The design Evolution
The inspiration came from the SWIFT foot launched glider, that still remains the most succesfull tailless ultralight glider that reached the market. I wanted to see if it was possible to design a better streamlined sailplane, still keeping the advantage of the foot launch method.
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| Year 2000: the main inspiration was coming from the Swift design |
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| Year 2000: first conceptual rendering for a foot launched version |
At this stage i started with a quite conservative aspect ratio and a thick wing section. One of the biggest issues was to find the right compromise for the pilot position respect to the wing spar, and minimizing the center of gravity shift between the pilot "running" and the "seated" configuration.
The lift distribution over the wing was close to elliptical, and two big winglets were implemented.
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| Year 2000: preliminar study |
The swept angle was limited to 15°. The wing surface was good enough for a low stall speed, making foot launching possible.
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| Year 2000: a very tight and streamlined fuselage pod. |
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In 2001-2002 i was focusing on running some aerodynamic and stability simulations. At that time, there was no "easy to use" software for that. Searching on the web, i was able to find some freely available basic VLM code (vortex lattice method) in FORTRAN. Those codes were mainly coming from NASA and some US Universities. No GUI and quite complex to be used. Nevertheless i was able to prove the concept.
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| Year 2002: Panels setup for VLM code. |
In 2004 the design evolved in an higher aspect ratio wing, and the swept angle increased to 22°.
The winglets were very nicely blended with the wing. The first free flight scale model was built and flown.
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| Year 2004: that wing was very sexy! |
At that point in time, a great source of inspiration was
Martin Hepperle's Website, and the wing section choosen for the wing was the MH-78. This wing section was specifically developed for footlaunched gliders.
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| Year 2004: MH-78 wing section. |
In 2010-2011 i started investigating the prone pilot position: fascinating configuration, but there are several drawback to this. The most annoying one is to find a good streamline for the fuselage.
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| Year 2011: prone pilot position study. |
After several studies, i still prefer the traditional seated position.
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| Year 2012: fuselage study. |
After a stop that lasted a couple of years, i focused in optimizing the fuselage shape. I thought it was good to take as a reference some well known fuselage designs. The one below is belonging to the Rolleden Schneider LS6 (the glider that i actually fly):
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| Year 2014: LS6 fuselage and pilot position - side view |
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| Year 2014: LS6 fuselage and pilot position - top view |
The LS6 is quite an old glider, but this fuselage design has been used on several sailplanes, from LS4 to LS8, proving a very good performance.
The difficulty with my design, is due to the fact that, more than a fuselage, i just need a pilot pod, since the glider will be a tailless one. So, i needed to optimize the shape in order to provide a good pressure gradient recovery on a reduced longitudinal length.
