Vortex generators
Posted: Wed Jun 29, 2016 7:09 pm
by WaiexN143NM
Hi all,
Question for all people flying;
Has anyone installed vortex generators on your aircraft?
- model of sonex aircraft
- your own design or from a company
- material used/ attachment method
- on wings or tail or both?
- cost?
- performance difference?
- worth time and effort?
WaiexN143NM
Michael
Re: Vortex generators
Posted: Tue Jul 05, 2016 7:57 pm
by fastj22
I’ve always viewed VGs as a way to deal with a wing that stalls too fast and has bad handling at slow speeds. I’ve not found that trait in my Waiex. It handles every predictably and controllable right down to as slow as I want to fly it.
What problem are you trying to address?
Re: Vortex generators
Posted: Wed Jul 06, 2016 1:56 am
by WaiexN143NM
Hi john,
Was just surfing the net on sonex stuff, happened to run across this posting from klaus in germany.
Google stol speed vortex generators sonex and see his posting w performance specs. Have seen a few pics of sonexs w vortex generators , just interested in any performace gains.
WaiexN143NM
Michael
Re: Vortex generators
Posted: Wed Jul 06, 2016 10:35 am
by radfordc
What a surprise…someone who’s selling something tells you how great it is.
Re: Vortex generators
Posted: Wed Jul 06, 2016 12:19 pm
by WaiexN143NM
Hi charlie,
Yep, was just interested if anyone else had experimented w vortex generators, post from klaus on the stol speed testimonials. Was curious to know if his claims of t.o. Distance , climb rate, stall speed , and cruising speed are to be believed.
WaiexN143NM
Michael
Re: Vortex generators
Posted: Wed Jul 06, 2016 1:34 pm
by gammaxy
An improvement of 15 km/h in cruise from something that can only increase drag is too good to be true. Most of airplanes that report an increased cruise speed with VGs do so by removing slats at the same time.
His low speed numbers are interesting, but like you, I’d be interested in hearing someone else’s report since this one is so suspect.
Re: Vortex generators
Posted: Wed Jul 06, 2016 6:02 pm
by NWade
IMHO, the NACA 6-series airfoil that the Sonex uses is not like the airfoils used by Cessnas or many of the STOL aircraft out there. Therefore it is less-likely to receive much of a benefit from VGs (or, at least less of a benefit than many airplanes).
Here are a few articles for reading:
https://en.wikipedia.org/wiki/NACA_airfoil#6-series
http://web.stanford.edu/~cantwell/AA200_Course_Material/The%20NACA%20airfoil%20series.pdf
Vortex Generators (VGs) are designed to do two main things: (1) Avoid separation bubbles where the airflow detaches from the wing, and (2) Force a transition to turbulent airflow. While laminar airfoils can have separation bubbles, putting VGs on - forcing turbulent flow all the time at that location - has the potential to reduce performance or cause as many problems as it solves; if you’re taking laminar sections and turning them into turbulent flow (with higher associated drag). I think this may be especially true given that the NACA 6-series airfoils were designed to provide low drag via laminar flow at typical cruising speeds/lift-coefficients. In this case, the VGs are essentially working against one of the main design factors behind the airfoil!
Besides - if you want a STOL aircraft, there are plenty of fine kit aircraft out there that will do the job better than the Sonex ever will. The Sonex has a role, and it performs its mission just fine; there’s no need to jam a square peg into a round hole.
–Noel
Re: Vortex generators
Posted: Wed Jul 06, 2016 6:39 pm
by fastj22
A local weight shift trike instructor installed VG generators on his rig. Says they improve handling at stall and increase cruise. They look like rubber stoppers stuck on the fabric. I trust his claims, but doubt it is universal to all aircraft.
Re: Vortex generators
Posted: Mon Jul 11, 2016 5:51 pm
by WaiexN143NM
Hi all,
Yep, was just reaching out to see if anyone had some real world experience w the vortex generators. I had seen a couple of pics of sonexes with them, and then saw the post from klaus.
Noel, in fact we are building a zenith 750 cruzer, for the arizona country backstrips . Will try some vortex generators after we get it flying, try to get some of the stol 750 performance without the drag of the slats. Bigger tires too.
