human powered flight

"patrick timony" wrote in message
m...
wrote in message
...

I think the HPOs like the English channel one, require so much energy
because they are not using their weight efficiently. The style of
natural flight they are trying to imitate is soaring. I am talking
about hovering flight like a bumble bee or a humming bird or a
butterfly. The butterfly is really important I think because it has
low aspect ratio wings and if you watch them you can see that they're
moving just like a swimmer doing the "butterfly", which is sort of how
I think a human powered stroke would have to work. But I think we are
built more for the crawl stroke or a combination of the breast stroke
and the crawl, becuase our legs are so much more powerful and the leg
stroke would have to support most of our weight. I think the stroke
that would work best would be one that allows the flyer to adjust the
speed and style of each limb to support his body maintaining a certain
position in the air. This would probably look like three dimensional
running. Actually it would probably look pretty much like an
exagerated doggy paddle, if you've ever seen a dog swimming in place
in the water.

All the Ornithopters I have seen on the net are using bird=like or
dragonfly=like wings. I think they should lower their aspect ratios,
start thinking about vertical take off, and use curves, concave
surfaces, and even spirals in their wing design.

Patrick

Have you ever seen a three-hundred pound butterfly?

Butterflies fly very nicely down in the low Reynolds number regime -- where
the air behaves more like honey -- using the "clap - fling - ring"
mechanism.
Their wings touch at the top of the stroke (the "clap"), then are peeled
briskly away from each other to start the circulation around the wing (the
"fling"), and at the bottom they touch again, shedding a vortex ring
downward (the "ring"), which pushes them upwards. They may or may not hold
the wings out midway on the upstroke for a short, fairly steep (but low sink
rate) glide.
This flight mechanism is why their flight path looks so erratic.

Other insects have waxy pads on the bottoms of their feet and can walk on
the surface tension of the water. But buttering up your tootsies won't let
_you_ walk on water, because some things just don't scale.

Tim Ward