This is substantially the same message I got from him, so he hasn't changed his mind about this stuff.

jackerbes,

Thank you for posting the Rich Thompson (KAOS2) data and article. I had read that with great interest a while back. That is one of the best posts done on KFm airfoils in my opinion. Although many will argue the validity of his testing as subjective, there was a whole lot of work and effort put into that! I don't think I've seen anything quite as extensive on the KFm threads, subjective or not.

I know this is the kind of thing that this Theory/Science thread needs, and more. Lab equipment, wind tunnels, etc are not in the grasp of most RC modelers, so I will enjoy any data shared with at least an honest attempt to show results from some controlled experiments.

Heck I don't have enough time to build 8 different wings right now for the same airframe, let alone do the article, graph, and all thar Mr. Thompson did. Hat's of there to that test program.

Given that wind tunnels and other equipment has existed for many years before I was born, still many full scale birds proved their worth, or failure, after all the testing and the first test pilot took it to the air. Hope some good RC test pilots share their real world flight data, if at least it has some real thought, and specifics to the reporting.

Fred

I have to agree with you about the quality of that study. It stands out as clearly the best effort to date in my mind. If anyone feels a need to impugn that effort I invite them to put their money where their mouth is and better it.

To be able to see some lift to drag data and compare it to the subjective results from studies like Thompson's would really be interesting.

I went part way through the KF Flying Wing thread (I think of it as the Zagnutz thread) and made a list of posts and documents that I thought might be of historical and technical interest to the K-F airfoil. I am attaching that list as a text file if someone wants to look at it. You can copy and paste the the links there to see the posts or documents.

There is some interesting stuff there from the Zagnutz thread discussions in the early days.

Jack

I have my own thoughts & concerns about steps / discontinuities which are too far back & too tall messing with airflow over ailerons and producing far too much drag on a wing. I've written about this before, but testing the concepts means building & flying. So I decided to build up a new KFm3 variant test wing to which 'extender' panels could optionally be temporarily added & removed behind each of the discontinuities/ steps.

I just finished up this new 48" span wing shown in the photos below to this point yesterday. It started at 10" chord in the center, and 8" at the wing tips. That's about 3 square feet of wing area. The hot melt glue did the trick for a fast build-up. I also used balsa aileron stock that I had on hand. The upper forward surface's Bluecor material was shaped / curved by rolling it over a ~4" tube before the wing went together to give it the shaping I wanted; the filler strip just behind the leading edge also helps produce the airfoil shaping of the leading edge.

The fixed forward / primary step is at about 38% of chord, while the fixed rear / secondary step is at 64% in the center, tapering to 56% of chord at the wing tips. Ailerons start just outside of the prop arc in the center, and end 1-5/8" in from the wing tips. I'll set the aileron servo today & start test flying it if all goes well.

I laid out this wing so that I could temporarily add and remove filler strips behind each of the steps to see how they affect the handling / performance of this wing. I can also mount a variety of wing tip plates / structures to see how they affect the handling. It's all very interesting, & all fun!

(I like Rich Thompson's comments at the end of his article about the value of subjective evaluation, and about the 'feel' of an aircraft in the hands of an experienced pilot. The cameras just don't pick up on a lot of what the pilot experiences as far as aircraft response to their control inputs while flying... that's the 'rest of the story'.)

I'll post updates as the flight evaluation progresses.


VIKING

From the chart it looks like Clark Y or symetrical are the best . Especially when you consider the weight to strength ratio and the torsional rigidity , which were left off the chart .

Viking,

That's a great start. I like your curved airfoil surface. I use the same basic technique on my KFM wings. Do you planr to do any quantitative testing along with the qualitative testing?

Some yarn tufts on one wing, and a keychain video camera would provide a lot of data. Add a video camera on the ground so angle of attack and airspeed can be estimated would be of great value in combination with your evaluation of the performance obtained.

Roger

This thread is great news. Instead of just talking about how awesome the KF airfoils are, we will prove it, and push the boundaries. I'll gladly put some lufts on my 60" twin boom KFm3 and post the video here. I can stick my keychain cam on the center of the wing pointing toward the tip. Should work great.

Flight of theBoomBox part 1 (10 min 1 sec)

Originally Posted by maguro

I've been thinking that we are going to need some aircraft designed for our testing purposes. The have to be easy to build, and capable of carrying any data recording equipment we might put aboard. There will have to be different types of aircraft as well. A high wing for trainer/cargo aircraft, and a mid-wing for aerobatic/high speed/high alpha performance.

The high wing is not hard to design with replaceable wings, but a mid-wing aircraft will need wings that are easily built and attached, without being too complicated. Existing designs that can be bent to our purpose are easier than designing from scratch. Does anyone have recommendations?