WaiexN143NM
Michael
Re: Vortex generators
Posted: Tue Aug 09, 2016 8:14 pm
by Jeffrylite
There was a guy (Bob)in Red Bluff several years ago, long time flyer and proud owner of his Sonex purchase. He subsequently sold it when life changes moved him too far from his airport. After owning it about a year or so, he bought a set of Vortex and applied them, tested, moved, tested, moved them again, tested. If I recall correctly he spent more than a dozen hours testing and his conclusion was that the Vortex did NOTHING to improve any of the aspects of the Sonex wing. I don’t recall the exact specs or all the things he did, but he had previous experience with Vortex on some STOL planes led me to believe that pursuing Vortex on the Sonex was a waste of time and money.
Re: Vortex generators
Posted: Mon Oct 14, 2019 1:16 pm
by WaiexN143NM
Hi robbie, all,
i started a thread about vortex generators a couple yrs ago. type vortex generators in the search box above. john, chris, noel, charlie, all had good responses. i had seen a pic and ad from a man in germany who had high claims.
One post talk of a man in red bluff, who, after much testing didnt see any gains.
The flyout to indiana sounded fun. jeffs plane the tri gear w the vortex generators, is it painted or vynl wrap ? and looks like a 3 blade prop, what engine is installed?
Let us know about the vortex generator testing and results.
safe flying
WaiexN143NM
Michael
p.s. u can go to page 1 of this thread to see earlier posts.
Re: Vortex generators
Posted: Mon Oct 14, 2019 5:22 pm
by Sonex1517
I believe the engine was a Rotax. The kit I ordered is around $60 so since it’s something I have been interested in, it’s worth it to me. I am not in any way invested in the design or the sales, and am just exploring the experimental part of owning an aircraft I built.
I’ve yet to see a single tangible report from anyone who actually flew or flies it. My goal is simply to report back on my opinion.
Re: Vortex generators
Posted: Tue Oct 15, 2019 9:30 am
by tx_swordguy
I put VGs on an avid flyer I had (predecessor to the kitfox line) The wing would dip and wobble up and down as I was coming in to land and made me feel uncomfortable. The VGs fixed that and made the wing rock solid up until it stalled (did drop my stall by 4 mph). The stall then came all at once and the nose dropped. I did not see any benefit or detriment on the upper end of the incredibly fast (80 mph cruise). I have never had any issues with the sonex wing dropping, in fact it wants to float for me. I also considered the VGs because of my good result with the avid. I do not believe they will benefit my particular sonex and therefore never put any on. They may?? help under the horizontal stab or along the rudder IF you feel you need more authority out of either, but I don’t think the wing itself will benefit. On a side note the B-52 bomber has VGs on the rudder and horizontal stab.
Mark
Re: Vortex generators
Posted: Wed Oct 30, 2019 12:13 pm
by Jlogan1
I just installed the stolspeed vortex generator kit. Install time was about 1.5hrs to do both wings. I have only had time to do a short flight but I noticed a more stable initial climb out and landing approach and also a solid 4 mph slower stall speed. Still need to see if they had any affect on cruise speed. It took 72 Vgs to do the wing. I plan on adding them to the horizontal stabilizer in hopes of getting a little more elevator control in the stall. The kit cost was $99 and was purchased through aircraft spruce. Looking forward to doing more flight testing once weather improves.
Re: Vortex generators
Posted: Wed Oct 30, 2019 4:53 pm
by Sonex1517
Great feedback! What measurement did you come up with for mounting them on the wing?
Re: Vortex generators
Posted: Wed Oct 30, 2019 9:32 pm
by Bryan Cotton
How are they to polish, I wonder.
Re: Vortex generators
Posted: Thu Oct 31, 2019 8:20 am
by Jlogan1
Hi Robbie, I just followed the instructions included with the kit which was to put the vgs highest point at 10% of the wing cord and that point the front edge of the vg at about 7%. It worked out the front was in line with the front edge of the 3rd row rivets on the wing!
Re: Vortex generators
Posted: Thu Oct 31, 2019 8:22 am
by Jlogan1
Bryan, the vgs are polycarbonate and held on with 3m double sided tape. They are on there secure for flight but can be knocked off. I will have to be very careful when i polish around them!
Re: Vortex generators
Posted: Mon Jun 01, 2020 10:13 pm
by Sonex1517
While it may be safer for me to discuss this November’s election, the current events in America, religious preferences, and sex all once, I will post some facts about my VG testing. I am not trying to change anyone’s mind. I am reporting what I learned in my airplane.
