aracer - Member
stumpy01 » This maintains the 'angle of attack' to the airflow, which will still generate lift but not as much as is created when the aerofoil is the 'right way up'.
As an expert on this, is that because the airfoil is more efficient the right way up, or is that actually Bernoulli? Anyway, don't aerobatic aircraft have symmetrical section wings (and presumably little to no inbuilt angle of attack), which work just as well both ways up? I'm fairly sure that is the case for many models at least.
Well, a flat board with a positive angle of attack will generate lift - just not much.
An aerofoil is designed for it's particular use; so for example, heavy lift transport will have quite a thick wing section giving it a pronounced aerofoil shape to provide plenty of lift at low speed (at the cost of increased drag), while something like a fighter jet will have a much shallower aerofoil profile as it will be able to generate plenty of lift at the higher speeds it will be travelling at.
So, an aerofoil will work best in it's design condition (which isn't generally upside down), but it will still generate lift when upside down if presented to the air at enough of an +ve angle.
Yeah, I think you are right - aerobatic aircraft do seem to have symmetrical aerofoil patters (or at least very close to), so when flying with the wing at a level attitude (probably slightly nose down) the wind wouldn't generate any lift.
To keep things simple for the CFD modelling I did on my dissertation, I chose to use a symmetrical wing as it made putting it all into the CFD software a lot quicker. I found an aerofoil generator online that was meant for model aricraft. You put in the NACA code of the wing you wanted and how many points you wanted and it gave you the co-ordinates as a tabulated file.
This isn't the one I used, but is basically the same thing: