Michael,

I have used on quickie designs for a number of years a quarter section of an ellipse (in the plan view) with the major axis the wing’s chord, and the minor axis at 2 ¼” to reach the full 52” span with 47 ½” constant chord. I carve to a zero camber line, with an elliptic cross-section. This provides a good approximation of the airfoil that decreases in chord and percentage thickness. It also is well rounded at the leading edge and sharply tapered at the trailing edge.

Around 1995 one of my quickie designs was measured by radar at 172 mph while flying the long course at about 15 feet altitude. This was on a perfectly calm evening at a contest in Medford Oregon with the radar operated by Fred Burgdorf (of APC Props). At the time, the next fastest quickie was in the low to mid-160’s, while most were slightly under 160. All were powered by Nelson engines, which at the time had an output power of around 2.8 hp. With a prop efficiency around 80 to 85%, my nomograph of power/speed/drag gives me a rough estimate of equivalent flat plate drag area of 10.4 sq. in.

Back then I had concluded that fuselage design was far more important to achieving top speeds and widely ignored in racing circles. This is assuming that the wing is well built with very low amplitude surface waves on the front 30-50% of the wing chord. Since quickie rules preclude the use of wing fillets, airflow separation at the wing/fuselage junction often occurred with traditional fuselage designs where the widest part of the fuselage was somewhat aligned with the maximum thickness of the wing. I found that moving the maximum width point to the trailing edge could add as much as 5 mph to top-end speed. I’ve experimented with several contours of how this fuselage width profile is implemented and believe that some do work better than others.

The original premise of this thread was which tip design was best for 180 mph. While I have heard reports that perhaps one of the newest generation of quickie motors has enough power to achieve this goal, I have not witness it personally. With my 12-year-old Thumper design, it would take 14.6% more power or an output of 3.2 hp. Or a better aircraft design, which is why quickie development is interesting under very restrictive design format.