

Analysis of the Human Bird Wings - mhb
http://www.wired.com/wiredscience/2012/03/analysis-of-the-human-birdwings/

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tokenadult
I had to follow back to the submitted article's author's earlier blog posts, a
couple of degrees of linking back, to figure out where the "log-plot of the
wingspan vs. mass for different birds along with the human with wings" came
from. It came from the author himself, without a validation study, and "anyone
can edit" Wikipedia. People who know their history of physics well will
remember that Galileo showed that in general, as an animal's size scales up,
its mass increases with the cube (third power) of the scale factor while its
surface area increases only with the square (second power) of the scale
factor.

<http://dinosaurtheory.com/scaling.html>

[http://galileo.phys.virginia.edu/classes/609.ral5q.fall04/Le...](http://galileo.phys.virginia.edu/classes/609.ral5q.fall04/LecturePDF/L14-GALILEOSCALING.pdf)

To scale up flight by arm motion to the mass of a human adult would have to
result in a very different wing loading from that of any bird. There is a lot
of hand-waving about electric motor power (at what weight?) for the wings in
the video being discussed here on HN, but no verifiable figures about what
energy is input into the wings versus what weight the total assemblage has.

As astute comments pointed out in the earlier main thread about the video, it
would be easy enough to verify this extraordinary claim just by letting some
professional journalists take a look at the rig and weigh it and photograph it
up close and do their own videography of a set of flights of the rig and its
operator. There is no reason to take an amateur, self-produced video with
unverified claims seriously about an issue that is so contrary to well studied
principles of aeronautics. Until there is better quality evidence, there is no
warrant for believing this extraordinary claim.

~~~
angersock
The electric motors--if using the heavy-duty outrunners mentioned in the last
thread--are on the order of 2-4 kg each, for a total of about 10 lbs. The
weight of the fabric/kite is on the order of 1kg
(<http://www.humanbirdwings.net/about/working-on-the-wings/>).

The batteries appear to be lightweight li-poly packs, so really powerful for
very light weight.

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postfuturist
Ignoring impossible feats of physics, the video is fake. There is a comment on
the first Wired article which points out incontrovertible evidence of poorly
done compositing around the 20 second mark with the guy on the left running
"through" the wingtip without bumping it.

Uncut, raw video from the side of complete take-off and landing (since there
is supposedly someone taking video from the side) would be enough to prove its
real. Too bad this isn't real.

~~~
CognitiveLens
That 20 second mark is pretty damning - the shadow cast on the wing by the guy
on the left is visible before his body is in front of the wing.

Thanks for crushing my dreams.

~~~
postfuturist
My pleasure. I worked on the visual effects team for a movie with a _lot_ of
compositing. This is cut-rate stuff. Can you imagine what sort of things we
will believe if someone were doing this sort of fakery with a real budget?

~~~
CognitiveLens
Exactly - I read the Wired article yesterday and didn't even think to second-
guess it even though in general I'm something of a skeptic. I just marveled at
how clever and technologically advanced humans have become.

Ironically, this _is_ a demonstration of how clever and technologically
advanced we are, but not in the way I originally thought!

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mcdillon
His take off speed and the angle of attack for his wings looks suspect. As
much as I want this to be real it looks like he is in a stall the moment his
feet lift off the ground. I am looking at this from a traditional fixed wing
aircraft view though so my views could be flawed.

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JackC
_"Either this part of the video was made with a real hand held camera, or they
have found better ways to 'fake shake' the video."_

Good fake camera shake isn't too hard. After you take your tripod shots to add
CGI to, also take some actual shaky footage of the same scene, or of anything
else about the same distance away. Then motion-track the shake from your shaky
footage and apply the same motion to your CGI shot. High-fives all around.

In conclusion: unrealistic camera shake would tell you something, but
realistic camera shake doesn't tell you anything. It's like, "yep, these look
like real people rather than cartoon characters, so this definitely wasn't
faked using old Simpsons episodes ..."

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marknutter
All of this discussion is a complete waste of time. The burdon is on the
publishers of this video to demonstrate these wings in front of a live
audience of reputable journalists and engineers. Until then, can we move on?

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ck2
Wouldn't you FIRST test the ability to glide back down before you add motor
and power to get in the air?

The lack of any video gliding down from a building etc. immediately made this
extremely suspect for me.

Then the fact I use an electric bicycle with a 48volt 1kwh battery for long
distances. It's lithium but it's still big and EXTREMELY heavy. So is the
motor. And those wings would need even more battery and more powerful motors.

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hcarvalhoalves
What's up with all the people trying to discuss the physics involved? The
video is blatantly fake, for other reasons entirely: the obvious viral factor,
shady YouTube channel, bad acting, fake camera movement, etc. This thing is
probably a Red Bull viral, inspired by that other "walking on water" viral.

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xutopia
A lot of people don't realize that there are motors on his backpack that power
the wings. The movement of the arms guides the brushless motors using
components seen in the Wii controller and only marginally assist the power
sent to the wings.

~~~
Sapient
That, and the perspective as he runs on the "takeoff" is completely out of
whack.

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angersock
Previous night's discussion with something more than just "I can tell from
some of the pixels."

<http://news.ycombinator.com/item?id=3732385>

It may be fake, but it isn't impossible.

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bh42222
Absolutely fake. If this is not obvious to you, learn more physics.

~~~
CrownStem
It looks as if the author -did- look at the event with a fairly in-depth
analysis, and the results were plausible yet inconclusive.

~~~
mcdillon
His results seem to suggest that the video wasn't CGI'ed, correct?

~~~
drostie
Well, no. They suggest that the camera shake wasn't added in after the fact
with postprocessing of an existing image -- or at least that the image was
fairly high-res and blur was also added after the fact. He doesn't rule out
that the whole video wasn't computer-generated, nor that the dude was running
into a greenscreen, nor for that matter a green cable that was digitally
altered out, or anything like that. Some of these would venture into "faked"
as opposed to CGI -- a cable which did not need to be shopped out might be an
example, although whether you could have a nice construction crane nearby to
operate it would be a worthwhile question, since the video doesn't give it
much place to hide and the larger it is the more dangerous it would be to hang
someone off of it and then move it from point A to point B.

~~~
angersock
There is a very real possibility that the wing was pulled by a cable. The kite
adapted is actually one of those ones you usually pull behind a boat and which
glides you up into the air.

~~~
drostie
That's also something I haven't considered. Whether or not this was really
done, if you wanted to create the same effect by faking it, you could do it at
least in part by doing two different "takes" -- one where you pull the guy
from the front and view with a camera behind him, and another where you pull
the guy up from behind and view with the camera on his head. There is a blurry
whitish splotch when he first gets air which could be a tree in the distance,
but if you wanted to fake it, that could be a way to disguise the cable.

This would give a plausible way to fake the first and the last scenes, where
you see the man from behind, as well as the "in the air" scenes where you just
see from his perspective: you could in principle put him in a boom lift
vehicle -- perhaps suspended from it or perhaps even just sitting in it -- and
the image would look very similar.

The side-view shot would be much more difficult to fake.

