What is meant by "dihedral"?

Modeling Subjects Aircraft
1

Can anyone explain in non-technical language what is meant by a wing’s dihedral? The dictionary definition did me no good:
“The angle between a supporting surface (such as a plane’s wing) and a horizontal line”.

Is the dihedral what is seen when you look at the airplane in profile and the wing may appear to slant down as your eye moves aft from the front? Am I close?

Thanks a lot,

Mark

2

Look at a plane head on. The angle that the wings point up is dihedral. On some Modern aircraft they actually point down, which is called anhedral.

Regards, Rick

3

Aaah, simple enough! Thanks a lot, Rick.

Take care,

Mark

4

cool, ya learn somethin’ every day here don’t ya?!![tup]

5

I remember this way: ANhedral, ANti. Anhedral slopes down.

6

Yup, dihedral is up, anhedral is down. The F-4 Phabulous Phantom has both. The tail planes/horizontal stabs have a bunch of anhedral. The wing has dihedral, or more correctly, polyhedral (where there is more than one angle change). The main wing is flat and both tips angle up.
Darwin, O.F. [alien]

7

Then there’s the F4U Corsair…

8

Dihedral affects the stability of the aircraft in a couple of ways. When the wing has dihedral in it the wing tips are higher than the wing roots. This means that the fuselage is slightly lower than the wing tips, which in turn lowers the longitudinal center of gravity making the aircraft more stable. Additionally, when the aircraft is banking the outside wing is flying at a higher bank angle than the inner wing. The inner wing will develop slightly more lift than the outer wing causing the aircraft to return to level flight at bank angles less than about 60 degrees.

Polyhedral allows a certain amount of lift at severe angles of bank. When an airfraft is banking at, as an extreme example, 90 degrees of bank the wing tips are straight up and down (assuming zero dihedral). The lift they are developing is perpendicular to the wing so all they do is cause the turn to tighten and provide no vertical lift. In cases like that the nose has to be lifted vertically so that lift can be provided by the engine. When a wing has polyhedral, such as the Phantom or Corsair, part of the wing is still providing lift at extreme angles of bank.

In the case of the Corsair, I’ve heard of two reasons for the polyhedral in its wing. One, as mentioned above, to provide lift at extreme angles of bank, but the other is more practical. The Corsair had a 13’-6" diameter propellor. To provide clearance for that monster fan the designers either had to install long, spindly main gear (not a good idea for hard carrier landings) or get the gear mounting points lower. Adding polyhedral to the wing and mouting the main gear at the lowest point accomplished two things, so that’s the way they did it.

9

Aircraft with both anhedral & dihedral, or polyhedral wings, such as the Corsair & Stuka, were commonly referred to as " Gull Wing".

Regards, Rick

10

I just happened to notice that two of the more common examples of American aircraft with polyhedral, the Corsair and Phantom, are both F-4’s [:p] Ain’t that strange?

11

a dehidral is when the wing is sorta angled so the wing tips sorta point up and
I heard somewhere that it is designed to a some stability to the roll of an aircraft.

12

Pure coincidence or some secret Government plot ?? HMMM, I wonder…[:D]

Regards, Rick

13

Partially correct, rj. They’re actually referred to as “inverted gull wing.” A Gull Wing aircraft would be where the inboard wing sections angle upward and the outboard sections are more flat. IIRC, there aren’t any where the outboard sections actually angle downward. Look at a B-25 head-on, it’s a gullwing. The Polish P.Z.L. P11 series fighters were gullwing, as well.

14

Man, you’re really nit picking. I said " commomnly reffered to", which they are.

Regards, Rick

15

Here is some more fodder for the mill. Some radio control model airplanes do not have ailerons, but instead rely on rudder movement to produce roll motion. A perfectly flat wing will produce very little if any roll movement when rudder is applied. The more dihedral that is present in the wing, the more roll you get with a given amount of rudder input.
I have one RC plane that has no ailerons, but has about 40 degrees total dihedral. Application of rudder will produce VIOLENT rolling movement. This thing will actually roll a lot faster than a similar plane with ailerons on a nearly flat wing.
The wing has a flat bottom, modified Clark Y airfoil and is high mounted on top of the fuselage like a Cessna 150 or 172.

16

The Fokker D.VII also had polyhedral wings
Quiz: what is the earliest airframe to feature polyhedral wings?

17

Thanks a lot for the info, guys! These are terms I hear a lot, and I appreciate knowing not only their definitions but also the aeronautical significance.

Well, I can always count on at least 5 people in this forum (and usually more) to have the answers.

Take care,

Mark