âûñøåå îäíî

I have a plane that I am working on, and it has a fully semetrical wing, and I was wondering how it works. From what I know about wings and lift is that they produce lift because the air has to move faster over the top, creating low pressure and getting pushed up by the higher pressure on the bottom, but this wouldn't work if it moved the same speed over top and bottom. This is what has been bothering me.

mulligan

What you know is correct, and in fact a symmetrical airfoil produces no lift AT zero angle of attack. However, once you increase the angle of attack of the airfoil, the air over the top travels farther than the bottom, therefore travels faster, therefore has a lower pressure, therefore you have a net upward force on the airfoil- lift.

An airfoil with camber will produce some lift at zero angle of attack, and of course the lift increases from that point as AOA is increased. You would also find that such an airfoil will produce zero lift at a negative AOA, -2 deg. for example.

mulligan

P.S. It'd be nice if you had a name

âûñøåå îäíî

I had a name, but it had some screwy charictors in it, and it was changed to what you see, at other forums i am refered to as FCM (funny charictor man)

Thanks for the answer, and does it have to have a positive angle of attack, or could it be angled up in relationship to the fuse. (i cant remember what that is called)

rmh

character
your mom's computer?

mulligan

You're referring to incidence.

You can go either way, but the flying characteristics of the plane will depend on the relative incidence between the main wing, the horizontal stab, and the fuselage (don't forget the fuse produces some lift and drag).

For a symmetrical airfoil, if you mount the wing parallel to the fuselage centerline, then in order to fly straight and level, your fuselage, along with the wing, will be angled up. Obviously, the fuselage is not as efficient (Lift/Drag) as the wing, so this will result in an implicit drag penalty during normal flight. So, you might consider adding a couple of degrees of wing incidence (relative to your fuse). However, if you plan on flying inverted a lot with the plane, you might want to keep the incidence at zero, so things will be the same right-side-up or inverted.

In general, you want your horizontal stab at the same level or below your main wing incidence (assuming both are symmetrical). For example, if your wing is at 0 deg., your stab can be -2 deg. to 0 deg. If your wing is at +2 deg., your stab can be at 0 to +2 deg. This is true for most aircraft with a traditional setup, as the stab typically produces a bit of negative lift as the plane is flying straight and level; this setup simply biases everything that way to help with neutral trim. Again, the exception would be if you planned on flying inverted a lot, in which case you might want to keep everything at zero incidence.