Posts Tagged ‘KFm3’



Hey everyone,

I just wanted to add a post to the blog on the Jupiter Project that we are just starting. This project is a collaboration with Dick Kline (the Inventor of the KF Airfoil) and rcFoamFighters. The original idea for this project started with a suggestion from Dick Kline, he asked if we could do a project that will compare the KFm3 and Clark Y airfoils.


Here is a brief intro to the project written up by Dick Kline:


When we filed for a patent on a stepped airfoil back in 1970, Dick Kline and Floyd Fogleman were hoping that it would be seen as a concept worth investigating because of the stall-resistance built into this idea. The Kline-Fogleman airfoil has many favorable characteristics that we felt could be investigated. However, we were met with a wall of resistance from all the experts. It was a terrible idea as far as they were concerned.

Our patent drawings, which showed a sharp leading edge were followed out the window in their wind tunnel tests. However, they were also applying conventional testing methodsto an unconventional airfoil. For example, there wasn’t any testing for a forward push directly behind the step. There was no camber applied along with a rounded leading edge. Our intention was to patent only a step, not an entire airfoil shape, because we knew that it worked in various configurations whether it was on the bottom or on the top. We chose to show the step on the bottom because we knew that L/D ratios reverse themselves when you go from subsonic to supersonic flight. And, we knew that the L/D was higher when the step was on the top, based on wind tunnel tests done at Notre Dame. Therefore, supersonically we would pick up the higher L/D ratios. So we showed the step on the bottom for that reason.

In a book called Fluid Mechanics by Frank White, he shows a number of NASA airfoils producing lift, then reaching a stall point. He also includes the KF airfoil which continues to generate lift out beyond 50º AOA even though it showed a flat upper surface and a sharp leading edge. Although this is a remarkable characteristic of stall resistance, none of the experts thought that it was worth investigating.

The KFm airfoils were embraced by the RC community starting in 2006, because Tony Bernardo decided to try a KF airfoil out for himself. He started a thread which is still going strong and has many contributors to the development of the KF airfoil concept. Today, people from all around the world have accepted the KF airfoil into their building techniques of RC aircraft. What they found was a very easy wing that they could build. Very inexpensive. Very strong. Very high in lift. And, very stall-resistant.

The acceptance of this radical concept still meets with great suspicion and disbelief. “It shouldn’t fly because it doesn’t look like a normal airfoil. It can’t work. It produces too much drag. It won’t fly.”

I have proposed an idea to the RCFoamFighters. What if we could demonstrate that a KFm3 airfoil can lift more weight than the icon of all airfoils: the Clark-Y. Wouldn’t that help to convince people that there is some merit to this radical idea of a stepped airfoil? If it can be demonstrated that the KFm3 can carry a heavier payload along with its ability to resist stalling, it should warrant a more in depth investigation, in my opinion.

Several years ago, Rich Thompsonproduced a comparison study between several KFm airfoils, a Clark-Y and a symmetrical airfoil. The KFm2 and KFm3 came out with very high marks overall. But this did not impress the people who are the experts. Maybe a real world weight-lifting test would persuade them to take a second look?

Who knows. Only time will tell.

In the meanwhile, what is known is that the KFm airfoils work extremely well in the UAV arena. That has been demonstrated successfully a number of times over. It takes a leap of faith to trust your camera, motor, batteries and servos to a strange-looking airfoil that is not supposed to work in the first place. And, have that aircraft return to you safely with all your precious equipment intact. Now, who wouldn’t want that advantage?.



After a few emails back and forth to Dick Kline, I developed a concept for the plane we could build for this project. We both decided it would be neat to build a plane in the style of a large Military Cargo Plane. Below is the Concept Drawing of the plane we will be building, the C-54KF Jupiter:

The C-54KF Jupiter (Concept #1)

The C-54KF Jupiter (Concept #1)


So in the coming weeks I will begin to build the plane out of EPP Foam. Once we get the plane built and flying good we will run it through a series of tests and comparisons with the KFm3 airfoil and Clark Y airfoil.

Last, here is the first video in the Jupiter Project Video Series: