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What is the angle of the canopy "wing/sail" to the lines?

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Herman
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Re: What is the angle of the canopy "wing/sail" to the lines?

Postby Herman » Thu Sep 30, 2021 9:24 am

Agreed. When I said aligned with the fly lines it would be more accurate to talk about the resolved summation of the tension in each flying line. Sergei determination to fully understand what’s going on throws up some interestly unusual questions!

Don’t forget the weight of the lines………. :lol: :lol:

sergei Scotland
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Re: What is the angle of the canopy "wing/sail" to the lines?

Postby sergei Scotland » Sat Oct 02, 2021 5:48 am

Herman wrote:
Wed Sep 29, 2021 9:00 am
As you know aerofoils produce lift and suffer drag. It is only convention to show the aerodynamic forces that way as it makes the analysis easier, but the forces could be resolved in other ways such as a single force at an angle to the chord. Arguably better for kite analysis as this would be helpful to analyse the effect of the kites central chord angle to the fly lines.
Obviously at steady state this single force would be aligned with the fly lines and the kite would be stationary in the window.
Absolutely. Which also means that lift of the kite in this steady state is somewhat directed forward in the window relative to lines. Which is really impossible if kite is 90 degrees to the lines. It is only possible if kite chord vector from LE to the traling edge is at the angle somewhat bigger then 90 degrees to vector of lines from the kite. Like chord of a sail of a sail boat going across the wind. This sail angle in slow wind is often close to 135 degrees.
Note that this angle has Absolutely nothing to do with Aoa. Kite choose to be in such point by itself. Just like you described.
Kite is stable at this point because:
1.if it moves down wind in the window a little : Aoa Increases so lift Increases. before drag Increases- as Aoa is good at this point - like 1-2 degrees. AS lift component point somewhat upwind - it moves kite back up the window.
2.if kite moves upwind a touch then Aoa gets smaller lift decreases quickly and its forward component as well so drag moves kite back.
Thats the picture I have atm.
In othe words when 1 happens resulting aerodynamic vector gets bigger and shifts forward relative to the lines.
In case 2 kite moved upwind resulting vector gets smaller and point more down wind - not aligned with the lines any more..
Hope it makes sense?

Herman
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Re: What is the angle of the canopy "wing/sail" to the lines?

Postby Herman » Sat Oct 02, 2021 9:44 am

The most dramatic demonstration of this I can think of is sitting a kite on its TE dead down wind trimmed out sheeted in. Trimmed for the demo it will just sit there pulling down wind. Rock the chord towards you by sheeting out or pulling the front lines and up she goes. DO NOT try that in anything other than an extremely low wind as you are in the middle of the power zone.

It is also why I tell people to trim in for a tricky light wind launch, but you have to be prepared to sheet right in once the kite is in the air to tension up the rear lines for control.


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