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
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Highlander
John, wanted to finally get a testimony that you can use in 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 were at 5% cord. Placed 60 mm repeat distances throughout the entire wing including across the fuselage for what it’s worth. I misread the instructions (60 mm spacing for the first 3 feet outboard wing and then 90 mm) so as to prevent adverse wing stall characteristics. More on that later.
The numbers that I achieve were without the wing cuffs, however, now I have added those, and it is done nothing but improve the handling characteristics, but not the speeds that I have noticed. Here are the results:
Original POH ( No Vortex) With Vortex Gen.
Vs= 31 Kts Vs 21 Kts w power
24 no power
Vso 28 Vso 17 w power
31 no power
Vx 46 Vx 49
Vg 57 Vg 44
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’s 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 before I actually went to the POA to find numbers recorded were drastically reduced. I don’t have an explanation as to why I got a 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 easily handled STOL set up. There are notable inaccuracies in my data in that the cuffs increase slightly the cord length which makes the placement greater than 5%. It is important to point out that in my power on stall, the attitude is so high as I’m 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, which I didn’t notice any difference in.
Am I going to change the placement on the inboard wing to 90 as you recommend in your webpage?… I’m really torn on that one. I don’t know how I can improve the characteristics over what they are now. So for now I’m just leaving things the way they are.
John, I want to thank you again for all the help you’ve given me and the countless other aviators that are out there flying much safer and enjoying low and slow attitudes. Blue skies Tail winds to you….
David
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