[dhmartens]

Actual hang gliders produced by nature.
(with video)

http://news.bbc.co.uk/earth/hi/earth_ne ... 391345.stm

"..They found that design of the seed is so good that it achieves a descent angle of just 12 degrees, a property that has led to the seed's shape inspiring the design of aircraft.
That means it falls just 0.4m each second, compared to 1m per second for many winged seeds that rotate as they fall. .."

[JoeF]

"15 cm" ... big seed glider .. Near 6 inches span!

[wingspan33]

Imagine if an ingenious human being had "reverse engineered" this seed - and created a hang glider 1000 years ago. Consider Leonardo DaVinci having seen this seed fly!

Many "what ifs" surround us every day. What may one of us see (in nature, or elsewhere) that could change the world?

[dhmartens]

If the seed glider has a 6" wingspan, and an average pumpkin weighs between 6 and 18 lbs and the worlds record pumpkin weighs 2032 lbs, then it would be easy to grow a seed glider with a 60' wingspan.

[JoeF]

https://en.wikipedia.org/wiki/Alsomitra_macrocarpa
See Scott Zona's photo at the wiki.

Other related pics and story: http://www.newtonsapple.org.uk/seed-dispersal-on-the-wind/

Prof. Ahlborn had published a paper in 1897, in which he had described the flying seed of Zanonia macrocarpa.[1] Etrich and his co-worker Franz Xaver Wels designed an unmanned glider of similar form and flew it successfully in 1904. Attempts to add an engine failed, but a successful manned glider was flown in 1906.[2]

Igo Etrich making a big glider following the subject seed glider. 1906 circa

glideretrich1906.jpg (172.18 KiB) Viewed 5186 times

https://www.google.com/patents/US952316

Reduced resolution image. See patent PDF for full image and second figure for rib batten patterns. Igo Etrich and Franz Wels, of Oberalstadt, near Trautenau, Austria-Hungary

US952316in1910Etrich.JPG (61.9 KiB) Viewed 5185 times

[Frank Colver]

Aint nature wonderful?

Something that isn't mentioned: The seed itself (weight) is positioned exactly where it needs to be to place the CG in the correct position for a stable glide.

I wonder how many trillions of these fell short until the ones with the proper seed position (CG) became dominant through successful propagation by getting farther from the parent plant? Nature is very good at the trial and error method of design development. Humans can't afford that long process in our machine designs. But we can learn from nature's long process and build on that. And we have! Thanks Otto, ET all, for starting to show us the way by your observations of nature's designs.

If the earth had no birds or insects for us to see flying, we certainly would not be flying now. Maybe a 1000 years from now, when someone discovered flight by accident. Maybe not.

Frank Colver

BTW - I'm glad to be flying again! Been rooted to earth way too long.

[KaiMartin]

Otto, ET all, for starting to show us the way by your observations of nature's designs.

However, its not that simple. For starters, a regular human is significantly more heavy than any bird. Weight matters in this case. There is a reason why elephants cannot jump.

If the earth had no birds or insects for us to see flying, we certainly would not be flying now.

Well, there would still be bats, flying squirrels, flying snakes and flying fish
Without competition from birds the bats probably would have evolved into much greater diversity both in size and style to take advantage of the vacated ecological niches. Along the same line, the earth would still be roamed by pterosaurs if birds had not outperformed them with their more versatile feathers. According to recent finds of palaeontology, many two legged dinosaurs had feathers. Several lines are believed to be capable of flying. All of today’s birds descended from just one of them, the Aves class. If it wasn't for Aves, one of the others would most likely have taken the sky.

Maybe a 1000 years from now, when someone discovered flight by accident. Maybe not.

Hang gliding sort of evolved from kites behind motor boots. Apparently, nature did not find kites useful (yet). BTW, balloons and zeppelins have no obvious analogue in nature, either. Given the many uses the military has for anything that lifts and can attack from above, I'd expect human flight to have been developed in the first half of the century no matter what.

BTW - I'm glad to be flying again! Been rooted to earth way too long.

Congrats!

---<)kaimartin(>---

[ARP]

" Apparently, nature did not find kites useful (yet). "

The ballooning spider sometime called the kiting spider does seem to have done so........

https://www.awesomestories.com/asset/vi ... otte-s-Web

And may be even 'electrostatic' lift for flight :- https://en.wikipedia.org/wiki/Ballooning_(spider)

[KaiMartin]

" Apparently, nature did not find kites useful (yet). "

The ballooning spider sometime called the kiting spider does seem to have done so........

This is very much unlike kiting. There is no kite at the end of the thread. There is no aerodynamic lift involved. There is no force transferred to the ground either, which is essential for a kite to rise.

At the diameter of the thread Reynolds numbers are single digit at best. So the air is viscous like honey to it. In a viscous fluid the dominant force is drag.
A balooning spider manages to generate so much drag with its long thread that it essentially gets carried away by the wind like a much lighter regular dust particle. This feat is awesome in its own right, but it is not related to the principle of operation of a man made kite.

---<)kaimartin(>---

[ARP]

Nature does not understand the terms humans give to describe how something flies. What ever you call the forces involved the spider is lifted into the air by the thread it throws out whilst it is on the ground. The combination of L/D versus gravity are what gets the spider into the air. If the lift is zero then the drag vector must have a vertical component in it, to offset the gravity, which you can interpret as lift.