Spring rains mean no yard work which equals more quality shop time!
I leveled the aircraft using the main spar in the cabin and upper longerons as reference lines. The tail had to come up several inches to reach level. I used a pair of bottle jacks and a padded timber under the fuselage to achieve this. The nose wheel remained chocked in place to keep the airframe somewhat stable.
First check completed was a diagonal measure from each wingtip to aft end of fuselage. Each measurement was was exactly the same, 15 feet 1/4″. That was a good indication that the wings were perfectly aligned.
Next check is to confirm zero or at least minimal equal sweep on both wings. To complete this check I dropped four plumb bob lines from the leading edge of the wings, two outboard and two inboard. A chalk line stretched from the plumb bob at each wing tip provides a reference line. The two inboard plumb bobs touched this reference line. This confirmed zero sweep and perfect diagonal alignment with the fuselage. These Van’s kits are absolutely awesome, put together a pile of prepunched pieces of metal and achieve precise results.
I verified the dehedrial of the wings to be 3.4 degrees with my digital level, exactly as specified.
The last check and adjustment to make is for the wing incidence. A four foot level is placed on the wing, forward end resting 1 inch forward of wing skin line on main spar. A spacer of 4 5/64″ is placed on the rear spar rivet line. The level should read 0 degrees when placed upon this spacer. I completed this check in 5 reference spots on each wing. The right wing is very close to the specification, the left wing needed a little tweeking to bring it into place. This was accomplished by moving the rear spar tab in the fuselage fork down about 2 mm until the incidence read 0 on the digital level. A “C” clamp on the rear spar tab will keep the wings in alignment until the bolt hole is drilled, locking the alignment in place forever.
After running thru this exercise using the digital level, i went back and checked each location again using just the bubble on the level to see what this would look like in the old days of analog measurement. Those reference spots that were .1 degree low or high placed the bubble just inside the sight glass “Level” line.
Again I am amazed at the precision of the CNC pre-punched VANs kit, both wings have practically zero twist (at least as measured using the method described above for setting incidence). I did take a lot of care and time when setting and locking the wing in the building jig which no doubt contributed to its straightness.