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Paraglider looks like a rather simple device for me. It does not have a complex engine that needs lots of technology to be built. It also does not need a powered aircraft just to be launched. Looking from the side I have an impression that it can cover serious distances along the ridge under right wind. While it is not convenient to have the airways bound to mountain ridges, it could still have had uses like patrolling borders or similar.

I am surprised, why the master that could build a bow, or possibly sails for the ship could not build a paraglider many years ago. What are the reasons why the paraglider is relatively recent invention? Is there something complex about is I am not aware of?

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  • $\begingroup$ Just a thought, since you don't know the subject. Do you actually mean a paraglider, or do you mean a hang-glider? The two are radically different aircraft! $\endgroup$ – Graham Mar 24 at 8:53
  • $\begingroup$ Hang glider has aluminium alloy or composite frame so I understand it requires advanced technology. It is not just silk and threads. If to make from wood, it would be a glider but probably too heavy for launching on foot. $\endgroup$ – h22 Mar 24 at 8:59
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    $\begingroup$ @h22 Modern hang gliders were built with bamboo or spruce frames and plastic tarp material for about a decade before they started appearing with aircraft tubing frames and ripstop nylon sails. $\endgroup$ – Zeiss Ikon Mar 24 at 12:31
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    $\begingroup$ @h22 You have that exactly reversed. Otto Lilienthal built and flew hang-gliders made of cloth and light wooden canes, back in the 1890s. His problem was the aerodynamics and weight-shift control authority, but there was absolutely no problem making it fly. In the 1960s, hang-gliders based on the Rogallo design again just used bamboo and tarps, with aluminium where available. Hang-gliders are relatively simple in concept and need relatively slack tolerances, at least if you're not building a serious racing machine. $\endgroup$ – Graham Mar 24 at 14:43
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    $\begingroup$ @h22 ... Conversely a paraglider is right up against the limits of aerodynamics, and the ram-air structure makes it very complex. It also needs very, very light fabric to allow the ram-air structure to inflate, compared to a regular chute which can get away with heavier fabric because you're just on a one-way trip down. Before the discovery of artificial fibres such as nylon, even the finest silk might not be light enough. $\endgroup$ – Graham Mar 24 at 14:47
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Paragliders as we know them depend on parawings with relatively high glide ratios and useful levels of steering. Neither of these qualities were well represented in the round parachutes (even the so-called glide 'chutes) in common use before modern flat canopy glide parachutes came along (in the 1970s?). Parawings as we know them were an outgrowth of these highly maneuverable parachutes, modified to have lower loading (for better sink rate) and optimized for horizontal flight, without the need to open in a near-vertical fall at terminal velocity.

If the knowledge had existed, parawings as we know them could have been built as early as the 1860s (when plain, round, uncontrollable silk parachutes came into use for stunt jumps from balloons). The missing ingredient, as it were, was simply the knowledge that such a thing was useful and possible.

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    $\begingroup$ Silk, as used for balloon envelopes, could have filled both roles in the 1860s. Lines might need to be a bit larger than Kevlar for the same load, and you'd want to avoid getting the thing wet (silk stretches when wet), but balloon silk, sewn with silk thread, and silk cordage could do the job. $\endgroup$ – Zeiss Ikon Mar 23 at 13:53
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    $\begingroup$ "Possible" -- possible for birds and possible for humans are very different conditions. The principles underlying heavier than air flight were still very mysterious in the 1860s. They weren't even fully understood in the early 20th century when everyone with a lot of money and a sense of adventure was building widowmaker airplanes. $\endgroup$ – Zeiss Ikon Mar 23 at 16:18
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    $\begingroup$ I was jumping at the start of the Ram Air revolution in the mid-late 70s, when a 7 cell canopy called the Strato Cloud was all the rage. I had a Paracommander, the heavily slotted round canopy that was most popular up to that time, and which could glide about 1/1. The Strato Cloud had an LD of a rogallo hang glider, about 4 or 5/1. I couldn't afford a Strat. An up to date rig with an SC, tandem container with single-point cutaway system, and tri-conical reserve was about 3-4k in 1977 dollars. You could buy a small car for that. $\endgroup$ – John K Mar 23 at 18:23
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    $\begingroup$ I think the parawing is safer than the Pinto @ZeissIkon! $\endgroup$ – GdD Mar 23 at 19:55
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    $\begingroup$ @ZeissIkon That doesn't make them simpler, it just makes them different. The challenge with a paraglider is stopping it collapsing in turbulence. They need millimetre-accurate Kevlar lines, and some really complex aerodynamics, and that's why so many paraglider pilots died in the 80s and 90s. $\endgroup$ – Graham Mar 23 at 23:11
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Ancient manned flights used either "birdman" wings or kites. Nobody even understood the problem of control, never mind solved it, and both were often fatal, birdman wings especially.

