Vortex Generators

[Peter Anglberger]

I am considering installing vortex generators on one of my Yatsenko Classics. I read PJ's comprehensive 2011 post found via the search function. One thing that is not entirely clear is the exact position chordwise. Should the tabs be centred on the high point or should the rear be coincident with the high point, or some other specific distance forward of the high point. I'm sure PJ will reply to this, but I would also be interested in locations tried by other users of vortex generators.

Regards,
            Peter

[Howard Rush]

There is no aerodynamic significance to the "high point".  I don't know where to tell you to put them, though.  It's probably a function of the wing upon which you are putting them.  Here's a picture of where I put mine and a picture of VGs on Dan Hune's Yatsenko Shark. 

[Chris Wilson]

"I found the best location was just near the Highpoint, which is further back than the initial 10% back that I was recommended"

http://stunthanger.com/smf/index.php/topic,23110.0.html

[Perry Rose]

A while back I did a google search for the v/g and found that on real planes it's important where they go.
http://www.stolspeed.com/installing-vortex-generators

[Louis Rankin]

We discussed this at the Paducah contest and came to this conclusion:  Ink them on with your rapidograph pen, high point or low point maters not.

[Avaiojet]

We discussed this at the Paducah contest and came to this conclusion:  Ink them on with your rapidograph pen, high point or low point maters not.

Designed to intimidate more than anything else?

[Brett Buck]

We discussed this at the Paducah contest and came to this conclusion:  Ink them on with your rapidograph pen, high point or low point maters not.

    I would caution against the "everybody is stupid but us" approach. Paul and David are pretty convinced they are doing something useful, and they are not particularly prone to deluding themselves. I have seen many things that couldn't possibly work - like turbulators made from flying lines we got out of the garbage can - have remarkable effects. Like the difference between making it through the pattern, and not making it.

   I don't have an vortex generators myself but I would certainly not dismiss it out of hand. I came in 4th, David won and Paul was 3rd.

Brett

[Randy Powell]

If they work on the wing, would they work on the stab?

[Chris_Rud]

I did a little experiment with VG's and here are my findings:



I just ordered two sets of VG's and will have them on my next years planes...

-Chris Rud

[Derek Barry]

I came in 4th, David won and Paul was 3rd.

Brett

And how many times did that happen before they started using them? Doug was 2nd with no gaybulators.

Derek

[Randy Cuberly]

My personal experience with them was that they improved the tracking and corner significantly on a Whitely Shoestring that was a little too heavy.
The airplane flew fairly well and was reasonably easy to get through a pattern with no real problems.  It was well trimmed as blessed by RJ W., Bart K., and Me...We all agreed that it flew a little "heavy", but was basically an "honest airplane".

I obtained some of Howards VG's and installed them on the Shoestring...Voila...different airplane!
The heavy feel was gone and the corner was much improved.  All that flew it agreed.  In fact it was the first airplane to appear here in Tucson with VG's and as a result of this success they began to "bloom" on a lot of other stunters here with very "mixed" results.

When I first put them on the Shoestring and sent a photo to Howard He very kindly informed me that I had installed them in a configuration that was angled in oppisition to normal practice (I think this was Howards nice way of saying I was stupid and put them on the wrong way!)  

So after about 20 flights I changed them to what was supposed to be the conventional pattern and surprise, surprise...they didn't seem to work nearly as well!  So I put them back on "Wrong" and they worked again...Go figure!

So my opinion at this point is that they work but better on some airplanes than others, and how they are installed does make a difference, but I haven't a clue as to why or how that should be on different wings.

Incidentally they were installed on the Stab also and remain there.

The biggest problem I had with them is keeping them on the airplane!!!  When they fall off, the flight characteristics of the airplane are noticeably different!  In fact it caused hingeing on the airplane when they came off the top of outboard wing and stayed on the inboard!!!

There's certainly nothing "scientific" about this post but it did simply raise a lot of questions for me!

I'm not at all sure I will use them on my New Shoestring as it's going to be significantly lighter and a litte larger than the one described above.  My opinion is simply that they do something and I'm not sure what!!

The configuration shown in the photos is the way they work best..."the wrong way".

Randy Cuberly



 

[Chris_Rud]

And how many times did that happen before they started using them? Doug was 2nd with no gaybulators.

Derek

LOL thats funny.

[Howard Rush]

I confess that I hadn't seen Chris's video until now.  Good job, Chris.  You went to a lot of effort to do a good experiment.  

