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I've actually researched this option. Using compressed air as a structural component is a valid construction technique and could be applied to hang gliders. It

by sraquo 12y ago

I've actually researched this option. Using compressed air as a structural component is a valid construction technique and could be applied to hang gliders. It won't work on paragliders because as ram-air wings, they need to collapse when they get unloaded. Otherwise once unloaded the wing will fall over in front of the pilot and probably get entangled with the pilot. The only heavier-than-air inflatable aircraft currently in production is the Woopy – http://fly.woopyjump.com/ http://fly.woopyjump.com/ – its design is very unconventional, with continuously running pumps and some weird flight control mechanism. It never passed certification because it's probably not as strong as other hang gliders. Some potential problems of inflatable hang gliders: * Ambient air pressure differences at varying altitudes, temperatures, etc. * Bird attack – sometimes eagles and other birds can get aggressive and try to claw a hang glider. What is a minor annoyance now could be a dangerous flaw if your glider is inflatable. * A failed inflatable wing can potentially gift-wrap around the pilot preventing them from throwing the reserve parachute in time. * Less rigidity than metal tubes – danger of buckling at higher speeds / wing-loading. * There's a certain stigma among HG pilots regarding the concept of inflatable aircraft due to controversy around Woopy and the general idea of riskiness. However, inflatable aircraft IS a practical strategy. The shortcomings listed above can be overcome given enough effort. For example, see http://www.prospective-concepts.ch/html/site_en.htm http://www.prospective-concepts.ch/html/site_en.htm – click on Projects / Air / Pneuwing (and other projects). Also, http://en.wikipedia.org/wiki/Goodyear_Inflatoplane http://en.wikipedia.org/wiki/Goodyear_Inflatoplane Lastly, in all likeliness the only advantage of an inflatable hang glider would be portability. I don't think it will end up lighter than a tube+fabric construction. The guys from Prospective Concepts seem to believe that they will achieve better glide performance with an inflatable design, but to be honest I doubt that. But then again, they know much more about their technology than I do.

annnnd 12y ago
Interesting, thanks for the write-up. About the paragliders: you mean when they land? It is true that the landing becomes more challenging, especially in case of wind (kitesurfers often help each other when entering / exiting). But I guess this could be solved - if nothing else, only the central area could be "reinforced". Let's wait a few years, I'm sure someone will try it. :)
- sraquo 12y ago
  No, I mean when the angle of attack of the wing gets too low in flight. This can and does happen due to gusts and thermal activity in the air. Normally a ram-air paraglider wing would collapse at low angle of attack due to lack of pressure inside the wing (it only works in a certain range of angles of attack), causing both the wing and the pilot to start falling, picking up speed and restoring angle of attack, and re-inflating again. It's kinda hard to explain concisely in more detail. With a rigid inflated paraglider wing however, if the angle of attack becomes too low, the wing might get unloaded (falls faster than the pilot) and will pitch down even further because that's what a plank wing does in the absence of pendulum weight provided by the pilot. So the wing dives down and gets entangled with either the pilot, the lines or both. I'm a bit rusty on the exact aerodynamics of paragliders because I only fly hang gliders, but this is roughly what happens. If you want to know more about how ram-air paraglider wings stay inflated, check out this doc – http://downloads.flyozone.com/pdf/PG/ozone_shark_nose_en.pdf http://downloads.flyozone.com/pdf/PG/ozone_shark_nose_en.pdf – it talks about a new ram-air intake technology and explains how ram air wings work.
sraquo 12y ago
I would like to add this document to the case for inflatable hang gliders: http://www.empa.ch/plugin/template/empa/*/107170/---/l=1 http://www.empa.ch/plugin/template/empa/*/107170/---/l=1 Why I am doing this at 5 AM..? I'm insane.

by sraquo 12y ago

annnnd 12y ago

Interesting, thanks for the write-up. About the paragliders: you mean when they land? It is true that the landing becomes more challenging, especially in case of wind (kitesurfers often help each other when entering / exiting). But I guess this could be solved - if nothing else, only the central area could be "reinforced". Let's wait a few years, I'm sure someone will try it. :)

sraquo 12y ago
No, I mean when the angle of attack of the wing gets too low in flight. This can and does happen due to gusts and thermal activity in the air. Normally a ram-air paraglider wing would collapse at low angle of attack due to lack of pressure inside the wing (it only works in a certain range of angles of attack), causing both the wing and the pilot to start falling, picking up speed and restoring angle of attack, and re-inflating again. It's kinda hard to explain concisely in more detail. With a rigid inflated paraglider wing however, if the angle of attack becomes too low, the wing might get unloaded (falls faster than the pilot) and will pitch down even further because that's what a plank wing does in the absence of pendulum weight provided by the pilot. So the wing dives down and gets entangled with either the pilot, the lines or both. I'm a bit rusty on the exact aerodynamics of paragliders because I only fly hang gliders, but this is roughly what happens. If you want to know more about how ram-air paraglider wings stay inflated, check out this doc – http://downloads.flyozone.com/pdf/PG/ozone_shark_nose_en.pdf http://downloads.flyozone.com/pdf/PG/ozone_shark_nose_en.pdf – it talks about a new ram-air intake technology and explains how ram air wings work.

sraquo 12y ago

I would like to add this document to the case for inflatable hang gliders: http://www.empa.ch/plugin/template/empa/*/107170/---/l=1 http://www.empa.ch/plugin/template/empa/*/107170/---/l=1 Why I am doing this at 5 AM..? I'm insane.