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foot launchable glider, I can ride a bus with

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ypsilon

Well-Known Member
Joined
Mar 1, 2016
Messages
325
Location
Austria
Hi everybody,

After having enjoyed reading this forums for year, this is my first post here. In fact it's the second, the first one I wrote the past hour, but it got lost, when my login expired :(. Not a good start. Anyway, let me give you some background about me. I am flying sailplanes and paragliders, both for many years now and still with a lot of enthusiasm.

I like sailplanes for their comfort, their large flight envelope, resilience to turbulence (which is both a key to the realm of wave flying), and of course in general their performance (Not to win records or competitions, but to stay aloft and fly XC on the less obvious days).

Paragliders OTOH are ingeniously engineer flying machines as well: roughly 12 kg including the harness, the reserve chute, the helmet, instruments, AND the wing. Also paragliders have come a long way from simple means of descent after a mountain hike, to real XC machines, allowing for FAI triangles beyond 300 km and straight line flights exceeding 500 km. Another feature of the paraglider is its low speed, that enables to land on tiniest field, and therefore on mountain tops as well. Not only for bivouac flying (i.e. landing in the evening on top, staying overnight, and relaunching the next day), but also for a relaxed lunch-break, after a few hours of flying.
As you can imagine, outlanding is pretty hassle free as well: Just pack your glider into the slightly oversize rucksack, and (hitch) hike home.

In my project I want to build a foot launchable glider, I can ride a bus with. To add some detail the glider should

  • be light enough to be carried to launch pads (more or less) easily (target ~25 kg, everything <30kg is a success)
  • fold so it can be stowed away in public transport and regular gondola cabins
  • be easy to fly, tolerant to turbulence
  • be controlled aerodynamically (please no weight shift other than for trim maybe)
  • be easy to launch, easy to land
  • exhibit a larger flight envelope than a paraglider (i.e. higher Vne)
  • reasonable performance (L/D 16 @ ~ 45 km/h would be great)

Now there are alternatives that almost meet the above requirements:

  • standard paraglider for low hour (<150h a year) pilots: L/D 9.5, Vne ~55 km/h
  • open class paraglider: L/D 11.5, Vne ~75 km/h
  • light king-posted hangglider (E.g. Finsterwalder Lightfex): L/D 10.5, Vne 80 km/h

As you can see, those alternatives aren't bad, but not quite what I want. I therefore started to sketch a rigid wing hangglider:

  • very low sweep (TE almost straight) tailless wing
  • relatively low aspect ratio
  • relatively large area
  • windglets for directional stability
  • positive cm airfoil (I admit it rightaway: It's the MH78, sorry for the lack of creativity)
  • Junkers type elevons (Inspired by the Mitchell Wing, I did some CFD simulations that suggest that this configuration, maintains some elevator control even when the outer wing sections are stalled already.


By now you will have understood that I am a day dreamer, but at least one with some engineering background.
I read pretty much everything about flying planks in this forum, and understand that there is a lot of concern about this concept in the context of foot launched sailplanes. Then again there are people like "Nurfluegel" who is known to know his trade, and who states that if he were to build another rigid wing hangglider, it would be a plank again.

Anyway, I hope to be able to spark some discussion on the viability of this project. I am not apodictic in any way: I don't mind a tail or more sweep, but don't want to compromise static balance beyond a certain point. I've yet to see easily foot launched tailed airplanes.

Ok, that's it for now. Sorry for the novella, looking for to reading about your ideas, concerns, and comments.

cheers,

Ypsilon


PS.: Totally off-topic, but maybe interesting for some of you as well, my other soaring related project: www.openvario.org
 
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