Why haven’t we made blow up wings to fly with them

[kingsbishop]

Just wondering because if wings are too heavy for humans to fly couldn’t we just use rip stop nylon (the material we use for hang gliders, paragliders etc) and inflate them and then we would have wings light enough for humans to flap and fly with I don’t know why humans haven’t done this?

 

[PeroK]

Just wondering because if wings are too heavy for humans to fly couldn’t we just use rip stop nylon (the material we use for hang gliders, paragliders etc) and inflate them and then we would have wings light enough for humans to flap and fly with I don’t know why humans haven’t done this?

 

[russ_watters]

Just wondering because if wings are too heavy for humans to fly couldn’t we just use rip stop nylon (the material we use for hang gliders, paragliders etc) and inflate them and then we would have wings light enough for humans to flap and fly with I don’t know why humans haven’t done this?

It isn't the weight of the wings that's the problem it's the weight of the person and the aerodynamic forces that take more muscle then we have.

 

[pinball1970]

Just wondering because if wings are too heavy for humans to fly couldn’t we just use rip stop nylon (the material we use for hang gliders, paragliders etc) and inflate them and then we would have wings light enough for humans to flap and fly with I don’t know why humans haven’t done this?

I am not sure what this suit was supposed to do exactly. From memory I thought it was supposed to be a sort of wing suit as you see him flapping but apparently it was more of a proto parachute.
It is in the video Perok posted.

 

[pinball1970]

Just wondering because if wings are too heavy for humans to fly couldn’t we just use rip stop nylon (the material we use for hang gliders, paragliders etc) and inflate them and then we would have wings light enough for humans to flap and fly with I don’t know why humans haven’t done this?

Besides the physics our anatomy rules out flapping. Birds have large breasts, very skinny legs and relatively large wings in terms of surface area. An Albatross has an enormous wing span.
We are leg heavy, arm skinny with small breasts relatively speaking.
Best we can do is glide not take off from the ground and these flying suit guys do that at crazy speeds, very dangerous.
Note how similar our Eiffel tower guy looked to these guys suited up?

 

[kingsbishop]

It isn't the weight of the wings that's the problem it's the weight of the person and the aerodynamic forces that take more muscle then we have.

Cant we just make the wings larger

 

[PeroK]

Cant we just make the wings larger

... and heavier!

 

[jbriggs444]

Cant we just make the wings larger

Make them longer and the torque gets worse. An acrobat can barely support himself on outstretched arms.

No problem, you think. We'll just brace the two wings together with a spar and maybe even a spring. Yes, you can do that. It is called an airplane or hang glider. But if you want to make the thing human powered, you have a problem with the power to weight ratio. You need an athletic human and an ultralight craft.

https://en.wikipedia.org/wiki/Human-powered_aircraft

A propellor is vastly more efficient than a spring-loaded wing-flapping arrangement. I imagine that graphite composite beams with a Mylar skin are more effective than inflated rip-stop nylon fabric.

Edit: Looked up some power to weight ratios on wikipedia.

For the engine alone we have figures like 2000 watts per kilogram (B29 engine) or up to 10,000 watts per kilogram (V22 Osprey). Or down as low as 30 watts per kilogram (Diesel engine in the Emma Maersk container ship). Or up as high as 153,000 watts per kilogram (Space Shuttle main engine).

For complete aircraft we have figures like 100-120 watts per kilogram (Spruce Goose, B17, B29), 300-350 watts per kilogram (Spitfire, P38, Bf 109, V22 Osprey). [Many high performance propellor driven craft in the 300's].

For an athletic bicyclist, we have 20 watts per kilogram as a 5 second maximum.

The McReady Gossamer Condor weighed in at 31.5 kg (craft only, no pilot). I seem to recall 300 watts sustained for the pilot of the Gossamer Condor. That would put that particular craft plus pilot around 300 watts on a (completely guessed at) 100 kilograms gross vehicle weight for 3 watts per kilogram sustained.

[Chased the wikipedia reference to https://www.trainingpeaks.com/blog/power-profiling/ and confirmed a rough factor of 5 difference between 5 second maximum and sustained power. That 3 watts per kilogram figure passes the sniff test]

Let us take the analysis one step further. With 3 watts per kilogram of power, what sink rate can we tolerate in our aircraft so that we can make up for it with applied power? Or, equivalently, what climb rate would we have if the aircraft had zero drag?

