Falcon airfoil?

[rebell]

Where did Carl Goldberg get the airfoil for the Falcon 56 and later the snr Falcon? What airfoil did he use? Included here is a pic of that airfoil.

The reason I am asking is that there is a story that he used one of his favourite shoe soles as a jig to trace the airfoil from, and I can not believe that a man with such a model aviation background would do it.

Thank for any info.

[Ken Myers]

I heard the same story many years ago. I do believe it is a semi-symetrical LAR though and not a specific example of any known type.

[Sparky Paul]

That resembles an NACA 23012 or 23015.
Check the thickness.

[BMatthews]

Free Flight modelers are a stubborn and resourceful lot and Carl spent more of his time designing and flying free flight than he did RC.

His Gentle Lady uses one of his own design airfoils that had previously been used in many of his nostalgia era free flight power ships. His famous Sailplane and Zipper used his own design airfoils as well.

We all joke about the shoe sole idea but in reality many good flying model has been made over the years by designers that new what they wanted from the airfoil and just rolled their own to fit. Some of these may not look very good if run through something like Xfoil but I'll bet that any poor points are not that glaring.

Besides, I'm not sure Carl himself actually designed the Falcon line. Like many other companies he used the talents of some of the more successful modelers of his day.

Anyone have some Falcon or Skylark plans to see who the designer is?

[Ollie]

Sparky is on it using the family of NACA 5 digit airfoils.

My eye ball is quessing about NACA 24012 or NACA 25012 and sharper trailing edge.

[rebell]

Thanks for all the info. The Falcon airfoil is 14% thick. I did not find the NACA 23014 or NACA 24014 or NACA 25014 yet. If anyone know where to find it. please let me know.

[Ollie]

Extend the top and bottom profile to a sharp trailing edge. Then remeasure the chord. You will find it thinner. Then use a program (such as Profili 2) that generates any NACA 5 digit airfoil shapes.

http://www.profili2.com/eng/default.htm
Or
http://www.pdas.com/naca456samples.htm
http://www.pdas.com/programs/23012.out
Or
http://www.df.lth.se/~pi/compis/files/ftp.mayn.de/pub/cpm/archive/education/mdlplne2/afmnu22.bas.txt

[rebell]

Thanks Ollie. I do have Profili2 and some other airfoil programs and lists as well, but those are not listed and Profili can only generate NACA 4 digit airfoils. The Falcon airfoil is listed in Profili, but does not compare to any of the other listed. The exact thickness is 13.68% @ 30.6%. (I rounded it to 14%) You will find a lot of profile thicknesses being rounded in different sources.

In CAD I projected a lot of similar airfoils over the Falcon airfoil, but found nothing that compare.

This is not serious. As I said in post #1, I just can not believe that CG used a shoe sole as profile. I just like to find proof of where it actually come from to show the shoe sole advocates.

[Sparky Paul]

in "Management" Profili will plot most NACA airfoils.
The Falcon appears to be an NACA 23013

[rebell]

Thanks for showing it out Sparky. I overlooked the drop down menu in Profili. To much in a hurry sometimes.

I now projected different airfoils over the Falcon and found that the NACA 25014 is the correct one. Here it is. Now I think I have the proof that the "shoe sole profile" is an old womans tale.

Thanks to all.