Has the NA63A airfoil been used in Stunt before ?
If you were to do a 60 size, here is another change I would like to see.
I really like the wings elliptical planform.
I think it would look even better if you were to duplicate that shape exactly for the stab/elevator.
OOPS Just had another look and you are really close with the stab/elev planform to the wing already. TE of elev is straight, flaps have slight curve, would be easy for builder to make them the same.
Thanks again for your comments, and ideas.
The answer about the NA63A airfoil being used in stunt before will take a bit of verbage to answer. I should probably post the answer under the design forum, but I'll give the answer here first.
The answer is yes, it's been used a lot, and on some significant designs. A search on the forum archives, under NA63A, should yield a lot of posts on the major forums, discussing this airfoil and it's use in stunt.
The problem is, that most uses are identified by the modelers name, or the design. Few of us go to the COORD files and pull out a recognised airfoil to use. It should not be surprising, as many airfoils were originally drafted, using one of a few methods in the past.
Methods such as, we hear of the old left tennis shoe trace, and I'm sure that some were drawn that way initially. Then there's the cases where a series of "French" curves were used, not to mention the old T.L.A.R. method.
In my opinion, the airfoils we use generally fall into 3, perhaps 4 types. These types do have very close examples in the NACA archives. The ones we use are so close, in many cases, that there is no fundamental difference between what we are using, and what are in the files.
These 3 are what I would tend to call the BJ (Greenaway) airfoils, (NA63A) Ted Fancher's Trivial Pursuit is a modern design that I believe uses the NACA 4 Digit airfoils. I thought Aldrich used the 4 digit 'foils, but my good friend Geoff, from Oz, mentioned that George may have used something closer to the NA63A. (I remember him once describing how he traced his tennis shoe, anyone else remember him saying this? ) Then, there's what I call the Pathfinder foil, and possibly a 4th. group of odd ball styles seen a few times then basically abandoned.
As it turns out, designers often copied the airfoils from proven performers. If one pays attention, it's possible to see the airfoil trends arrange and group themselves based on external influences across the country, and I'm sure, throughout the world. For instance, areas that tend for stable air conditions, tend to wind up using similar airfoils. Conversely, windy, or turbulent areas affected by those conditions. tend towards a different airfoil that addresses the conditions better.
Airfoils are chosen for specific reasons, but will often work reasonably well when encountering different conditions, so there's sometimes a mix going on. based on the designers personal likes.
Let's look first to the 4 digit airfoils. They are most notable for their blunt large radius leading edges. They are a bit draggy, esp at higher percentages. but they seem to make up for that by offering high lift, and reasonable stall characteristics, stalling often at a higher AOA than many of the others we use. Of the designs we are familiar with today, the Trivial Pursuit is perhaps the best example
The drag can be of use with overpowered designs to help tame the beast. The major drawback may be that they are more easily affected in turbulence as the large blunt leading edge can have less ability to penetrate.
The NA63A, is very similar to BJ's airfoils in both style and performance. This can also be said of a close relative the Eppler168, 169 series.
Modifications are easy to dial in using many of the airfoil lofting programs, but the entire series shares much of the same performance. Now, I'm talking about very close, similar, not necessarily exact airfoils.
The characteristics that these particular airfoils seem to have in common is a smaller radius on the leading edge, compared to the 4 digit foil, even though the percentage of thickness is the same. These airfoils seem to penetrate turbulent air better, and don't seem to be upset as easily as the 4 digit foil. They appear to have less inherent drag, but produce good lift in our use.
These modified airfoils appear in areas where wind, and turbulent conditions are more common. Most noticeable designs are Big Jim's designs, and their derivatives, Randy Smith's SV designs, Gieskes Nobler, and the Moon brothers various designs, as well as Walkers Impacts.
The third airfoil commonly used is the one I call the Pathfinder Airfoil. It was derived fro Aldrich's FlightStreak 'foil, with the rear half forming a straight line tangent to the high point, and the trailing edge. This modification came about to allow building multiple combat wings using a flat surface instead of a jig. It's interesting that some of the top full sized aerobatic designs use a similar airfoil sometimes on both the main wing, and the stabilizer. These airfoils have now shown up in the COORD files for many airfoil lofting programs.
Designs using these foils are many of the various Pathfinders, and some of Pat Johnston's designs. They seem to work well, and offer a combination of penetration, lift, and decent drag characteristics in our use, as well as simplified construction. I'm of the personal opinion that this 'foil, combined with a fixed trailing edge extension, as used on the Flight Streak, may well be the best airfoil to use in a non-flapped design.
The fourth group has all the failed, strange, or seldom used airfoils from our history. Diamond, high point at the center, sharp pointy airfoils that were unable to make the cut in all the competition.
So, realizing that these airfoils, while not necessarily exact, are similar enough that there is no real difference. As an example, when I drew the plans for Brodaks popular Cardinal Profile, The foil used was the NA63A modified. Gordan Delaney's Pathfinder L.E. uses this same airfoil, sized for the design.
Topic: Going to my archives to finish one of my old designs (Read 4833 times)