3 ms·

There's thermals (a spot on the land that is warmer than the surroundings so the air rises there), and there's topography that causes rising air (for example wh

by ajuc 6y ago

There's thermals (a spot on the land that is warmer than the surroundings so the air rises there), and there's topography that causes rising air (for example when the wind blows at a face of a hill - the air has no choice but to go up). RC gliders can stay in air basically forever flying back and forth in rising air along a hillside. It's called slope-soaring and it's great fun.

dmos62 6y ago
> RC gliders can stay in air basically forever flying back and forth in rising air along a hillside. And there's been some effort to have autopilots do it automatically https://ardupilot.org/plane/docs/soaring.html https://ardupilot.org/plane/docs/soaring.html
jojobas 6y ago
Somewhat more impressively, albatrosses do that on the forward faces of waves, soaring for days far away from thermals and hills.
- tim333 6y ago
  There's research that they use dynamic soaring more, getting energy from the different wind speeds at sea level and a bit above https://www.youtube.com/watch?v=uMX2wCJga8g https://www.youtube.com/watch?v=uMX2wCJga8g
  - crubier 6y ago
    Gotta love the end of the video aha! But the whole video is very interesting. As a kayaker myself I can definitely “feel” the phenomenon they are talking about of extracting energy by alternating on two sides of a flow gradient.
    - frandroid 6y ago
      Next up in kayagliding...
  - sails 6y ago
    That is very interesting. I always assumed sea birds used combination of wing in ground effect [1] and the lift of wind hitting the front of waves to cover long distance, but this explanation makes much more sense for birds crossing oceans. [1] https://www.youtube.com/watch?v=vkVVnx70FgI https://www.youtube.com/watch?v=vkVVnx70FgI Edit: It just occurred to me that the albatross is in some way surfing the wind in much the same way a surfer pumps along a wave to generate speed.
StavrosK 6y ago
Here's an RC glider doing 545 mph with that technique: https://youtu.be/MoaWlKC3wIM https://youtu.be/MoaWlKC3wIM I don't know how they manage to control it or measure the speed, but it looks legit.
- ajuc 6y ago
  Wow. That's not how it usually looks like :) Usually it's very slow and relaxing. Looks like this: https://youtu.be/Ev5fSVi1PrA?t=152 https://youtu.be/Ev5fSVi1PrA?t=152
- sails 6y ago
  That is dynamic soaring [1] which is I guess a subset of slope soaring, and is pretty rare and nuts. It generally requires flying in the lee of a slope rather than in front of it. Regular slope soaring is relatively more sedate, fun and accessible if you have the right slope. [1] https://en.wikipedia.org/wiki/Dynamic_soaring https://en.wikipedia.org/wiki/Dynamic_soaring > Dynamic soaring is sometimes confused with slope soaring which is a technique for achieving elevation.
stx 6y ago
> RC gliders can stay in air basically forever flying back and forth in rising air along a hillside. It's called slope-soaring and it's great fun. This was my thought also. The Andes Mountain Range are rather mountain range right next to the ocean. I would think that is a pretty ideal place for a bird to slope soar for a long distance.

by ajuc 6y ago

dmos62 6y ago

> RC gliders can stay in air basically forever flying back and forth in rising air along a hillside. And there's been some effort to have autopilots do it automatically https://ardupilot.org/plane/docs/soaring.html https://ardupilot.org/plane/docs/soaring.html

jojobas 6y ago

Somewhat more impressively, albatrosses do that on the forward faces of waves, soaring for days far away from thermals and hills.

tim333 6y ago
There's research that they use dynamic soaring more, getting energy from the different wind speeds at sea level and a bit above https://www.youtube.com/watch?v=uMX2wCJga8g https://www.youtube.com/watch?v=uMX2wCJga8g
- crubier 6y ago
  Gotta love the end of the video aha! But the whole video is very interesting. As a kayaker myself I can definitely “feel” the phenomenon they are talking about of extracting energy by alternating on two sides of a flow gradient.
  - frandroid 6y ago
    Next up in kayagliding...
- sails 6y ago
  That is very interesting. I always assumed sea birds used combination of wing in ground effect [1] and the lift of wind hitting the front of waves to cover long distance, but this explanation makes much more sense for birds crossing oceans. [1] https://www.youtube.com/watch?v=vkVVnx70FgI https://www.youtube.com/watch?v=vkVVnx70FgI Edit: It just occurred to me that the albatross is in some way surfing the wind in much the same way a surfer pumps along a wave to generate speed.

StavrosK 6y ago

Here's an RC glider doing 545 mph with that technique: https://youtu.be/MoaWlKC3wIM https://youtu.be/MoaWlKC3wIM I don't know how they manage to control it or measure the speed, but it looks legit.

ajuc 6y ago
Wow. That's not how it usually looks like :) Usually it's very slow and relaxing. Looks like this: https://youtu.be/Ev5fSVi1PrA?t=152 https://youtu.be/Ev5fSVi1PrA?t=152
sails 6y ago
That is dynamic soaring [1] which is I guess a subset of slope soaring, and is pretty rare and nuts. It generally requires flying in the lee of a slope rather than in front of it. Regular slope soaring is relatively more sedate, fun and accessible if you have the right slope. [1] https://en.wikipedia.org/wiki/Dynamic_soaring https://en.wikipedia.org/wiki/Dynamic_soaring > Dynamic soaring is sometimes confused with slope soaring which is a technique for achieving elevation.

stx 6y ago

> RC gliders can stay in air basically forever flying back and forth in rising air along a hillside. It's called slope-soaring and it's great fun. This was my thought also. The Andes Mountain Range are rather mountain range right next to the ocean. I would think that is a pretty ideal place for a bird to slope soar for a long distance.