Turbulator

[Larry Wong]

Turbulator zig-zag 90deg.

[Randy Cuberly]

Interesting Larry.

Have you flown it enough to determine if it made a significant difference?

Could you please tell us a little about the airplane.  How much it weighs, wing loading etc.

Randy Cuberly

[Steve Helmick]

Better looking than mouse turds on the wing.  Steve

[jfv]

How did you make them?

[Larry Wong]

Yes And won't get knocked off as easy, I got 6 flights today and so far it seam the same as the Vortex that was on before,  

[Larry Wong]

I got them from a glider Co.  Wings & Wheels  But $$$ oh well 

[RC Storick]

I am sure this will stir the Rat Dropping crew but when I talked to the guy from NASA this looks more in line with what he said would work best. However placement is a experiment . From what I could gather from that conversation was the ones he had seen on CL planes were placed in the wrong spot and in effect killing off some of the lift.

Milage may very Notice place ment ahead of high point of airfoil.

[Joe Yau]

I got them from a glider Co.  Wings & Wheels  But $$$ oh well 

Could you post the link?   I'm quite interested in trying some.

[Steve Helmick]

Google worked!  Steve

http://wingsandwheels.com/tapes-seals/turbulator-tape.html   

[Howard Rush]

It's like comparing walnuts to wool.  They do different things.  The trip strips are to cause the flow to transition from laminar to turbulent at a specific place.  VGs bring high speed air down next to the surface.  Tell your "guy from NASA" to show us some analysis or experimental data.  

See Peter Germann's reply #18 to http://stunthanger.com/smf/index.php/topic,30917.0.html for an interesting turbulator story.  Here are some other stunt applications I saw at a recent contest.  I don't know what effect they had, but they didn't seem to hurt:

[RC Storick]

I'm sure you have a spread sheet on your data. Now Howard unless you have a wind tunnel equipment in your garage and sophisticated equipment your blowing smoke.

But then again without wind tunnel testing equipment its all a SWAG. And the GUESS being the biggest part of this experiment.

If you looked at the video 2 things are apparent one is the VG's are a upside down V channel and the second thing was they are placed ahead of the high point of the wing causing laminar flow. But I cant prove any of this.

[Howard Rush]

I'm sure you have a spread sheet on your data. Now Howard unless you have a wind tunnel equipment in your garage and sophisticated equipment your blowing smoke.

These and their placement are more in line with what we were talking about.
But then again without wind tunnel testing equipment its all a SWAG. And the GUESS being the biggest part of this experiment.

I used XFOIL and showed the results in other posts.  It's easy to model a turbulator in one of those programs (well, except for 3D effects).  Just specify where you want transition to occur, rather than having the program figure out where it would be naturally. 

Somebody put me onto a paper written by guys at the U of Illinois (as I remember). They did wind tunnel testing of various zigzag turbulator shapes.  Curiously, the shapes corresponded to the available patterns of pinking shears.  That's how Science is done.

Frank Williams does have a wind tunnel in his garage.  Maybe he'll do some experimenting.  He's always trying cool stuff.

[RC Storick]

That's how Science is done.

  Curiously seems to me is trial and error is first then some spread sheet to follow.

[Howard Rush]

Google worked!   Steve

http://wingsandwheels.com/tapes-seals/turbulator-tape.html  

That tape is kinda big.  You can get the local vinyl mask cutter to make zigzags out of mask material cheaper.  Mike Haverly made us some lattice trip strips for stab LEs on his vinyl cutter.  I tried different thicknesses, but wasn't very rigorous in testing.  One ply seemed to work best.  They look cool made from clear vinyl.  I had them on last year's plane.

[Howard Rush]

  Curiously seems to me is trial and error is first then some spread sheet to follow.

That's why you see the mountain of bent aluminum at the end of the Boeing Field runway.  They don't do calculations first.  They just keep building airplanes until one flies.  Then they write it up.

[Howard Rush]

...and the second thing was they are placed ahead of the high point of the wing causing laminar flow. But I cant prove any of this.

I sure couldn't prove that.

[RC Storick]

I sure couldn't prove that.

Well because your not using the suggested shape droppings you couldn't disprove it either.

[Mike Griffin]

Sometimes I think technology has left me behind.  I am still amazed by how a laser cutter works.

