0620: "Wings"

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knight427
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Re: "Wings" Discussion

Postby knight427 » Fri Aug 07, 2009 6:26 pm UTC

Cedric Tsui wrote:What's more.

Hot Glue melts at 250-380°F. There would be a little bit of burning skin.


But when does it begin to lose strength
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Re: "Wings" Discussion

Postby Werewolf » Fri Aug 07, 2009 6:31 pm UTC

The man in the black hat is AWESOME. I love all his comics. Especially "Journal". (Glances at avatar.)

(Oh, and one last thing. Neoliminal just failed hard, by completely missing the point of the joke and pointing out how it could have been funny (The way that it already was.) That is all.)

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Re: "Wings" Discussion

Postby lihan161051 » Fri Aug 07, 2009 7:00 pm UTC

nbonaparte1 wrote:A couple hundred cubic miles of oxygen and a match and Titan's atmosphere goes bye bye.


Or becomes a few hundred cubic miles of CO2 and H2O, and a whole lot of heat and noise, and maybe some wind. ;)

(It would release a bit more energy than that if the atmosphere actually went bye bye.)

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Re: "Wings" Discussion

Postby lihan161051 » Fri Aug 07, 2009 7:05 pm UTC

Sucram wrote:What one needs to do this effectively is a modified "auto-belay". Otherwise as soon as he flaps his wings the effect the bricks are having on him will change.
Ok..more to the point.. it won't be consistant like atmospheric pressure and gravity. With the autobelay, one simply adjusts the settings and hey presto it pulls 91% of your mass regardless of how high you are or if you're flapping. When you flap, you'll go up, you can glide and you can fall...but more slowly.

Feel free to contradict my hypothesis.
Or to supply me with your skill in adjusting auto-belays...I have the device but not the brains.


Or a cylinder with a really, really long piston travel, and a vacuum pump ..

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Re: "Wings" Discussion

Postby Rufaellie » Fri Aug 07, 2009 7:09 pm UTC

Most awesome.

But somehow when I got to the ending the first thought that came to my mind was Mr. Mister: "So take, these Broken Wings, and learn to fly again..."
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Re: "Wings" Discussion

Postby lihan161051 » Fri Aug 07, 2009 7:23 pm UTC

thicknavyrain wrote:Does anyone else remember Randall discussing this very same concept at one of his talks for MIT? Atleast I think it was, or maybe Google. Seriously this EXACT idea was drawn out and brought up. Anyway, very, very awesome comic, although even if the wings fell off I'm sure his descent would be a lot slower than usual so BHG isn't that much of a dick after all.


Depends on how much the wings weigh, since the bricks are counterbalancing both the guy flying and the wings. When the wings fall off, if enough mass falls out of the system with them, the bricks might actually almost exactly counterbalance, resulting in no fall at all. Of course, BHG's natural reaction to cheerfully flipping him off from that hanging position would be to cut the rope .. :D

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Re: "Wings" Discussion

Postby Kadzar » Fri Aug 07, 2009 7:23 pm UTC

Decorian wrote:He does seem to be flying in a circle. But that would probably be harder as you would then have the problem of the rope not being perfectly vertical, and you would need to take into account that reduced lift in the weight of the bricks.

A simpler option would be to just fly vertically upwards by flapping with a hummingbird style forwards and backwards power strokes. Of course then you'd need an extra 'wing' or tail between your legs to stabalise yourself.


Okay, you do realize no human could actually do this, right? Hummingbirds can flap their wings several times per second. They can do this because they have a very high metabolism which eventually kills them.
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Re: "Wings" Discussion

Postby lihan161051 » Fri Aug 07, 2009 7:30 pm UTC

knight427 wrote:
Cedric Tsui wrote:What's more.

Hot Glue melts at 250-380°F. There would be a little bit of burning skin.


But when does it begin to lose strength


Consider what it takes to disassemble a golf club: a vise with wooden jaws, a very strong spring, and a heat gun.

Chuck the club shaft in the vise with the spring compressed between the vise and the club head, and heat the shank of the club head with the heat gun until the epoxy lets go, catapulting the club head across the shop.

I s*** thee not, that's actually how they do it. And the temperature it took seemed to me to be well below the temperature required to actually melt the epoxy, depending on how far the spring was compressed.

No, don't try that at home either. Especially not with your dad's golf clubs. :D

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Re: "Wings" Discussion

Postby Griffin » Fri Aug 07, 2009 7:31 pm UTC

I was under the impression Icarus lost his wings by flying to low, not to high - that it was the moisture from the ocean that caused them to fall apart.

