FSII Original Vortex Generators

There is one vortex generator on every rib and false rib except the most inboard rib. The forwardmost vg measures 10.5" back, the next measures 11.5" back, and the rearmost measures 13" back. This staggered distance pattern repeats itself out to the last available rib. (All measurements are from the centerline of the leading edge to the front edge of the vg, measured with a thin flexible measuring tape - different than we did the MKIII. Actual placement was by stretching a string from tip to tip and marking them from the straight line)

During flight tests we tried various locations, both forward, rearward and staggered. No matter where we put the vg's, they worked at least to some extent to make the stall slower, the climb better, and the handling just above the stall much better. We even came up with some very unconventional arrangements, but this placement works very well overall.

Climb with vg's is 200' a minute better than without, slow flight at 40 mph is good, you can do brisk coordinated turns and the airplane does not feel like it is on the edge, it feels solid. Power off stall is around 35 mph with a clean, gentle break when it lets go, with a normal recovery by easing the stick slightly forward and letting the airspeed increase to 40 mph. Power on stall at 4500 rpm is slightly slower, at around 32 mph, and typically, it will sort of nod in and out of a stall, if you hold the stick still it just bobs along, breaking and then catching itself with no tendency to fall off to either side. With the stick further back, the stall break is clean and recovery is good. Stall in a coordinated turn is straightforward, no tendency to fall off to either side. Have not done any cross control stalls, because I have no spin training, and I'm sure it would.

The biggest plus seems to be that it now has that elusive quality that is hard to describe, but you know it when it's there. Without the vg's, it flew good. Now it flys sweet. The results are well worth the trouble.

Since the rebuild, we have gone with Stolspeed vortex generators, they work at least as well if not better, were a lot less hassle, and look a lot better. Spend the money - it's worth it.


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