Archive for the ‘KF Airfoils and Dick Kline Articles’ Category
(Post updated 10/6/09 with new graphic from Dick Kline. Now includes 9 KFm Airfoil Variations. See below)
I just wanted to post a new graphic that Dick Kline was so kind to share with me. As many of you are probably already aware, Dick Kline the inventor of the KF Airfoil is always tuned into how we in the RC community are using his cool invention. Mr. Kline also enjoys creating computer graphics of many things. Well recently Dick Kline sent me his revised graphic that depicts the well known variations of the KF Airfoil as well as some new versions that people are experimenting with. Dick wrote me a few brief emails below with the attached graphic. I wanted to post it here and share it with the rest of the RC Community and all that may be interested.
Here’s the Emails:
I wanted you to have a copy of the visual I came up with showing all the different variations of the KFm Airfoil Family. They have multiplied like rabbits.
Well, two more additions have arrived. One is an under-camber with the step on the top. So, that goes next to the under-camber with the step on the bottom. I’m told that they both work extremely well.
So, here’s the KFm Family of nine airfoils…
(Here’s the graphic made by Dick Kline, many thanks to him for providing it!) (updated 10/4/09)
Click on the image to Download a PDF copy.
Later I will try and get some written descriptions of each Airfoil and what benefits each provides. So please stay tuned, we want to keep this blog going as a good resource for KF Airfoil information.
If anyone would like to contribute their findings on the KF airfoil please feel free to email us at email@example.com. We are hoping to help Dick Kline spread the word of his cool invention and share the collective knowledge we all have.
Happy Flying to all,
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:
THE JUPITER PROJECT.
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:
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:
I just wanted to post a quick write up on some RC Models with KF Airfoils. Both Frank and I have been pretty amazed with the results we are getting with the planes that have featured some of the various versions of the KF airfoils. So far Frank and I have experimented with the FMm2 airfoil (Top of the wing version) and the KFm4 airfoil (top and bottom version). Some of the planes that have featured them are the, new Bullet Plane, Tailless Delta Wing and the experimental forward swept wing plane. All of these planes seemed to fly with better stability than planes without KF airfoils. Frank mentioned how he was amazed with how much extra lift they seem to have and how they “Feel Locked In On Rails”.
So I just wanted to start keeping a sort of log and special area on our website with information on KF airfoils. As some of you may already be aware we recently started the category on our blog dedicated to “KF Air Foils and Dick Kline Articles”. In this area of the blog we will try and keep all the information as related to KF Airfoils and on occasion we may even have other articles from the KF Airfoil inventor, Dick Kline himself. Dick Kline has already been kind enough to contribute some articles and write-ups on his cool invention. Both Frank and I are very grateful to have Dick Kline as a friend. I’m hoping in time to make this area of the Blog a good resource for people to learn, share and discuss the different versions of the KF Airfoil and also a good place where all of us RCer’s can help Dick Kline prove the value of his simple but awesome invention.
Last, if anyone feels so inclined to want to share their findings or examples of KF Airfoil RC planes, please feel free to contact or email us at firstname.lastname@example.org . We will be glad to post any good articles or videos that may help others learn from your findings.
Before I close this article I just wanted to link a couple of videos you may have already seen on YouTube of examples of KF airfoil planes.
This video is on the two delta wing planes Frank made. One with the KFm4 Airfoil and one with out. We fly them back to back and see how they handle.
This video was made by our friend Ken or ‘Wildhover” on YouTube. He made a cool video for us to let us know of his findings on the KFm2 airfoil on his scratch built Euro-jet. Ken jokes that it is boring, but I know I thought it was good and informative. Big thanks to Ken for sharing his findings and for giving us permission to have it on our Blog.
Last is a video of Frank’s newest plane with the KFm2 Airfoil. There has been some argument that KF airfoils cause too much drag. I think Frank’s plane shows it’s not very slow, or hindered by the KF airfoil. It shows its still a very fast airfoil and also Frank notes how super stable the plane flys.
I just wanted to do a quick follow up post on the new “KF Condor RC Plane” that I posted video of on our YouTube Channel. A few months ago I bought the book Dick Kline wrote, “The Ultimate Paper Airplane” . It’s the book where Mr. Kline tells his story of how his paper airplanes lead him and his friend Floyd Fogleman to the invention of the “KF Airfoil”. It’s a really good book that tells about the theory of why the airfoil works and also tells about it’s wide range of flying benefits. The book tells of the many shows and articles that Dick Kline was interviewed on and for. From David Letterman to 60 minutes, Omni Magazine and so on. His airfoil was even tested by NASA. Dick Kline also has a patent for this awesome invention.