Or am I just horribly mangling the story in my memory?
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Re: "Wings" Discussion

Postby lihan161051 » Fri Aug 07, 2009 7:48 pm UTC

Kadzar wrote:
Decorian wrote:He does seem to be flying in a circle. But that would probably be harder as you would then have the problem of the rope not being perfectly vertical, and you would need to take into account that reduced lift in the weight of the bricks.

A simpler option would be to just fly vertically upwards by flapping with a hummingbird style forwards and backwards power strokes. Of course then you'd need an extra 'wing' or tail between your legs to stabalise yourself.


Okay, you do realize no human could actually do this, right? Hummingbirds can flap their wings several times per second. They can do this because they have a very high metabolism which eventually kills them.


Well, our metabolism eventually kills us. It just takes longer.

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Re: "Wings" Discussion

Postby highlyverbal » Fri Aug 07, 2009 7:49 pm UTC

I second the motion that the joint conditions of a) using glue and b) having mythy friends only is ONE problem.

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Re: "Wings" Discussion

Postby Kalos » Fri Aug 07, 2009 7:57 pm UTC

Griffin wrote:I was under the impression Icarus lost his wings by flying to low, not to high - that it was the moisture from the ocean that caused them to fall apart.

Or am I just horribly mangling the story in my memory?

I've heard so many different versions of this story, but if I recall, the "official text" states that he was warned not to fly too low neither too high, though flying too high was what got him killed.

Randall continues his trend of heavy-handed dialogue, but he did bother to draw something this time (and it looks good.. we like it when you draw something, keep doing that), and the joke was fairly clever.

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Re: "Wings" Discussion

Postby Sprocket » Fri Aug 07, 2009 9:12 pm UTC

There are people who aren't into Greek Mythology?
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Re: "Wings" Discussion

Postby Tenth Speed Writer » Fri Aug 07, 2009 9:16 pm UTC

For non mythology geeks: Google Daedalus and Icarus.


For all else: 5 points to anyone else who immediately jumped to the Iron Maiden song.
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Re: "Wings" Discussion

Postby drewster1829 » Fri Aug 07, 2009 9:20 pm UTC

dcxk wrote:
According to Henry Petroski, modern accident reconstruction investigators have determined the altitude that Icarus must have been at and the temperature would have been very cold.
Classical retcons are not allowed. Obviously Icarus flew (holding his breath mind you) out of earth's atmosphere to the sun (to a proximity sufficient to melt the wax), whence he was slungshot back to earth, only to fall to his death in the exact same inertially translated coordinates which he would have reached had he merely fallen.
It's the only historically correct and scientifically consistent explanation!


How did he "fly out of Earth's atmosphere to the sun"? It's a little difficult to provide sufficient impulse with his wings without air to push against...perhaps an extended bout of flatulence propelled him? :wink:
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Re: "Wings" Discussion

Postby Ghavrel » Fri Aug 07, 2009 9:21 pm UTC

pueben wrote:The ending is a reference to Greek mythology characters Daidalos and Ikaros. Daedalus was a "skillful artificer" who created wings for his son Ikaros, who then flew too close to the sun.
...
His nearness to the devouring sun softened the fragrant wax that held the wings: and the wax melted: he flailed with bare arms, but losing his oar-like wings, could not ride the air. Even as his mouth was crying his father’s name, it vanished into the dark blue sea, the Icarian Sea, called after him.


I'm not complaining at all, mind you, but I'm fairly confused as to why you reference Ovid, and use a translation of Ovid, but refer to Daedalus and Icarus with a transliteration from the Greek. :|
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Re: "Wings" Discussion

Postby Meat_Grinder » Fri Aug 07, 2009 9:51 pm UTC

Alright, I'm here to spoil all the fun.
How come the bricks are not in the air?
It's got to be a powerful laser, not a heat lamp.

On topic of dieing.
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Re: "Wings" Discussion

Postby uggie » Fri Aug 07, 2009 11:48 pm UTC

The physics is wrong. Lift=Weight or you go splat. The density of the atmosphere has nothing to do with that fact (unless you happen to be noticeably buoyant at those densities...). What does change is the velocity you need in order to generate adequate lift. Since the dynamic pressure goes as the square of the velocity and is linear in density:

Lift=1/2*rho*V^2*A*Cl so:

Lift_earth=1/2*rho*Ve^2*A*Cl
Lift_titan=1/2*1.5*rho*Vt^2*A*Cl

Dividing (titan over earth is easier) the two cancels all of the terms except the velocities:
.14/1.5*Ve^2=Vt^2 or velocity required for stable flight on titan is ~30% that of earth with the same wings.

