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The Windward Turn Theory

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The Windward Turn Theory

Old 5th Apr 2018, 18:58
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The Windward Turd Theory

ttp://www.dynamic-soaring-for-birds.co.uk/html/windward_turn_theory.html#Windwardturntheory

Utter rubbish!

Last edited by Jet_Fan; 4th Aug 2018 at 21:36.
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Old 5th Apr 2018, 19:33
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Originally Posted by Jet_Fan View Post
Windward Turn Theory

Utter rubbish!
There, I fixed that for you. No comment on the "theory" yet though.
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Old 5th Apr 2018, 19:44
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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.
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Old 5th Apr 2018, 20:01
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Originally Posted by FE Hoppy View Post
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.
He has a new theory. Have a read.
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Old 5th Apr 2018, 20:02
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Originally Posted by oceancrosser View Post
There, I fixed that for you. No comment on the "theory" yet though.
Thanks. The board won't like me put up links yet.

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.
According to the author, this effect is what produces lift and not the wind gradient.

Last edited by Jet_Fan; 5th Apr 2018 at 20:16.
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Old 5th Apr 2018, 22:59
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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.
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Old 6th Apr 2018, 05:47
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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......
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Old 6th Apr 2018, 06:50
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Originally Posted by Wizofoz View Post
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.
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.
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Old 6th Apr 2018, 08:51
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Originally Posted by abgd View Post
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.
He is postulating a reverse of the "Downwind-turn"- he thinks by gaining groundspeed downwind, then turning into-wind, you gain airspeed and can climb.

It's barking, but he won't be told.
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Old 6th Apr 2018, 15:55
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Just out of curiosity:

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Old 6th Apr 2018, 22:36
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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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Old 7th Apr 2018, 05:52
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Presentation about dynamic soaring by the present speed record holder.

about an hour long

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?
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Old 7th Apr 2018, 05:58
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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.
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.
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Old 7th Apr 2018, 07:32
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Originally Posted by A Squared View Post
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.
Exactly. I don't know why some people insist this is the case. It's almost like a mental illness.
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Old 7th Apr 2018, 12:31
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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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Old 8th Apr 2018, 12:53
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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.
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Old 8th Apr 2018, 13:46
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Same as Windmills, it is Perpetual Motion..... Until the wind stops.
.
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Old 8th Apr 2018, 14:06
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Originally Posted by scifi View Post
Same as Windmills, it is Perpetual Motion..... Until the wind stops.
.
Presume you are being frivolous? In case not: windmills can harvest energy from the wind because they are anchored to terra-firma Flying machines are not...
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Old 8th Apr 2018, 15:52
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Originally Posted by Chris Scott View Post
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.
Yeah, he thinks hes found an all new force that everyone else has missed.
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Old 9th Apr 2018, 09:48
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Originally Posted by Jet_Fan View Post
Yeah, he thinks hes found an all new force that everyone else has missed.
Nothing new here Its the same force that makes your groundspeed increase when you turn downwind and decrease when you turn upwind
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