Airfoils

If you go to the airfoil listing within Profili,(under the single foil shape on the menu bar) and select a foil from the list, say, Clark y or NACA 0018, and select it, you will get a small dialog box with a picture of the foil and several selections below it.

If you select Export to file, it will create a text file of the coordinate information for that selection.

I think this is what you asked.

If what you need is info on which foils are good for which applications, that is a different matter.

Hope this is helpful.

Curt

PS Edit: If for some reason you dont have the archive of reference foils with Profili, let me know and I may be able to email them to you.

Jim;

The only ones that I have seen that are included and used a lot with stunt are the NACA series, which you can generate pretty easily.

I have used some of the symetrical foils available in Profili and made some major mods to them within Profili to generate some stunt airfoil approximations. I think that once you get pretty close, for the most part one flies as well as the other.

To the best of my knowledge, there is no easy way to import an ASCII text file with coordinates into Profili. You have to hand jam all of the data in, which can be a bit tedious....

http://amber.aae.uiuc.edu/~m-selig/ads.html

Howard;

What program are you using to generate plots and/or .dxf files?

I use Excel, then Generic CADD, then Visual CADD. It's not the way a normal person would do it.

These produce a very blunt LE and many prefer to modify to a bit sharper LE. The Twister is very close to a 0022 with slight reduction in LE radius. (of course it is no longer the same foil!)

I'm sure there are others here that know which foils they're using.

Curt

PS you might try Martin Hepperle's web site (see links on SSW site) for info and coordinates. Also I think NASA has a couple of good sites. And University Illinois Urbana Champagne UIUC has a great deal of foil info. None give any recomendations for CL Stunt other than general info that I have found.

Nasa stall/spin projects for the FAA have some relevent info (Wright Patterson) and Nasa Lewis in Cleveland also if I recall.

There is a function on the foils menu of Profili that will generate NACA sections. Then you delete the co-ordinates from the reflex sections that John and I have talked about and move the max thickness point forward then you are away. Unfortunately you will have to type in the co-ordinates for any of the composites.

Larry Cunningham, among others, uses them and seems happy with them.

Depending on the intended purpose, the 4-digit sections may not be ideal. For example, they have a fairly full curve behind the high point. Depending on your building technique and intended purpose, this may add unnecessary complexity. Also, George Aldrich said on several occasions that he believed that the 4-digit series is too fat at the leading edge.

Symmetrical NACA 63 sections and NACA 63A sections have the same leading edge shape and a reflex curve in the rear section towards the trailing edge. The 63A-series has a fuller curve behind the high point before it goes into the reflex section. NACA 63A 020 with the reflex curve removed and replaced with a straight line and with the high point moved forward to 30% is the same as the section that Claus Maikis drew for his Koala stunt trainer. John Miller found that NACA 63-series sections with the reflex curve removed and the high point moved forward were very close matches for the sections used on several classic models that he was drawing new plans for.

I have fiddled on the computer with several composite sections and have produced interesting results. I am looking forward to testing the results in practice but I must stress that my flying skills are not up to the evaluation. 'Luckily' I have several very competent Aussies who will test the theory for me--on my models--while I watch.

One of the first sections I created was a simple section similar to the RC guys' fun-fly wings--a simple ellipse with straight lines back to a thin, but not sharp, trailing edge. The second was the NACA 63 series with the reflex curve behind the high point removed and the high point moved forward. Then I grafted the ellipse and the front portion of the NACA 63 series section to the rear portion of the standard NACA 4-digit series sections with the high point at 30%.

To explain the fun-fly section, I created a formula in Excel that generated the co-ordinates of a circle at 5 degree increments and drew straight lines tangent to the circle back to a small vertical trailing edge. having loaded that into Winfoil, I squashed it to produce the thicknesses I wanted to look at. I know that there are complex polynomial equations that will produce ellipses of all sorts. This is not that complex--just a squashed circle.

Here's where I think it got interesting. Matching thickness for thickness and high point for high point:

Irrespective of the exact LE radius, the 4-digit NACA section has the fattest front portion, the ellipse is next thinnest and both NACA 63 series have the thinnest front portion.

The ellipse grafted on to the rear portion of the NACA 4-digit section is, according to Bob Reeves when he was drawing the TwistMaster, exactly the section of the Twister.

The NACA 63 series front portion grafted to the rear portion of the NACA 4-digit section is, as near as Winfoil can display, the same as a Saftig section whose co-ordinates appeared in a South American plan published Stunt News a couple of years ago.

To return to the question, Profili will allow you to change thickness and move the max thickness point. You can also delete co-ordinates so the modified NACA 63 and 63A sections are easy to generate.

Most stunt sections have the high point no further back than 30%, including the flaps.

Also, as noted elsewhere in this discussion, actual NACA sections can be as thick as 25% but when the trailing edge is truncated to provide a suitable 'landing' for flaps and flaps added, the final hybrid section is significantly thinner. Many of the popular designs going around at present, regardless of the actual shape but including flaps, seem to have root thickness around 18% and tip thickness between 18% and 20%. High point positions seem to range between 25% and 27%.

All this 'research', if that's the right word, is at present, only desk generated theory. If anyone wants to share the data and experiment with it, please email me. At this point it's all theory from a, perhaps, compenent engineer who is most definitely not capable of pushing any model to the limits to test the theory while expecting to take it home in one piece.

Apologies for the lenght of the post.

Was wondering when you were going to jump in with you welth of knowledge. Good post..

Without your help on the TwistMaster plans I would still be trying to get that rib correct, can't thank you enough.

My only addition to your reply is to let everyone know that Brodaks Profile Cardinal is using the modified NA63a foil. It was about as close as possible to the foil that Windy used on is original. This also leads me to believe that the Patternmaster foil will be an extremely close match as well, but, since I don't have an example of it here, I can't say for sure.

The Profile Cardinal has earned a reputation over it's short life span of being a very good handling plane. Of course, there are other considerations as far as design, to keep in mind as well, but I believe the foil does lend itself well to our style of flying.

I have compared the NA63a series to several other top, modern, and one Classic design so far, and found the similarity more than close. Some of these designs are perennial winners in the stunt wars, and very popular. Again, there are other aspects of the designs to consider, but it's interesting that they seem to share the same foil, and one that's not as recognizable as the NACA 4 diget airfoils, which are probably the most widely used on stunt ships.

I don't have a plot of Igor Bergers (sp) specially developed foil, but find his work interesting. He may have developed a superior foil for our use. I wonder just how far off his foil might be from the NA63a series modified with the high point moved forward to ~28%.

Keep up the good work. It'll be intersting to see the results in the future.

Best wishes,

John Miller