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?