wrote:

Adverse yaw IS the modern term for the "well-digging" effect. What
really happens when you warp the wings of a 1900 or 1901 Wright glider
left-leading-edge-down? You roll sllllllooooooowwwwwwwly to the left,
and yaw rapidly to the right. Why, well it is differential drag caused
by differential AOA. Higher drag in the UP-warped wingtip......
Harry

I tend to switch off when there are too many upper case words and
exclamations for providing emphasis in a discussion. Still, I found this
document written by Culick of CalTech helpful. Perhaps a little heavy in
parts. Here is his discussion of adverse yaw and how the Glider's outer
wing in a turn dropped - the effect the Wrights called 'well-digging'.
Notice that the wing-warping method altered the trailing edges of the
outboard panels.


From this URL:
http://www.wrightflyer.org/Papers/SETP01_Culick.pdf

"With or without anhedral, the glider having fixed tail also several
times exhibited a second problem associated with adverse yaw. As a
gentle turn, having relatively small roll angle, was being connected to
level flight, the outer wing of the turn dropped and struck the ground.
The Brothers called this event “well-digging.” Wald (1999) has best
explained the cause of the problem. Suppose the glider is turning to the
left, say, and the wings are warped, the trailing edge of the left wing
warped downward to increase its lift and stop the turn. Due to adverse
yaw the wing is slowed, the lift is initially reduced and the wing
actually drops. If the glider is sufficiently close to the ground, the
tip of the wind would strike the sand.
In 1902 the new vertical tail, because it provided directional
stability, did help the aircraft turn. But also because it was fixed it
had a serious shortcoming—it was effective only if the aircraft had
translational motion laterally, i.e. slipping.
When a turn was initiated, adverse yaw swung the aircraft such that the
lift (to the side) generated by the tail would correctly compensate the
swinging motion."


Brian Whatcott Altus OK