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Old Apr 12, 2012, 07:34 AM
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So many of you have contributed to the development of the KF concept.

I wanted to share this info that I just received from India with all of you.... because many of you have done so much to help develop the KF vortex concept. Tony65X55 brought the idea to the RC Groups back in 2006.
It has evolved in many different ways since then and opened up the creativity in many RC pilots and designers. It is truly a collaborative effort on a rather large scale. It is truly a wonderful adventure.

Dick

Subject: Re: KF Airfoils

Dear Mr Kline,

Thank you for writing in to me.

I began working with KF airfoils when my friends, Ashfaq Ali and Arvind, and I had to design a glider for a competition. The glider itself had to be un-powered and could have only one control, while still being able to manoeuvre through a 75m course with twists and bends, on being propelled using rubber bands. While looking for airfoil profiles that could be used, we came across the KF series of airfoils and found it perfect for our purpose. We made a delta wing glider utilising the KFm3 profile (Unfortunately, I do not have any pictures of it. Ashfaq might have some. I'll ask him to mail them if he does) and the performance was pretty good.

Later, we found that though the KF airfoils were used widely in RC planes, there was not much theoretical or computational data available for it, and so, Ashfaq and I decided to do some CFD analysis ourselves. Our initial work, which was presented in the papers that you mentioned, consisted of comparison of lift, drag and moment coefficients of NACA 0009 airfoil with a KFm3 airfoil having similar thickness and chord dimensions, over a range of different angles of attack, at Mach 0.3. The results, along with the pressure and velocity contours are available in the attached document.

It can be observed from the graphs that, when compared to a conventional symmetrical airfoil,
Lift coefficient was slightly lesser at low angles of attack, when compared to symmetrical airfoils, although it was positive and higher at 0 deg.
The drag coefficient was high at low angles of attack , but much lower at higher angles.
NACA 0009 stalls at about 5.5 to 6 deg, but the KFm3 resisted stalling for a much wider range, as can be seen from the graphs.
Except for certain angles, the stability was very good, much better than symmetrical airfoil
In our free time, we are also working on the analysis of other profiles in the KF series. Recently, we also started considering the possibility of use of the KF profile in actual aircrafts. We are comparing the performance of wing of a Cessna 152 and the changes when NACA profiles are replaced with KF profiles.

I'll keep you updated.

Please do let me know if you would like to know anything more about our work.

With Regards,
D Abhinav
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