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The Windward Turd Theory
ttp://www.dynamic-soaring-for-birds.co.uk/html/windward_turn_theory.html#Windwardturntheory Utter rubbish! |
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Why is it utter rubbish?
dynamic soaring on the leeward side of ridges is very popular in the model gliding world. It's principally the same thing. |
Originally Posted by FE Hoppy
(Post 10108546)
Why is it utter rubbish?
dynamic soaring on the leeward side of ridges is very popular in the model gliding world. It's principally the same thing. |
Originally Posted by oceancrosser
(Post 10108537)
There, I fixed that for you. No comment on the "theory" yet though.
Looking forward to reading your opinion on this. The Leeward Turn The albatross gains momentum in the leeward turn using a component of aerodynamic force to act as a propulsive force. This component provides the acceleration which is seen as an increase in ground-speed rather than airspeed. Thus it gains horizontal momentum and kinetic energy without losing potential energy other than a small drag loss during the turn reversals. This propulsive force is a component of the horizontal resultant which, in turn, is the vector sum of the horizontal component of lift and the drag force. |
If you write "Dynamic Soaring for Birds," I guess the target audience is birdbrains.
I think the description of loss and gain of kinetic energy may actually be correct, when viewed from a ground-based frame of reference. But the kinetic energy determined from that frame of reference is wholly irrelevant -- until it's time to land, anyway. |
I've actually had significant communications with the author- he tried pushing this barrow on some physics sites I hang around on.
It was explained to him ad nauseum that you cannot gain lift by turning in a constant wind, but he was unreachable by logic and facts. He's also a "downwind turn" proponent, which tells you all you need to know. Most worrying thing is he is also still an active instructor...... |
Originally Posted by Wizofoz
(Post 10108850)
It was explained to him ad nauseum that you cannot gain lift by turning in a constant wind, but he was unreachable by logic and facts.
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Originally Posted by abgd
(Post 10108895)
The point of dynamic soaring is that the wind isn't constant. Over the sea, there's more of it the higher you go, and there are also gusts, and the ability to slope soar over the crests of waves. I have the flu and my brain is currently too fuggy to contemplate his exact theory though.
It's barking, but he won't be told. |
Just out of curiosity:
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Dynamic Soaring is completely real, just not the way the gut in the OP believes it to be.
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Presentation about dynamic soaring by the present speed record holder.
I have been aware of apparently ludicrous speed claims on youtube for years and have often wondered if they were actually true. The speaker in the video, Spencer Lisenby, seems convincing. 519mph and running into transonic effects. The next glider will be swept wing. I wonder if there is a theoretical speed limit? |
Dynamic Soaring depends on crossing wind gradients. This guy's theory is about "dynamic soaring" without crossing wind gradients.
Second paragraph from the top. In the windward turn, the albatross maintains height and loses momentum due to the unbalanced drag force. The loss of momentum is seen as a loss of ground-speed rather than a loss of airspeed. Airspeed is constant because the tendency to lose airspeed due to drag is balanced by the tendency to gain airspeed from the increasing headwind components, whilst turning relative to the wind. |
Originally Posted by A Squared
(Post 10109890)
Dynamic Soaring depends on crossing wind gradients. This guy's theory is about "dynamic soaring" without crossing wind gradients.
Second paragraph from the top. As someone else remarked, the opposite of the "downwind turn". If you start with the belief that you can gain airspeed by turning from crosswind to upwind, you know that everything which follows is nonsense. |
Of course, we're overlooking the real problem with the theory -- it doesn't account for the much larger kinetic energy effect of east and west turns. :}
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Quote (my emphasis):
"In a leeward turn, aerodynamic forces combined with a large angle of bank and a large angle of drift provide a propulsive force enabling acquisition of ground momentum and ground kinetic energy without gaining airspeed or losing potential energy. During the climbing part of the wing-over, extra potential energy is gained due to the propulsive force." What "propulsive force"? I may be missing something (don't answer that!) but, on the face of it, that is gobbledygook. Pity, because the sight of an albatross sustaining flight - mainly in ground-effect - with no apparent form of propulsion is awe-inspiring. Cannot see how - assuming the wind is horizontal and constant at any given height above the sea - energy can be harvested to maintain flight-sustaining airspeed simply by manoeuvring. Sounds like "perpetual-motion" to me. |
Same as Windmills, it is Perpetual Motion..... Until the wind stops.
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I don't understand and me 'ead 'urts! :confused:
I always thought seabirds were just ridge soaring on waves. |
Originally Posted by scifi
(Post 10111196)
Same as Windmills, it is Perpetual Motion..... Until the wind stops.
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Originally Posted by Chris Scott
(Post 10111139)
Quote (my emphasis):
"In a leeward turn, aerodynamic forces combined with a large angle of bank and a large angle of drift provide a propulsive force enabling acquisition of ground momentum and ground kinetic energy without gaining airspeed or losing potential energy. During the climbing part of the wing-over, extra potential energy is gained due to the propulsive force." What "propulsive force"? I may be missing something (don't answer that!) but, on the face of it, that is gobbledygook. Pity, because the sight of an albatross sustaining flight - mainly in ground-effect - with no apparent form of propulsion is awe-inspiring. Cannot see how - assuming the wind is horizontal and constant at any given height above the sea - energy can be harvested to maintain flight-sustaining airspeed simply by manoeuvring. Sounds like "perpetual-motion" to me. |
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