My goal is to build a pedal-powered hang-glider capable of traveling at least 80 kilometers per hour. Is such a unit possible in principle, or do we need orders of magnitude more power?
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1$\begingroup$ Use your feet to power yourself off a high mountain top. You can probably hit 80 on your glide down. $\endgroup$– JimOct 1, 2022 at 15:12
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$\begingroup$ Sure, a glider, (in descent), but not sustained, level, flight at 80kph. $\endgroup$– Charles BretanaOct 1, 2022 at 15:55
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4$\begingroup$ The fully fairing-enclosed recumbent bicycle is pretty much at the peak of efficiency when it comes to extracting locomotion from a human body. They have extremely low drag and are able to utilize a large percentage of the rider's muscles. The hour record (furthest distance traveled within an hour) is 92 km/h, the instantaneous absolute speed record is ~144 km/h. You are asking to achieve ~60% of the absolute top speed that an elite athlete was able to attain in the most efficient vehicle imaginable, using a vehicle that wastes a significant amount of energy just fighting gravity. $\endgroup$– Jörg W MittagOct 1, 2022 at 22:16
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2 Answers
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A hang glider that weighs, say, 275 lbs, with an L/D of 12, needs 23 lbs of thrust for level flight, or roughly, 4 HP. If you want to be able to climb with a decent rate, you need more than double that, say 10 HP minimum.
A human can make just over 1 HP in a short burst, and maybe a .1 HP sustained for a minute, even less for extended periods.
So yeah, you're off by a couple orders of magnitude. It's only possible by having massively large wings, made from exotic materials to keep the massive wings light enough. For a regular hang glider, even a high end one, foggedaboudit.
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80kph in level flight? No, not with current technology. Current record holder is the Musculair II with 44.26kph. See Human Powered Aircraft.
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$\begingroup$ So after all, I'm talking about a hang glider, and not about aircraft with a rigid wing, and the materials are different now. But speed is not something that is obligatory for me, the main thing is to take off $\endgroup$ Oct 1, 2022 at 14:31
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2$\begingroup$ I think you'll have a harder time with the hang glider than other designs, if hang gliders were much "easier", these human powered aircraft competitions would have a lot more designs like that. $\endgroup$ Oct 1, 2022 at 14:39
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$\begingroup$ @Entaldalpe Your question is contradictory. Are you asking about a foot launched glider, or a human powered aircraft? They are 2 very different things. $\endgroup$ Oct 1, 2022 at 15:48
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3$\begingroup$ @Entaldalpe: "The materials are different now" – Even if you had a magic material that would allow you to reduce the weight of the vehicle to 0, that only improves your efficiency by ~30%. Even with the less advanced materials from 30 years ago, the weight of the pilot is already 2/3 of the total weight, and you cannot eliminate that weight, no matter how exotic your materials are. $\endgroup$ Oct 1, 2022 at 22:23