There are many people who have tried the KF Airfoil with good positive results, including my brother Frank and myself. We have both noticed a real difference when comparing similar planes with and without the KF Airfoil. The biggest good benefit I noticed was the slow speed stability of the KF airfoil equipped wing. Also the KF wing was much more responsive, I believe because the KF airfoil keeps the air over the control surfaces better. This is all just my theory, but something we at rcFoamFighters want to explore more. And thankfully we have a new, good friend to help us, Mr. Dick Kline himself.
So, having said that, my next project I have decided to build with a KF airfoil will be a plane inspired by one of Dick Kline’s Paper Airplanes, The Condor. This plane will basically feature a KFm2 airfoil to resemble the wing of the paper airplane. I really like the look of this paper Airplane because it is unique with the smaller wings on top and rear of the fuselage. So I have drawn up a basic template for the plane in AutoCAD and I am now beginning to build the plane, so please watch our YouTube channel to see how it all goes.
Below I just wanted to share some pictures and a short write up Dick Kline himself sent me about his amazing plane, the Condor.
(below picture) Dick Kline with his Condor paper Airplane and a Wright Bros Replica Model
(Short email about the Condor from Dick Kline)
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.”
Another picture of a version of the Condor
Here is a picture of the RC Plane I plan to make. Note that the RC plane will more resemble the Condor Paper Airplane version as pictured in Dick Kline’s book “The Ultimate Paper Airplane”. The Verison in the book appears to have a little different tail and the small wings on top of the rear of the fuselage appear to be larger. Anyway, here’s my attempted to make a plane in the style of the Condor.
I just wanted to share a few write ups Dick Kline was so kind to share with us. In the two PDF’s provided (Links below) Dick Kline reveals his Theories of how the KFm3 Airfoil works so good as a “Heavy Lifter” and why the KFm4 Airfoils “Fly So Fast”. These articles were written by Dick Kline himself and rcFoamFighters would like to thank him for sharing them with us and for letting us share them with you and the rest of the world.
Click on the below picture to view the PDF write-up on KFm3 Airfoils
What makes the KFm3 airfoil a heavy lifter? (By Dick Kline)
Click on the below picture to view the PDF write-up on KFm4 Airfoils
What makes the KFm4 airfoil fly so fast? (By Dick Kline)
Again rcFoamFighters would like to thank Dick Kline for the above write ups on the KFm3 and KFm4 airfoils. For our viewers that may not know, Dick Kline is the inventor of the KF airfoil idea that originated some 40 years ago. rcFoamfighters has been blessed by being able to share information and ideas with this great man. Dick Kline has being doing his best to reveal to the world what benefits the KF airfoils have and how great they work. rcFoamFighters has experienced great results by using the airfoil idea Dick Kline has invented and we will be doing more videos in the future to showcase its awesome flight characteristics.
Thanks to all,
Big News! Dick Kline Inventor of the KF AirFoil Contacts rcFoamFighters.
The following posts are excerpts from e-mails sent to us from Dick Kline along with information provided by him on the various types of KF Airfoils. If you are thinking about experimenting with any of these airfoils or just want to know more about them this information should be very helpful.
(Copy of Email from Dick Kline to rcFoamFighters on 3/28/09)
Hi Frank and Paul…
You both are more than welcome to do a video of the KF airfoil.
I’m delighted that you are interested in this concept that has been trashed by the experts for over forty years. They claim that it is too high in drag. However, when the step is applied to a flat plate it appears to go faster. The KFm4 goes even faster than the other KFm variations.
When a KF step was applied to the end of a prop it increased the thrust by almost 9%. If the step produces too much drag, how can it become more efficient.
Personally, and I’m no expert, but I believe that 50% of the KFm4 produces no direct friction or drag because it is air against air. That’s kind of mind-blowing to think that half of the airfoil doesn’t come in direct contact with the air around it.
Have you guys ever heard of the Kamm effect? In the 1930s, Wunibald Kamm who was a German aerodynamicist, chopped off the rear end of his racing car. At that time it was thought that the tear-drop shape was the most aerodynamic. The blunted rear end proved to be more aerodynamically efficient, which is why most cars today come with blunted rear ends. That includes the hybrids, which are looking for fuel economy.
In fact, the Boxfish has inspired blunted rear end designs.
Here is one study done in 1998 that shows some positive characteristics of the step concept.