Mike

[Serge_Krauss]

When I was a kid, I experimented with HL glider wings, just before Ron Whitman and others were using sharp wing high points. My gliders were a bit heavy, with smooth wing surfaces(steel wooled). They flew fast and didn't like to turn. One day I glued a thread spanwise across the wing a bit ahead of the high point. So this wasn't with V-shaped turbulators or trippers. The wing immediately flew more slowly and slightly prone to upsets. These were pretty thin wings, compared to a CL stunt model's, but they seemed to have acquired more lift for a given speed, even in the glide. I tried this on the LE of a Skyray stab, and it "seemed" to help turns, but I think this was like sharpening the LE, which has been said here to make these thin, low-RN surfaces work better. I always saw that as turbulation, but never understood how such a thin-diameter thread could affect boundary layers. It obviously did something.

So, my question is are the V-shaped turbulators, spaced advantageously, better than just upsetting the boundary layer continuously across the span. I'd like to know the boundary layer thicknesses on our models. Have I missed something in these conversations?

[Avaiojet]

I got them from a glider Co.  Wings & Wheels  But $$$ oh well  

How thick are those things?

I can probably make them cheap. Any width, size, angle, etc. They'll stick and you can paint over them!

[Howard Rush]

Have I missed something in these conversations?

Only the most fundamental, most often repeated thing.

[Howard Rush]

How thick are those things?

Charles, perhaps if you disable the Safe Search function on your computer, you could follow the link that Steve gave you.  Better yet is the question, "how thick should they be?"  This will require a little more research, but a clue is here on this thread. 

[Randy Cuberly]

  Curiously seems to me is trial and error is first then some spread sheet to follow.

Robert,
You're obviously an intelligent guy, and for that reason I'm always stymied by your overt attitude against analysis and scientific process.  It just doesn't make sense to totally decry analysis of anything.  Yes, practical data is always needed to build proper analysis and trust your answers.  I think that's what Howard is trying to convince you, and everyone else, is the best way to attack a problem.  If you're not capable doing the analysis then at least depend on the analysis of others that are capable, to direct the experimentation. 

I truly believe that without the benefit of analysis and totally depending on experimentation, we would still be trying to put a rocket into space.   Even the Chinese that formulated Black Powder hundreds of years ago had rudimentary methods of analysis that they depended on to direct their work.

You do great work but I garantee that most of what you do is built on the work of others...it's that way for all of us and especially real scientists and engineers. 

Analysis makes it much easier to test the validity of data and and determine a direction that doesn't continually end in failure.

As I said, given this...why would you continue to totally ignore the results of analysis as if it was a disease.

Randy Cuberly

[RC Storick]

What I am against is every time I say something I am instantly wrong. It was dismissed when I mentioned I talked to someone who knows what they are talking about. Right away it was show me the DATA. My suggestion is that they do their own research. When I wanted to bend aluminum tubing without a kink (its not sand)  I called NASA direct to ask how they did it. As a mechanic I don't claim (as some) to know everything. However I know this for a fact I know where to find the answer to a question. I usually go to the source.

I don't need a spread sheet to tell me how it feels.

For anyone who's interested in how to bend aluminum tubing without a kink. NASA does it with liquid nitrogen. Obviously You wont have that but you can do it with Bismuth. The engineer I talked to sent me a free ingot.

[Douglas Ames]

FWIW - The Turbulators (Vortex Generators) that are installed on the main flap of a Boeing 767-300 are ahead of the high point, (very much a flat-bottomed airfoil) but then again it's designed for high AoA's 0-30 deg. + wing AoA.

[Avaiojet]

Charles, perhaps if you disable the Safe Search function on your computer, you could follow the link that Steve gave you.  Better yet is the question, "how thick should they be?"  This will require a little more research, but a clue is here on this thread.  

Well, when you know how thick they should be, let me know. I can get paintable material up to 5 mils thick.

AND, can provide only what is needed for any given model.

[Mark Scarborough]

Well, when you know how thick they should be, let me know. I can get paintable material up to 5 mils thick.

AND, can provide only what is needed for any given model.

the point Charles,, is that you asked a question to which, if you are attempting to market something,, you should be prepared to do the research,, as I and many others have told you,,, use a little innitiative man,,

[Avaiojet]

the point Charles,, is that you asked a question to which, if you are attempting to market something,, you should be prepared to do the research,, as I and many others have told you,,, use a little innitiative man,,

Mark,

I really don't try to market anything. Most of my graphics, Warbird actually, go out of the Country, to large scale R/C model builders. I've been making graphics and masks for almost 20 years, I have a large repeat customer following.

I read the Post about these items being expensive so I thought I could help out. They are currently offered in rolls.

Unfortunately, the more research that goes into an item the more costly it can get. Even you know that.

