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Vortex Generators
Dear 6ers,
While talking with an RV4 owner over the weekend he brought up the subject of VGs. At one time he put VGs on the inboard wing and experimented a bit but later removed them because he thought they made the plane float on landing (his conclusion, not mine). This got me to thinking about installing VGs on my 6A. I found an affordable set https://www.aircraftspruce.com/catal.../stolspeed.php At AS&S. I've seen kits online in the 400 dollar range and most claim improvement in low speed handling and reduction in stall speed. I have also read about using turbulator tape for gliders with similar effect. My sailplane is covered with this stuff and I keep a roll handy for repairs or replacement. I know some RVs use turbulator tape on the tail but has anyone tried this on the top of a wing? Also, any real world experience with the AS turbulators? Thanks Kirk RV12 Sold RV6A Flying |
I would recommend following the VG mfgr's installation instructions carefully.
JMHO: Putting VG's inboard but not outboard on the main wing is not particularly safe, in that you may stall one outboard wing while the inboard is still flying, a recipe for abrupt spin entry. Instead, you always want the inboard wing to stall first, so that you retain some aileron control authority as stall initiates. Hence, better to install VG's outboard only, or on the entire wing, as is typically recommended. And, once VG's are installed on the main wing, you normally want them on the tail as well, so you can retain control authority down to the roughly 9% lower stall speeds that you now have on the main wing. -Paragon Cincinnati, OH |
Turbulator tapes on sailplanes are put in different places, for different purposes than VGs on wings.
The 23013.5 airfoil on RV 3/4/6/7/8 is famous for having a very sharp stall. We don't notice this on RVs because the aspect ratio is low and the rectangular wing stalls inboard first and has a gradual progression of stall area, even if each section stalls abruptly. It is likely that VGs would soften the stall some, probably make the airplane 'float' as described. Not saying that is good or bad. There is likely to be a penalty in top speed, probably a good fraction of the gain in low speed. So you are just shifting the whole airplane performance curve slower. |
VGs For The Masses
When are they going to vortex alternators? Sorry.
Kitplanes did an article a while back about an RV-6 owner experimenting with VGs on his plane. They did a little, but very little. I’ve never installed any. I’ve seen them go on airplanes from time to time and have never heard of any owner say they made a huge difference, although most report modest improvements in reduced stall speeds and improved handling. One thing I’ve never seen discussed is, I think they’d make it harder to wash the airplane. I’ve never seen or read of an improvement in cruise speed or top speed. I’ve been around the block a few times and I put VGs in the fad department, with various scientific wingtips, t-tails, blimps and curb feelers. Sexy, fun to talk about and experiment with, but in the end, not very useful for our airplanes. |
Check this thread for actual flight test data on a similar wing: https://vansairforce.net/community/s...ight=Stolspeed
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Nigel Speedy conducted flight tests using his RV-8 with and without VGs. One thing he did not do was experiment with the chordwise location of the VGs. His article appeared in Kitplanes.
"Vortex Generators on an RV-8": https://www.kitplanes.com/vortex-generators-on-an-rv-8/ |
I have a set on my -8, I'll give them to you if you come touch up the paint. :)
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I know several guys who have installed VGs on their Bonanzas. Most have removed them. Performance gains were not significant and washing the plane became hazardous to fingers.
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On an RV, with good low speed handling and low-ish stall speeds, not sure what real advantage there might be (need to read the Kitplanes article - I may change my mind after that!) |
If you put vgs on a tailwheel airplane and they work, then the airplane will stall at a higher aoa. I expect for most rvs that will mean hitting the tailwheel first. It could also mean running out if aft stick at fwd cg. A good airplane design means everything is matched. Landing gear, tail size, cg range etc.if you then go changing one thing without changing the other things there is a good chance things won’t work anymore.
Supercub stol guys started adding slats to their airplanes and discovered they needed to change several other major things to make them work, like the gear and the tail. Extending the stall range inboard is a very bad idea. You might drive the outboard wing to stall first, leading to a loss of roll control at the stall. Please don’t play with areodynamic mods without taking appropriate safety precautions and consulting with qualified people. Knowitall pilots at the coffee shop are not necessarily qualified people. |
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