The rate at which work must be done to achieve vertical velocity $v$ is given by $P = mgv$ where $m$ is the craft mass, $g$ is the acceleration of gravity and $P$ is the required power. We want to solve for $v$:$$v=\frac{P}{mg} = \frac{P/m}{g}$$We know $P/m = 3$ watts per kilogram and we know that $g = 9.8$ m/s^2.

I make the result 0.3 meters per second -- a tolerable gliding sink rate of about one foot per second in a human powered craft.

This is a reasonable fit with what Wikipedia has to say:

A sink rate of approximately 1.0 m/s is the most that a practical hang glider or paraglider could have before it would limit the occasions that a climb was possible to only when there was strongly rising air. Gliders (sailplanes) have minimum sink rates of between 0.4 and 0.6 m/s depending on the class.

 

[phinds]

Just wondering because if wings are too heavy for humans to fly couldn’t we just use rip stop nylon (the material we use for hang gliders, paragliders etc) and inflate them and then we would have wings light enough for humans to flap and fly with I don’t know why humans haven’t done this?

Learn some basic physics and you will understand.

Or, alternatively, lay flat on the floor with your arms outstretched, perpendicular to your body and lift your body up by just pressing your palms onto the floor.

 

[pinball1970]

Cant we just make the wings larger

Put it all together.

Our legs are heavy so the wings would have to compensate for that.
1Kg is heavy for a lot of birds, we weigh in at about 80Kg average for a grown guy, so the wings have to compensate for that
The enormous wings would require huge chest, arm and back muscles to operate them, not necessarily just because they are heavier but because of the amount of air they would have to displace.
The motion if you watched peroks vid is complicated, it's not just up and down it rotates requiring shoulder work.
So...extra large, pecs, arms back and delts = extra weight = slightly larger wings to compensate.
One other thing is that larger birds take advantage of thermals to do the lifting for them. Flying takes a lot of energy and our bodies cannot do it.

 

[BillTre]

Or, alternatively, lay flat on the floor with your arms outstretched, perpendicular to your body and lift your body up by just pressing your palms onto the floor.

Just to flesh this out, in grad school I had a room mate who was a national champ on the rings.

He did a lot of holding himself up with his arms extended sideways (as ring competitors often do).
His arms and chest muscles were extremely well developed. He did not do non-rings events and didn't run much since he considered his legs to be "dead weight" which he would have to support with his arms.

All that is without any attempts to power flight.

 

[kingsbishop]

Put it all together.

Our legs are heavy so the wings would have to compensate for that.
1Kg is heavy for a lot of birds, we weigh in at about 80Kg average for a grown guy, so the wings have to compensate for that
The enormous wings would require huge chest, arm and back muscles to operate them, not necessarily just because they are heavier but because of the amount of air they would have to displace.
The motion if you watched peroks vid is complicated, it's not just up and down it rotates requiring shoulder work.
So...extra large, pecs, arms back and delts = extra weight = slightly larger wings to compensate.
One other thing is that larger birds take advantage of thermals to do the lifting for them. Flying takes a lot of energy and our bodies cannot do it.

Could you get about a few flaps in before you get tired if you had weightless wings because if humans can do chin-ups surely a human could get a few flaps before they sink down?

 

[BillTre]

It might work if you fill the wings with He or H₂.
If they were big enough they could hold you up and slow flapping might provide some directional thrust.

 

[jbriggs444]

Could you get about a few flaps in before you get tired if you had weightless wings

With weightless and infinitely strong wings, many things become possible. You'll still need to figure out what kind of stroke you will use. A sculling pattern like a hovering humming bird, but majestically slow? That could work. Then you need to add some spring loading to deal with the huge torques.

If a rotary ornithopter can work with actual obtainable materials, an oscillating version should be doable with unobtainium.

 

[kingsbishop]

With weightless and infinitely strong wings, many things become possible. You'll still need to figure out what kind of stroke you will use. A sculling pattern like a hovering humming bird, but majestically slow? That could work. Then you need to add some spring loading to deal with the huge torques.

If a rotary ornithopter can work with actual obtainable materials, an oscillating version should be doable with unobtainium.

What about that spider silk (stronger than steel) and really light material they are talking about what if they made the wings out of that?

 

[jbriggs444]

What about that spider silk (stronger than steel) and really light material they are talking about what if they made the wings out of that?

They are already using carbon fiber.

