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Yeah, it's horribly inefficient to do this (flapping wings) at larger sizes. Birds, bats, insects actually evolved to flap less as they get larger: https://www.

Yeah, it's horribly inefficient to do this (flapping wings) at larger sizes. Birds, bats, insects actually evolved to flap less as they get larger: https://www.researchgate.net/figure/Wingbeat-frequency-versus-wing-length-For-comparison-the-slopes-of-two-predicted_fig3_13904663 https://www.researchgate.net/figure/Wingbeat-frequency-versu... A condor with a 10-ft wingspan might not flap for hours - so it glides, just like an airplane: https://www.sciencealert.com/giant-andean-condors-can-fly-for-five-hours-without-flapping-their-wings-even-once https://www.sciencealert.com/giant-andean-condors-can-fly-fo... A hummingbird (4 inch wingspan) flaps at 60 Hz though. It can hover too, just like an insect.

trhway 5y ago
>A hummingbird (4 inch wingspan) flaps at 60 Hz though. It can hover too, just like an insect. during hover hummingbird doesn't flap the wings up/down, instead it flaps it in horizontal plane. On each stroke, back and forward, the wing is set at an angle of attack and thus is kind of like propeller during each flapping stroke pushing air down : https://youtu.be/naE7fK-gCPs?t=110 https://youtu.be/naE7fK-gCPs?t=110 Hummingbird weights 3 grams. An APC 4x4 prop at 3000 rpm would generate 4 grams thrust consuming 0.2 Watt. Such energy density would mean 6 KWt for human, ie. 60x our regular power. So no wonder : https://www.lib.niu.edu/2000/oi000811.html https://www.lib.niu.edu/2000/oi000811.html "Hummingbirds are sugar addicts. Their metabolism is so incredibly fast that they need to refuel about every 10 minutes. Each day they consume 50 percent of their body weight just to maintain their normal weight. Hummingbirds burn from 6,600 to 12,000 calories per day. If a man had the metabolism of a hummingbird, he would have to eat almost 300 pounds of hamburger a day to keep from wasting away."
- straphka 5y ago
  Just so you know, those numbers are way off. If you think about it how would a hummingbird consume that amount of calories in half its bodyweight? See https://www.birdspot.co.uk/bird-brain/how-many-calories-do-hummingbirds-eat-in-a-day https://www.birdspot.co.uk/bird-brain/how-many-calories-do-h... I mean, when extrapolated to human size it's still 125k calories a day, but 6600 for a bird of 3g is just not possible.
  - vkou 5y ago
    They are (deliberately?) juxtaposing calories (the scientific unit of energy) and kilo-calories (the nutritional unit of energy). Unfortunately, the latter are, confusingly, also called called 'calories', despite one nutritional 'calorie' being 1000x of a 'regular' calorie.
    - adrian_b 5y ago
      Yes, that must be the source of confusion. 6000 to 12000 calories, not kilocalories, per day, means 1.5 g to 3 g per day of sugar, which is plausible for a humming bird.
    - FunnyLookinHat 5y ago
      I thought it was accurate - k-cal are usually represented as Calories (capital C) as opposed to the individual unit of measure: calories. See: https://en.wikipedia.org/wiki/Calorie https://en.wikipedia.org/wiki/Calorie
  - chrisseaton 5y ago
    125k calories is about half a chocolate bar. It’s not a lot.
    - deleted 5y ago
      [deleted]
    - alisonkisk 5y ago
      It's 125k kcal.
  - alisonkisk 5y ago
    Only the "6,600 to 12,000 calories per day." is way off, because it's physics cal not nutritional (k)cal. And it's more like 100lb of hamburger for a human, not 300lb.
k__ 5y ago
By that data we already build our planes like birds. If a 10ft bird flaps its wings less than once an hour a plane sized bird would probably fly for days without flapping its wings

trhway 5y ago

>A hummingbird (4 inch wingspan) flaps at 60 Hz though. It can hover too, just like an insect. during hover hummingbird doesn't flap the wings up/down, instead it flaps it in horizontal plane. On each stroke, back and forward, the wing is set at an angle of attack and thus is kind of like propeller during each flapping stroke pushing air down : https://youtu.be/naE7fK-gCPs?t=110 https://youtu.be/naE7fK-gCPs?t=110 Hummingbird weights 3 grams. An APC 4x4 prop at 3000 rpm would generate 4 grams thrust consuming 0.2 Watt. Such energy density would mean 6 KWt for human, ie. 60x our regular power. So no wonder : https://www.lib.niu.edu/2000/oi000811.html https://www.lib.niu.edu/2000/oi000811.html "Hummingbirds are sugar addicts. Their metabolism is so incredibly fast that they need to refuel about every 10 minutes. Each day they consume 50 percent of their body weight just to maintain their normal weight. Hummingbirds burn from 6,600 to 12,000 calories per day. If a man had the metabolism of a hummingbird, he would have to eat almost 300 pounds of hamburger a day to keep from wasting away."

straphka 5y ago
Just so you know, those numbers are way off. If you think about it how would a hummingbird consume that amount of calories in half its bodyweight? See https://www.birdspot.co.uk/bird-brain/how-many-calories-do-hummingbirds-eat-in-a-day https://www.birdspot.co.uk/bird-brain/how-many-calories-do-h... I mean, when extrapolated to human size it's still 125k calories a day, but 6600 for a bird of 3g is just not possible.
- vkou 5y ago
  They are (deliberately?) juxtaposing calories (the scientific unit of energy) and kilo-calories (the nutritional unit of energy). Unfortunately, the latter are, confusingly, also called called 'calories', despite one nutritional 'calorie' being 1000x of a 'regular' calorie.
  - adrian_b 5y ago
    Yes, that must be the source of confusion. 6000 to 12000 calories, not kilocalories, per day, means 1.5 g to 3 g per day of sugar, which is plausible for a humming bird.
  - FunnyLookinHat 5y ago
    I thought it was accurate - k-cal are usually represented as Calories (capital C) as opposed to the individual unit of measure: calories. See: https://en.wikipedia.org/wiki/Calorie https://en.wikipedia.org/wiki/Calorie
- chrisseaton 5y ago
  125k calories is about half a chocolate bar. It’s not a lot.
  - deleted 5y ago
    [deleted]
  - alisonkisk 5y ago
    It's 125k kcal.
- alisonkisk 5y ago
  Only the "6,600 to 12,000 calories per day." is way off, because it's physics cal not nutritional (k)cal. And it's more like 100lb of hamburger for a human, not 300lb.

k__ 5y ago

By that data we already build our planes like birds. If a 10ft bird flaps its wings less than once an hour a plane sized bird would probably fly for days without flapping its wings