Why do older airplanes have the wing curved upward like a 787?

Question

I was just wondering one day about because the 787 uses a wing flex to reduce wing tip vortex, but back in World War 2 they didn't know about wing tip vortex, so then why would it be curved upwards?

You can see in the middle picture the wing is curved upwards. I see this on a lot of commercial airplanes too like the Boeing 737

@fooot that's about actual flex, this one is about dihedral. — Federico, Aug 07 '15 at 15:53
@Federico It's not clear what is meant by "curved wing", and the 787 is much more notable for wing flex than dihedral. — fooot, Aug 07 '15 at 15:56
@fooot I agree, but don't get thrown off course by the wrong assuptions behind the question: 787's wing flex is not there for reducing the wingtip vortex. — Federico, Aug 07 '15 at 15:58
@Federico Exactly, the linked question explains the reason for that, which seems to be at the basis of this question. — fooot, Aug 07 '15 at 16:00
@Ethan the question linked in my first comment explains the reason and consequences of the wing flex. — fooot, Aug 07 '15 at 16:01
The newest edit changed Curved wing to wing flex, so I think this can now be safely closed on @fooot's duplicate identification. — FreeMan, Aug 07 '15 at 16:05
@Federico Actually doing a little research and the wing flex of the 787 reduces the strength of wing tip vortex to prove you wrong just look up wingtip device on wiki and raked wing tip is there and it acts just like a winglet — Ethan, Aug 07 '15 at 16:19
@Federico the raked wingtip actually reduce the vortex affect by 5.5% instead of a winglet which reduces it 3 to 4%. I know its off topic but its a fact. — Ethan, Aug 07 '15 at 17:50

GdD · Accepted Answer · 2015-08-08T12:43:48.530

13

You are confusing 2 concepts here, dihedral and winglets. What you are showing in the picture is dihedral, which is not a curvature but an angle positive from the horizontal. This angle helps improve lateral (roll) stability in flight. This is nothing new, almost all commercial jets have dihedral. Winglets improve efficiency. A Boeing 787 has both.

edited Aug 08 '15 at 12:43

answered Aug 07 '15 at 15:18

GdD

53,842
6
147
212

The raked wingtips on the 787 aren't really winglets but they have the same function. – fooot Aug 07 '15 at 15:22
Yeah winglets are there to reduce wing tip vortex and the 787 has a different system than winglets to reduce wing tip vortex by having the wing curving upwards decreasing the strength of the vortex. The 787 has no winglet – Ethan Aug 07 '15 at 15:23
3

The original poster is not referencing winglets in their post, or a wing rake. They are referencing that the wings on a 787 are very flexible and bend upward noticeably during flight. That's what he's confusing with the dihedral design. It's flexibility v. structured angle. – Jae Carr Aug 07 '15 at 16:10
I do actually @PeterKämpf as I don't agree on your interpretation of the question. – GdD Aug 08 '15 at 12:46

Why do older airplanes have the wing curved upward like a 787?

1 Answers1