So, if no one makes an inquiry, then so be it. They can purchase the stuff from the current supplier in large rolls.

One would think the research would have already been done by those marketing the product?

The question was quite simple. All one has to do is measure the thickness.

You don't need reverse engineering for this.

[Serge_Krauss]

Only the most fundamental, most often repeated thing.

Well, Howard, that was helpful. I probably should have asked why VG's are superior to turbulators, but I don't understand why localized high energy whirlwinds are better than just affecting the airflow across the span. If that still offends, 'guess I'll go back out and miss some more.

Edit: This thread with VG's shown across the span was probably not the best place to ask, but I'll leave it.

[Howard Rush]

All one has to do is measure the thickness.

All one has to do is to click on the link Steve provided.

[Steve Helmick]

The FF guys do their experiments in a way that may (or may not) prove useful for CL Stunt experiments.

For example, when you're putting turbulators on the wing of a FF, you find that when you get it/them in the right place, you suddenly need to add incidence, because it starts diving. You can also do some interesting things by putting turbulators on one wing and not the other, or only out toward the tips.

For stunt, I'd put a turbulator on the top of (for instance) the stabalizer and see if it changes the inside/outside corner. Or put a turbulator on only the inboard wing, but not the outboard...don't forget to add tipweight to compensate. I'm pretty confident that it will prove interesting, maybe even educational. Especially if you are using a nice lightweight hardpoint handle.  Steve

[Howard Rush]

Well, Howard, that was helpful. I probably should have asked why VG's are superior to turbulators, but I don't understand why localized high energy whirlwinds are better than just affecting the airflow across the span. If that still offends, 'guess I'll go back out and miss some more.

It's like comparing bees to tires.  They do different things.  The trip strips are to cause the flow to transition from laminar to turbulent at a specific place.  VGs bring high speed air down next to the surface.  I guess I should have mentioned that earlier.  My understanding of either is limited--for all I know that zigzag tape may be some sort of hybrid--but I think that we might get a clue from learning whatever of the physics we can.  

I have used VGs on my wing.  Despite their being expensive and making the wing hard to clean, it feels like they help a little in corners.  The main benefit I get from them is the ongoing banter with Derek, Dennis. et al. You can see from the pictures above that many of the top fliers at the recent world championships use zigzag strips, but not discrete VGs. I put some of these the tail of one airplane to see if I could get the transition to stay put and make it fly better upside down.  I haven't tried them on a wing yet.  I think there might be some benefit to using both VGs and boundary layer trips.  Now that would be ugly.  I would need to read some and learn more to get more of a clue as to where to put either before adding another variable.

[Howard Rush]

The FF guys do their experiments in a way that may (or may not) prove useful for CL Stunt experiments.

For example, when you're putting turbulators on the wing of a FF, you find that when you get it/them in the right place, you suddenly need to add incidence, because it starts diving. You can also do some interesting things by putting turbulators on one wing and not the other, or only out toward the tips.

For stunt, I'd put a turbulator on the top of (for instance) the stabalizer and see if it changes the inside/outside corner. Or put a turbulator on only the inboard wing, but not the outboard...don't forget to add tipweight to compensate. I'm pretty confident that it will prove interesting, maybe even educational. Especially if you are using a nice lightweight hardpoint handle.  Steve

That's an interesting thought.  I put a trip strip on the bottom LE of the stabilizer of my last IC airplane to try to fix the outside-to-inside transition of the horizontal eights, but I think the problem was that I only practiced that transition half as much as the transition the other way.  It did confine the ugliness to the bottom of the airplane.

[Gerald Arana]

I think what I'm going to do on my next ship is a strip of horribly orange peeled paint along the LE! (Or just back from it)

I inherited a ship that is very poorly built with lots and lots of orange peel in the paint job and it flies great. Probably the best flying ship I have and the good thing is I don't have to worry about smashing it to bits!

Excellent for practicing those low bottoms. Heh, heh!

Jerry

[Joe Yau]

Better looking than mouse turds on the wing.  Steve

well, if they were in clear or light-grey color wont be so bad..

[Steve Helmick]

My recollection is that the FF guys said the turbulator strips (whatever kind) turbulated the airflow specifically to make it reattach to the airfoil aft of the turbulators. There were some oddities, like "terraced airfoils", where the top aft was stepped kinda like a hillside rice paddy. The current "hot thing" in F1A (Towline Glider) is "LDA", or Low Drag Airfoils. I'm not sure if there's more than one, but apparently they're the shizzle ("bee's knees"). I doubt they'd turbulate an LDA airfoil at all. Turbulators slow the glider in all flight regimens.  

