Trip Strips

[Frank Donnelly]

I read an excellent article by Dennis Nunes entitled “Turning to the Dark Side”. In the article he mentions adding Trip Strips to the horizontal stabilizer’s leading edge to eliminate hunting. It’s a bit difficult to see the orientation of the strips in the photo provided in the article but it looks like the scalloped edge faces aft. Can anyone confirm that?
Second question. There is a mention in the article of using them on the wing. I understand that the intention is to break up the airflow; but what purpose would this serve? In other words what is trying to be achieved by placing the strips on the leading edge of the wing?
Thanks,
Frank

[Dennis Nunes]

I read an excellent article by Dennis Nunes entitled “Turning to the Dark Side”. In the article he mentions adding Trip Strips to the horizontal stabilizer’s leading edge to eliminate hunting. It’s a bit difficult to see the orientation of the strips in the photo provided in the article but it looks like the scalloped edge faces aft. Can anyone confirm that?
Second question. There is a mention in the article of using them on the wing. I understand that the intention is to break up the airflow; but what purpose would this serve? In other words what is trying to be achieved by placing the strips on the leading edge of the wing?
Thanks,
Frank

Thank you for the compliment on the article. The "scalloped edge" or wavy size faces the leading edge of the stabilizer.
We are still experimenting with the trip strips on the wing. They are similar to Vortex Generators. I don't know or understand how they work, but they have helped my "not-so-light" plane turn better in corners.

Dennis

[Frank Donnelly]

Dennis, Thank you for the quick response. So if I got this right by placing the strips on the stabilizer you were able to mitigate the hunting issue. Placing them on the wing leading edge is an experiment in getting tighter corners. Based on your experiments with different material would you recommend starting with Gorilla tape?
By the way the article you wrote contained a wealth of information way beyond Trip Strips. I learned a lot, and got some great ideas. I know it had to take a considerable amount of time to put all of that together. Thanks for making it available.
Frank

[Dwayne Donnelly]

Please  any pics? How big are the strips, how tall etc.. Thanks 

[Dennis Nunes]

...Based on your experiments with different material would you recommend starting with Gorilla tape?...

  The reason I went with the Gorilla Tape was to find something that would say in place and not come loose. Believe me Gorilla Tape DOES STICK! Perhaps too good. I haven't tried to remove them from my plane yet. I'm hoping that with a little heat from a heat gun they can be removed without ruining the dope finish.
  The Crystal Clear Vinyl Static Cling product from Decorative Films really helped me to see if they worked and is great for testing. As these can be removed and repositioned if necessary. But these require a extremely smooth surface (like glass) and have a tendency to come off or become loose in time as we found out, with warm weather.
  The Gorilla Tape is a more of a permanent solution. Some that I fly with have been using vinyl electrical tape, but I don't know the brand. It's .008" thick , comes in different colors and has been working pretty well. We have found that the material needs to be at least .007"-.008" thick to be effective and about 3/8" wide.
  Attached is a PDF file on how I made my trip strips, the tools required and where they are placed.

  Hope that helps,

  Dennis

[Will Hinton]

Dennis, if and when you decide to attempt removing the gorilla tape, certainly try the heat gun but with much discretion, then, when you get an edge to lift a bit, apply lighter fluid in copious amounts and then try to slowly peel it off.  I have used lighter fluid in this manner on just about every kind of adhesive there is, and the only failures I have had for good results are the original gorilla glue, (the expansion kind) and ca.  It won't hurt your dope either, or it never has any of mine.  It's the old warning they give us on everything, "Try a test trial first."
Hope this helps.

[Steve Helmick]

Dennis, if and when you decide to attempt removing the gorilla tape, certainly try the heat gun but with much discretion, then, when you get an edge to lift a bit, apply lighter fluid in copious amounts and then try to slowly peel it off.  I have used lighter fluid in this manner on just about every kind of adhesive there is, and the only failures I have had for good results are the original gorilla glue, (the expansion kind) and ca.  It won't hurt your dope either, or it never has any of mine.  It's the old warning they give us on everything, "Try a test trial first."
Hope this helps.

Howard is a big believer in "Vortex Gensets" but says they're different than "Turbulators". I don't see how, since FF guys have used MANY types of "Turbulators" for many decades, and they all do the same thing...get the airflow to attach or reattach to the surface of the wing or other flying surfaces. Some are an eyesore, while others are very easily knocked off with a cleaning rag.  Steve

[Dennis Nunes]

...Some are an eyesore, while others are very easily knocked off with a cleaning rag...

  That's also one of the reasons why I liked the "clear" Gorilla tape is that they are almost invisible.
  On my plane that had VG's that I took to the NATs this last year, I should have started a betting pool to guess how many VG's got knocked off the wing while traveling from Stockton, CA to Muncie, IN, during the NATs, and then back home again! 

  Dennis

[Howard Rush]

Google "airfoil laminar-turbulent boundary layer transition" (without the quotes) or "laminar separation bubble" (with the quotes) to get the lowdown on the theory.  Igor and Frank Williams explained what happens with this transition on a stunt plane tail a few years ago on the Preacher's board.  Left to its own devices, the transition will wander around while one is trying to fly level, changing the lift on the tail.  A sharp LE or trip strip can make it stay put or move less abruptly.  Igor explained it as:

"It all means that such stab has at low [elevator] deflections some discontinuity, which could lead to nonlinear or abrupt changes of something somewhere what can be reason of unwanted inputs to pitching. Pilot sees the model goes slightly somewhere where he does not want him. He tries to push him back by a small deflection, but he sees it is not enough. So he slowly adds little bit until he reachs that discontinuity and model does something abruptly. That is instability which cannot be handled by pilot and that is reason for hunting."

After Dave Fitzgerald did his tail tests awhile back, all the West Coast stunt guys have been using tails with sharp LEs.  The first picture is my old Impact tail with a clear tape lattice made by Mike Haverly.  I think the lattice makes it easier to fly level, but it worth putting on just because it looks cool.  The second picture is the tail of the 2014 world champion Max Bee.  Behold that it has a sharp LE, zigzag tape at the LE, and more zigzag tape farther aft: in the white space in the star behind the blue area and in the white space behind the red and yellow stripes.  One wonders which took precedence, the trim scheme or aerodynamics.

[Brett Buck]

After Dave Fitzgerald did his tail tests awhile back, all the West Coast stunt guys have been using tails with sharp LEs.  The first picture is my old Impact tail with a clear tape lattice made by Mike Haverly.  I think the lattice makes it easier to fly level, but it worth putting on just because it looks cool.  The second picture is the tail of the 2014 world champion Max Bee.  Behold that it has a sharp LE, zigzag tape at the LE, and more zigzag tape farther aft: in the white space in the star behind the blue area and in the white space behind the red and yellow stripes.  One wonders which took precedence, the trim scheme or aerodynamics.

    Tail experiments started with taped-on-wire turbulators on the otherwise flat stabs with rounded radius leading edges. At the time, the issue was inconsistent corner exits that we figured were causing the separation bubble to form over tiny AoA changes. David's original airfoiled stabs were like Igor's, with the high point further forward. Mine have the high point as far back as I can make it, the theory being that you want a positive normal pressure as far as you can manage it, and David's second Thundergazer (monocoted) stab is much more like that.  And as noted, while PJ thinks I am not sufficiently skilled to tell the difference, I have found no change whatsoever when adding any form of flow control device to the stab.

   I have tried several cases with flat stabs and pointy things attached to the LE, and in those cases I did find some advantage to turbulators, just like in the case of the radiused LE, right where the flat part starts.

    Brett

[PJ Rowland]

Ohh brett, leave it alone.

Only now you tell me you *only* trialled them on the stab and found no improvement? Im not surprised.. try the wing where I said..

I guess by your own experiences; guys like Igor, David, Paul, Howard, Derek, Chris, and 20 other fliers dont have a name are also "wrong" ? Or perhaps ALL airframe design of all these stuntships is somehow interior to the inifity?

Having studied the plans it was a solid design, with much more side area than ANY other plane i had previously seen. There are a multitude of reasons that the infinity didnt benifit from any flow control over the stab. The infinity is also a relativly "thin" stab and certainly the highpoint isnt "gamechanging" far back.


Look Ive personally trialled many things, including Stab plates as advocated by Randy smith designs, and used to win a few Nats titles. You dont see me jumping up and down complaining they dont work.. I said they work on some, they didnt work for my stab airfoil design.

I apologise I said you "didnt have the skill"  to see a difference.

Clearly you do!
Now lets see if your ego has the skills to let it go.

Ive NEVER been against you, and have only had complete respect for you as a serious stunt flier. A little in return would be appreciated.

[Brett Buck]

Ohh brett, leave it alone.

Only now you tell me you *only* trialled them on the stab and found no improvement? Im not surprised.. try the wing where I said..

I guess by your own experiences; guys like Igor, David, Paul, Howard, Derek, Chris, and 20 other fliers dont have a name are also "wrong" ? Or perhaps ALL airframe design of all these stuntships is somehow interior to the inifity?

   PJ, I am just giving you a bad time, you realize that, right?  I am pretty sure I could tell the difference - if in fact there was one. I diagnosed Howard's tip weight changes, to the gram, by merely walking by the circle while talking to someone else.

  But -  you are dead certain that you know it always "helps" in some undefined subjective way, and therefore left having to explain negative results by ever more complex and elaborate theories, most of which boil down to "well, it certainly helped,  that's a given,  so lets figure out why you can't detect it". Negative results are still results, theories need to explain it. You, like everyone else, have a *theory*, subject to replication - or not - and always needing to evolve with new evidence. Not immutable truth that must dismiss negative results through some other means.

   In the case of the stab in particular, I have explained what I am doing and why at least a half-a-dozen times (including 45 minutes ago, off-line) and in fact, it probably *isn't* subject to the same issues associated with flat stabs or flat stabs with pointy leading edges, or airfoiled stabs with the high point forward, and consistent with most of the results to date. It may have other issues and may also not be the optimum solution, but I think the underlying idea is right and I will stick with it until further evidence suggests I am wrong.

     Right now, my current airplane has a much more fundamental set of issues, so I am going to get that back to the expected baseline performance first. Then and only then again try various adjustments just like we always do. First in line after I establish my baseline performance are zigzag strips on the stab, which, while I do not see a big problem that would required a flow control device, may still alter the flow regime around the hinge line, and is worthy of experimentation. But I am also willing to admit any evidence that I get, it may be a breakthrough improvement, or may do nothing again.

    Brett

[Lauri Malila]

In free flight we went from wire turbulators to zigzag (Oraguard stone protection film). Then back to Kevlar wire because we couldn’t tell the difference in use and wire looks prettier.
Now, with modern airfoils the best seems to be sprayed on granulate turbulator (2-component acrylic + glass or cotton powder). L

[PJ Rowland]

No problems Brett.

I will admit (and have been guilty ) of not being able to discern humor through an online medium.

I got a chuckle over the tip weight comment.

I do see your point of view., there are countless possible reasons why flow attachment devices may not be objectively felt.

Lauri. Freeflight flow attachment is a completely different animal, im not sure there is much cross over.
I did extensive testing of trip wires. Simply creating a drag force isnt enough to increase lift. (Although it can )

The "zigzag" strips everyone is using are really just VGs the difference being the are .005 to .007 in height.

[Dwayne Donnelly]

No problems Brett.

I will admit (and have been guilty ) of not being able to discern humor through an online medium.

I got a chuckle over the tip weight comment.

I do see your point of view., there are countless possible reasons why flow attachment devices may not be objectively felt.

Lauri. Freeflight flow attachment is a completely different animal, im not sure there is much cross over.
I did extensive testing of trip wires. Simply creating a drag force isnt enough to increase lift. (Although it can )

The "zigzag" strips everyone is using are really just VGs the difference being the are .005 to .007 in height.

Please where can one purchase those zig zag strips?
Thanks

[Curare]

In free flight we went from wire turbulators to zigzag (Oraguard stone protection film). Then back to Kevlar wire because we couldn’t tell the difference in use and wire looks prettier.
Now, with modern airfoils the best seems to be sprayed on granulate turbulator (2-component acrylic + glass or cotton powder). L

I feel this explains why dirty models seem to fly better than clean ones.

