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There are a few things to consider for a good aerobatic airfoil. … Modern aerobatic aircraft are rated ±10g (note that FAR/JAR only requires ±6g in the aerobatic category), so a thick root airfoil helps to keep the structural mass down. …

All you can do with any airfoil analysis software is to calculate the stall angle of attack and lift coefficient. … For a single airfoil no stall speed can be defined - this is only possible for a specific airfoil on a specific airplane. Foilsim allows you to add this information via the "size" button. …

However, the thicker an airfoil is, the higher will be the flow speed on both sides, due to the displacement effect of the thicker airfoil. …

because they have blunter noses which work over a wider angle of attack range, the blunt nose also allows to use effective slats or Krüger flaps, they have plenty of camber in the aft section of the airfoil … Part of that advantage is used up by making the airfoil thicker so suction on the lower side is also higher than on conventional airfoils, but an advantage remains. …

in German normally denotes chord (Tiefe), but since we later see $\bar{y}_n^{(s)}$ for the camber line (Skelettlinie), it here stands for Tropfen, denoting the thickness distribution of the uncambered airfoil …

The difference is that one figure looks at 2D flow around an isolated airfoil, where L/D ratios of up to 200 can be reached, while the other figure is for the 3D flow around a whole airplane, warts and …

All points you mention are correct (for the nitpickers: Point 5 is only true below transsonic speeds). That the pitching moment of the wing is drawn nose-up is probably because it is positive this way …

The next two digits stand for the year this airfoil has been designed. Add '19' in front and you have the full year. … So the "150" in FX 71-L-150/30 tells us that this airfoil is 15% thick. The last digits are again optional and denote the relative flap chord in cases of control surfaces, this times in percent. …

You are right, lift is concentrated in the forward part of an airfoil, especially at high angle of attack. … Below you see the pressure acting on an airfoil symbolized by arrows (yes, that is XFOIL at work), and arrows pointing at the airfoil indicate pressure higher than ambient air pressure, and those pointing …

Critical speed or Mach number is the speed at which the speed of sound is locally reached somewhere along the flow around an airfoil. … The picture below shows one result for the BACJ airfoil at Mach 0.8, and you can see that the speed on the upper surface reaches Mach 1.3. …

This airfoil is listed in the airfoiltools site, and I took the liberty to copy its XFOIL results here: I selected the Reynolds numbers 500,000 and 1,000,000, which should be at the low end for a man-carrying … To achieve a lift coefficient of 1.89 with that airfoil will need a much higher Reynolds number, but max. L/D is already around 120. …

The optimum airfoil is a cambered line of zero thickness. If operated at just the correct angle of attack, it will produce the highest L/D possible. It's cross section is trivial: It has none. … This airfoil will not be practical for any purpose other than establishing a theoretical optimum figure. Real airfoils need a blunt nose and some thickness. …

The drawing in your answer shows the contour of the tips of the local pressure vectors when they are plotted perpendicularly to the local airfoil contour. Yes, this will change with angle of attack. … The stagnation point is below the highest distance between airfoil and pressure contour near the nose (in the blue region). …

Dynamic lift is always created by "flow turning", or more precisely, by adding some vertical impulse to the oncoming flow. There are several and equivalent ways to describe this: If you draw a big …

[Does] the location of the camber in the MAC's airfoil correspond with the aerodynamic center? No. … Generally, the more an airfoil is cambered towards its rear end, the higher its pitch moment coefficient will be. …