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Old 07-21-2008, 10:44 PM
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BMatthews
 
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Default RE: Concept airfoil design- des it work?

Well first off both your diagrams are just you trying to imagine how the air flows. Your streamlines have little to do with reality I'm afraid. I would suggest you don't even bother to try since the air will flow how it wants to flow and you can't alter it other than by studying pressure variations.

There's a slick tool for doing this called Xfoil. You can download the command line versions for free (google for 'xfoil download") or get it when you pay for the unlock code for Profili2. Having used the Profili2 option I can heartily recomend paying the pittance that he's asking in order to have a really nice all in one airfoil analysis and drawing tool. It makes accessing the Xfoil tasks simplicity itself. Meanwhile I've tried to read about how to use the command line version and after a couple of tries didn't bother.

In checking my newly unlocked version of Profili2 I just learned that you don't even need to measure and produce a table of coordinates. The latest version will produce it's own coordinates from a nice raster scan. So if you draw up the airfoil as accurately as you can with a very thin line you can then scan your drawing to an image file and import it. Profili will produce a coordinate table and you can then request a lift drag polar chart. From comparing this to other polars you can determine how your own airfoil stacks up against the competition. Or if you can do it in CAD and then export it as a gif or jpg or bmp you can just open the file with Profili to import it. VERY slick.

I seem to be trumpeting Profili all the time to the point it seems like I was the guy that wrote it. But really I'm just another happy and very enthusiastic customer. This is just a great program that really deserves our attention. He's turned it from just another airfoil drawing program into a full on wing tool.