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Airfoil trailing edge

Airfoil trailing edge

Airfoil trailing edge


I'm trying to simulate an airfoil in Fluent, and I'm working with airfoils of the NACA 65 series, which are very thin.
The problem is that this airfoils become incredibly thin at 90% of the chord length or sooner ( < 0.8 mm of thickness), a geometry that would be impossible to fabricate.

I've been trying to engross the shape of the trailing edge, basically with a circunference of 2 mm diameter at it's end and connecting it with tangent arcs to the original airfoil. However, this aproximation is very poor since it would change the direction of the stream, and that's really important in my project.

I've included an ilustrative image.

¿Does someone know a better aproxximation to this problem?

Thank you!.

RE: Airfoil trailing edge

I don't have the book handy, but I think I remember Abbott and Von Doenhoff discussing the subject in "Theory of Wing Sections".
There's a way to do it without altering the chord or the mean-line, just the thickness.
Nearly all aircraft that use NACA 6-series airfoils refer to them as "modified 6-series" in their official literature. At least some for that very reason.


RE: Airfoil trailing edge

I don't have a dimension, but I think the trailing edge of the F104 needed covers to prevent lacerations of the ground crew.

Mike Halloran
Pembroke Pines, FL, USA

RE: Airfoil trailing edge

that'd be good for bird-strike !

another day in paradise, or is paradise one day closer ?

RE: Airfoil trailing edge

Getting a little off topic, but now seems like a decent time to ask:

I too have always heard the story that the F-104 was dangerous to ground crew because of the leading edge. Apparently the LE radius was only 0.00016 inches (source not firm).

Does anybody know if this is true or just something of a myth? One of my aero books by Anderson describes them as "razor thin".

Maybe someone has some physical experience with these aircraft?

I've seen a couple of them up close and personal (no barriers around). I walked right up to one at the New England Air museum. The LE definitely had a tight radius but it didn't really come off as dangerous. Seemed like it would take some carelessness to injure yourself.

Anyway, the F-104 is another brilliant Kelly Johnson design if I remember. I love those old interceptors! Sorry for not really contributing to the question, but curiosity's got me on this one.

Keep em' Flying

"I intend to live forever, or die trying" - Groucho Marx

RE: Airfoil trailing edge

Possibly helpful reference. Hard to know if this is still available. SF Hoerner's book Fluid Dynamic Drag is still in print, too.

Horner, S. F., Base Drag and Thick Trailing Edges. J. A. S., p. 622, October, 1950.


RE: Airfoil trailing edge

Regarding the "dangerous" leading edges of the wings of the F-104 I agree with Liftdivergence that, while the edge is very thin, it should not be dangerous to personnel. I think that the reason for LE covers is just the other way round: to protect the LE from dents. Such dents could trip the boundary layer over the wing, with potentially disastrous results at high speed.


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