I can't see much difference in the video on insides, which you'd think is where it would matter.  Either the tufts are stiff or there's not much separation.  It might be interesting to put the camera back farther and look at the flow on the flaps.  Use the smallest, most flexible tufts you can see.  One trick is to use fluorescent tufts in UV light.

Chris's VGs are on backwards, but if there's no separation, it doesn't matter.

[Howard Rush]

The biggest problem I had with them is keeping them on the airplane!!!  When they fall off, the flight characteristics of the airplane are noticeably different!  In fact it caused hingeing on the airplane when they came off the top of outboard wing and stayed on the inboard!!!

You wax your airplanes or something?  Elmer's rubber cement applied with a Starbucks stirring stick should work OK.  UHU Twist & Glue holds the VGs on a little better than rubber cement, and it dries faster.  VGs still come off when you want them to.  They leave some glue on the surface, but it’s easily removed (from catalyzed polyurethane clearcoat) with isopropyl alcohol.  I don't know how it would affect a dope finish.  I got my UHU in Poland.  Amazon has it here, but I don't know if it's the same stuff. 

[Howard Rush]

And how many times did that happen before they started using them? Doug was 2nd with no gaybulators.

Says the guy who couldn't make the Nats finals without VGs.

You can pay me now,
Or you can pay me later,
But you can't win at stunt
With no vortex generator.

[Randy Cuberly]

Hi Howard,

Waxed, Yes but cleaned with Isopropol Alcohol.  It is a doped surface...Old technology, like me!

I've used several different brands of rubber cement to no avail.  Haven't tried the UHU stuff.  I'll look for some. 

Thanks,

Randy Cuberly

[Derek Barry]

Says the guy who couldn't make the Nats finals without VGs.

You can pay me now,
Or you can pay me later,
But you can't win at stunt
With no vortex generator.

I think my top 5 qualifications outnumber yours, with or without VGs....

I cant blame the judges for being a little sleepy on those first couple flights of the day can I? Stuff happens...

Derek

[frank williams]

"I can't see much difference in the video on insides, which you'd think is where it would matter. "

Howard .... check the triangles again .... with and without the VG's ..... there is a blast of separation about half way out the span without the vg's.
Chris's plane is fairly light and has a super thick airfoil (probably not too prone to stalling)...... think what it might look like with one of my battleships.

Frank

[Brett Buck]

And how many times did that happen before they started using them? Doug was 2nd with no gaybulators.

   So, they're SO good that even though they are doing something pointless or counter-productive, they can easily overcome it with magically special skills? More to the point, you see absolutely no connection between long-term willingness to reject dogma and objectively evaluate a large number of alternatives, and long-term domination of the event?
  
   Actually, they *do* have special skills, the most important special skill being able to change to something that works better, even if what they have is pretty good already.

     Brett

[Howard Rush]

I think my top 5 qualifications outnumber yours, with or without VGs....

You whupped me back when
I was without 'em
Now it's reversed
Til you cease to doubt 'em.

[Derek Barry]

  So, they're SO good that even though they are doing something pointless or counter-productive, they can easily overcome it with magically special skills? More to the point, you see absolutely no connection between long-term willingness to reject dogma and objectively evaluate a large number of alternatives, and long-term domination of the event?
  
   Actually, they *do* have special skills, the most important special skill being able to change to something that works better, even if what they have is pretty good already.

     Brett

I do see the connection, Dave and Paul are two of the best at building, trimming, and flying control line airplanes and if something is working for them they should use it. That does not mean that I will be gluing those little turds all over my planes. I think the only reason people use them is to annoy me, kind of like electric motors.

Derek

[Doug Moon]

You whupped me back when
I was without 'em
Now it's reversed
Til you cease to doubt 'em.

Howard is on a roll!!

[Doug Moon]

....snip.... I think the only reason people use them is to annoy me, kind of like electric motors.

Derek

Haha!  That is funny. 

[Doug Moon]

They do work.  You can see them all over real planes, military, commercial, and personal.

After reading about these things for many years it is evident they do something and what it is they do is proven out as well.  There are many illustrations and wind tunnel tests pics and videos as well showing what these things do and how.

They show the most improvement on a flying aircraft when it is put in a situation where it is approaching its stall speed.  These allow for a slower speed before it stalls, due attached boundary because of the type of airflow caused by the devices.  That is it.  That is what they do.  They are very helpful on small aircraft during final approach.  Giving the pilot more control in a vulnerable situation. BUT since the VGs are affecting the boundary layer at all times the second improvement is that the air is more consistent across the wing at all times creating more over all control.

