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May 16, 2009, 04:00 AM
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Zone wing airfoils

Hello everyone,

This is the public release of the Zone series of airfoils for DLG wings. They were developed by me independently of other airfoils... The main design goals were simple:

(1) Get the minimum drag
(2) Given (1), get the most lift
(3) Optimize for both smooth and rough air


(4) Try to keep it thick enough to still be able to hold a servo
(5) Try to keep the hingeline thick enough that it shouldn't flutter if faced

The idea is to be able to cover a lot of sky efficiently, and to be able to get back from downwind when nothing else can.

The foils are the Zone-52 through the Zone-21. The number associated with the airfoil is the Re*sqrt(Cl) for which the airfoil was optimized. If in doubt on your own wing designs, a two panel wing can go with the Zone-52 at the root, the Zone-40 at the panel break, and the Zone-25 at the tip. For a three panel wing, one can try the Zone 52-46-36-21 sequence. Either of these won't be the best that you can do but it will be pretty good. More on that later.

Phil Barnes made some interesting observations when he first examined these airfoils a few months ago. The Zone* series has a great deal of similarity in profile to the AG* series. More than I had realized. Earlier in the design process I did a check and they were much farther apart than they are now. My efforts to thicken them converged the root and mid sections towards the AG* series. The differences make quite a change in performance though. Anyway, as one progresses to towards the tip airfoils, the similarities disappear.

I have provided comparisons at 0, 2, 4 degrees of camber and sometimes more. It was getting cluttered so I didn't go farther. 0 is obviously the speed setting. The response of each airfoil to the progression of camber change should give you an idea of what the series can do. The performance differences between the AG* and Zone-* should be evident.

In practice, I have found that the 0, 2, and 4 degree camber settings work well. There is a learning curve flying a wing with these airfoils. Expect to be able to cover more sky, but also expect to have to pay more attention. I do not consider these beginner airfoils. Also the thermal setting works pretty well for loitering around, and is practically always the desired camber when in a thermal. This is different than the AG* series where thermal camber is often not useful.

The prototype Zone wing has an AR of 10.5, same as Supergee-II. It has been tested at up to 5oz ballast and the prototype isn't all that light to start with, and the wing handled the weight with ease. It could handle more. Phil and I flew it in some wind that was bad enough that we almost couldn't assemble or throw the model. We were able to go upwind, pick up lift, climb out with it, go back upwind... The wind had taken shingles off the gazebo on the field! Enough of fish stories.

Included are some plots of the Supergee-II wing analysis results comparing AG* and Zone-* airfoils. No attempt has been made to optimize the wing for the Zone foils. The green line is the 52-40-25 sequence and the yellow line is 52-36-25. Notice how this second version is a little better? Anyway these plots should show what these foils should be capable of.

When I began this process last year, I designed a wing and used its camber progression to create criteria for the airfoils at different stations. Then I spent hundreds of hours developing the Zone wing series. Then I plugged them back into the wing and started optimizing. It turns out the original wing wasn't all that good compared to what I could really do with these new foils. So much for that approach!

A wing with these foils is going to be thin. Very thin. So I recommend nothing lighter than HiLoad60 for the cores. Phil and I are using Spyder in the prototypes. I spent a great deal of time getting these foils as relatively thick as they are. I can do better but then construction and flutter would start to become significant issues. I figure this is it for this year.

I want to give special thanks to Phil Barnes, for his encouragement, for helping to make the first prototypes, and for many other things. I want to thank those others who have known about this project for a while and have also given me a great deal of encouragement. You know who you are, and if you want then chime in! Also a special thanks goes to Al Anderson who has let me work around the clock on his machine doing all the number crunching for more nights than I care to think about. Including this one!

The Zone project is a work in progress. You have the complete set of airfoils as they stand right now. There are many other innovations in the project and details will be forthcoming as I or Phil get around to it.

Gerald Taylor

PS - I forgot to supply one crucial piece of information! The hingeline is at 70%. All analysis assumes a bottom hinge.

