Wing Tips

[repub]

Will someone please explain the reason for downward curving wing tips like on the A-10 Warthog and what is the proper name for them.

[SargeNZ]

Hoehenia (SP?) tips. Something like that.

On an aircraft that does not have these tips a vortex is created at the wing tip as the airflow from the top and bottom intertwine, causing drag. The tips help to prevent the two airflows creating a vortex and thus reduce drag, BTW it is called induced drag.

[Pook]

I belive the reason for the turned down wing tips is an atempt to push the tip vortex away from the edge of the wing thereby reducing the negatve effect this would have on lift.

The vortex is caused by the diffrence in presure between the top and the bottom surfaces of the wing. As the high presure air escapes from under the wing at the tip it creates the tip vortex.

The pic attached below shows a few diffrent wing tips and their theoretical effect on the tip vortex.

The first one shows a typical wing tip and aproximently where the vortex would form.
This would reduce the lift created by the wing as the part of the tip under the vortex would create little lift.

The second and third layout show ways in which this can be improved.

Piers

[Ollie]

In any case the affect on the induced drag of a variety of wing tip treatments is very small compared to even small increases in aspect ratio. One of the practical advantages of the down turned wing tip is that it provides a skid to protect the rest of the wing of a sailplane from the ground.

On most models, the main benefit of various tip treatments is more esthetic than aerodynamic.

[repub]

Thanks for the info. I am looking into building a DeHavalind Beaver model and I have seen pictures of both types of wing tips and wondered why the difference. Don't think I will worry about it and just make wing straight.