Finally… Here is a list of the positive characteristics that the KF airfoil has shown to date:
1. The KF airfoil handles a wide range of speed from very slow to very fast.
2. Normal airfoils are designed to either generate a lot of lift in order to carry more weight, which means they must be thicker to produce more lift, or they need to be thinner in order to fly faster thus sacrificing lifting heavier loads. The KF airfoil can do both of these jobs extremely well.
3. The KF airfoil has a much greater range for its center of gravity (CG). A conventional airfoil would normally have a CG about 33% back. The KF airfoil can be moved back as much as 40%, thus allowing it to carry a heavier load. The further back the center of gravity is the more desirable it is because of the center of balance. And, it can also handle a shifting CG and still give you control authority.
4. The KF airfoil has great control authority. It’s control surfaces remain effective through a large range of angle of attack (AOA). Even beyond a 60º AOA. This is also evident by its ability to have a very fast roll rate with full aileron and rudder control at very high angles of attack.
5. Normally, all flying wings require some reflex in flight. Reflex, which will produce some drag, means that the ailerons are angled upwards slightly in order to keep the nose of the aircraft pointed up. It is also well known that flying wings are extremely unstable and stall easily in flight. The KF airfoil requires zero degrees reflex on a flying wing which means no drag from the reflex action. It is a very stable platform. It is capable of flying without stabilizers or rudder, which means that two components which cause drag are eliminated.
6. The KF airfoil appears to have better air penetration. High winds seem to have little effect on how it performs. People have reported not being able to fly their aircraft during strong wind periods while the KF airfoil continues to fly smoothly. It appears as if it rides on rails.
7. In addition, the KF airfoil doesn’t appear to be affected by weight increases. It has been reported that the handling of the aircraft doesn’t seem to be affected by adding additional weight. In one case, 4.5 oz. of lead was added and it was able to handle the added weight with ease. In another case, a KF glider which was facing 22 mph wind, flew very well when nearly 100% lead weight was added to it.
8. At high angles of attack, the KF airfoil remains unstallable. The center of gravity and center of pressure appear to move backward thus preventing a loss of lift.
9. The possibility exists that the KF airfoil may be more fuel efficient because one quarter of the airfoil produces little friction due to the trapped vortex pitting air against air. A normal airfoil produces friction over the entire surface.
10.Unmanned aerial vehicles are extremely expensive aircraft. The loss rate in the military is rather high – over 20%. The KF airfoil is a minimal structure which is very strong and simple to build. It would greatly improve on the survivability of these planes because of all the reasons outlined above. In addition, because it penetrates the air so well and is extremely stable, it will produce better photography. Because of a better center of gravity, it will be able to carry more weight, either extra cameras or extra batteries for longer flights. And, because of its ability to penetrate air better, it is not affected as much by higher wind gusts. It has been shown to fly in strong winds when all other RC aircraft were grounded.
And, now for the most amazing aspect of all… the KF airfoil has no apparent bad habits, vices or negatives that have shown up. All airfoils have their positives and their negatives, because each one is designed to do a specific job. Thus, a given airfoil can do certain things well, but do poorly in other areas. To date, nothing negative has appeared on the KF airfoil.
The concept behind the Kline-Fogleman airfoil may be hard to understand because it is so different from present aerodynamics. The KF concept uses a vortex, which attaches itself to the KF airfoil behind the step and becomes part of the airfoil. This means that one-quarter of the KF airfoil is air against air. This also means less friction and greater efficiency penetrating the air. It is important that the step be between 7% and 9% at 50% of the chord on top. When the step is on the bottom, the step should be at 40% of the chord. When the step is on top, it will produce higher lift than on the bottom, but the airfoil works well right side up or upside down. With the KFm4 airfoil, which has the step on the top and bottom, 50% of this airfoil is air against air, which means no direct friction or drag.
– Dick Kline
P.S. I’d be very interested in your own personal experiences with the KF airfoil concept. I think that there may be a difference between what is seen or studied in lab conditions is not the same as what happens in the real world. So many people who first see the KF airfoil react to it by saying, “That thing can’t fly.” Somehow it does inspite of everything that we have learned about the way a wing is supposed to generate lift.
Thanks again, guys, for your interest.
Pictures of KFm Airfoil Variations:
Pictures of Kline-Fogleman Effect:
rcFoamFighters would like to thank Dick Kline for
sharing his thoughts, words, time and the above documents
We will soon be using KFm Airfoils on up
coming projects and seeing how they perform.
Please click on the below link for more in depth information
on the performance of the KF airfoil provided to us from Dick Kline along with the information in this post.