Quickie Q2 Lite Construction Manual - page 78

CANARD SURFACE SMOOTHNESS IS CRITICAL 

.....

During the Quickie program we built and installed a canard that 

resulted in very poor low-speed performance. Stall speed was 10 mph 

higher than predicted and tuft tests showed stall angle-of-attack 

over three degrees lower than estimated. We later traced the problem 

to a wavy upper surface; the canard must be smooth.

.....

Of course, the big question is "how smooth"? The best way to 

check this is with a steel pocket ruler, the flexible kind that's 

only .0211 thick, or with a plastic drafting ruler. Hold the ruler as 

shown in the sketch, pushing it to the surface with two fingers 2 

inches apart. If the surface is a smooth curve between your two 

fingers the ruler will lay down following the curve with no gaps. If 

the surface is bumpy or wavy the ruler will touch the surface only in 

3 or 4 places. Take a feeler gauge to measure the gaps between the 

ruler and your surface. If you have a gap of more than .005 inch, 

your surface is too wavy. Check this in several places from the 

leading edge back to 50% chord. The bad Quickie wing had gaps of 

about .012 inch. After refinishing with gaps of less than .005 inch, 

its stall angle of attack increased from 8 deg. to 12 deg!

.....

The best time to use the ruler and check for smooth surface is 

when sanding the Featherfill with the spline. Recheck after sanding 

the 70S black primer. It will not change when white paint is sprayed 

on.