Flight Testing
It’s essential to do proper flight testing before and after installing any VGs. Instructions for the flight testing procedure are at Fight Testing.
Record the results, don’t depend on memory! Not only will you be able to measure the differences, but you’ll learn a whole lot about the handling of your aircraft.
Preferably select a time when the weather is looking stable for a couple of days (ie- a large high pressure cell spreading over your area). Do the first flight tests without VGs early one morning, install the VGs during the day, and flight test again with VGs early next morning when conditions will be consistent.
How many VG’s do I need to order?
120 VGs is enough to do 9.9 metres (32 ft) of wing at this spacing.
80 VGs is enough to cover the horizontal stabilizer or vertical fin
Does exact placement of VG’s on wing affect aircraft performance?
There’s been plenty of discussion about the exact placement of VGs and how it affects aircraft performance, especially for different models. Historically, the margin is considered to be 8-12% of wing chord back from the leading edge to the highest point of the VG. There’s lots of talk around the hangar fliers of finding the ‘sweet spot’, but my experience doesn’t show any dramatic improvement at any one point.
From 8-10% I could detect no difference at all in stall performance. I would recommend not placing the VGs farther back than that, in case they become buried in the thickening boundary layer and suddenly lose effect at a high angle of attack, just when they are most needed. At stall angle of attack, the VGs should sit slightly ahead of the airfoil’s highest point.
I have tested them at much farther forward positions and found the effectiveness unchanged. Originally, I recommended 7% setback but now I recommend 5% to be more in the middle of that range. The vortexes once generated are very persistent and stream right back to the trailing edge of the wing. I couldn’t measure any change in drag at cruise speed with the VGs at any position. If you try other positions and get significant results with your aircraft, please let us know so that others can benefit.
Should positioning of VG’s be tailored specifically to each aircraft?
Generally, the installation diagrams will suit most aircraft. There are specific measurements for the Zenith 701, 801, and 601 aircraft on their respective pages in the main menu. For canard style aircraft place the VGs along a line at 50% of chord of the canard, at spacing of 30mm.
What adhesive is used for Stolspeeed VG’s
This adhesive comes as a thin sheet, sandwiched between two backing layers. It’s a solvent-free acrylic adhesive that’s safe for all paint surfaces.
Once pressed firmly onto a clean surface, it forms a strong, flexible bond. It won’t come off from sudden impacts but can be removed by gently pulling on the VG while sliding a razor blade underneath.
How do I remove a VG if it is placed incorrectly?
If you need to remove any VGs, just pull on the fin while slipping a sharp blade under an edge. If the adhesive is still fresh, then you can remove any still stuck to the surface by just rubbing with your thumb to roll it into a ball.
If the adhesive is old and dried, then WD40 works fairly well. If that still doesn't work, then soak the adhesive with 3M Adhesive Remover and carefully scrape off with a single-sided razor blade.
How much stall reduction should I expect?
Note for aircraft with slats:
The easiest and tidiest way to remove the slat brackets, is just to cut them off about 12mm from the skin, along the profile of the leading edge. Then they look like miniature stall fences, and you don't have to fill the holes in the skin.