Measuring (and removing) Twist August 10th, 2007
With one set of skins on the wing, I hung two plumb bobs from each end of the wing, and measured the distance from the string to the rear spar. The idea is that when the distance is the same for both plumb bobs, the wing does not have any twist to it (ok, maybe ‘minimal twist’) . To adjust the distance, you adjust the angles clamped to the spar (which is why I used threaded rod to hold them up.
When I set this up, waited for the plumb bobs to settle, etc, I was surprised to see the difference between the two measurements was less than 0.1″. The only adjustment I had to make was about 1/2 turn to the nut holding the threaded rod for the inboard side of the spar.