I think where the 9% comes from is contrasting the Velocity ratios for earth normal density versus what titan has (.14/1.5). Either way, you still need Lift=weight=14% of earth weight. :D

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Re: "Wings" Discussion

Postby smiffy » Fri Aug 07, 2009 11:57 pm UTC

Two things occur to me in this discussion about flapping about in a thicker atmosphere.

I have read accounts about people doing "dry-dives" in hyperbaric chambers, undergoing hyperbaric therapy (e.g. Recompression for the DCI/The Bends) or operating in pressurised chambers (Caissons)used for digging tunnels and bridge-foundations underwater. The last of these were extensively used in the great civil engineering projects of Late 19th-C London and New York.
A paraphrase of a Victorian Gent who took a picnic while visiting a caisson wrote:After we stepped into the airlock, more air was pumped in. We grew uncomfortably hot. When we tried to fan ourselves with our newspapers, the air was so dense that they shredded. The champagne that we brought with us was flat, and we were obliged to use corkscrew upon the stopper. The flavour was markedly different, too. Our post-postprandial cigars burnt like fireworks and the smoke was uncomfortably hot and bitter upon the palate.
(IIRC the workings were roughly 20m (70ft) of Sea water, so about 3 Atm absolute pressure)
I missed out on a similar Dry-Dive, when some members of my dive club visited the DDRC in Plymouth, as it would have interfered with a wet-dive later on.
(They didn't smoke, and drank cola instead of champagne, they reported extreme belching when pressure was released again!)

The take home message is that there will be greater strain on the wing surfaces and joints in thicker atmospheres.

Secondly a friend of a friend has this to say:
major_clanger (an LJ user) wrote:At 95K, Titan is about 2.8 times colder in absolute terms than Earth, so for a given pressure the atmosphere is 2.8 times denser. Given that the surface pressure on Titan is 1.4 times that on Earth (the comic gets the number right, just not what it refers to) then Titan's atmospheric density is four times that on earth. With the gravity being a seventh what is is here, it thus ought to be about thirty times easier to fly (although the increased density means extra drag as well).

A hot hydrogen balloon ought to work really, really well on Titan!

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Re: "Wings" Discussion

Postby lordlicorice » Sat Aug 08, 2009 12:51 am UTC

knight427 wrote:leaving you with no counterweight to slow your decent.

It took me a minute to decide this is accurate. I was missing the fact that the counterweight does work against gravity :oops:

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Re: "Wings" Discussion

Postby Faranya » Sat Aug 08, 2009 1:55 am UTC

You know, the better solution to this, instead of using a random pully system, is to go to Titan.

Come on we can do it.

We almost have the technology.
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Re: "Wings" Discussion

Postby Achmos » Sat Aug 08, 2009 6:17 am UTC

Tenth Speed Writer wrote:For non mythology geeks: Google Daedalus and Icarus.


For all else: 5 points to anyone else who immediately jumped to the Iron Maiden song.

Yay! I earned 5 points by being a metal-head! :D

This was a very good comic, mainly because it had greek mythology being referenced in it.
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Re: "Wings" Discussion

Postby SEE » Sat Aug 08, 2009 7:59 am UTC

knight427 wrote:
Omegaton wrote:
And yes, Godwin's Law strikes again...


Actually Godwin’s Law does not apply when you are literally referencing Nazis. It occurs when you compare another poster to Hitler/Nazis to discredit and insult them. At least that's how I understand it.


Only a Nazi would say that Godwin's Law doesn't apply.

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Re: "Wings" Discussion

Postby ironkurton » Sat Aug 08, 2009 8:26 am UTC

I got this feeling that this was a very vague reference to Defcon 17. Greek Myth (Myth = Adam Savage), Rope dangling from a high place (idiots trying to bunjee jump off the Riviera), plus people getting arrested (said idiots). I may just be reeling from last weekend too much to let it go.

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Re: "Wings" Discussion

Postby WhiteAvenger » Sat Aug 08, 2009 9:17 am UTC

Concerning the paranthesising of the alt-text: I'm for
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Re: "Wings" Discussion

Postby Deus » Sat Aug 08, 2009 1:08 pm UTC

Oh Deadelus and Icarus you crack me up.

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Re: "Wings" Discussion

Postby haruspex » Sat Aug 08, 2009 5:12 pm UTC

I think a lighter-than-air balloon would be a better method than rope/pulleys/bricks. Granted, the bridge provides the platform (both literal and metaphorical) for the mythology reference.

Bonus points for a vacuum balloon, although you would first need element 404, unobtanium, in order to contain the vacuum.

