbus.

http://business.timesonline.co.uk/article/0%2C%2C13130-2256673%2C00.html

It's a graceful looking aircraft.  Look at that dihedral, it looks more like a sailplane rathered than a powered aircraft!

Its basically a 747 designed with the knowledge gained from research for the 787, should be a great plane!

An artists impression. The real thing will look quite different.

LOL!!!!

The expected wet blanket!   

So, you're saying the 787 WON'T have a dihedral like what is shown?   

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Isn't wing flex essential in calculating dihedral design?  The aerodynamic properties of the wing's shape must be it's shape in flight, not standing static where the wings may/will sag.

Oh yea, I forgot to add the  

I knew the pic is an artists rendition.  It was a light post with light commentary, before the wet blanket was cast over the thread.  And in order to conclude the picture is an exaggeration, we would have to have some sort of factual info, such as a pic of the real plane, or some reporting on the subject.  But to assume the plane won't look like what is depicted without substanciation, is just that.....assumptions, or wet blankets, take your pick.

Now, the real plane, once it rolls off the assembly line may or may not have such a graceful dihedral.  We don't know.  But until then, we have what Boeing releases in their press info.  Now, is Boeing given to releasing false information on their aircraft?  If Boeing practices releasing false info, then to be suspicious is warranted, but I have yet to be convince that Boeing practices falsification of press releases.

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What does your friend base that statement on?  Current practices?  The Boeing 787 and 747-8 will be making large uses of composites, by nature are much more flexable that the currently used metals.

Surely, you've seen Voyager and other Rutan planes in flight, whth their composite wings and all.  The flex on those wings seem unnatural as well.

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Take a look at the first pictures we saw of the 787 and compare them with how it looks now. Boeing does seem to take a fair amount of artistic licence when it comes to pictures of their future aeroplanes.


Whats more, composites need not be more flexible than metals. By composites I assume they mean things like Carbon Fibre. Which is lighter than metal. But as far as i'm aware not much more flexible.

I fly composite aircrafts (DA40's) so I'm more than familiar with the material.

Both me and my friend judge that picture from an aerodynamic view. You DO NOT want that kind of heavy flexing. If it was desirable, we'd already have it today, but alas we dont.

You will lose lift efficiency since flexing decreases the wing span.  (compare a standard bank, you will lose altitude if you do nothing to counter it)
An ex Airbus A330 F/O, currently flying Fokker 100's simply said
"Too much bending.. Loss of lift.."

No offence, but I agree with him.

Boeing often releases pictures of their new fleet (just like Airbus), but the actual product will differ greatly.
Like I wrote earlier, if you want proof: check out the early 787 (or 7E7 as it was called) renders.
The early pictures had Shark fin, futuristic cockpit windows. But the latest drawings shows a fairly conventional design.

Early design
http://www.volvo.com/NR/rdonlyres/6A6973E9-C39F-4506-A70C-74D19D351D26/0/7E7_2_s...

Final design
http://www.boeing.com/companyoffices/gallery/images/commercial/787/images/k63304...

I have no idea if that's a current impression or not. Both drawings look like the work of the same artist. I don't see the point in this argument as nobody except the design team can possibly know. Let's wait & see shall we?

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Spot the difference....

Exhibit 1) Professionally doctored 787 artist's impression...




Exhibit 2) Boeing artist's impression of the 747-800

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Birds flex like that, sailplanes flex like that, Rutan's planes flex like that.  Why is this aerodynamically inefficient?  Seriously, I'd like to know that.

The previous challenge was excessive stress on the metals would cause failure.  So, rigidity had to be built in.  With composites, that challenge is no longer an issue.

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Rutan's aircraft generally all have a ridiculously high aspect ratio and tonnes of fuel aboard them to go flying very high or very far...

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Long held practices often die a hard death:  "That's the way we always did it...." - famous last words.

Reminds me of battleship admirals poo-pooing the advent of the aircraft carrier.

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Long held practices are often those that ultramodern techniques owe everything to. Composites are nothing new in aircraft. The Mosquito was a composite aeroplane. As was every other aircraft before metal became the prefered material. The Write flyer was made of Carbon Fibre as when you get down to it thats exactly what wood is.

The problem with saying "composites" is that it literally could be anything from paper maché to alloy.

Excuse me, but the Mosquito was wood and paper.  When I'm referring to composites, I'm referring to carbon fiber, I think that's the long held assumption.  And I always thought carbon fiber was a type of plastic, an oil product, not wood.   

I don't think any paper was involved in the construction of the Mosquito.

It's quite possible the 787 will make use of a new hi-tech wing based on the Rutan designs. I wouldn't know about that but it's generally accepted that swept wings don't need as much dihedral as a straight wing. In fact they need very little at all. If you have too much dihedral the aircraft becomes too stable & could be difficult to control in some situations.

We're not actually talking about dihedral per se but wing flex. Even if they do flex as much as on those artists impressions they would sag on the ground which brings more problems.

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I think veneer was the thinnest layer in the composite...


*Apart from the plans...

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That is apparently true depending on fuel load. Note the B-52 wing has a large anhedral when at rest. It also has outriggers at the wingtips to prevent them dragging on the ground. All wings flex to a greater or lesser extent depending on the design & type of structure.

I found an interesting discussion on the subject here. http://www.airdisaster.com/forums/showthread.php?t=77005
The forum members seem to know what they're talking about. "Verbal" presumably works for Boeing & lists his occupation as Stress Analysis Engineer. Most of the specific details will still be a closely guarded secret.

PS. This is on the 787 but I understand that the 747-8 will use a lot of the same features.