I installed the kit from Aircraft Spruce this past winter. I have done some fairly extensive testing, and this past weekend during my WINGS training, my CFI and I wrung out the Sonex thoroughly.
First thing is that prior to this, my Sonex would actually stall. It made loud oil can sounds just as it did, then the nose dropped. This no longer occurs in the same airplane, no other mods that could change it. The airplane will not stall. It wallows, it wiggles, it washes around. No break at all.
I release the slightest amount of back pressure and it’s flying again. Most interesting to me was no oil can sound at all. It used to be very pronounced.
Second thing is in a turning stall, it no longer threatens me with bad behavior. I will be the first to admit I had not been aggressive with this test in the past. Sunday we did turning stalls with the stick in my lap. No bad behavior.
In both of these tests my airspeed indicator was pegged at the bottom and my LRI danced far down in the red.
Third thing was Minimum Controllable Airspeed (MCA). This blew me away. I can turn the airplane at MCA like never before. We practiced an engine out procedure and lost less than 300’ - more like 250’. This does not change my personal decision of no turning back below 800’ AGL but it was eye opening. I was able to make an aggressive left 45° bank, rudder almost to the floor, at 70 mph with the stick back.
In my opinion, the LRI truly pays off at MCA. I can play around and know when I have lift remaining.
Finally, landings. I am able to land my Sonex more consistently, more smoothly, and - most important for me at 1C5 with a nearly constant crosswind - maintain better control with the VG’s, especially for whatever reason with a crosswind from the right. I was finally able to successfully wheel land the airplane, something that eluded me previously. I’ll blame my poor piloting skills for that.
Last weekend I was able to keep it on one wheel longer than I ever was able to in a strong crosswind.
I installed the VG’s on the wings, the horizontal stabilizer and the vertical stabilizer per the kit plans.
Clearly this is a somewhat touchy subject. But in the interests of factual data, I wanted to report my own experience. Your experience and opinion may vary greatly.
Re: Vortex generators
Posted: Mon Jun 01, 2020 10:33 pm
by Rynoth
Robbie, thanks for the report. Your empirical evidence is very intriguing to me. Were the generators installed on the top or the bottom of the horizontal stabs (I’m assuming the bottom)? I’m curious how they would be installed on a Waiex at the tail.
Re: Vortex generators
Posted: Mon Jun 01, 2020 11:06 pm
by Sonex1517
Bottom on my Sonex. The Waiex - that would be interesting!
Re: Vortex generators
Posted: Tue Jun 02, 2020 1:42 am
by NWade
Thanks for bravely posting your results, Robbie!
I’ve been down with a back injury the last few weeks. But once my plane is flying I hope to do some airflow tests similar to what Dick Johnson did for sailplanes in the 1970’s through early 90’s. I’m betting there’s a laminar separation bubble happening on the top surface of the wing and the VGs are helping to “fix” it. But there may be a more-optimal position for them and something like sailplane zigzag tape may provide a good solution (depending on the thickness of the boundary layer at the separation point). Will certainly post my results once I get into flight test.
Take care,
–Noel
Re: Vortex generators
Posted: Tue Jun 02, 2020 7:37 am
by GraemeSmith
Interesting report Robbie. Seriously. I really think these things ARE worthy of examination.
MOST of the flight characteristics you report - I get without VG’s. The “oil canning” on the stall - I call that the “burble”. I haven’t been able to observe any skins actually oil canning - so I’ll go with it being the air “burbling”. I call it my “audible stall warning”. It’s very handy when flying acro as it let’s me know if I’ve pulled too hard and caused an accelerated stall on the wing.
I would be interested in what speed decay you are getting in 60 degree steep turns compared to before. I’ve got less hp than you - which is a factor - but I really struggle to keep up speed in steep-steep turns while holding altitude.
And are you painted or polished? Cause I can see polishing around them could be a real drag (pun intended)
–
Perhaps we could both wool tuft our wings and video them - that would show the separation point and we could compare to see the difference. I’m thinking of doing that anyway to get a real sense of the stall and to try and calibrate my AOA better.
–
And constructively / interested in observations - I would be very leery of putting VG’s on the horizontal stab. It might give control authority longer - but if it prevents the stab from stalling then the plane will not nose over so easily when the main wing stalls - that means you might have to positively push to execute a stall recovery when previously the plane would have dropped its nose.