Last edited by G_T; May 16, 2009 at 12:40 PM.
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May 16, 2009, 10:16 AM
Oleg Golovidov
olgol's Avatar
Gerald, thank you very much for releasing this to the public. That was a lot of hours spent. The wing analysis is very interesting and shows a great promise.
Please catch up on your sleep now. Do not spend any more time in the middle of the night running xfoil.
May 16, 2009, 10:38 AM
Yep, Naza-controlled Tricopter
tonyestep's Avatar
This is a splendid project, a great example of what a serious approach to modeling can accomplish. It will be cool to see what happens when these appear on competition planes. Kudos to Gerald for doing it, and for giving his results to the world of HL.
May 16, 2009, 11:26 AM
Make Flying Fun
OK, got the foils! Panel demensions and chord recomendations etc?
Thanks for the goodies!
May 16, 2009, 11:45 AM
Just fly...
This all sounds really cool!!! Thanks, Gerald. Thanks, PB!!! (with hang loose gang sign)
I really love to see the innovations that all of you guys come up with.
Can someone build me a wing please? I can't build to save my life! LOL!!

May 16, 2009, 11:52 AM
Hit my smoke....
Hostage-46's Avatar
So It would be interesting to hear a pilot's perspective on flight characteristics vs SuperGee. What were the design goals? Have they yet been realized?

Dan in Dallas...
May 16, 2009, 04:42 PM
Jimn8uay's Avatar
Ok, excuse my ignorance, but I'm trying to search for info on converting files from .txt to .dat or something I can use in Profili. I know I've done this before but I'm brain dead and just can't figure it out. I can export but can't import. Anyone, please? Thanks.

May 16, 2009, 05:09 PM
Oleg Golovidov
olgol's Avatar
Gerald, if you don't mind posting planforms of your wing and tail surfaces, I think there will be quite a few scratch builders who may want to try the Zone. Depending on the fuselage choice, you may get a group build going of Zone-Gee, or TabuZone, or Zonish.
May 16, 2009, 05:12 PM
Oleg Golovidov
olgol's Avatar
Originally Posted by G_T
In practice, I have found that the 0, 2, and 4 degree camber settings work well. There is a learning curve flying a wing with these airfoils. Expect to be able to cover more sky, but also expect to have to pay more attention. I do not consider these beginner airfoils.
Gerald, can you explain what you mean by the above, please. Pay attention to speed? Do not fly too slow? Too fast?
I flew your Zone for about 1-2 minutes and it seemed to be nice handling model. Not enough to notice anything special of course.
May 16, 2009, 05:22 PM
dougmontgomery's Avatar
Gerald, It was nice to talk to you at Poway and I really like the overall look of your new DLG. The Tail group, flying stab mount(nice engineering and mold work) and Wing impressed me. Good luck on all your hard work and time you put into this.

May 17, 2009, 12:46 AM
Registered User
Thread OP

That is an excellent question and one I probably should have already answered.

It's a little difficult to explain. In a nutshell, when we fly planes with the same airfoils or nearly the same all the time, and similar designs, we develop almost instinctive reactions and decision making. The Zone doesn't react quite the same, so flying them optimally takes a little retraining. Some of it is the airfoils but a part of it is the wing design. It is doing exactly what I intended. But that is different than any other plane I've flown.

The experience starts with flying the plane sort of ok, and the more one flies the more one learns. After a while I looked around and saw that I just wasn't flying like any one else any more. Perhaps I never did and am just noticing it more now. Hard to say. If someone who was at BASS can chime in then perhaps we can get another opinion as everyone there saw the Zone fly in a variety of conditions, and by then I had a bit of a handle on the plane.

Please consider everything I'm saying here as subjective, based on flying the Zone prototype at Poway where I was starting to learn how it flies, and at BASS where I had a better idea of what to do with it.

The Zone signals air very well. Better than other planes I've flown, but it is not harsh about it. It really tells you when there should be something going on in the area. However since it signals so well one has to not assume that everything being signaled, particularly if it is a weak signal, is going to be something that is worth persuing.

The Zone is designed to range farther than anything else, and to get back when nothing else can. Theoretically, it has a small advantage over other planes in this regard. It is not huge; we're not talking miracles here! But it is enough to make a difference. For instance, one sort of has to creep up on getting used to its ability to get back. One can push a little bit longer, lower, farther... That takes experience with it to develop a little faith.

Another difference is optimal CG. I found through experience that the Zone flies better, or I should say it is easier to fly well, when the CG is set such that the dive test has more of a pullout in speed mode than what one would usually set. If one doesn't do this, then I find the cruise mode in particular is difficult to fly well. Also as I've mentioned before, being a little positive stable in speed helps coming back up wind in gusty air as the plane can then extract a little energy from the gusts and lulls.

The camber settings are 0,2,4 degrees. One ends up using the 4 degree setting in a lot of cases where the equivalent float setting for the AG* airfoils won't work out. But going beyond 4 degrees in practice is chancy at best. Really it is not worth the attempt, unless you have perfect glass smooth conditions and then, maybe. I haven't had that yet to try.

In my experience is this design can handle a huge ballast load with impunity. It just smooths the flying out through increased inertia and airspeed, but still handles basically the same. The plane never gets to feeling heavy on the sticks, at least not to me. And I have other planes that can't handle half the ballast of the Zone and still be able to climb. The Zone doesn't seem to care. Phil and I have flown it up to around 430g ballpark in high wind and it would move around easily enough, and climb in lift just fine.

Landing flaps are more effective than normal. Not quite as much throw is required. Even with high ballast if one throws full flaps down (say 45 degrees) the plane practically stops. So it's easy to bleed off too much speed too soon on landing approach and actually land short. It doesn't stall so much as stop coming back! That takes a few flights to get used to, or one can just reduce the throw a little.

Visually the AOA of the forward fixed part of the wing is approximately the same for best L/D for each camber setting (I designed the foils to work like this). So one can really use fuse angle to indicate camber adjustments. If it starts flying a little pitch up then more camber should be used or it should be flown slightly faster. Nose down means too much camber or too much speed for the camber. If this is encountered the plane will accelerate.

This has to do with something I did deliberately in the first Zone wing design. I arranged the foil and wing design so that the circulation bubble dissipates at approximately the same wing AOA across the entire wing at the same time. The bubble will be present when flying at max L/D or slower but not if one flies much faster than that. So what happens if one flies too fast is once a critical speed is reached, the lift drops by a notable ammount but the drag stays the same. As a result the model will pitch down briefly, and visibly accelerate. This behavior is visible over long distances and is intended to signal when the plane is being flown suboptimally. Now since the drag did not increase, as this is not a stall, energy was not lost. So one can just pull back on the stick to slow it back down, recovering the altitude, and then fly a little faster, or one can keep the speed and decrease the camber. So effectively the wing is "tuned" to give optimal performance over a narrower speed range for each camber setting, in return for better performance when it is being flown at the right speeds. BTW, all of this does not apply to speed camber.

Another difference is how the trim speeds should be set and how ballast should be chosen. Each camber setting should be trimmed for its best L/D. Now these speeds are not as far apart as most think. Particularly, many pilots don't trim speed settings to be very efficient. Sharing speed with launch exascerbates this, as one wants no pitch response to speed changes on launch. But ideally one would want enough stability in speed mode so an efficient airspeed will be automatically maintained. So I recommend trimming speed for best calm distance coverage. Then when flying if one needs a little more to come upwind for instance, one can touch a little on the stick to speed it up a bit. If that is insufficient then it is time to add some more ballast. If the Zone is flown too fast for the optimal speed setting, there is less penalty for it than with other planes so it is a little more forgiving in that regard, but it should still be avoided if possible.