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Re: "Wings" Discussion

Postby Platypodes » Sat Aug 08, 2009 7:49 pm UTC

Meat_Grinder wrote:Alright, I'm here to spoil all the fun.
How come the bricks are not in the air?

He's not done setting it up yet in panel 4. Notice that he's not wearing his wings and that he's only holding the rope in his hands, not harnessed to it.

I would assume he hoisted the bricks up, tied the rope on, and cut off the extra rope. If he had started with a rope that was too short to reach the ground at both ends, the setup process would have been a good deal more troublesome.
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Re: "Wings" Discussion

Postby knight427 » Sat Aug 08, 2009 8:35 pm UTC

SEE wrote:
knight427 wrote:
Omegaton wrote:
And yes, Godwin's Law strikes again...


Actually Godwin’s Law does not apply when you are literally referencing Nazis. It occurs when you compare another poster to Hitler/Nazis to discredit and insult them. At least that's how I understand it.


Only a Nazi would say that Godwin's Law doesn't apply.


Now, there's someone who know how to Godwin!
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Re: "Wings" Discussion

Postby phillipsjk » Sat Aug 08, 2009 9:00 pm UTC

SecondTalon wrote:
Ghavrel wrote:Being a Liberal-Arts Major, interpreted the comic from a post-colonial perspective.
You!

Yes you!

I like you.

:shock:

Me too.

The actual disclaimer says:
XKCD wrote:Warning: this comic occasionally contains . . . advanced mathematics (which may be unsuitable for liberal-arts majors).


The disclaimer does not say liberal-arts majors are unwelcome; just that the advanced mathematics may be hard for them to understand.
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Re: "Wings" Discussion

Postby Deus » Sat Aug 08, 2009 9:39 pm UTC

Tenth Speed Writer wrote:For non mythology geeks: Google Daedalus and Icarus.


For all else: 5 points to anyone else who immediately jumped to the Iron Maiden song.


I KNEW THAT!!!

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Re: "Wings" Discussion

Postby Krid » Sat Aug 08, 2009 10:08 pm UTC

lihan161051 wrote:Depends on how much the wings weigh, since the bricks are counterbalancing both the guy flying and the wings. When the wings fall off, if enough mass falls out of the system with them, the bricks might actually almost exactly counterbalance, resulting in no fall at all.


Pfft, that's an easy problem. Treat it like a swing to generate some lateral momentum and you'll increase your tension on the rope, resulting in a force imbalance that would lower you.
It would be a bit harder if the wings weighed enough so the bricks would be heavier than you, but in that case you can just swing over to the brick's rope and climb down to remove some of the bricks.

haruspex wrote:I think a lighter-than-air balloon would be a better method than rope/pulleys/bricks. Granted, the bridge provides the platform (both literal and metaphorical) for the mythology reference.


Balloons have fewer and less ideal failure modes.

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Re: "Wings" Discussion

Postby Ghavrel » Sat Aug 08, 2009 10:11 pm UTC

phillipsjk wrote:The disclaimer does not say liberal-arts majors are unwelcome; just that the advanced mathematics may be hard for them to understand.


Shh! Whose reading comprehension skills are you going to trust, here?! :mrgreen:
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Re: "Wings" Discussion

Postby The Utilitarian » Sun Aug 09, 2009 2:10 am UTC

Sprocket wrote:There are people who aren't into Greek Mythology?

Some of us merely prefer Norse mythology as our go-to option. Less incest, more regenerating goats.
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Re: "Wings" Discussion

Postby xeroxorex » Sun Aug 09, 2009 8:03 am UTC

http://en.wikipedia.org/wiki/Colonizati ... zoob2ttn-5

Oh and, I don't know why anyone would have any doubt of this working perfectly, probably weighing 60kg he hoisted 54.6 kg of bricks into the air 50 feet (halfway up) the trestle. This would be fine because he would still weigh 5.4 kg, plenty to keep him on the ground. Then he tied himself on, then the girl handed him the wings, then he flew up. The heat lamp had a parabolic dish on it, focusing the IR rays onto a small radius of both the wings. The temperature probably got up to around 250 degrees Fahrenheit, which was enough to weaken/melt the glue, but seeing as it was focused on his wings instead of on his skin, I don't think he would be burned, unless he was wearing shorts and a tee-shirt, which would be stupid when you could fall and get scratched up on the gravel below the trestle.
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Re: "Wings" Discussion

Postby tahrey » Sun Aug 09, 2009 11:57 am UTC

Lemme think on a few things here...