[Lauri Malila]

I feel this explains why dirty models seem to fly better than clean ones.

Absolutely! Unfortunately we are so anal about surface finish of our airplanes.
I agree that Re's and such are differend between ff and cl, but personally I don't see much in use difference between zigzag or straight wire. But people often see what they want to see. We have found that with zigzag cut from plastic film, you manage with less thickness than with round wire, but in my opinion it's just the sharp edge that makes the difference in function. I got fed up with the thin ones because while they work well in dry conditions, they completely lose their efficiency in wet conditions. L

[Dennis Nunes]

Please where can one purchase those zig zag strips?
Thanks

Hi Dwayne,

I'm not aware of anyone who sells them. I made my own trip strips. It 's easy. Attached is a revised PDF file on the tools needed, how to make them and where to place them to start with. I would recommend trying vinyl electrical tape (.008" thickness) rather than Gorilla packaging tape that can be purchased from Home Depot or Lowes.

Dennis

[Dwayne Donnelly]

Hi Dwayne,

I'm not aware of anyone who sells them. I made my own trip strips. It 's easy. Attached is a revised PDF file on the tools needed, how to make them and where to place them to start with. I would recommend trying vinyl electrical tape (.008" thickness) rather than Gorilla packaging tape that can be purchased from Home Depot or Lowes.

Dennis

Thanks Dennis, as usual my brain over thinking things. I get it now. 😆😆

[Gerald Arana]

I feel this explains why dirty models seem to fly better than clean ones.

I acquired a Thunderbird that has a horrible (IMO) finish, orange peel, and it flies great.....but looks like 'L.

So, what would be wrong with a trim stripe in the place of VG's that is orange peeled on purpose? Say black?

Jerry

[Ken Culbertson]

This talk of smooth finish has me thinking.  I use satin spray paint (Rustoleum mostly) then gloss clear.  Covers better, more colors to choose from and easier to touch up than gloss.  Being electric I fly the planes twice before finishing.  Once after they are sealed to see if there are any x-acto #11 issues and once again before clear to make sure nothing has changed.  A couple of 1 minute test hops usually does it and one pattern.  I have noticed that the planes seem to fly a little bit better with the satin finish than the gloss.  Could be the weight but I am not a "soak them till they drip" type so the clear is not adding enough weight to be a factor.  Could be me, I like satin and you do fly better if you like what you see.

Is the COF that different between satin and rubbed out gloss?  If it is then why do we make them so shiny?  I actually think the Satin looks better especially on military colors as long as you are electric.  Unfortunately, the IC slime won't go away on satin and you have to shine it.

Ken

[PJ Rowland]

There are many things have "can" have a dramatic effect on the planes ability to fly through a corner.

Guys that use open bays know what Im talking about..

[Howard Rush]

So, what would be wrong with a trim stripe in the place of VG's that is orange peeled on purpose? Say black?

A trim stripe could trip the flow from laminar to turbulent if you put it far enough forward that the flow isn’t already turbulent, and if it’s about the same height as the boundary layer.   I don’t think it would do the same thing as VGs even if it’s orange peeled or black.

[Brent Williams]

Has anyone experimented with adding a multitude of little 1/8" dots made from vinyl or tape, much like the inverse of the surface of golf ball?

[Howard Rush]

Please where can one purchase those zig zag strips?

Icare in Canada may have it.  Google zackenband turbulator.  Be careful how you spell it or you’ll get some German porn stuff.

[Howard Rush]

Has anyone experimented with adding a multitude of little 1/8" dots made from vinyl or tape, much like the inverse of the surface of golf ball?

In development at Jive Combat Team Laboratories.

[Howard Rush]

Making them fills my shop with smelly smoke, though.  Continued development awaits a better exhaust fan.

[Curare]

Making them fills my shop with smelly smoke, though.  Continued development awaits a better exhaust fan.

Is there a science behind using circles?

[Howard Rush]

There is, but I can’t say I know it. Wind tunnel guys use them.  They (the dots) are smaller than 1/8”.