File :-(, x, )
Anonymous
Will /an/ help me do some math? How large would an eagle (or other soaring bird of prey) have to be to support 400 pounds? Assuming it is not flying and not gaining any altitude, just gliding down to the ground.

Bald eagle stats-
Max weight: 16 lbs
Max wingspan: 8 feet

Most internet sources say that an eagle can carry half of its body weight. Also, ambitious souls are welcome to factor in the square/cube law.
>> Anonymous
try using an adean condor to do it the can carry 300 pound deer caracass
>> Anonymous
That's pretty easy to figure out. If an eagle can carry half his body weight and you need him to carry 400lbs, then the eagle would need to weigh 800 lbs.

Ask yourself what times the known max weight would equal 800lbs? The answer is 50. So the eagle would need to be 50times larger than the current eagle. Multiply 50 times the known max wingspan and you get 400ft.

So an eagle would need to have a 400ft wingspan to carry 400lbs.
>> Anonymous
I once read that if an average sized human were to fly, his wingspan would have to be 70 feet.
>> Anonymous
     File :-(, x)
> Also, ambitious souls are welcome to factor in the square/cube law.

My awzum calculation says that the current bald eagle is the bestest bald eagle (lift on y axis).
>> Anonymous
>>326005
I think what OP was getting with the square/cube thing is that a bird at this size could not actually fly. Something about muscle density in that a 1 pound bone can be supported by 3 cubic pounds of muscle, but a 2 pound bone must be supported by 9 cubic pounds (hypothetically). Or something like that. This shit is why I'm not an engineer.
>> Anonymous
>>326121
I'm sure there's more with fluid mechanics and biological system too.

I think what the OP was getting at is that a bird that is twice as big would weigh 4 times more. Hence, at one point the bird simply wouldn't fly. However, this limit is the most lax one, for the reasons above.
>> Anonymous
OP here
>>325996
Is this true? Aren't condors scavengers and so don't need to be built to carry much?

I'm trying to write a fantasy story but still keep it all somewhat within the realm of physics and biology, so I didn't want to cop out and go lolMAGIC. But I guess I have to anyway.
>> Anonymous
Exactly the same difficulties attach to flying. It is an elementary principle of aeronautics that the minimum speed needed to keep an aeroplane of a given shape in the air varies as the square root of its length. If its linear dimensions are increased four times, it must fly twice as fast. Now the power needed for the minimum speed increases more rapidly than the weight of the machine. So the larger aeroplane, which weighs sixty-four times as much as the smaller, needs one hundred and twenty-eight times its horsepower to keep up. Applying the same principle to the birds, we find that the limit to their size is soon reached. An angel whose muscles developed no more power weight for weight than those of an eagle or a pigeon would require a breast projecting for about four feet to house the muscles engaged in working its wings, while to economize in weight, its legs would have to be reduced to mere stilts. Actually a large bird such as an eagle or kite does not keep in the air mainly by moving its wings. It is generally to be seen soaring, that is to say balanced on a rising column of air. And even soaring becomes more and more difficult with increasing size. Were this not the case eagles might be as large as tigers and as formidable to man as hostile aeroplanes.
>> Anonymous
>>326308
You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes.

>>On Being the Right Size
>>J. B. S. Haldane
>> Anonymous
Also,

The Great Bustard
The male of this huge bird is possibly the heaviest extant bird capable of flight, alongside the similarly-sized Kori Bustard. An adult male typically is 90-110 cm (3-3.7 ft) long with a 2.1-2.5 m (6.9-8.2 ft) wingspan and usually weight from 10 to 16 kg (22-35 lb).[1] The heaviest known bird was about 21 kg (46 lb), although larger specimens have been reported and not verified.

So a bird 3 times heavier than a bald eagle can still fly...one could possibly conclude that an eagle could be up to 3 times bigger before reaching some sort of thoeretical limit.

Some engineer or avian physiologist had already done all this and it should just be a matter of finding their calculations