Falling at 9% of normal acceleration will mean you touch down more survivably, and it'll probably be more like 7-8% because of the loss of the wings (which would have to be very heavy and almost unflappable to make up even 9% of typical bodyweight) and the additional flailing of arms. It's cumulative after all.
Fall 20m (66ft, 7 storeys) at 9.8m/s^2 (roughly 2 seconds, terminal velocity about 44mph) and you'll be pancake.
0.8m/s^2, not quite so bad (about 7 seconds, terminal velocity about 12.5mph - still kinda painful and may result in soft tissue injury or even a fracture if you land badly, but equivalent to falling 8.5m/28ft/3 storeys on earth).
Presumably BHG also knows this or has dead-reckoned it; he's a murderous dick, true, but doesn't seem to do things that more than injure the people he knows / classes as sort-of-friends.

Can't help thinking that the additional lift caused by the bricks and rope moving relative to yourself and the pulleys would be negligble vs their gross weight and your own. Nowhere like, e.g, the altering buoyancy experienced at varying depths (the deeper you go, the heavier you seem and vice-versa) whilst SCUBA diving.

The heat lamp being labelled, well, it's a stickman cartoon. It needs some kind of exposition so you don't think BHG's just aiming a CFL or some kind of magical X-ray device at his pal. Given that you can buy halogen-incandescent and IR-based space heaters that effectively warm the people/objects in a room without so much heating the air in-between (just a wire element or an IR bulb with a concave reflector behind them), and the severe curvature of the reflector on the pictured lamp, it's not too fanciful to imagine it's got quite a narrow beam on it. The output will be fairly concentrated (albeit not laser-like) and aimable as a result, particularly over what looks to be a reasonably short, theatre-spotlight kind of distance, and if there's enough visible light output he might be able to cast a couple hundred 'C-worth of heat onto the wings without hitting his buddy more than enough to cause brief pain or minor blistering. Nothing noteworthy after the crash damage is considered.

As for the 9% figure itself, I must admit I'm also baffled as 9% is not half of 14% (something no-one seems to have picked up on yet). I can only assume there's some kind of non-linearity in how much lift a certain density of fluid gives you. That, or he's chucking in a small engineering fudge factor so that you get 2% of bodyweight's worth of vertical acceleration, rather than exhausting yourself in order to do no better than maintain a constant altitude.

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Re: "Wings" Discussion

Postby Orion Salvaje » Sun Aug 09, 2009 11:59 am UTC

He should try this http://www.youtube.com/watch?v=RecckjgLyqo
They add ballast according to the weight to get a neutral buoyancy, but compensating only for 91% of the body weight he could try to take off. Easier than the bricks and must really feel like flying.

Although if you look for efficiency wings straped to your arms is not the way to go. As someone said here we don't have a keeled sternum, efficient human powered aircrafts use pedalling to move a propeller. There are several of this (http://en.wikipedia.org/wiki/Human-powered_aircraft) both heavier and lighter than air.

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Re: "Wings" Discussion

Postby tahrey » Sun Aug 09, 2009 12:00 pm UTC

xeroxorex wrote:the same thing, but far more succinctly, and somehow three hours earlier but my browser didn't show it til after i wrote what i did


ah, CRAP :mrgreen:

LinuxTheKid
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Re: "Wings" Discussion

Postby LinuxTheKid » Sun Aug 09, 2009 8:25 pm UTC

Orion Salvaje wrote:He should try this http://www.youtube.com/watch?v=RecckjgLyqo
They add ballast according to the weight to get a neutral buoyancy, but compensating only for 91% of the body weight he could try to take off. Easier than the bricks and must really feel like flying.

Although if you look for efficiency wings straped to your arms is not the way to go. As someone said here we don't have a keeled sternum, efficient human powered aircrafts use pedalling to move a propeller. There are several of this (http://en.wikipedia.org/wiki/Human-powered_aircraft) both heavier and lighter than air.


Now if only we could stabilize that for outdoor flight

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Re: "Wings" Discussion

Postby zaz » Mon Aug 10, 2009 3:15 am UTC

Assuming a mass of 65 kg, if he fell from 20 m with the bricks attached, his velocity when hitting the ground should only be about 5.95m/s, which is somewhere between the velocities for falling from 1 metre (4.43 m/s) and 2 metres (6.26 m/s) in a normal 9.81 m/s^2 acceleration situation. I did ignore air resistance, but that would slow you down even further, so I'm pretty sure he'd be OK. My numbers are slightly different than others, so I'm wondering if I did my math right.

Also, I didn't think of the Iron Maiden song, but I did think of the two Thrice songs that reference the myth.


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