One of the things I learned while I was actively flying F1A was that a slick finish (i.e., film) glided faster. And towed faster. I know that the faster glide is a bad thing in light, turbulent lift...stuff like we locally fly stunt in quite often. But towing faster is not for those that are not young, fit, and fleet afoot. A nice orange peel finish might just save us from both turbulator strips and mouse turds on the wing and tail surfaces. Should get about the same appearance points deducted, don't you think?   Steve

[Lauri Malila]

Steve,

Off topic as usual but so what;
The 2 wings in the left are LDA's. If you compare with classical Benedeck (right), you'll see that biggest difference is in the front part of wing bottom. That makes a huge difference in drag at high speed; while "old school" model bunts to 80..85 metres with a good start, the LDA's go to a little over 100m (50m towline).
Sink rates are about similar but normal Benedek handles thermals better. LDA's also glide a bit faster and that makes trimming and flying them a little more tricky, all warps etc are much more critical. Many people prefer classical airfoils in basic rounds and keep LDA's for those calmer fly-off flights.
Also LDA's are turbulated, usually near 50..60% chord while classical foils have turbulator at 7..10%.
Usually a turbulator (in LDA) makes glide better untill about 1/32" dia but also eats start heights effectively.
In my LDA's, I use either wire turbulator dia. 0,3mm or 0,18..0,20 mm zigzag. Total width of zigzag is 8mm in root and it tapers to 5mm towards tips. The guy who had to make the cutting program hates us now.
Also, some of the first generation LDA foils require turbulation on underside, too. Otherwise they do funny stuff in high speeds.
But propably because of slightly higher Re, they can be covered with plastic film. For classical benedek, ste micro-structure of covering (like in doped paper) is quite important..
About the difference of straight wire and zigzag; not much in glide if model is good, but during tow the zigzag makes model more stabile, especially near stall speeds.
I guess that Howard is right about zigzag working a little as vortex generator too. L

[Lauri Malila]

Another pic, turbulator more visible..

[Dave_Trible]

I think what I'm going to do on my next ship is a strip of horribly orange peeled paint along the LE! (Or just back from it)

I inherited a ship that is very poorly built with lots and lots of orange peel in the paint job and it flies great. Probably the best flying ship I have and the good thing is I don't have to worry about smashing it to bits!

Excellent for practicing those low bottoms. Heh, heh!

Jerry

It's always seemed funny to me.  As a kid and through the teen years I built countless 1/2a ships as well as the larger stuff and without fail the ones I went to great pains to put on a slick pretty finish never flew as well as the ones that we just put on enough dope to resist fuel for a while.  The cruddy ones always flew best.  One might look into why a golf ball is full of divots.  I'm told of an auto study where a really rough  body got better milage than a slick one.

Dave

[Steve Helmick]

I'm with you on that, Dave T.  

One note for Laurie...It's disappointing to see the use of round wing joiners is still persistant. I met Hans Seelig and his son here, and the son (?) had an F1A he flew. The wing joiner was a stack of clock spring material, so was square. I assume it fit into a square brass tube socket in the wings, but details aren't clear in my memory of this. Anyway, it was stiff vertically, but would flex forward if the model was dorked into the ground on a line cross or such. I thought it was absolutely brilliant, and tried to find flat clock spring stock, but failed. Maybe it would be possible to find online. Since it's a Digital world, any suitable spring stock might be rusty,  dusty, and crusty!  

And for Howard...it seems to me that the "dimple tape" would do pretty much the same thing as the VG? I'm not sure what this stuff would be like...maybe actually holes in the tape? It seems to me that somebody tried that for our planes, but can't recall the results reported. I still think it would be best to try this sort of thing on only one surface of one side...might be a little risky, but it should indicate clearly that it's doing something, whether good or bad.     Steve

PS: Smiley icons annoy Dirt, Tim and Howard. Gotta love it...   

[Lauri Malila]

Yes Steve, we are using more and more square joiners, but made from carbon. New ones have also boron on compression side. Clock spring material is hopelessly too weak for modern models, and it must be rigid to all directions. We routinely bend 6,5mm spring steel joiners.
My new carbon skin wings have 8mm joiners. They are conical and drilled and actually lighter and stiffer as solid 6,5mm ones.
It's actually really stupid to have the joiner in center of wing, better would be to have take-apart tips. L

[Larry Wong]

.it seems to me that the "dimple tape" would do pretty much the same thing as the VG? I'm not sure what this stuff would be like...maybe actually holes in the tape?

