Stolspeed VGs installed on Highlander / Superstol

Thanks for the VGs. They lowered my stall speed by 2 knots and dramatically improved the elevator and rudder in slow speed flight.

I ended up winning the OZ STOL 2021 with our SuperSTOL XL VH TWL, thanks to your VGs among other things.

Harry
NSW, Australia

Highlander

John, I wanted to finally get a testimony that you can use on your webpage. This is regarding the Just Highlander. Equipment includes 26 inch bush tires and no major modifications to the structure and design, in a tail wheel configuration, and 90 mm placement on the horizontal standard stabilizer undersurface. That was not changed during the testing. The engine is a 100 hp normally aspirated Rotax engine.

The testing was done before wing cuffs were applied to the leading edge of the wings, which helped to stabilize the stall into a very general falling leaf type of altitude loss, but not a sudden loss of control. The placement of your VGs was at 5 percent chord, placed at 60 mm repeat distances throughout the entire wing, including across the fuselage for what it is worth. I misread the instructions (60 mm spacing for the first 3 feet outboard wing and then 90 mm), which was meant to prevent adverse wing stall characteristics. More on that later.

The numbers that I achieved were without the wing cuffs. However, now I have added those, and they have done nothing but improve the handling characteristics, but not the speeds that I have noticed. Here are the results:

The figures that I have great confidence in are the stall speeds with power on and power off. That is where it made the most remarkable difference. It is such a drastic improvement, I wonder how good the POH figures were originally when the builder tested the aircraft.

However, the difference in handling and stability that I noticed, even before I actually went to the POH to find numbers recorded, was drastically improved. I do not have an explanation as to why I got better performance on the glide speed, nor can I explain that variability in the best climb numbers.

In summary, the STOLSPEED VGs turned this airplane into the most docile and easily handled STOL setup I have flown. There are notable inaccuracies in my data in that the cuffs slightly increase the chord length, which makes the placement greater than 5 percent. It is important to point out that in my power on stall, the attitude is so high I am basically hanging on the prop. So this requires the placement of the VGs to be more forward to hold the airflow on the wing.

It certainly did not hurt the overall performance at cruise, where I did not notice any difference. Am I going to change the placement on the inboard wing to 90 mm as you recommend on your webpage? I am really torn on that one. I do not know how I can improve the characteristics over what they are now. So for now, I am just leaving things the way they are.

John, I want to thank you again for all the help you have given me and the countless other aviators out there flying much safer and enjoying low and slow attitudes.

Blue skies and tail winds to you
David