Van's Air Force
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VGs
- Thread starter whd721
- Start date
Flinthillsjim
I'm New Here
I will be installing and flight testing Micro Aero VG's on my RV-9 when I return from Oshkosh. I have used VG's on everything from my J-3 Cub to Cessna 400 series twins (no I have not put them on my antiques or aerobatic aircraft). I will be happy to share the results of the tests on the RV-9 with you after I get back from the big show. If anyone has real data and placement recommendations for the RV-9 I would welcome their input prior to our flight testing.
I will be at OSH in my '39 Waco Cabin biplane in its original black and orange CAA colors camped with the round engine crowd south of the Theater in the Woods if anyone wants to drop by and talk about all things aviation.
I will be at OSH in my '39 Waco Cabin biplane in its original black and orange CAA colors camped with the round engine crowd south of the Theater in the Woods if anyone wants to drop by and talk about all things aviation.
Flinthillsjim
I'm New Here
OK, here are the results:
Used Micro Aero installation instructions and the install template provided for the RV-9. Results: Absolutely no change to stall characteristics.
Moved the template aft 1.5 inches and INCREASED STALL SPEED 2 KTS.
I was shocked. Micro Aero VG's have worked great on numerous aircraft I have owned but I couldn't find a "sweet spot" to make them work on my RV9. After two time consuming attempts I tossed in the towel and decided to be happy with the 9 as built. I had installed them with the double sided tape provided so I simply removed and sent them back.
If anyone does the hard work of finding the "sweet spot" and lowers the stall speed on this airfoil please let me know where it is. All I can tell you is what doesn't work and recommend starting .75 (3/4) inches aft of the recommended install position for your first attempt.
Used Micro Aero installation instructions and the install template provided for the RV-9. Results: Absolutely no change to stall characteristics.
Moved the template aft 1.5 inches and INCREASED STALL SPEED 2 KTS.
I was shocked. Micro Aero VG's have worked great on numerous aircraft I have owned but I couldn't find a "sweet spot" to make them work on my RV9. After two time consuming attempts I tossed in the towel and decided to be happy with the 9 as built. I had installed them with the double sided tape provided so I simply removed and sent them back.
If anyone does the hard work of finding the "sweet spot" and lowers the stall speed on this airfoil please let me know where it is. All I can tell you is what doesn't work and recommend starting .75 (3/4) inches aft of the recommended install position for your first attempt.
humptybump
Well Known Member
Jim, you're experience may not be unusual. There may be a "sweet spot" that is not easy to find.
I say this because the builder of my RV-8 experimented with VGs and he had the same experience as you. When placed where the instructions indicated, he found not improvement in slow flight or stall speeds. He tinkered for about a month and then removed them.
I say this because the builder of my RV-8 experimented with VGs and he had the same experience as you. When placed where the instructions indicated, he found not improvement in slow flight or stall speeds. He tinkered for about a month and then removed them.
pierre smith
Well Known Member
Yep
....that, and they "ugly up" the airplane....and the wash cloth gets hung up on them
Besides, the slowest landing airplane Van builds doesn't need them, does it?
Best,
....that, and they "ugly up" the airplane....and the wash cloth gets hung up on them
Besides, the slowest landing airplane Van builds doesn't need them, does it?
Best,
Capflyer
Well Known Member
Some reference on VG's by Dave Hirschman of AOPA: http://www.aopa.org/News-and-Video/All-News/2013/January/1/Efficiency-Stuck-on-vortex-generators.aspx
Both Dave and I fly similar RV4's. About a month ago we did some ACM. In a turning fight I could not keep the same tight turn radius as he was without stalling, he just kept on going. It drove me crazy as he continually out turned me. I commented to him about that on the ground and he pointed to the VG's.
Both Dave and I fly similar RV4's. About a month ago we did some ACM. In a turning fight I could not keep the same tight turn radius as he was without stalling, he just kept on going. It drove me crazy as he continually out turned me. I commented to him about that on the ground and he pointed to the VG's.
Thanks for your post Flinthillsjim.
I am surprised at the results. The article by Dave Hirschman discusses the results I hoped for.
It is surprising that in this thread there are two no votes and one yes. I would have thought there would have been some consistency.
I accept that the VGs are "Butt Ugly", grab a washing cloth and will bite a hand, but the reduced staff speed and improved control at slow speeds would be worth it.
I installed a set of VGs on my Cherokee and love them. Somewhat like a dog that chases cats, poops in your yard and sheds year round but is a great hunting dog, its worth it!
I am surprised at the results. The article by Dave Hirschman discusses the results I hoped for.
It is surprising that in this thread there are two no votes and one yes. I would have thought there would have been some consistency.
I accept that the VGs are "Butt Ugly", grab a washing cloth and will bite a hand, but the reduced staff speed and improved control at slow speeds would be worth it.
I installed a set of VGs on my Cherokee and love them. Somewhat like a dog that chases cats, poops in your yard and sheds year round but is a great hunting dog, its worth it!
humptybump
Well Known Member
I have not read a reference other than the Dave Hirschman article. I have looked for a second source to confirm his success with VG's on an RV.
I have talked with a small number of people in the other column.
I have talked with a small number of people in the other column.
Eddie P
Well Known Member
Hey I noticed in the AOPA article that there was mention of adding the VG's to the underside of the stabilizer too. Did you added the VG's to the under side of the stabilizer as well, on the RV-9? Also, being that the airfoil is different in the RV-9 vs the -4, there could be a unique difference here and the "sweet spot" may be farther forward on the higher camber "Roncz" RV-9 airfoil. I wonder if the higher aspect ratio wing puts more emphasis on chord wide placement (tighter sweet spot).
I know in the article he mentions he has not lost any top end speed but I wonder if, over time, if he's noticed anything? As usual, no free lunch... wondering where and how much of a penalty it is, besides the odd look and cost. But as a potential safety device, the idea of a softer stall break seems desirable as a "just in case". For sure no one ever tries to stall and spin on base to final but it sure seems to happen a lot anyhow in terms of aggregate numbers for GA. If a set of VG's can do what the article claims they seem to be worthy of "experimentation" in the most basic way an "Experimental Aircraft" is meant to be worked with. But I too would love to see a few more data points.
Steve Barnes
Well Known Member
Undisputable advantage of VG's
VG's are a major deturance for people sitting or leaning on the leading edge of your wings.
VG's are a major deturance for people sitting or leaning on the leading edge of your wings.
Eddie P
Well Known Member
And just a few more links...
Larry Vetterman's writeup at VAF:
http://www.vansairforce.net/vetterman/vg.htm
Micro Aero's website (not a whole lot of details but links for PDF info sheets)
http://www.microaero.com/index.html
AOPA's Dave H. in a video about his RV-4 (partner to the article link posted earlier in the thread)
http://www.aopa.org/AOPA-Live.aspx?watch=Z2NjgzNjolLWlQL0T7hAIreKMwt7Wtbp
Doing a Google "image" search showed a few RV's with VG's.
And a few chat threads I hadn't seen (among others)
http://www.vansairforce.com/community/showthread.php?t=41674
I like that VG's would keep people off the wings but I bet there might be some hangar rash on those VG's! Pierre is right though, it also hangs up the cleaning rag in addition to blue jeans
As far as installation, I haven't found any data on that; I bet there is a detailed set of placement instructions especially since (I think) the VG's that Micro Aero sell (for example) actually sell for specific RV aircraft I believe. There are other VG makers, like those that you can purchase from AircraftSpruce, that seem more experimental as I have not seen any feedback printed on anything but Vetterman and MicroAero (MA being mostly mentioned or "marketed").