 

[DaveC426913]

I'm no aero engineer but surely it can be debunked a lot simpler than all these equivocations, can it not? I think @phinds had the most comprehensive yet succinct experiment with his pushups.

Make the wings zero weight and unlimited in size if you want, that doesn't reduce the effort required for human muscles to lift their own weight against air. The torque would be crazy.

Or am I barking?

 

[kingsbishop]

I'm no aero engineer but surely it can be debunked a lot simpler than all these equivocations, can it not? I think @phinds had the most comprehensive yet succinct experiment with his pushups.

Make the wings zero weight and unlimited in size if you want, that doesn't reduce the effort required for human muscles to lift their own weight against air. The torque would be crazy.

Or am I barking?

Humans can easily lift themselves up with chin-ups, pull-ups and many other ways I don’t see how it is different for wings?

 

[jbriggs444]

Humans can easily lift themselves up with chin-ups, pull-ups and many other ways I don’t see how it is different for wings?

If you have a long wingspan, the force has a large moment arm. That means that the torque gets very large. The leverage works against you.

Chin-ups, pull-ups, push-ups, etc. They are all done close in to the body where leverage is good. Try to hold up a paint can hanging from the end of an outstretched 10 foot pole and it is more difficult than one at the end of an outstretched arm.

 

[kingsbishop]

If you have a long wingspan, the force has a large moment arm. That means that the torque gets very large. The leverage works against you.

Chin-ups, pull-ups, push-ups, etc. They are all done close in to the body where leverage is good. Try to hold up a paint can hanging from the end of an outstretched 10 foot pole and it is more difficult than one at the end of an outstretched arm.

But if the wings are weightless wouldn’t it be able to fix that?

 

[Swamp Thing]

if wings are too heavy for humans to fly

But if the wings are weightless wouldn’t it be able to fix that?

As others have stressed, the problem is not the weight of the wings.

The problem is that if you want to fly by flapping a pair of wings (even weightless wings), you have to keep a lot of air moving pretty fast in order to get the lift you need. This takes a certain amount of power, and the human physiology can't deliver that amount of power. Plus, in order to keep that air flow going, the wings need to have a large area -- which means your arms have to produce lots of torque. More torque than modern humans can possibly produce.

Imagine this: You have a pair of long, weightless poles, say 3 meters each in length, strapped to your arms. You lie on the ground face down, arms outstretched. You try to raise your body off the ground, say a few centimetres, by levering down on those weightless poles. You are not allowed to press down directly with your palms, elbows etc -- you have to raise yourself on the far ends of the two poles, which are a couple of meters away from your shoulders.
Would you be able to do this?

 

[Lnewqban]

Humans can easily lift themselves up with chin-ups, pull-ups and many other ways I don’t see how it is different for wings?

Welcome, @kingsbishop !

It is different for wings because they don't have the solid connection to Earth that your bar for chin-ups has.

Wings need to move through air quick enough to create a semi-solid support from the surrounding air.
That semi-solid cushion of air can't sustain the wings flying at the same horizontal level: they constantly slide downwards.

That is what gliders do, glide from certain altitude (to which a towing airplane took them) all the way down to the ground.
The airplane has an engine that provides enough energy to compensate for that constant fall and climb faster than it and the glider fall.

Can you imagine doing chin-ups with a bar that constantly moves downwards faster than you can pull upwards?
You will not be able to gain or maintain any altitude.

 

[Swamp Thing]

.
Not strictly as per OP's spec, but interesting:
.

 

[PeroK]

Humans can easily lift themselves up with chin-ups, pull-ups and many other ways I don’t see how it is different for wings?

Because you can't do chin ups holding onto the air!

 

[PeroK]

But if the wings are weightless wouldn’t it be able to fix that?

How can wings be weightless?

 

[kingsbishop]

How can wings be weightless?

Inflating them well they won’t be weightless but they will weigh so little.

 

[PeroK]

Inflating them well they won’t be weightless but they will weigh so little.

Go and manufacture them, then. Make yourself a billionaire.

 

[fresh_42]

I think it has been made clear that it is not about the weight of potential wings.

There is a reason bird bones are hollow and vultures have trouble taking off if they have eaten too much. And last but not least, a reason why Leonardo da Vinci wasn't successful. And my favorite argument: such wings would have been on the market by now for a long time (cp. the various links above).

This thread has served its goal. Thank you for your participation.