Below is a brief story Dick Kline emailed us in 2009 about the the KF Airfoil and Condor Airplane: ----------------------------------------------------- Here's the brief story on The Condor. When I developed my first stepped airfoil, it had the step on the bottom. I was pleased with the way it flew, but like so many of us, I wanted to experiment some more once I nailed down the step on the bottom. When I placed it on the top I found out that it produced higher lift than the one on the bottom. It would climb higher and travel a longer distance. Later tests at Notre Dame confirmed that the step on the top was able to generate higher lift over drag. I then played around with placing the elevators on the upper surface just in front of the rudder. After many different experiments and many different flights I had perfected The Condor, which would be the plane I would use to challenge the Wright Brothers distance record. In spite of very strong winds coming in off Cape Hatteras, I was successfully able to outdistance the distance record for the first manned flight of 122 feet. I did this in 1985 down in Kill Devil Hills, NC right on the spot where the Wright Brothers first flew. My distance was 401 feet, four inches. On the fourth flight that day of the Wright Brothers historic flight they traveled quite a bit further, so I was lucky that their first flight was just 122 feet. Here is the data from the wind tunnel at Notre Dame. It would have been a lot higher if we had a rounded leading edge and a little camber. But we were interested in seeing exactly what the step produced by itself. Later, everyone would follow this configuration out the window and get poor results. This was our big mistake. But we also knew at that time that the step worked in different configurations and we couldn't patent them all. All we wanted was to patent a step in the hopes that it would produce stall resistance to other airfoils. All the experts trashed this idea as too high in drag, yet the KFm4, with a step on the top and a step on the bottom, increases the speed of the wing. If the drag was so high, how could this be? All in all, it has been a wonderful adventure and I feel very grateful and lucky for it. I have come in contact with many truly wonderful people in the RC community. From my perspective, the world could take some lessons from the RC people on how to work together, how to openly share information and knowledge freely and produce an environment of creativity and experimentation. This way everyone benefits and the learning curve climbs way up for everyone. The gentleman who conducted these tests at Notre Dame was Professor John D. Nicolaides, the first head of NASA.
Below is a Diagram of some of the different types of KF Airfoils Dick Kline sent us back in 2009. There are even more variants out there now. Please feel free to post about any KF Airfoil variations you may have used or seen.