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747-8 (Read 2696 times)
Reply #15 - Jul 24th, 2006 at 4:24pm

dcunning30   Offline
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Quote:
Take a look at the first pictures we saw of the 787 and compare them with how it looks now.


This message thread is regarding the 747-8, not the 787.  But anyway, since you insist on talking about the 787, I'd have to ask which set or artists drawings are you referring to?  I haven't been able to locate a photograph of the actual plane yet.  If you're talking about comparing artists drawings, your argument looses impact.

Quote:
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.


Flexibility is one of the well discussed attribute of composites.  For such a large aircraft, you don't wan't rigitidy, you want the wings to flex to absorb turbulence, just like you want tall skyscrapers to flex, for similar reasons.
 
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Reply #16 - Jul 24th, 2006 at 4:30pm

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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...
 
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Reply #17 - Jul 24th, 2006 at 4:42pm

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I see your point regarding the sharkfin.  But back to my original point regarding the dihedral, here's one of the current pics of the 787, and my point regarding the wings are once again reinforced:

...

Unless, in some future time period, the wings will be depicted with less flex, I'll still maintain my original point regarding the 747-8.

 
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Reply #18 - Jul 24th, 2006 at 4:47pm

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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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Reply #19 - Jul 24th, 2006 at 4:52pm

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Agreed!  It's a current pic.  But anyway, it was just light thread.  It's really nothing worth debating about.  It's still a graceful looking pic.  We'll see if Boeing delivers or not.  No biggie!
 
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Reply #20 - Jul 24th, 2006 at 5:09pm

C   Offline
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Quote:
I have no idea if that's a current impression or not. Both drawings look like the work of the same artist.


Spot the difference....

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

...


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

...

Wink Grin
 
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Reply #21 - Jul 24th, 2006 at 5:11pm

Nexus   Offline
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It still wont look like that.
It's a drawing, and it's not aerodynamic efficient.
And I dont see the problem in pointing that out.

Composites are great, but they wont defy the principles of aerodynamics.

Give good, reasonable arguments why you benefit from such an excessive wing flex?

 
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Reply #22 - Jul 24th, 2006 at 5:16pm

dcunning30   Offline
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Quote:
It still wont look like that.
It's a drawing, and it's not aerodynamic efficient.
And I dont see the problem in pointing that out.

Composites are great, but they wont defy the principles of aerodynamics.

Give good, reasonable arguments why you benefit from such an excessive wing flex?



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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Reply #23 - Jul 24th, 2006 at 5:31pm

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If composites were the answer to problems like that then aircraft wing spars would all be made out of laminates of douglas fir.
 
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Reply #24 - Jul 24th, 2006 at 5:43pm

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Quote:
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.


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... Smiley
 
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Reply #25 - Jul 24th, 2006 at 5:46pm

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Quote:
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... Smiley


Rutan's planes are designed with maximum effeciency so they can achieve the performance and fuel effeciency never before heard of.  By the way, what was one of the selling points of the 7E7, performance and fuel efficiency?
 
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Reply #26 - Jul 24th, 2006 at 5:48pm

dcunning30   Offline
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Quote:
If composites were the answer to problems like that then aircraft wing spars would all be made out of laminates of douglas fir.


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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Reply #27 - Jul 24th, 2006 at 5:53pm

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Allright

Here's the deal, you get rid of 20% weight, then you gain 20% more range

What the 787 did was to have an extensive use of light-weight materials, AND adding bleedless engines (which means no performance loss when running air conditioning and anti-ice systems)

It's NOT about their "hightech" superduper dihedral wing design.
 
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Reply #28 - Jul 24th, 2006 at 5:56pm

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


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.
 
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Reply #29 - Jul 24th, 2006 at 6:01pm

dcunning30   Offline
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Quote:
It's NOT about their "hightech" superduper dihedral wing design.


Given what you itemized, then why have the dihedral like that at all since it appears you and others are arguing that less dihedral, or "flex" seems to be better?  If this is so, then we can conclude birds have a less efficient dihedral, sailplanes have a less efficient dihedral, and the high performing Rutan planes have a less efficient dihedral.  It is the more rigid dihedral that is being espoused here is actually more aerodynamically efficient.

I hope you understand my logical quandry here.  I'm certain the brain trust among posters is quite high, but the arguments against the 7E7 dihedral make no sense to me.
 
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