This article is written about the conference given by Dr. Richard Stallman (President of the Free Software Foundation) in Barcelona, 10 may 2012 (Universitat Politècnica de Catalunya, Auditori de l'Edifici Vèrtex). We had planned to show and discuss a GNU wing, but the conference ended too soon, and this time it was not possible. I wrote this text which try to justify the GNU name attached to many of my projects. Experts on GNU/Linux operating system, also will understand why. However, many are unaware of the concept of free flight. This article tries to give more details about this curious relationship free flight - free software.


1. INTRODUCTION

Free flight, consists mainly of flying gliding wings capable of takeoff and landing on foot, from high places and without assistance. Wings are light, and easily collapsible and portable. The most popular free flight wings are hang gliders and paragliders.

It is difficult to determine precisely where the free flight originated. No doubt converge several places with people working independently without knowing almost nothing of each other.

One of the major development sites, there is no doubt on the coast of California in the early 70's. Some manufacturers, including "hippies", built their own wings in plastic and bamboo. They fly in dunes and cliffs above the beaches. There are no sufficiently established manufacturers, and design and construction are "home made". Quickly, bamboo is replaced by aluminum and plastic nylon. The designs are improved, and manufacturers are beginning to appear. A free flight historian could give more details.

Some articles have appeared in magazines such as "Low and Slow" and "Popular Mechanics" show some plans to build yourself your own wings. Other exchanges of drawings are produced by post or by photocopy. There is a tradition of amateur builders who enjoy not only flying but building their own models, from small RC planes, kites, wood gliders... But it was not always easy to get good plans...

In the case of paragliding, this is started in the late 70's when a Frenchs skydivers fly with their canopys from some peaks of the Alps. Soon added to the new sport climbers, mountaineers, ... and history repeats itself. The undeniable advantages of the paragliders (minimum weight and volume, ease of transport and use ...) facilitates rapid progress to achieve real gliders...


2. SOURCES OF INSPIRATION

  I will mention three sources of inspiration for the wings GNU:

  1 - The model of mathematics and physics.

Can be easily understood that the mathematics and physics that we learned, are free, because it published in countless books for study and can be used wherever necessary, whether in programming, the design of wings, or in the bridges ...

  2 - The work of the Californian Michael Sandlin, a pioneer of free flight, which has been publishing for many years (even before me) complete plans of gliders in tube and fabric. His plans are freely available in CAD ​​format and picture format. Contain much detail and are of great quality. Furthermore, the same Sandlin has built and flown their models, demonstrating the success of them.

  3 - The GNU concept of freedom. The model of freedom-respecting software licensing with the GNU General Public License (GPL), is applicable to other fields of engineering. In particular, in the case of the design of free flying wings, the source code, is comparable to the plans in vectorial format DXF/DWG. It is not easy to copy a wing, but it is easy to copy a DXF file. A DXF file can describe, so completely and accurately, a creation as a paraglider or hang glider.


3. THE GNU WINGS

Since 1999 I have published on the web, various wing designs completely free. The plans are available for free study and copy. Some designs do not move from the conceptual idea or a sketch, others are detailed in DXF, and even physically materialized.

Many of my designs are prefixed with "gnu" It's fun and remember that the design is free and published under a license like the GPL. Other wings are not called gnu but follow the same concept (like many GPL programs which need not necessarily start with the letter "g" or "gnu").

These are some of the GNU wings:

Glider	Idea	Drawing	Plans DXF/DWG	Built
gnupwing			Yes	Yes
gnuswing	Yes	Yes
gnuportaglider		Yes
SPS2008			Yes
gnu-V		Yes
gnuSTAR		Yes
gnuEASY			Yes
gnuLAB1			Yes
gnuLAB2			Yes	Yes
BHL			Yes	Yes

And why GNU wings?

The interest of publishing wings under GNU concept. There are several reasons, depending on the particular model, though subsisting always the idea of sharing and not unnecessarily close to work.

For gnupwing, the goal is clearly to share code (plans), so that others can study it or make replies. Also returning to the public domain the original plans of a NASA-kite I took as a model.

For gnuLAB (later called gnuLAB1) is very important. Surely the first glider totaly published online for your free copy. The main objective was precisely to have someone copy, and so save me the work of building ...

The case of gnuLAB2 is the project design and complete construction, showing that the wing GNU flies perfectly.

BHL's case is different. In mid-2011 a major and leading manufacturer of paragliders (perhaps the "Apple" of the paragliding), present a model very light and "revolutionary" and shrouded in secrecy ... Looking at some pictures of this model, the concept reminds me the gnuswing, so recognizing the beauty of the idea, I decided to go a step further and make an improved version also published as GNU. To carry out the project, I have even the support of a Spanish manufacturer of paragliders. Perhaps will be the first GNU glider built in series (currently in beta testing). Its original name is just fun "BarretinaHyperLite" and the version of the final model may be another. A Russian designer has also released recently and quite independently, its own model, including software for the design.

 
4. DOCUMENTATION AND SOFTWARE

As a complement to the wings, I added two very important pillars:

PDH "Paragliding Design Handbook".

A book, I'm still writing, which exhibits all the paragliders design technique.
Other articles on the web complement the art.

LEparagliding2.0

The program that I built from scratch to design my gliders. Programmed entirely in gnuFortran. Read text files with the data, and generates DXF files with 2D and 3D plans, and other text file listings. You do not need graphical environment. Undoubtedly, the code is not everything refined it should be, but it works (I follow the rule of simplicity UNIX, which is to make the machine work, instead of the programmer time). I love the Fortran! I learned Fortran on the old VAX terminals of the university, and I still use.
 
5. DERIVATIVE WORKS

A great success for GNU glider would see how an outside manufacturer copies it improves if necessary, and put it into production.

Until now, only I have news for some amateur models to scale and the BHL case discussed above.

Also some surprises, which I have not worked at all:

- A doctoral thesis of an aeronautical engineer ETSEAT-UPC on study of deformations in a paraglider. It needed an accurate model and took the gnuLAB2 as a model:

http://upcommons.upc.edu/pfc/handle/2099.1/14030

- A flight simulator that also takes gnuLAB2 model:

http://www3.telus.net/cschwab/simPG/
http://www3.telus.net/cschwab/simPG/simGlider.pde


Conclusion: to encourage young engineers / scientists in the field of programming or in other very different fields, to release free their work. It is absurd to hide the principles of mathematics and physics.

Pere Casellas, Teià  May 13, 2012


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