camber or thikness ?

[borntofly5]

hi guys i am new to this forum and i am from pakistan, i want to ask that a max lift of an airfoil depends upon aerofoil thickness or camber ? ;) thanks i would appreciate for your help and valuable time... :)

[cockney steve]

a plank of wood that's 50 cm thick, is not an aerofoil....give it an angle of attack and airspeed and it will develop some lift.

camber the upper-surface and you'll have a more efficient lift....but the thickest part of your aerofoil will still be 50 cm thick,


Now, if you camber the underside of your aerofoil as well, you can further improve the lift as well as considerably reducing the thickness.

I suggest you buy or borrow some aeromodelling books you can learn an awful lot about aerodynamics , principles of flight, etc. as well as the theory behind various "standard" NACA aerofoils.

The physics involved in making high-performance model aircraft, are the same physics that enable full-size ones to fly.

Start with the basics and then progress. good luck.

[borntofly5]

thank you sooo much bro but camber makes more lift right ?

[Lightning Mate]

The physics involved in making high-performance model aircraft, are the same
physics that enable full-size ones to fly.

Ever heard of Reynolds number?

[DaveReidUK]

Ever heard of Reynolds number?Ah, the number that allows you to use a wind tunnel model to predict the characteristics of a full-size aerofoil. :O

[Lightning Mate]

Yes.

density x velocity x dimension divided by viscosity.

[24Carrot]

The short answers are (sub-sonic, real aircraft):

1) Thickness increases both stalling angles of attack (positive and negative). So thickness improves the range of usable angles. It makes high lift possible.
Good aerofoils have round leading edges and sharp trailing edges, so basically increasing the thickness makes it easier for the air to follow the aerofoil's surface.

2) Camber makes the aerofoil asymmetric, so it has a Lift Coefficient at zero angle of attack. It may slightly reduce the range of usable angles.
Because these aerofoils are asymmetric, we must be careful about what we mean by angle of attack.
A useful example is flap extension. This increases the camber of the wing.
The aircraft may stall at a slightly lower angle of attack (as measured by aircraft attitude), but has a much higher Lift Coefficient when it does, so it can fly slower before stalling, and still touch down with the wheels in roughly the same position whether flapped or flapless.
The slightly lower stalling angle of attack (as measured by aircraft attitude) comes from the tighter curve the air has to follow on the upper surface.
The higher lift coefficient comes from the greater air deflection downwards.

There is an interesting historical discussion of all this in section 4.14 of "Fundamentals of Aerodynamics" by John D Anderson, but be warned that the book is rather expensive, very mathematical, and covers much more than this topic, so you may want to borrow rather than buy.

Interestingly, model flight tests and early wind tunnel experiments at low Reynolds numbers gave the impression that thick aerofoils would be high drag, and this is true for models, but not for real-sized aircraft.