For stunt planes we see a slow down our speed during maneuvers and the VG will help with tracking as it helps the air stick to the wing better when the airspeed has slowed. You will note the second square or triangle is easier and tracks as well as the first one.  Or you may notice better tracking to keep your maneuvers right on top of each other.  I feel this is due to the consistency of the air passing over the wing as it is "cleaned" while passing across the VGs.

It would be most interesting if we could see Chris's plane in the air going slower where a hard corner actually stalls the wing.  Then with the VGs at the same lap time and see if the stall is lessened or gone.

It is also noted that Chip Hyde posted on his FB page pics of one of his pattern plane with VGs on it and stated he got this from the CLPA guys and his plane flew like it was on rails like never before.

I have also noticed many of the RC planes for sale now have them as well.  Many of the little foam planes have them molded into the foam.

Here is what I found back in 2011 when I tested them. Other people report the same or near same results.

http://stunthanger.com/smf/index.php/topic,23110.msg222103.html#msg222103

Why dont I have them on my most recent plane?  No time to test before the big show.  So I forged ahead as normal.  It worked out pretty good...but not good enough...

[Howard Rush]

I think the only reason people use them is to annoy me, kind of like electric motors.

Worse yet, those people have Corian countertops.

[Paul Walker]

. I think the only reason people use them is to annoy me, kind of like electric motors.

Derek

[/quote]


Dang, you finally figured it out!

Now I will have to remove them from my planes and replace them with turbulator strips. You can't possibly complain about those!

[Brett Buck]

I think the only reason people use them is to annoy me, kind of like electric motors.

   That *is* actually a pretty good reason.

     Brett

[Derek Barry]

Worse yet, those people have Corian countertops.

Good lord man! Why would you have such a thing?

Derek

[Derek Barry]

. I think the only reason people use them is to annoy me, kind of like electric motors.

Derek




Dang, you finally figured it out!

Now I will have to remove them from my planes and replace them with turbulator strips. You can't possibly complain about those!

 Turbulator strips? 

In all fairness, at least yours match your plane. Howard could at least print yellow and orange VGs for his own planes. Don't get me started on Dave, I bet he will have them going down the side of the fuse and around the spinner and on the wheel pants by the next Nats. Hey, at least he is giving Howard  pierogi money.

I will come back next year with my VG free machine and kick all your butts. 

Derek

[Steve Fitton]

Could you use VGs in lieu of an area tab on the outboard flap of some hypothetical plane? 

[Brett Buck]

Worse yet, those people have Corian countertops.

    Derek is right on that one. When I come in from a long day of stampeding mastodons off a cliff, just to feed my family, I want it cooked in the dirt over a buffalo-dung flame, no synthetic materials for me. Probably poisonous, anyway. 

   I mean, Ryan Seacrest probably has Corian countertops - 'nuff said!

    Brett

[RC Storick]

The NASA engineer who I talked to and he watched Chris Ruds video "Chuckled and said pretty much useless" But I knew that. Flame away

[Randy Cuberly]

The NASA engineer who I talked to and he watched Chris Ruds video "Chuckled and said pretty much useless" But I knew that. Flame away

I worked at Cape Kennedy in the 1970's and knew a lot of NASA Engineers... I was an assistant to the Chief propulsion engineer for NASA...Some of those guys were briliant...and some of them were as dumb as posts...

I doubt that any real aerodynamicist worth his salt would call them useless.  If they are why do you see so many on full scale aircraft...Is it only because they want the extra weight? 

Did this NASA Engineer fly Stunt?  Missile aerodynamics is a little different...things change a little around Mach 7 or so...besides aerodynamics don't make a lot of difference in space! 

Randy C. 

[Doug Moon]

The NASA engineer who I talked to and he watched Chris Ruds video "Chuckled and said pretty much useless" But I knew that. Flame away

I guess the guys who built this plane aren't up to speed on the facts for and against VGs...

In this application there is some significance as to where they are placed. 

[Doug Moon]

These guys are a clueless too.

[Doug Moon]

Oh yeah, don't forget these guys too..

[Doug Moon]

So, we have proven the airline engineers are out to lunch on the aerodynamic capabilities of those teeny tiny little fins placed on the wings of their aircraft in very specific places.  I mean the NASA guy said they are worthless right?  Or maybe he just meant they were worthless on Chris's model.  But wait, isn't the air going over Chris's wing the same air that goes over the wing of an airliner?  I am not sure.  But if it is the effect would be the same.  Must be different air.  It has to be.

Look at this, their engineer are lost too...

