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    <title>Hip Pocket Aeronautics Plans Gallery - Airfoils &amp; Propellors</title>
    <link>https://hpa.aeromodelling.gr/plans/categories.php?cat_id=28</link>
    <description><![CDATA[work in progress...]]></description>
    <pubDate>Sat, 18 Apr 2026 04:59:57 GMT</pubDate>
    
    <item>
      <title>ARA D family of sections for Props</title>
      <link>https://hpa.aeromodelling.gr/plans/details.php?image_id=1858</link>
      <pubDate>Wed, 15 Apr 2026 10:06:17 GMT</pubDate>
      <description><![CDATA[AJ Bocci's paper from Aeronautical Quarterly on the ARA D family of airfoil sections for propellers]]></description>
          <category domain="https://hpa.aeromodelling.gr/plans/categories.php?cat_id=28">Airfoils &amp; Propellors</category>
              <author><![CDATA[example@example.com (Jmk89)]]></author>
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    <item>
      <title>Source Code. Tail Volume Coefficient (Vh), Static Margin etc</title>
      <link>https://hpa.aeromodelling.gr/plans/details.php?image_id=240</link>
      <pubDate>Fri, 06 Feb 2026 21:22:23 GMT</pubDate>
      <description><![CDATA[Not an aerofoil nor a propeller but this seems the best available location.

C# (.Net Core 6) Source code to calculate Tail Volume Coefficient (Vh), Static Margin and other odds &amp; ends for a model.  

Derived (polite term for wholesale pilfering) from John Barker's (Hepcat on HPA I &amp; HPA II) spreadsheet this also allows you to run the McCombs approximation for the model and apply a scaling factor to the tail area without having to edit the model's configuration file.

Content.

 Source code (C#)
 Example configuration files  (.JSON)
 Notes on use. (PDF)

The code was written to be easy to follow should be fairly easy to port to other versions of the .Net framework or another language and development toolset entirely.

If you want to build the util as is you'll need to install .dotnet (Windows, Linux or Mac) and Visual Studio Code which are (as of April '23) free to download and use.]]></description>
          <category domain="https://hpa.aeromodelling.gr/plans/categories.php?cat_id=28">Airfoils &amp; Propellors</category>
              <author><![CDATA[example@example.com (TheLurker)]]></author>
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    <item>
      <title>SVG Aerofoils</title>
      <link>https://hpa.aeromodelling.gr/plans/details.php?image_id=45</link>
      <pubDate>Sat, 31 Jan 2026 09:18:32 GMT</pubDate>
      <description><![CDATA[Package Contents:

A readme.txt containing the following notes.

Selig format aerofoil .dat files as downloaded from coord_seligFmt.zip  on http://m-selig.ae.illinois.edu/ads/coord_database.html

JSON format versions of the Selig files.  The JSON formatted data files use the aerofoil name.

SVG aerofoil plots for (nearly) all of the source data files sized for a 100mm chord. If you need another size open the file in your favourite SVG drawing tool (Inkscape, Corel, Adobe etc.) and rescale to suit.  Or build and run the AerofoilMake util (see notes below).

A handful of the source files were not processed because they recorded the ordinates in an exponent form or because they contained the older above/below a datum format.  The exponent forms weren't processed because I discovered them fairly late on and I couldn't be bothered to rejig the code to deal with them.  An exercise for the interested reader.

Source code to:
 - Convert Selig format to json format data.
 - Code to generate svg file from json format data.

The zip file structure is :

  - Code (See later notes)
  - Dat
  - JSON
  - SVG

The SVG directory is broken out into sub-directories A to W.  Some of the sub-directories are further sub-divided where there are large classes of an aerofoil.  For example, SVG\E\Eppler and SVG\N\NACA.

I _strongly_ recommend retaining the directory structure when you unpack the zip file. You can re-organise it afterwards.

*CAVEAT EMPTOR*
The SVG plots are a specified using a single Cubic Bezier Curve path.  This seems to give good results for the couple of dozen that I've checked and certainly better results than a polyline. Generally speaking the more ordinate points the smoother the plotted curve.  Be warned that there may be dud plots , either because of a DAT to JSON conversion error or because a single path type is inadequate.  If you do find a dud please let me know and I'll look into it.

Code
Note well. The code is _nowhere_ near production quality and my work colleagues would have a fit if they saw it, but it's just about good enough for hacking about at home.

The code is organised as three projects in a Visual Studio solution and uses .Net Framework 4.5 so any version of MS Visual Studio from 2013 onwards (including Community Editions) should do.  

2026 note.  The code should port to Visual Studio Code with little or no trouble.
 
Project: Aerofoil.
Builds a DLL providing methods to load ordinates from JSON data, generate a plot sized for a given chord (in mm) and save the plot to an svg file.

Depends upon NewtonSoft.json.dll.  Included. 

Ignore the inheritance / interface stuff for the SVG output.  I got side-tracked into creating a small GP SVG creation library which was completely unnecessary so I ripped it out.  You can simplify the SVG creation a great deal for this special case if you're so minded. 

Project: SeligToJson

Command line.  Walks a collection of .dat files in a named directory, convert each to a JSON format file in suitable for use by Aerofoil and then write to target directory.

Project AerofoilMake
Command line.  Take a single named JSON file, a chord in mm and an output directory.  Writes resulting svg file to output directory.

Notes:
All source code, json and SVG output files public domain.  No rights reserved for these.

The .DAT files are due to Selig and treat these as for individual use only.]]></description>
          <category domain="https://hpa.aeromodelling.gr/plans/categories.php?cat_id=28">Airfoils &amp; Propellors</category>
              <author><![CDATA[example@example.com (TheLurker)]]></author>
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