slickporsche

I am looking for airfoils to be used on 74 inch scale aerobatic model with a high aspect ratio wing. Also is anyone familiar with these two airfoils MA-14.9S, and MA-12S? I m not looking for any "snap crash and burn" airfoils, as I have enough of them. Cleans stall characteristics are good , as long as it is controllable, and still allows reasonably slow landings.

All Day Dan

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I've used the NACA 0015, 0017 and 0019s for the past 40 years. They've always worked great for me. Here's my favorite software.
www.compufoil.com
Dan.

slickporsche

THanks for the input I really appreciate it. Are you the Dan Reiss who has marketed all the wonderful kits and plans through the years. Like House of Balse etc.? I have compufoil on my computer, but have not learned how to use it yet. I was messing with it today for a while. Can I look up the airfoils you mentioned there, or do look elsewhere for them? It looks like an easy program to use once I get it figured out.

All Day Dan

My Feedback: (5)

Slick, I do publish construction articles of my planes in Flying Models every now and then but that's as far as I go. They get to sell the plans. There are no kits around for them as far as I know. Compufoil has the NACA four digit airfoils in it along with hundreds of others. Go to view and open up Toolbar 1. You'll see the GEN NACA button there. Click on it and use the pull downs to modify the airfoil. I also use the NACA 2515 and 2417 for my scale planes. It's a little more stable for landing but screws up the aerobatics. Here's an image of me with my latest plane. Dan.

CoolerByTheLake

Slick, hope you don't mind me jumping in. Dan, this is not an areobatic airfoil, but I see your still on line so here's my question, I'm trying to match up an airfoil on a plan I have for the a ducted fan jet. The closest I have came is the N.A.C.A 2410 or the s6061, I know they are for slope soaring, but the s6061 matches almost perfectly with the plans. What can you tell me about them. Thanks

slickporsche

I have two drawings that I am working on in cad, a scale extra sc, and a scale cap 232. The goal is to use the scale outline, and not *******ize it by enlarging the wings, stab, or rudder. I would like to try the scale airfoil on the Extra. On the cap I think I will use a different airfoil. Maybe. I do like scale, but too many planes out there have many changes made to them for the sake of creating a more friendly model. If they are built light to fly, and not built to crash, then most will fly good. A high wingloading is the real killer of scale airplanes, and that is why it is best to build them with at least a 80" wing span. The Extra has a really different airfoil in that it is thick, and blunt at the leading edge, and then there is no curve for the rest of the airfoil. It is of course fully symetrical, but from about 20% back from the leading edge, it is straight.

slickporsche

No problem, I do not mind you cutting in. I would like to ask you this ,and that is why you do not want to use the airfoil that is on the plan? Are you refering to an actual building plan or a 3-view?

slickporsche

Hi Dan

Iwill need to get busy with that foil program. That is a nice looking Tony you have there. Iwould like to build one sometime in the not too distant future. I did see the button you are talking about and will mess around with it. I would like to find a catalogue with airfoils, and a description of each and their plus and minus attributes. At one time Isaw something like that, but cannot remember where it was.

CoolerByTheLake

[size=2][/size Slick, it's not that I don't want to use it , I don't know what it is!! See post http://www.rcuniverse.com/forum/m_10644438/tm.htm The Plans are for a Y/a Starfire, if that helps.

All Day Dan

My Feedback: (5)

Cooler, I don't know much about airfoils especially for full size aircraft. I am only familar with what works for R/C models. I never try to duplicate an exact scale version of any plane. What works at 400mph will not be suitable at 80mph if it is scaled down exactly. I am more interested in decent flying characteristics and, best of all, landing in one piece. Dan.

CoolerByTheLake

Dan, the airfoil in question is a model airfoil, not full sized aircraft. Check link I posted above. It explains it.

All Day Dan

My Feedback: (5)

Got it. Dan.

slickporsche

Personally If I had plans for a "Yellow Aircraft Starfire?", I would not be concerned about the airfoil. It will work fine. I'm quite sure the designer knew what was a good airfoil for the job.