Another difference is just plain speed. The Zone just flies faster in all camber settings. Not a lot, but noticable. If everything in the analysis is correct, the sink rate is actually microscopically better even though the speed is higher. This translates to ability to cover more ground in the same time. So I find myself launching and running farther away on speculation than ever before. If I hit what I expect to be there, few will chance going that far to hook up. If I fail to hook up, then I can still get back just fine and still have a little altitude to try something else.

When there is a minute left before a round starts, we're often scouting air. Then I'll have the Zone in speed, and be pushing it a little. I can cover quite a stretch of sky and get back in short order. So I can test farther out right before the round starts and that is an advantage.

When Phil and I got ready to make the first set of Zone tails based on my design and foils, I chickened out. By the numbers these should have worked well, but they just looked tiny compared to what I was used to. So I enlarged them, particularly the vertical. Now I had designed the vertical around using a 4 degree launch preset and for it to be very efficient at that setting. When I tried it with the larger vertical, which really has I think a touch less area than a Sueprgee-II vertical, the plane yawed the other direction on launch! I backed off the preset and tried again... Anyway with the current vertical on the prototype I can't use any rudder preset as it is too effective. The plane launches very straight. Next time I'm going to drop the size back down closer to the seemingly too small design and see what happens. That will reduce the drag a little.

With thermal camber, even in rocky air, the Zone likes to settle into a groove on a turn. But the elevator control is a bit different. When first entering a turn, elevator control is pretty normal compared to most planes, but during the sustained turn less elevator than usual is needed. One has to back off a touch and let the plane fly. Fuse angle is a good thing to watch until one is used to it. If one has the CG too far back, and the plane will fly with the CG WAY back, then the plane will sort of tuck as it enters a turn. This is just a pain, and another good reason to not fly a Zone with a very rearward CG. I'm not used to seeing this sort of behavior in other planes and I see very little of it now in the Zone. It may be that early on, I was flying just a touch too slowly. Recently I've done tight figure 8s with the Zone and it grooved like it was on rails.

Notice how some planes like a tight turn, and others only a big one? I find the Zone isn't particularly picky.

The Zone airfoils have a different Cm than the AG* series. The camber peak and shape is different. So the CG location will not have quite the same relationship to the "neutral point" approximation many people use in checking CG. So one can't quite substitute foils into an existing design and expect the CG to be optimal at exactly the same place.

Tip stalls - what tip stalls? It's a non-issue with the Zone. But a good part of that has to do with the tip design of the Zone wing which is quite special, and very carefully engineered. It is less like the tips on other planes than it appears to be, and is more efficient than one would guess.

A normal stall, if done, seems to me to lose less altitude in recovery than most planes. But I only get stalls when I try to get them anyway, so I'm not sure I care one way or the other.

The Zone is very quiet on launch, launches high, and is silent in flight. That's one thing I really like. It may mean absolutely nothing but I take it as a sign I didn't do anything too terribly wrong!

I guess lastly, I find it the most fun to fly. It can take aggressive flying, and likes it. I think I'd go so far as to say it encourages it and practicaly requires it. I'd say it drives more like a sports car than a cadillac. I haven't found any real weaknesses so far. I can't say that about most commercial planes I've owned.

Unfortunately I'm the only person who has flown it since the last round of CG, throws, and trim settings. It flies a wee bit differently now - better IMHO!

So there you have it. An un-reliable brain dump from one pilot who is still learning his new prototype.

May 17, 2009, 04:41 AM
Peewee Paraparaumu New Zealand


Firstly..... a big "thank you" to Gerald for sharing his foils and thoughts and design process.

Maybe the goal posts are moving on model design?

Does anyone have a picture of the zone???

Best regards
Peter Williams
May 17, 2009, 10:57 PM
Master of the Wind
G Norsworthy's Avatar
Originally Posted by Jimn8uay
Ok, excuse my ignorance, but I'm trying to search for info on converting files from .txt to .dat or something I can use in Profili. I know I've done this before but I'm brain dead and just can't figure it out. I can export but can't import. Anyone, please? Thanks.