Re: Vortex generators
Posted: Tue Jun 02, 2020 11:13 am
by Bryan Cotton
GraemeSmith wrote:And constructively / interested in observations - I would be very leery of putting VG’s on the horizontal stab. It might give control authority longer - but if it prevents the stab from stalling then the plane will not nose over so easily when the main wing stalls - that means you might have to positively push to execute a stall recovery when previously the plane would have dropped its nose.
Do you ever want the tail to stall in a conventional (non-canard) airplane? I would think not. Stalled means no control for the tail.
Thanks Robbie for the written observations.
Noel, look forward to your zig zag tape experiment.
Re: Vortex generators
Posted: Tue Jun 02, 2020 11:50 am
by GraemeSmith
Bryan Cotton wrote:
GraemeSmith wrote:And constructively / interested in observations - I would be very leery of putting VG’s on the horizontal stab. It might give control authority longer - but if it prevents the stab from stalling then the plane will not nose over so easily when the main wing stalls - that means you might have to positively push to execute a stall recovery when previously the plane would have dropped its nose.
Do you ever want the tail to stall in a conventional (non-canard) airplane? I would think not. Stalled means no control for the tail.
ABSOLUTLEY you do. It is an UPSIDE DOWN aerofoil - providing a DOWN force to keep the nose heavy aircraft level. (Hence as you load an aircraft into further aft CG - less down force with its induced drag is required and the aircraft flies faster or more efficiently - all other things remaining equal.)
In level flight in designed CG range - when the aircraft flies slowly and stalls - what SHOULD happen is that the horizontal stab stops providing enough down force to keep the nose up because it stalls or at least provides not enough “down lift”. The tail rises and the nose drops and the plane accelerates out of a stall.
So anything that keeps the horizontal stab flying “better” and providing more efficient down force - compromises your ability to have the nose drop and fly out of a stall.
Re: Vortex generators
Posted: Tue Jun 02, 2020 11:59 am
by Bryan Cotton
So that would imply the stabilizer could stall before the wing. What happens then?
A classic stall removes lift from the wing, causing the nose to drop.
Edit: lots of stuff out there about deep stall, generally related to T tails or icing. Here is one article.
https://www.aviationsafetymagazine.com/ … ne-stalls/
Having worked for two airframers in my career, I’m going to stick with the tail should never stall.
Re: Vortex generators
Posted: Tue Jun 02, 2020 1:06 pm
by tx_swordguy
Robbie, Thanks for the report. I was very happy with the VGs on my avid and glad you are happy putting them on the sonex. I expected the changes in the stall for you and I expect a more solid turn to final with little to no bobble if you get close to the “stall” speed in the turn. I found my avid just mushed down in altitude but never truly stalled. I could be nose high with virtually no indicated (at least not accurate) airspeed and it felt like I had turning control and it was stable but I was dropping altitude. It was definitely a strange feeling but all you had to do was drop the nose or give power and you were in complete control. I did not expect the solidness you are describing in the steep turns at low air speed. That is a definate win
Mark
Re: Vortex generators
Posted: Tue Jun 02, 2020 10:12 pm
by Sonex1517
I’m polished, and Bryan, since I used double sided tape I am trying to be careful not to make it turn black. Right now my leading edges and prop have dead bugs all over. A good thing as it means I’ve been flying. A bad thing because I have a lot of clean up to do and no time to do it.
It really was the solid feel in a steep turn that was the eye opener. These VG’s work. I was very skeptical going into this.
I’ll close in saying I had no intention of doing the horizontal stabilizer or vertical stabilizer. Then someone much wiser and more experienced than I explained why I should. And It was all about when the tail stalled vs the wing. I’m very satisfied with the results.
It may not interest everyone, and I’m sure some people question me for doing it. Oh well, it’s my plane.
This is exactly why I built.
Re: Vortex generators
Posted: Wed Jun 03, 2020 12:05 pm
by Area 51%
The tail stalling prematurely on the Cessna Cardinal is why they introduced a slotted stabilizer in the later models.
Probably more cost effective to go with the generators.
Re: Vortex generators
Posted: Wed Jun 03, 2020 12:45 pm
by Bryan Cotton
Area 51% wrote:The tail stalling prematurely on the Cessna Cardinal is why they introduced a slotted stabilizer in the later models.
One disadvantage of a flying tail, like the Cardinal or Cherokee - it’s a straight airfoil. When you have an elevator you are essentially getting a highly cambered airfoil when you have elevator deflection.
