[JoeF]

Flight by bats, birds, and insects
(during the study, look for insights affecting recreational hang gliding)

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Start:
Animal Flight: Wing Structures and Wingbeat Mechanisms


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A Portrayal of Biomechanics in Avian Flight


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Humans in recreational hang gliding mostly do not invest in muscle mass to do wing flapping. Recreational hang gliders mostly do not power flight by flapping, but relies on gravity to propel the flight system through the air while sinking; when sinking in rising air flight time may be extended.

[JoeF]

[JoeF]

[JoeF]

[JoeF]

Nova's long feature:



[The fifth time: the caterpillar disappears ...
No longer walker, but now a pilot that glides much ... ]

Soaring is key to the monarch's long journey to Mexico.

Recreational hang gliding's future history might have an instance where someone follows some monarchs from Canada to one of the 12 special places in a certain area of Mexico.

[KaiMartin]

Flight by bats, birds, and insects
(during the study, look for insights affecting recreational hang gliding)

The flight of insects is very much unlike the flight of large birds. This is not a fluke of evolution. But there is a fundamental physical reason: Size matters.
The air treats insects quite a bit differently than larger creatures. To be more precise, the Reynolds number (Re) of the problem matters. This is a figure which scales with air speed and size of the wing.
For most insects the Reynolds number is in the range of Re = 100 to Re = 1000. By contrast, a hang glider operates at Re = 100 000 and above. Airfoils and more importantly, movements need to be appropriate for the Reynolds number at hand.

There is a second reason why size matters for flight heavier than air: The strength of a muscle is roughly proportional to its cross section. This area grows with the square of the size of the creature. But the volume of the muscle grows with the cube of its size. This is why ants can carry loads 50 times their own body weight while we humans feel hauling a 45 kg glider to the start is already close to the limit. It is also the reason why ants have no trouble running up a tree at full speed while we humans consider rock climbing an exhausting activity.

Consequently, a common fly scaled to the size of a hang glider would not be able to fly at all. It probably would already have a hard time to lift its belly from the ground.

If we ask mother nature for tricks and tips on how to fly, the answer is very probably to be found among large soaring birds. Condor, eagle, vultures and of course the fabulous albatross are the usual suspects.

Humans in recreational hang gliding mostly do not invest in muscle mass to do wing flapping. Recreational hang gliders mostly do not power flight by flapping, but relies on gravity to propel the flight system through the air while sinking; when sinking in rising air flight time may be extended.

Unfortunately, at the size of a human the mechanics required to perform an efficient flapping tends to cost more in terms of weight than the flaps thrust can gain.

That said, I am a big fan of gleaning tricks from nature. After all, evolution spent literally millions of years optimizing the performance.

---<)kaimartin(>---

[ARP]

Large diameter slow revolving propellers are more efficient than fast moving short diameter propellers hence the large propellers used on HPA's. As whales and dolphins use a form of flapping motion using their tails then a similar propulsion system might provide the means for a human pilot to propel a light weight hang glider through the air. Using the whole body with a simple crank operating a flexible shaft on which a wing equivalent to a whales tail would provide the thrust. The cadence of the wing movement should be matched to the pilots movement providing the thrust to overcome the air resistance of the air to the craft. I guess about 20-30lbs of thrust would be required. An undulating flight motion might result as with some bird flight but hopefully motion sickness would not be a problem. Take off from the ground might be tricky but a hill launch could get the craft into the air before flapping begins. No experiments conducted so far but another one of those 'to do' projects that never seem to get to the top of the pile.

Tony

[JoeF]

Gem offers by KaiMartin and ARP ! Those insights surely will be followed and deepened as recreational hang gliding moves through the coming decades.
Re awareness! Very slow flight opportunities!
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MothWingPart.JPG (30 KiB) Viewed 4432 times

look for insights affecting recreational hang gliding

Examining the strategy of the monarch butterflies to travel may give insight affecting recreational hang gliding. Pause in XC to fetch nectar and water. Use some winds and not other winds. Have a destination and stick to the plan as best possible. Gather in appropriate places. Trespass gently and bless observers with color delights.

Recreational hang gliders (RHG) may grow keen in watching the wafted direction of insects, the trending directions of soaring birds, and the timing of flapping-non-flapping of birds. Recognizing that insects may down a hang glider pilot could move RHG pilots to wear goggles and design flight clothes to keep flying insects out of interiors (very especially those insects that may bite and sting). Land not into bee hives! Is the flight plan going to involve mosquitoes. Insect distractions at launch? Insect presence in thermals? Bird-thermal indicators?

The lore of a particular insect, bat, or bird seems to attract some RHG pilots to name their hang glider wings after the creature: Wasp, Falcon, Bat, Seagull, ...

Decorating hang gliders' wings, tents, clothes, cars, harnesses, bags ? Patterns found in the insect world may inspire the artists in us or those serving recreational hang gliding.

Gifts from recreational hang glider pilots to others could carry art and image inspired from the insect and bird and bat world. Have a drink HERE.

[KaiMartin]

Here is a collection of bird features I feel are both feasible and potentially beneficial for some kind of "new" hang glider:

a) Feathers
* Feathers are way more modular than a sail.
* A wing made of feathers rather than a continuous sheet of sail cloth does not require lateral tension. Compared to flex wings or rigids this eliminates the main constraint for the stability of the airframe.
Less stringent mechanical requirements on the frame can be exploited for less weight, or joints to quickly fold and unfold. This is actually the next feature I'd like to see adapted from birds.
* Bird feathers are not made of advanced materials with incredible high tensile strength or hardness. They consist of keratin, which is literally the same stuff as our finger nails. Bulk properties of almost any human made plastic has comparable or better bulk properties. Sure enough, bird feathers play tricks with intricate three dimensional structuring. Man made feathers for a hang glider may compensate by using composites of different materials. Maybe a carbon tube for the rachis and Mylar covered Styrofoam for the vane.

b) Mid wing joints.
* traditional HG come with just one joint -- the big one at the nose. Consequently, it can readily fold and unfold in half. This results in the famously 6 m long packages.
Add two more joints span-wise like birds and bats do and the package is at about 2m. Big difference in the required travel logistics.

c) Pitch instability
* No bird and no bat soars with a pitch stable configuration. There are probably good reasons why mother nature universally opted for stabilization by permanent pilot (brain) input. IMHO, this is because instability offers both superior agility and efficiency. We humans are well equipped to stand and walk on two feet. So we may "just" need a proper handle bar.

d) Wing warping for roll control
* Warped wings should allow for super fast roll rates compared to weight shift induced differential sail tension.

e) A horizontal tail, close to the main wing for yaw control.
* Unlike a traditional tail plane such a tail would add to the total lift of the wing.

f) Align the pilot with the wing rather than have him dangle from a single point.
* This is probably a requirement to be able to deal with pitch instability. The pilot must reliably feel the current orientation of the wing so he/she can react properly.
* I imagine, being attached to the wing will induce an even more immersive sense of flight.

g) A straight wing without vertical control surfaces.
* A straight wing supported by a spar at the aerodynamic centre of the airfoil can bend under load without excessive reduction of lift. This should allow for more light weight construction.

If all of these traits were united, the glider would look suspiciously like an oversized bird :^)

---<)kaimartin(>---

[Bob Kuczewski]

If all of these traits were united, the glider would look suspiciously like an oversized bird :^)

---<)kaimartin(>---

Some things are difficult to improve!!