Is my character's wingspan designed well?

Question

My question is simply whether my character as shown in the picture,

1. Would it be able to fly and
2. Would it look believable if it did fly?

I have seen similar posts but all refer to wing types more specific to birds and I have noticed that bats seem to generally have a smaller wingspan, so I need a specific answer for webbing-based wings.

The creature in question is around 6 foot 8 inches tall and each wing is that in length and about 3x his width which is 2.27 feet. As a result, the area of each wing is about 2.27x3x6.8, which is 46 square feet.

The skeletal structure is mostly solid in the torso legs arms and head when it gets to the hands and fingers the bones start to become more hollow the further out you go.

The claws do not add much weight as they are more similar to fingernails than teeth.

Answer 1

An actual approximate weight would be useful, but the answers with the data you've given so far are:

1. No, and
2. Sure, see Dr. Kirk Langstrom.

As evidenced by our representation of angels, dragons, etc., humans are more than willing to buy into the ability of a creature to fly even if it physically could not.

As a mammal (I presume), your creature isn't going to have hollow bones, so we should look at the bat, whose bones are delicate and lightweight to get around that fact. The largest bat is the Giant Gold-Crowned Flying Fox - a heck of a name! - with a wingspan of ~1.7m, and a mass of 1.4kg.

If your putative creature's mass is approximately that of a proportionate weight lifter, you've got (in fermi numbers) a hundred times the mass, and about two-and-a-half times the wingspan. So no. The wings wouldn't be able to support the mass of the body, the muscles would be unable to propel the wings, and the whole apparatus wouldn't work.

Looks cool, though.

Answer 2

The Yale University's Yale Scientific magazine was so nice to calculate in 2013 what wingspan it would take to get a human to fly:

Thus, an average adult male human would need a wingspan of at least 6.7 meters to fly. This calculation does not even take into account that these wings themselves would be too heavy to function.

That is a 75-kilo human male. Or for Feety people: 22 feet wing to carry 165 lbs. And it adds that the wings themselves were not included in the calculation or even functional. Oh, and we have the angel question, which pretty much explains why the mission statements don't work.

So, let's critique:

• The wings are way too short
• The wings are by far not having enough area: Wings make lift by the area!
• Hollow or very fragile bones are a must
• Where's the bird-sternum?!

Calculating wings

Wings generate a force based on a coefficient $\theta$, airspeed and air density $\rho$, as well as the wing area $A$ $$F=\theta\frac 1 2 \rho v^2 A$$

For simplicity... let's take $\theta=1$ (which is a very simple wing geometry - it could be up to about 2), plug $\rho=1.225 \frac{\text{kg}}{\text m^3}$ and $v=3\frac{\text m}{\text s}$ - a stiff walk. Now, balance out the $F=mg$ with $m=75\text{ kg}$ and $g=10\frac{\text{m}}{\text s^2}$... $$A=136 m^2$$

If we assume glider aircraft wing geometry of 12 widths per length and basically rectangular setup, the wings are 3.36 meters tall and 40.48 meters wide - if he crawls through airspace slowly.

If we go fast, like... running the 100 meters in 10 seconds (and thus running 10 meters per second), our hypothetical wingman only needs wings a meter high and spanning 12.25 meters wide. With proper Delta-wing geometry ($\theta=2)$ we get to wings 8.6 meters wide and 0.71 meters high... and still requiring an Olympic record run and to be weightless. Yes, we're still ignoring wing weight.

Or muscles. We totally ignored muscles and the best geometry to attach them. Like, to have wings flap, you need muscles that pull the arms forward strongly. Which best is done by having them attached along the length of the path. This is why birds have this really odd protruding sternum. Where are those on the beast you create?

As dictated...

The surface area of the wings is approximately 8.33544 m²... with Birdwing $\theta=1$ he needs to run an astonishing $v=12.12 \frac {\text m} {\text s}$ to get off the ground. This is pretty much impossible. With Delta-Wings of $\theta=2$ he needs only $8.57 \frac {\text m} {\text s}$ to get lift, which is still rather on the unbelievable side, because of how his wings would give him drag when running. And still, I did not account for the weight of our Bat demon properly - the calculation uses a total mass of 75 kilos on a $g=10\frac {\text m} {\text s^2}$ planet, so... no, he is not able to fly, at best get into gliding from a cliff.

Answer 3

Gut feeling.. 2-3 times wing span, more compact, more muscle

The posture seems to a bit elongated overall.. The upper body could be less tall, more compact, wider.. overall, don't forget you'll need a wide and strong breast with prominent clavicle bones.. shoulders are good, wing span is minimal.. it looks a bit like Lilienthal proportions now, but Lilienthal was a jumper and he didn't mind to live dangerous. My gut feeling says your character could need about 1.5 times this wing span and a good sprint to take off.. and for agile flight, it will require strong wrists ! the hand needs to be bigger imho, the arms and wrist thicker.. with stronger musculature. All that would make it heavier, so consider 2.0 times the wing span shown.

Center of gravity considerations

A humanoid character able to fly would prefer to do that horizontally. As shown, your character is a bipedal dancer, rather than a flyer. Consider drastically compact the body, and try minimize the weight of the back, tibia bones and feet. If you can't.. enlarge the wing span to 3.0 times: when its full body length "hangs" under the wings, the takeoff lift required will be considerable and flight will be slow.