The above data, plotted for various surface roughnesses.ĭata for plain-flapped sections of a variety of flap lengths and flap deflections. The above data, plotted for various Mach numbers to examine compressibility effects. Where available, wind tunnel data has been imported, largely from the UIUC Low-Speed Airfoil Tests and NACA-TR-824.ĬFD data has also been imported for a select number of airfoils, such as for NACA0012 from the NASA Langley Turbulence Modeling Resource.įor each airfoil, I share the DAT and DXF files, show the parameters for a Venkataraman (four-spline) fit, list the top 20 most similarly-shaped airfoils, and show this data:Ĭl vs alpha, Cd vs alpha, Cm vs alpha, Cl/Cd vs alpha, Cd vs Cl - and cubic curve fits for these. Data was also generated for plain flapped sections with varying chord length and deflection angle. A handful of sections were sourced from NACA-TR-824 and other freely available sources.įor each shape, scripted JavaFoil batch runs were used to compute the lift, drag, and moment polars for a variety of Reynolds numbers, Mach numbers, surface roughnesses. The sections presented herein are provided largely by the UIUC Airfoil Coordinates Database or generated programmatically by Martin Hepperle's JavaFoil. So now I have 5318 airfoils and many many GB of data cataloged. and where I could find it, wind tunnel and CFD data. However, if the wing was in fact not flat on the bottom at every rib position, then the next critical question becomes: Exactly how does the maximum camber percentage vary along the span? The precise answer will determine whether or not the YM15 and YM18 occur along the span, but finding that answer might present a rather sticky wicket.I was trying to find a nice airfoil my homebuilt plane, then things got a little out of hand and I ended up making a website with all of the airfoils I could find, all of their JavaFoil-computed data for varying Re, Mach, roughness, flap setting, etc. If it was, then all sections should be obtained by scaling the original Clark Y. So the critical question is whether the Fokker D.XXI wing was flat on the bottom at every rib position. The details are given in NACA TN-1016, but suffice it to say here that the Clark YM15 and YM18 in the UIUC database are convex along the entire bottom. By this process, you can generate Clark Y sections that are not flat on the bottom, and the deviation could go either way (convex along the entire bottom, or concave on the bottom, i.e. Skipping a lot of hand waving about aerodynamics, this is not always desirable, which may be the reason for NACA devising a scheme whereby the basic thickness distribution of the Clark Y can be scaled to an arbitrary thickness and combined with a camber line which has been derived by scaling the basic Clark Y camber line to obtain the desired maximum camber percentage. The convenience of the flat bottom is purchased at a price: the thicker the section, the greater the value of the maximum camber (as a percent of chord) occurring at 40% of the chord.Ī wing tapering from a 20% flat-bottomed Clark Y at the root to a 9% flat-bottomed Clark Y at the tip will have camber that is markedly decreasing toward the tip. Scaling the ordinates of the original Clark Y will yield sections which are flat on the bottom from 20% of the chord to the TE.
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