CoolerByTheLake

Slick, just trying to line up materials. I would just as soon buy the wing and stab cores from Y/A. I have sent 3 e-mails about cores and nothing yet. Here's my idea http://www.rcgroups.com/forums/showthread.php?t=1472810 I need the airfoils/cores to shape the foam for the wing and stab attchment points on fuse, b-4 it gets glassed. Won't start till fall, but like to know these things in advance. Sorry to take up you space here. Thanks.

slickporsche

Hello

Please tell me about your plans. Are they from YA or some other source. Myself , Ihave built several jets from kits, and have had good luck with the Dynamax. If you are having trouble with getting the foam cores you can always cut them yourself as I do. There is lots of info on the web about cutting foam cores, and it is really easy if you pay attention to some of the standard practices. The other thing that would be possible with that design, and is what Iwould do, is build it from Balsa like a conventional plane. For me to do that , Iwould need some good views of the fuse, and then I would get it into a good cad program and draw up the structure. I am very familiar with that particular jet, and it would not be difficult at all.

The lost foam method works, but is messy and time consuming, as I have done that also. I prefer to make a plug, and a female mold myself. However it is more work, and money. That is why I have suggested the balsa built up method. These kit manufacturers want way too much money for their products, especially jets and specialty aircraft. Because of this, I have decided to scratch build from plans. Ihave plans as I said for a Dassult Mirage, and for a very large F-16, that I also intend to build. The only thing the Mirage might need of glass, is the inlet ducts. Then of course a canopy needs to be formed. Another thing to build if you scratch build is a vacuum machine, for canopies and what ever. All made from wood, and very easy.

I hope you do well with your project and get to actually fly it. Where in Minnesota are you! I'm originally from Eau Claire wi. If you have any further questions, feel free to contact me. I have been building and flying for so long I cannot remember. LOL

BMatthews

Slick, a good airfoil that works at model size and speed for the Extra and that would be in keeping with the scale airfoil shape would be the Eppler 474. It has the same sort of shape but at model speeds would be a touch more stall resistant than the blunt nose/flat rear shape of the full size Extra.

Some years back some local buddies were looking for a more stall resistant option for their models for Control LIne Fast Combat. The popular design at the time used a flat rear section very much like the Extra that was designed by Phil Granderson. It did OK but had a nasty habit of suddenly stalling if the loop/turn size was tight and the model slowed down too much from consecutive maneuvers and reversals. I suggested the E474 and the guys built a half dozen using that airfoil. They were immediately sold on it and used it to good effect over the next couple of years. It allowed the model to either turn tighter or to turn the same but not bleed as much speed. And when it did stall it more or less just wobbled a bit on the lines instead of coming in at them. And that's a good thing when you're looking at a 125 mph skill saw heading your way...

In any event if you were to use the E474 on an Extra model I think you'd be happy. If it were to have a problem it would likely be that it resists stalling so well that it won't snap cleanly on demand if the wing loading is too light. But it's easier to add stall strips to the wing to encourage a stall than it is to correct an overweight plane with a stall prone wing that wants to snap and spin.

slickporsche

Thanks I will look into it . Ido like good snaps, but have had models that were nearly impossible to fly, because of unpredictable snaps. Unlike a full size aircraft where you have an airspeed indicator,and a real good "seat of the pants feel", we do not have that luxury with the r/c models. Problem with me is I'am tired of r/c models with lots of changes to make them supposedly more flyable. I'm currently drawing this thing so that it is exact scale in outline, and hingelines, gear placement and those kind of things. I will not *******ize it, except maybe a more friendly airfoil. I have also found that extreme double tapered wings are a problem on a scale model, maybe more than the airfoil.

I am also working on a plan for a Cap 232, which I had planned to use a Eppler 169. Both will have plug in wings, so I could experiment with different airfoils if I want. The full size Cap is a real snap rolling plane , so I decided to use a different airfoil on it for sure. It is very similar to the one the Extra uses. THe Extra use a MA-14.9S on the root, and MA-12S for the tip. I cannot find any info on either of these, so that is why I thought to try RCU.

