747-8

[dcunning30]

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.

[Nexus]

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.

[dcunning30]

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.

[Hagar]

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?

[dcunning30]

Agreed!

[C]

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

[Nexus]

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?

[dcunning30]

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.

[Woodlouse2002]

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

[C]

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...

[dcunning30]

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...

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?

[dcunning30]

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.

[Nexus]

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.

[Woodlouse2002]

[quote]

Long held practices often die a hard death:

[dcunning30]

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.