Larry Vetterman's writeup at VAF:
http://www.vansairforce.net/vetterman/vg.htm
Micro Aero's website (not a whole lot of details but links for PDF info sheets)
http://www.microaero.com/index.html
AOPA's Dave H. in a video about his RV-4 (partner to the article link posted earlier in the thread)
http://www.aopa.org/AOPA-Live.aspx?watch=Z2NjgzNjolLWlQL0T7hAIreKMwt7Wtbp
Doing a Google "image" search showed a few RV's with VG's.
And a few chat threads I hadn't seen (among others)
http://www.vansairforce.com/community/showthread.php?t=41674
I like that VG's would keep people off the wings but I bet there might be some hangar rash on those VG's! Pierre is right though, it also hangs up the cleaning rag in addition to blue jeans
As far as installation, I haven't found any data on that; I bet there is a detailed set of placement instructions especially since (I think) the VG's that Micro Aero sell (for example) actually sell for specific RV aircraft I believe. There are other VG makers, like those that you can purchase from AircraftSpruce, that seem more experimental as I have not seen any feedback printed on anything but Vetterman and MicroAero (MA being mostly mentioned or "marketed").
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flyboy1963
Well Known Member
another placement consideration
I see that some installers, I belive it's the savannah guys, who kind of knock-off the Heintz CH-750, but without Leading edge slats, they put the VG's at one point on the wing, but move them to a more forward position in front of the ailerons. thus, the wing root will be forced to stall first, and the potential is that the VG's nearer the tip are still keeping the flow attached over the aileron into the stall. of course, we'd NEVEr move the ailerons in the stall, right? ..... but could it be a bacon saver in the incipient stage if you feel the burble of the root stall, while you are manipulating the ailerons in a turn?
I see that some installers, I belive it's the savannah guys, who kind of knock-off the Heintz CH-750, but without Leading edge slats, they put the VG's at one point on the wing, but move them to a more forward position in front of the ailerons. thus, the wing root will be forced to stall first, and the potential is that the VG's nearer the tip are still keeping the flow attached over the aileron into the stall. of course, we'd NEVEr move the ailerons in the stall, right? ..... but could it be a bacon saver in the incipient stage if you feel the burble of the root stall, while you are manipulating the ailerons in a turn?
Eddie P
Well Known Member
I attached ( link below ) an article I stumbled upon regarding VG's on a RV-6 with a test boom and calibrated data. This is the first article showing "data" on the mod that can be looked at objectively. Interestingly, and expectedly, the specific empirical data resulting tests show both positive and negative effects on this specific aircraft mod.
I am not aware of any tests this extensive on any other type of RV aircraft. Though it is said that RV-4's might have excellent results with VG's, it would be nice to see such a test with that aircraft type too. Clearly there is a resulting reduction in stall speed but there also seems to be some test flying and that might possibly lead to some tweaking required for the person who wants to really make sure they are getting what they hope to get and in a safe manner. And yes there is a slight cost on high end top speed as expected - not much - but there is not free lunch.
It seems like if you travel a lot in an RV the VG's might not be worth it but if you are mostly barn storming, formation, local area flying and aerobatics... it might be something to look at assuming the pilot knows it's not just a "stick on and forget" modification.
http://www.iwantarocket.com/pitot/pitot.htm
I am not aware of any tests this extensive on any other type of RV aircraft. Though it is said that RV-4's might have excellent results with VG's, it would be nice to see such a test with that aircraft type too. Clearly there is a resulting reduction in stall speed but there also seems to be some test flying and that might possibly lead to some tweaking required for the person who wants to really make sure they are getting what they hope to get and in a safe manner. And yes there is a slight cost on high end top speed as expected - not much - but there is not free lunch.
It seems like if you travel a lot in an RV the VG's might not be worth it but if you are mostly barn storming, formation, local area flying and aerobatics... it might be something to look at assuming the pilot knows it's not just a "stick on and forget" modification.
http://www.iwantarocket.com/pitot/pitot.htm