Steve I think you got it, A Golf ball finish, But those dimples are HIGH TEC.

[Howard Rush]

Well, when you know how thick they should be, let me know. I can get paintable material up to 5 mils thick.
AND, can provide only what is needed for any given model.

OK, Charles, here you go.  From the link Steve gave you, you know how thick the expensive stuff is.  This link (and JavaFoil, also from Dr. Hepperle's site) will tell you how thick to make turbulators and where to put them for a specific model: http://www.mh-aerotools.de/airfoils/turbulat.htm

[John Sunderland]

Howard I know you know more of the answers and the calculations than any of us, but if you built anything other than an orange and yellow Impact and did some trial and error testing of others findings without factual quips that provoke we would all be more impressed!

[Curare]

Acutally, here's some food for thought from outside the circle (groan). If we're doing F1A, we may as well get some input from other places too.

Not so long ago, when RC sailplanes were made of balsa, once of our best pilots in australia swore black and blue that he could increase the efficiency fo any sailplane by covering the bottom with monokote and using tissue on the top. Now as we know surface finish does have an effect on boundary layer thickness. In this instance there's no imperical evidence, apart from the fact that no one could catch him in a thermal.

I've made jokes for years that my pattern planes always seem to fly worse after they've been cleaned. (they're electric so they get a squirt with some polish once a year whether they need it or not!). Still, I'm not sure whether the joke is all BS.

Could it be that the surface finish needed for max appearance points is actually degenerating flight qualities? Who's going to be the first to mist their model with something lumpy to see if you get better corners?

[Howard Rush]

Could it be that the surface finish needed for max appearance points is actually degenerating flight qualities? Who's going to be the first to mist their model with something lumpy to see if you get better corners?

The F2B Champion of the World has several seasons worth of insects on his wing's leading edge. 

[Russell Bond]

You mean his "turbulators" hahahaah!!!  

He said he can't clean the insects off because the paint will come off with them. We don't believe him now, do we???

[Igor Burger]

I not need to clean them, I fly F2B, my model have 347964 wings, and only 2 of them I built myself, so it is is not BOM compliant, but I do not care, I am ok in FAI also with them :-P

[Avaiojet]

OK, Charles, here you go.  From the link Steve gave you, you know how thick the expensive stuff is.  This link (and JavaFoil, also from Dr. Hepperle's site) will tell you how thick to make turbulators and where to put them for a specific model: http://www.mh-aerotools.de/airfoils/turbulat.htm

Thanks for that Howard. A bit hicker than I thought.

[Howard Rush]

Thanks for that Howard. A bit hicker than I thought.

Than I thought, too.  If I can figure it out, I'll put in Igor's turbulator location, then work backwards to see what it's for.

[Serge_Krauss]

I haven't visited Martin Hepperle's pages for some time and hadn't  seen this one. He has posted many clever things of interest to me over the last decade or so. Here he's answered one of my main questions, that of turbulator height/position. Thanks for the link. 'probably should revisit Simons too, although I think I trust Hepperle more.

SK

[Steve Helmick]

Another tidbit of information I recall from the Free Flight days, regarding turbulator strip height.

The late & great Bob White (a World Champ in F1B and many time USA team member) used strips of basswood for turbulators, got them in the right place (he built his same design for decades), then sanded them down in thickness until they no longer funtioned. Once they didn't work, he removed them and replaced them with strips of the thinnest size that did work. I think he started with 1/32" square, but maybe 1/20".

This seems to me like a reasonable enough method, but for our use, I'd consider (again) trying it on top only and/or one side only, as a method of taking the results from the "I think it's better" stage to the "Oh, it definitely works" stage of testing. You may want to do this with your backup...or second backup plane.  Steve 

[Avaiojet]

Than I thought, too.  If I can figure it out, I'll put in Igor's turbulator location, then work backwards to see what it's for.

All this science and math is well beyond me.

I know of no vinyl material, that I can get, which has the required thickness needed for any given cord length.

[RC Storick]

All this science and math is well beyond me.

Pie R round / Cornbread R Square unless you using new math and bake it in a round tin.

[Curare]

Kline fogelman for stunt?

[Mark Godfrey]

Speaking of bending aluminium tube.
Have you tried submerging it in water plugging the end with silly putty freezing it and then bending it?
Works for me but I don't have the spreadsheet to prove it.


M

[Robby Hunt]

Another possible source: http://svsponline.co.uk/Zig-Zag-Turbulator-Tape.html