The under belly of a Lola chassis has VGs on it to get the air traveling under the car to stay attached to the car in the negative pressure areas so when it passes through the rear tunnels the desired effect is achieved.  These guys must be kidding themselves that there is actually anything at all happening, even though they have 100s of millions of dollars in their programs and time in the wind tunnels....

[Doug Moon]

Whoa what is this?  It is the front end under belly of an LMP2 (LeMans Prototype 2) Nissan.  Another team of crack pot engineers thought it would be helpful to put these little do dads on their car all in the name of speed.  What are they trying to do here?  Keep the air stuck to the car as it goes UNDER the car.  They are trying to get the best possible grip in all situations by using these things to create an active boundary layer.  What a waste of their time.

[RC Storick]

They work on real aircraft. Exact quote "we don't fly in scale air" But I knew that.

[Doug Moon]

I don't see any VGs here but this is a funny pic.   

[Paul Walker]

Hey, cut Sparky some slack here.

I'm sure he has put in hundreds of flights on his planes testing them out. That's how he knows!

Otherwise it would be foolish to make procolmations like he did without real facts and data. Right?

Sparky said it so it HAS to be true!

[Doug Moon]

They work on real aircraft. Exact quote "we don't fly in scale air" But I knew that.

Can you please elaborate so we know what you are talking about?  These one liners dont say much.  Maybe you are just  

Do our wings not stall the exact same way an airliner's wing would stall, or the exact same way an aerobatic full sized aircraft would stall?  

Why on earth would stunt plane wings not be beholden to physics?

Please explain..

[Doug Moon]

They work on real aircraft. Exact quote "we don't fly in scale air" But I knew that.

They work on cars and those things aren't even flying......

[RC Storick]

If it makes you feel like it does something by all means do it. Oh and by the way I bet they are bigger than a 1/16-1/8 tall

[Doug Moon]

If it makes you feel like it does something by all means do it. Oh and by the way I bet they are bigger than a 1/16-1/8 tall

Wait a minute. You mentioned scale, look at that first pic I posted with the VGs place toward the front of wing ahead of the moveable surface behind.  If you scaled that wing down to our size their VG would be but tiny bumps hardly noticable.  PJ discussed this at length years ago.  In scale ours, and the ones you find on many aerobatic RC aircraft now, are actually larger.  But hey it doesn't really matter right?  Their air must be different than our air.

You made it sound like you have hard evidence they don't work and those who think so are fools.....  Care to elaborate or is it just more one liners with not much to offer.

[RC Storick]

Care to elaborate

No. I'm not going to debate this. Just keep doing it. When Brett Buck has concrete evidence they work and they are on his airplane I might think about it.


Yes Brett I put that much faith in what you say "sometimes".

[Derek Barry]

Doug,

You posted a number of pictures of heavy planes with relatively small wings and high wing loadings. I am sure that VGs do help these types of planes, however, if you build a 700 sq. inch plane at 63 oz. you will realize that VGs are not needed.

Derek

[RC Storick]

As I see it , everyone is trying to come up with some new innovation and the last true innovation in stunt was the NOBLER.

I think it was Palmer who did differential flaps, how good did that work? If it worked good why aren't we using them? To Paul you could put a engine on a toilet seat and win so VG's are a moot point.

[Brett Buck]

As I see it , everyone is trying to come up with some new innovation and the last true innovation in stunt was the NOBLER.

I think it was Palmer who did differential flaps, how good did that work? If it worked good why aren't we using them? To Paul you could put a engine on a toilet seat and win so VG's are a moot point.

  Differential flaps didn't work well, so nobody uses them.

The last very significant  innovation in stunt was electric feedback control (2010?). Prior to that, and going back in time,

electric/lithium polymer batteries (early 2000s),
tuned pipe and/or low pitch props (86)
the low-aspect ratio tail (early 80's),
increased tail moment (sorry howard) and associated aft CG (78/9),
increased tail volume (71-72). That takes us back to the early 70's.

     BTW, since you are an expert on the history of stunt, what innovation did the Nobler introduce? Because it's almost certainly not what you think, and it's almost certainly something you would be arguing against vehemently if some did it now. To save you some time, it wasn't coupled flaps and it wasn't the 4-2 break/slow flying. 

    Brett

[Paul Walker]

Doug,

You posted a number of pictures of heavy planes with relatively small wings and high wing loadings. I am sure that VGs do help these types of planes, however, if you build a 700 sq. inch plane at 63 oz. you will realize that VGs are not needed.

Derek

Like "others", you miss the point entirely. They are not there to make a porker fly. They are there to make things more consistent.