The effect of sweepback on adverse yaw on flying wings

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captarmour

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Feb 9, 2013
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Roseau, Dominica.
In a left hand turn with OHS (all moving wingtips) would not the wingtip on the outside of the turn be tilted upward therefore tilting its lift vector backward? Am I missing something?
I wrote this earlier "U may find you may need to fly with the wingtip aileron free floating to see what angle it orients itself before u connect it. Don't be surprised if it is pointing down quite a bit."

Bob Hoey said this "Left, the lead feather is set at negative 27 degrees (this is not a typo), the second is at -19 degrees, the third at -15 degress and, the remaining stationary feathers are reduced 4-5 degrees per feather until the aft one is at zero. Other combintions of angles have not worked as well as this one." HoeyVulture

He also said this "To test this theory I built a wingtip that had the 3 forward feathers mounted on a single spanwise axis. There was a change from adverse yaw to proverse yaw as the initial bias position of the ailerons was changed. The best bias position was with the forward feather at a whopping big -27 degrees of incidence relative to the chord of the rest of the wing. I built a model of this wing tip and ran it in the NASA DFRC water tunnel. These tests confirmed that the flow over the forward tip feather was smooth at -27 degrees, but would stall (on the bottom) at -35 degrees, and stall (on the top) at -22 degrees" BirdLetters

does this answer your question?
 

John Newton

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Dec 5, 2012
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Derbyshire, England
Just recieved a servo end point adjuster, looks like it will be ideal for setting control surfaces to go up/down only as discussed previously in this thread, could also be useful for drag rudders as well where you usually want the servo to move over half of the rudder sticks movement (the drag brake being closed when the rudder is moved the other way) to open the drag brakes.

Servo End Point Adjuster | Model Radio Workshop
 

John Newton

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Dec 5, 2012
Messages
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Location
Derbyshire, England
Just taken a look at Bob Hoey's bird gliders, what a genius!!! Amazing design and build quality! Very elegant method of sweeping the wing without effecting location of the neutral point (aerodynamic centre)
 

John Newton

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Dec 5, 2012
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Location
Derbyshire, England
If I understand it correctly on the bird models both "aileron" tip feather sets are pitched downward by a very large amount, giving low thrust, when rolling the one on the outboard side of the turn has its pitch reduced slightly producing more thrust and therefore proverse yaw, am I correct? Recently joined twitt, will have to look into Bob's work more.
 

captarmour

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Feb 9, 2013
Messages
368
Location
Roseau, Dominica.
Exactly. Jehovah knew what he was doing when he designed the birds, extremely well thought out. I guess he had an advantage in that he had already designed the air.
 
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