Roger

It is another of Tony65x55's designs but the Piranha would be a good one to test mid wing airfoils on, I built one a while back with both KFm3 and 4 wings for it but I had a bad landing cause me to abort testing before I got to try the KFm3.

I love this thread and am subscribed.

I would like to offer up my CNC machine and meager CAD/CNC skills for testing purposes if you find a need for them. I can duplicate designs with more than a fair amount of accuracy, I also have a larger UAV style plane I am working on with a KFm3 airfoil that wouldn't be hard at all to swap out other airfoils on. It is a high wing style aircraft with a 60" wing. currently made from 9mm EPP on the wing.

I have video of it on youtube under rcFFBloodyMicks channel if anyone is interested.

I will keep watching this thread, PM me if I can help with anything.

Jon

Originally Posted by maguro

Viking,

That's a great start. I like your curved airfoil surface. I use the same basic technique on my KFM wings. Do you plan to do any quantitative testing along with the qualitative testing?

Some yarn tufts on one wing, and a keychain video camera would provide a lot of data. Add a video camera on the ground so angle of attack and airspeed can be estimated would be of great value in combination with your evaluation of the performance obtained.

Roger

Yes, as I mentioned in the other thread a couple of weeks ago, I have a keychain video camera that is set for close-up focus, which will work well with the yarn tufts or fluorescent orange thread taped to the wing's surface in various areas. (Newegg & DHL have taken a ridiculous amount of time to deliver the class 6 microSD card I ordered for this camera way too long ago... I'm STILL waiting...)

I want to get a close look at the circulating vortexes behind the steps, as well as the affects of the steps on the airflow. Hopefully this video technique will show this well enough. I'm particularly interested in what's happening in the wing tip areas on various wings.

(Later, I'll re-post the observations of the very noticeable drag reduction on the Soarbird4 wing achieved by eliminating the upper (KF sytle stepped) layer in the very outer end of the elliptically up-swept wingtip. It would have been neat to video the before-and-after on that morphing experiment right on the wing, but the excess material was cut away & thrown away... ah, well)

This on-wing video camera technique, along with significantly placed thread / yarn tufts should allow us to get a good look at what's happening... so for those of us on a shoestring budget who certainly can't afford a wind tunnel, we can optionally just put the little inexpensive camera where it's most helpful.

VIKING

What is so exciting is the solutions that people come up with and do it without expensive equipment. Finding ways around barriers and solving problems is for me the greatest kick you can get. Once the barrier is overcome, then it looks so easy and simple to someone else, but not until the creativity and problem-solving brain kicks the door in with the solution. I love it.

I am considering using a page from Burt Rutan's book and creating a sting to measure lift, drag, and moment that can attach to my car or truck. Anyone tried this yet? Have a design that might work?

Roger

Here it shows the Kline Fogleman profile from our patent drawing with a flat upper surface, sharp leading edge and a step on the bottom at 50%. Our original intention was only to patent a step, not an entire airfoil configuration. The reason was we knew that it worked right side up or upside down. And, that when the step was on top it produced higher L/D. The reason we put it on the bottom was because we knew that when an aircraft goes from subsonic to supersonic the L/D characteristics reverse themselves. Therefore, we showed it on the bottom in the patent drawings. We learned this from smoke tunnel testing done at Notre Dame by Dr. John Nicholaides back in 1971. It was part of the segment shown on CBS 60 Minutes with Morley Safer in 1973.

Interestingly enough, the KF on the bottom showed that it resisted stalling out beyond 50º AOA. The experts didn't seem to care or even wonder how this was possible. Go figure.

Dick,

Notice something else. Every other curve has pretty much the same slope. This is typical of most airfoil lift curves. They only change around the stall. The KF airfoil has a parabolic shape not a straight line till stall. Very interesting.

I want to plot some lift curves for KFM1 through KFM4 airfoils at a few typical model airspeeds. That data would really be interesting to see.

Roger

Originally Posted by maguro

I am considering using a page from Burt Rutan's book and creating a sting to measure lift, drag, and moment that can attach to my car or truck. Anyone tried this yet? Have a design that might work?

Roger

I remember photos of Burt Rutan putting airplanes on his vehicle and racing across the California desert to do testing. So I think this is a great idea! Good enough for trend and record setting, full scale airplane design testing, good enough fo us!

which book do you have, and who is the publisher?

Fred

Originally Posted by maguro

If you are an Aeronautical Engineering student looking for a good project, let me recommend this one.

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I am an AE student and I this is one of the projects I intend to tackle.
I am hoping to get access to the school's wind tunnel to run a few KF wing segments in.
At the same time, building a large RC aircraft with an interchangable wing set-up would also have to be done to for "real world" data, perhaps with an Eagletree on board.