One way to do it is save the files on your computer then open and save again, but delete the .txt and add .dat. Then use AeroPlot to open the file, scale to the chord, and create a .dxf. Now you can open the .dxf with autocad or other, draw in the wire shelves, and print.

In this case they are all decimals but if you get one with scientific notation you will have to manually type it out and change to decimals in order for AeroPlot to read it.
May 18, 2009, 01:52 AM
Jimn8uay's Avatar
Thanks..knew it was pretty simple just had a hang-up with windows, (and my brain!) as usual.

May 18, 2009, 04:24 PM
Registered User
Thread OP
Hello folks,

I've been getting requests for the Zone planforms. Please be patient with me. This is a pretty busy time of the year for me as I'm an organizer in an event that goes off this weekend, with >200 contestants showing up from around the world. When things settle down I'll get more Zone details out.

But I have a little more work to do first. I'm in the process of doing the analysis for the next version of the Zone. I'm taking lessons learned from the first and doing further analysis to improve the optimizations.

In particular I'm going to be analyzing the AR to determine the optimal value for min sink in thermal camber, given actual plane weight. Perhaps there is a microscopic improvement to be had. The wing construction is designed to be quite a bit more durable than conventional DLGs, incorporating an armored leading edge that can take midairs without damage (has done so twice so far), and incorporating all Spyder cores for a large improvement in dent resistance. The very thin wing negates the penalty of the denser core, but the wings are slightly heavier than normal (more so towards the root than the tip). I'm also changing servos. So now I can plug some real numbers back into the analysis and make a round of improvements. The first prototypes have an AR of 10.5. I chose this as a compromise, since I knew the wing was going to be quite thin. Higher AR looked better but I decided not to go for it on the first round. Now I have a better appreciation for what I can get away with in shoe-horning an RDS installation into the wing, and on flutter behavior. So if the analysis says I should go a little higher then I'm willing to do it. If the AR of the wing changes then I'll appropriately tweak the area of the horizontal, but otherwise I'm extremely happy with it.

Secondly, I'm doing more work on the vertical. That's actually the harder part of this process. This has been spurred primarily by Oleg's questions and comments, and some emails we've been bouncing back and forth. He's playing the roll of a proper skeptic quite well, and making me work hard! It has actually been quite beneficial. The analysis I'm doing now is more complete than what I did originally. So the vertical may get some changes. So far I don't know. From what I've run, it is a bit sensitive to how clean a throw a person has, particularly when a rudder preset is not used. I guess I don't yaw a plane quite as much as some so it works extremely well for me. But if you throw a hook shot in calm air then you won't like the current vertical quite as much as I do. I haven't decided to quite what level I'm going to add tolerance. This is designed as an expert's contest plane, after all.

I haven't started doing serious work on the fuselage yet. I've been using Taboo pods as I had a few around and so did Phil. They are easy to work with and can hold a lot of ballast. But I have something else in mind for later. Phil and I have some ideas...

The Zone is a work in progress and it will be a while before it is finalized. I'm rather pleased with the first prototypes and I expect the second version will be even better. So if everyone wants, then I can release the generic design for the second when I'm done with this round of the analysis. But it won't be proven. Or I could release both designs. Or I can wait until some future time after the second version is flying, and I can't predict when that will be. Up to you guys.

Structurally there are some things I want to try that are a bit less conventional. I really don't want to throw those over the fence until they are tested. So I have less interest in releasing some of the wing structure in the near term.

Of course the airfoils can be used in other designs! Just be a little cautious if you use the Zone-vertical to use a fairly high AR, definitely don't go less than 25 square inches for a normal tailboom length, and possibly add a small rudder preset for calm conditions. I'm starting to consider adding a switch control so I can turn it on and off on the fly as dictated by the conditions for each launch, while keeping it slaved to the elevator preset switch.


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