That did not change until in the first part of the 19th century Sir George Cayley defined control as a specific problem to be solved, and that would take almost a hundred years more. Meanwhile, early attempts at parachutes were uncontrollable and swung wildly, sometimes fatally.

But even kites still had rigid sticks to hold their shape, the idea of a wholly non-rigid aircraft, shaped by the airflow, seems not to have appeared until kiting enthusiasts Francis and Gertrude Rogallo came up with it shortly after WWII. The control system was key to making it work. I am not sure who first invented the parawing, but Francis Rogallo subsequently adopted the technology in his day job, designing lightweight spacecraft recovery systems, and went on to popularise it along with other kite-derived flexible wing forms. For a time both the parawing and the biconical delta (the latter patented by others back in 1909 and 1910, and as a kite just a year before the Rogallos' unrelated patent) were known as "Rogallo wings".

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    $\begingroup$ It was less than one hundred years from Cayley's carriageman quitting his job (because Cayley's flying steam coach nearly killed him) to the First World War, by which time the control issue was undeniably solved. $\endgroup$ – Zeiss Ikon Mar 23 at 17:51
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    $\begingroup$ Woops, Cayley's was a glider, but Cayley was born only just over a century before the Wrights demonstrated controlled powered flight. $\endgroup$ – Zeiss Ikon Mar 23 at 18:06
  • $\begingroup$ Well spotted. I have corrected my timing. I suppose that "almost" is a matter of opinion. $\endgroup$ – Guy Inchbald Mar 23 at 19:10
  • $\begingroup$ Thanks! I was surprised to find out that basically history of early aviation is 'waiting until everyone realizes the real problem to solve is control' - that's what Wright brothers did (plus finding a light enough engine). $\endgroup$ – Tomáš Kafka Apr 9 at 8:27
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An airfoil made only of textiles consists of many air cells which are open at their leading edge.

"it's easy to make an airfoil from only strings and textiles and make a parachute", is perhaps not so easy! it's non-obvious idea which is complex in design.

The first guy to fly a parachute thought of it when he wanted to escape his jail cell. after he was freed he pursued the idea until he had the first jump from a hot air baloon in 1797. it took 153 years until the parachute was shaped like an airfoil, because airfoil technology was developed in the 1900's.

https://www.history.com/this-day-in-history/the-first-parachutist

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    $\begingroup$ This is a great answer, it may even be that the right one! $\endgroup$ – h22 Mar 25 at 6:44
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  1. Material:

You cannot build today's paragliders without modern materials The ropes need to withstand several kN of force while keeping diameter to a minimum to reduce drag. The glider must be almost impenetrable for pressurized air, which is impossible with cotton. If you build a paraglider with classic materials, it will be too heavy to fly and way too prone to collapse mid-air.

  1. Computers:

Paraglider started as a high-risk equipment back in the 80s. They used to have glide ratios of 2:1 which allowed steering away from steeper mountains, but that's it. Today we can actually fly with glide ratios of 8:1 and up, but those where only possible with extensive computer simulations. Another aspect is safety: Today's entry-level paraglider can sort out all but the most severe disturbances without human intervention, thanks to extensive simulation. Back in the days catching a harsh turbulence meant deploying your reserve chute, if you where lucky enough to have one.

So simply put, a paraglider looks simple, but is fairly complicated. We do annual checks where we measure the individual ropes' length, knowing that a single inch of stretch could alter the flight characteristics to a fatal degree - it's easy to see that it was troublesome to find these perfect proportions.

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  • $\begingroup$ Is it really true that computer modelling is extensively applied to the design of modern paragliders? That would seem to be extremely challenging due to the extreme flexibility of the aircraft; my understanding that it is not much applied to the design of modern hang gliders. Could be the basis for another ASE question; if you have some knowledge on this you could ask and self-answer. $\endgroup$ – quiet flyer Mar 26 at 15:48
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    $\begingroup$ @quietflyer As an active paraglider pilot I followed the development of ever better wings over the years, and remember that all companies attributed that to "better software", but struggle to find solid sources right now. You mention that this would be challenging - it surely is - but it would be even more so to do it with bare trial&error. $\endgroup$ – Zsolt Szilagyi Mar 28 at 0:01

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