On Mar 8, 2022, at 9:50 PM, Michael Dunning <dunningme@...> wrote:

David,

The comment was strictly about the tailoring of the hinge moment. The rest was a fun history tangent.

Jay,

I noted a couple concerns in the provided LS(1) airfoil after running through the usual XFOIL file conversion hoops (remove tab delimiters, normalize the X/Y scale). While the max thickness is recovered correctly, the max thickness location, max camber and max camber location are considerably off from the published numbers:


Airfoil Tools (untrusted)


NASA TM-X-72843 (trusted, usually)


Regardless of that, my initial results at 2 degrees angle of attack are off in all respects from the first JavaFoil result you posted when using your (normalized) coordinates:



The two tools are never going to match but I do expect them to generally agree. My XFOIL results for zero lift AoA and where cl = 0.461 occurs are in line with the Airfoil Tools published numbers at RE=1M and the NASA published wind tunnel data, so I feel confident ruling out gross user error with the tool at least. The wind tunnel data in Figure 6 (PDF pg 28) is in general agreement and even the XFOIL over-prediction of max lift occurs at the typical +15%...and max lift AoA prediction is closer than usual at 15 vs 16 degrees actual.

Both my initial checks, the Airfoil Tools plot, and the NASA report show any cl < about 0.5 occurring at negative angles of attack. I'm doubtful but possibly this is due to the plans-template-level-line vs. chord line references? Again, not sure how JavaFoil works.


In the meantime, I need to stop and calibrate XFOIL with the wind tunnel data from the NASA report before I can be of any further use to you:
NASA-TM-X-72843 "Effects of thickness on the aerodynamic characteristics of an initial low-speed family of airfoils for general aviation applications"

Regards,
--
-MD
#2827 (still thinking about planning on visualizing how to finish building)