BMatthews

I see you found that old thread about aerobatics airfoils over in the Aerodynamics forum. Here's a link for those that want to review it;

http://www.rcuniverse.com/forum/m_72..._2/key_/tm.htm

I noted that what I suggested here may look contradictory to what I mentioned over there. At the time it didn't seem like you were too worried in this thread about achieving good departure maneuvers and instead are more worried about unwanted and unexpected stalls. But the trick is you can't have it both ways. If you have a model that stalls, snaps and does all those other 3D things easily and with a nice sharp break then it's going to be at least somewhat prone to surprise stalls during slow flight such as landings. And in particular landings on windy days as you experience a loss of airspeed as you come down through the wind shear effect that extends up to about 15 feet off the ground. The key to avoiding such "surprises" is to know the model and avoid flying it in a way that puts it at risk of suddenly slowing down for whatever reason.

Some other factors come into it as well. Control surfaces on a lot of 3D capable models these days are rather wide. If you're coming down the pipe to land and a wing needs some correction to level it some folks will input a small amount of stick and patiently wait for the wing to roll back to level. Others will input a quick jab to jerk the wing back to level. The issue with the "jab" style of control inputs is that the large motion of the down travelling aileron can and does alter both the camber and the angle of attack of that wing radically for a moment. And in fact it can force that wing to stall. And even though it's only for a quarter second the effect of the stall is enough to produce a stall and sudden snap to that side instead of lifting the wing as was intended.

Any of this sound at all familiar? I've seen it a lot of times and even had it happen a few times to me until I learned the cause and avoided it from that point. And I can't help but think it may be an issue with some of the hotter and heavier aerobatic models these days.

In that other thread much discussion is aimed at how to match the airfoil to the weight of the model. In effect it came down to the lighter the wing loading the thinner the airfoil could be. That information still applies. But it also assumes that you're willing to live with the bad things that it brings to the table as well as the good things. The good things being the snappy post stall stuff that is so popular these days. The bad things being the sensitivity to stalling and sudden unwanted snaps as well as a sensitivity to how you work the ailerons during slower flight. Just like Goldilocks checking out all the porridges it's a case of finding the balance between airfoil and wing loading that is "just right" for you and your needs.

Hopefully this helps rather than confuses. I know it leaves you wondering what to do. But as I mentioned above if in doubt go with a less stally airfoil than you think you need for your expected model wing loading. You can always trim for your snap break later by adding stall strips and ballast weight to optimize how the model works out. But adding helium and anti stall strips seldome works out quite as easily...

slickporsche

Yes, I had those kind of things happen to me way back when I first started flying r/c. Itoo learned how to handle it and when it was not good to fly. THe old Byron Christian Eagle is one of those airplanes. It was and is a good flying plane, but not dummy proof. A lot of the old kits where like that and not really good for inexperienced fliers. Ithink it was around 1980 where the mfg's started using airfoils that were designed for models. THat improved things for the average modeler that did not have much skill, and many who still do not. The average "stick basher". I don't know if you have much experience with warbirds, but there is another problem area for many. The larger models have really made that segment of the hobby practical. That is where the wing loading can be too much for most airfoils,and where energy and airspeed are everything, and without either of course your goose is cooked.

You are absolutly correct about the problem with large control surfaces and the windy day thingy. I think the deal there is they try to land like it is a normal and much less windy day with a very shallow approach, which gives them little airspeed and very poor control at best. Many fliers will not fly if there is much of a breeze, because they do not understand how to fly in the wind. That is one of the things I teach my students in addition to control setup,aerobatics, and proper C.G.

In my original post, Iwas trying to find someone that is familiar with airfoil that the full size Extra SC uses, to determine if it would be worth pursueing or not. I have it almost totally drawn, but have not added larger control surfaces, because it does not seem necessary. I think the Eppler would be a good place to start, and could be changed or modified later if desired. I also like to use flying tail surfaces, with an airfoil. That tends to be better than a slab for the rear surfaces.