Vortex Generators

[GlennM]

If you repair bicycles, you can't do it by yourself, though.

[Anticept]

2 hours ago, Madhatter said:

I just want to add one thing. You don't have to be an Aeronautical Engineer to change or improve things in aviation, you just have to be persistent even when you fail. I know a lot of people who have done incredible things that they were not trained on. Even a person who repairs bicycles for a living can make a difference in aviation. 

Agreed! I just don't know enough about VG engineering to confirm or deny anything you are saying

Q: are you experimental?

[Madhatter]

I am experimental. 

[Tom Baker]

I think the bicycle repairman comment went over a few heads.

[Madhatter]

I think you are right. I figured it would be obvious. 

[GlennM]

Yes, I know the feeling

[IndianaCTSW]

On 4/19/2021 at 7:52 PM, Madhatter said:

For several months I have been working on trying to reduce stall speed with the use of vortex generators.  I installed vgs on wings and stabilator at various % chord and even used two types of vg's however was unable to provide a significant reduction in stall speed. 

About a month ago I was having a conversation with Tom Peghiny about vg's and he brought up a possible issue of something not having to do with stall speeds. It involved possible boundary layer separation in cruise on the top of the cabin. I installed string tufts along the top of the cabin and with a video camera mounted on the vertical stabilizer and found that no separation occurred in cruise. Later that day I ran the full video and saw that the boundary layer completely separated during the flare to landing. I guessed that this might affect the tail due to significant disruption of airflow on the stabilator so I added 22 vg's about 2 inches behind the windshield. Flight tests showed no boundary separation during flare  to landing with the vg's. Cabin vg's definitely would be a positive addition due less drag and maybe better stabilator control when landing to avoid sudden descent that we all are aware of on a CT. I discussed this issue with Anni Brogan, owner and test pilot for Micro AeroDynamics and came to the conclusion to add vg's to the stabilator. I added 40 vgs to the stabilator at 4% chord and tried them in a convergent pattern and a divergent pattern. I settled on the vg  pattern NASA did in a study and is recommended on stabilator type aircraft. I installed string tufts on the stabilator before and after installing vg's and videoed them with a camera mounted on the gear leg.

Then the flight tests started and all I can say it was a game changer  when it came to landings, like night and day comparison. There was total stabilator control all through te flare  to the landing. Over several dozen landings over a number of days I tried to force the plane to stall out of the flare with no luck, I flew on calm days and also with 11 kts gusting to 17 kts. Sometimes a gust

 would balloon the plane up and still had effective stabilator control. All landings were done with engine at idle. Once I prolonged the flare so long I got the angle of attack so high the bottom of the tail scraped the runway and the plane continued to a nice landing. If you flare at 6 ft above the runway I'm sure nothing will help except some power.

I also performed approach, departure and accelerated stalls at altitude and found no change in handling. I generally don't do full power stalls in my plane as I have an E Prop which gives me a higher angle of attack and with the vg's my concern is a possible tail slide if I hit turbulence at the wrong time.

My vg's are now permanent.  If anyone decides to do this change the vg kit is available from  Micro AeroDynamics for $395 and includes everything.  I would suggest that you should attach the vg's temporarily with the double faced tape which is included and evaluate your plane's performance before making them permanent. Do your own analysis for your aircraft as some planes may differ. Mine is a CTSW.

The videos I have included are not geat and I had the mike on so they are noisey,  they are my first attempts for a film career

 

Sorry to revive an old post but am curious about doing this now. My main question is even though you did not see a reduction in stall speed did you see improved aileron control before stall speed with the VG’s over the wing when you had them in front of the aileron?

[Madhatter]

I was not looking for improved aileron function in stall. That is not something that is going to work in a deep stall configuration because the wing is no longer flying, that's what te rudder is for. There was no significant benefit to having vg's on the wings with this airfoil. The vg's above the cabin and on the stabilator prevents the stall in a prolonged flair and that made a huge difference in the landing characteristics. 

[FlyingMonkey]

2 hours ago, Madhatter said:

I was not looking for improved aileron function in stall. That is not something that is going to work in a deep stall configuration because the wing is no longer flying, that's what te rudder is for. There was no significant benefit to having vg's on the wings with this airfoil. The vg's above the cabin and on the stabilator prevents the stall in a prolonged flair and that made a huge difference in the landing characteristics. 

Do you have some pictures or other information on where you placed the VGs to get the most benefit?
 

EDIT:  Never mind! I see the pics in the opening post.  Thanks!

[ctbob]

Can the pictures from the original post be reloaded for us Neanderthals?

 

[Madhatter]

[ctbob]

Did you have to get FD’s okay for this?  I’m interested in doing the same based on your research 

[Madhatter]

FD will never approve this, it is not in their advantage to do so at this point. I was already ELSA due to being the first to use the E-Props on a Flight Design in the US. My vg's are extremely significant in a prolonged flare. You however will have to evaluate your aircraft in all phases of the flight envelope to be sure nothing else has changed. There were no changes in my aircraft between vg's and no vg's except for the prolonged flare characteristics. In my opinion MicroAerodynamics vg kits are the way to go, they give you everything you need. They are the leading developer of vg's in certified and experimental aircraft. They expressed an interest in developing vg's at one time for FD but FD made it too difficult for MicroAerodynamics to deal with.