Question to Vortex Generators users

[Claudio Chacon]

Hello Gentlemen,
I've seen in several pictures, that the most commonly used shape for VG's seems to be the one shown in the sketch below.
Can you guys please help me with the (aproximate) measures? (A,B,C,D)

Which would be a good starting point to install them relative to the high point of the airfoil?
I've seen as well, that they are fixed on the wing in a certain angle. Which should be that angle?
Separation between them?

I'm eager to try them on my plane, so your help will be much appreciated.

Thanks!
Claudio.

[Joe Yau]

Hi Claudio,

I guess you must of missed this post..
http://stunthanger.com/smf/index.php?topic=23110.0;all

[RC Storick]

Which would be a good starting point to install them relative to the high point of the airfoil?

[Howard Rush]

Here's what the ones I make look like.  They are about 4.6 mm high, but may be way too big.  I'm still experimenting with location and spacing, but here are a couple of examples.  The ones on PW's wing are PJ's, in his recommended location.  There is nothing special about the "high point". 

[Claudio Chacon]

Hi Claudio,

I guess you must of missed this post..
http://stunthanger.com/smf/index.php?topic=23110.0;all

Hi Joe,
I didn't read that post before, thank you. It contains a great deal of information, not only the thorough PJ's explanation but also Doug's experience after trying them. Terrific post on the subject!

Thanks again,
Claudio.

[Claudio Chacon]

Here's what the ones I make look like.  They are about 4.6 mm high, but may be way too big.  I'm still experimenting with location and spacing, but here are a couple of examples.  The ones on PW's wing are PJ's, in his recommended location.  There is nothing special about the "high point". 

Thanks for your input, Howard.
I'm affraid I don't quite understand what do you mean when you say that "there's nothing special about the high point"?
Do you mean that it doesn't make any difference to locate the VG's over, before or aft the high point of the airfoil?

[Howard Rush]

Assuming that VGs have an effect on stunt planes, it matters where the VGs go.  The best chordwise position is probably a function of VG spacing and wing design.  I started by picking a chordwise position that worked on other people's airplanes. 

There is no aerodynamic significance to the "high point".  The air doesn't know when it passes it. 

[Claudio Chacon]

Assuming that VGs have an effect on stunt planes, it matters where the VGs go.  The best chordwise position is probably a function of VG spacing and wing design.  I started by picking a chordwise position that worked on other people's airplanes. 

There is no aerodynamic significance to the "high point".  The air doesn't know when it passes it. 

OK. Got it.
Thanks.

[Doug Moon]

A quick google image search will show you that slower flying planes, Alaskan bush types, and many private single engine planes will have the VGs placed ahead of the highpoint of the wing.

I tend to think our models are more along those lines as we slow our down considerably when we maneuver through certain points in the pattern. We are already at low speeds 55 mph or so. When I tested them I placed them just in front of the high point.  I had seen the illustration below and noted the placement on slower flying aircraft and thought it made sense. Then PJ's extensive work in the area only proved the forward area to be a good starting point.

I also saw the test pic as well and the split off happens pretty far aft the high point. But they placed them forward for the best results.

Personally, I would put them just ahead of the high point.

[Howard Rush]

We fly at an airport.  A Cessna 182 was parked next to our circle last week.  It had a plethora of VGs on the wing at 10% chord and some corotating ones on the vertical stabilizer.  The pilot said they work a treat.  They come from a company north of town.  I'll have to stop by sometime and see what those guys are up to.

[Claudio Chacon]

A quick google image search will show you that slower flying planes, Alaskan bush types, and many private single engine planes will have the VGs placed ahead of the highpoint of the wing.

I tend to think our models are more along those lines as we slow our down considerably when we maneuver through certain points in the pattern. We are already at low speeds 55 mph or so. When I tested them I placed them just in front of the high point.  I had seen the illustration below and noted the placement on slower flying aircraft and thought it made sense. Then PJ's extensive work in the area only proved the forward area to be a good starting point.

I also saw the test pic as well and the split off happens pretty far aft the high point. But they placed them forward for the best results.

Personally, I would put them just ahead of the high point.

Yes, Doug. That will be the place where I will install my VG's to start my tests with.
Thanks so much for your advise.
Claudio.

[Doug Moon]

We fly at an airport.  A Cessna 182 was parked next to our circle last week.  It had a plethora of VGs on the wing at 10% chord and some corotating ones on the vertical stabilizer.  The pilot said they work a treat.  They come from a company north of town.  I'll have to stop by sometime and see what those guys are up to.

Take your plane and see what they think!!

[PJ Rowland]

I initially started at 10 % of the chord, my thoughts were based on seeing actual full sized planes.

It didnt take long to realise that having them that forward - didnt work as well as moving them back.  The configuration I use is the same as the image of Paul Walkers impact. with the exception of the VG's on the Stab.

I have said there are probably multiple configurations that can be trialled, and alot of area's that they could be placed inorder to gain different effects. I simply found a close to "optimum" location for my designs. By Optimum I mean ; Minimal VG's for visual impact with close to 95 % effectiveness of running multiple sets.