What the difference between "Semi-Symmetric" and "Flat Bottom" airfoils?
Both producing lift and both can be used as main wings, i heard "Flat Bottom" is better but do "Semi-Symmetric" can better than FB airfoil at something? Like lifting or stability?
What do they even mean?
Flat bottom gives better low speed lift, semi-symmetric is good for stuff like prop fighters and airliners. Symmetric is good for supersonic stuff
@IICXLVIICDLXXXIIIDCXLVII No idea, other than you can use it to make custom propellers.
Not to toot my own horn but i made this a while back which explains most of the aerofoils here
@TheFlightGuySP
This always confused me, why is it available for wings if it's meant for props? Were wing propellers a planned feature at some point?
@IICXLVIICDLXXXIIIDCXLVII This airfoil is actually meant for propellers, hence the name NACA'PROP'.
@IICXLVIICDLXXXIIIDCXLVII NACAPROP airfoils act as if they are in a constantly stalled state. Controls on this airfoil tend to be less effective, and it takes significant speed to actually fly an aircraft with NACAPROP wings, because as mentioned above, the airfoil acts as if it is constantly stalled.
Afaik it only affects the lift the wing generates, Flat Bottom is better for low speed planes like a Cessna 172, Symmetric is usually better for faster planes like fighter jets since they don't need the extra lift and it can make level flight more difficult, Semi-Symmetric is somewhere in-between, not entirely sure what it is used for.
In short, here's the difference between the 3:
Symmetric - No lift at 0 AOA (neutral pitch) regardless of speed
Semi-Symmetric - Some lift at 0 AOA, increases with speed
Flat Bottom - Even more lift at 0 AOA, also increases with speed
There's also a hidden airfoil type named "NACAPROP" that can only be set with XML editing, I'm not sure how it works but GuyFolk seems to always use it so it might be better for PSM capable planes.
@MrShenanigansSP, i just tested both airfoils on my craft, "Flat Bottom" produced more lift as my plane won't pull it's nose down with neutral Trim, "Semi-Symmetric" wasn't faster.
Both same planes with different airfoils started flying from USS Wasp, flied some seconds on altitude of 5,000~ meters with 100% Throttle on same engines
It was tested on low physics
Results:
Semi-Symmetric - 1400 km/h average
Flat Bottom - 1450 km/h average
@MrShenanigansSP, maybe I'll try it out on Wasp
Flat bottom like produces more lift at low speeds I think and semi-symmetrical is like a hybrid of both of them flat bottom and symmetric (I could be wrong) symmetric is also good for high speed
Just noticed stock Wasp uses "Flat Bottom" airfoil