** Kline-Fogleman (KFm) Airfoils - Advanced Theory/Science ** - Page 8 - RC Groups
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Sep 15, 2010, 10:18 AM
High Altitude Flyer
viking60's Avatar
Originally Posted by A Useless Geek
Bruce, I'm not sure that Steve can get that fine a granularity in the foam he's using. I kinda like your heat shaping technique with the covering iron, but that really takes a deft hand and quite some bit of experience to get right, doesn't it?

[NOTE: let's not let this get too far off into build-land, else we need to take it to the other thread. Heh. I'm one of the worst offenders, of course.]

Since you asked this question here, I'll answer it here...

[This is something I foresaw when the KF discussions thread was split in two directions... there will always be crossover subjects as we experimenters apply 'theory' to materials, then go out & fly the results, and report back. So I don't think that anything should necessarily be labeled as 'off topic' on EITHER discussion thread.... it's all too thoroughly inter-related. Unless some of us are actually 'Applying the Theories' and report the techniques and results - (otherwise known as 'Building & Flying'), it's just so much chatter... and having "Build It This Way" postings in one place without some of the "Why It Works" included may not serve our wider purposes, either...]

IF a builder happens to have a heat iron and a heat gun, they can do some experimenting and practicing on scrap material. Getting the right heat setting, not using too much heat with the iron OR the heat gun is the main thing each has to get comfortable with. From there, if someone discovers that they have ten thumbs & no inclination to invest a bit of extra time, that's OK too... this is supposed to be fun, after all.

The builders of the foamie 'ten minute wonders' may have no time or reason to use these techniques, and that's OK too. K.I.S.S. certainly has it's place- it's all fun!

But demonstrating these very workable techniques for others to possibly try certainly has value. Knowing that inexpensive foam can be very effectively heat formed and heat-tempered is a good thing- it opens up possibilities.

(Applied Aerodynamics is the practice of fine-tuning controlled air movement in practical ways- theory into form, very closely inter-related.) It's nice to know that we are not limited by the fact that foam is typically sold in flat sheets or blocks!

The FUN continues!!

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Sep 15, 2010, 05:29 PM
Onward through the fog.
Cybernaught's Avatar
Theory gives the explanation and practice shows how it works, proving or dis-proving the veracity of the theory. Explanation and reality. Are you going to "do" it or "think" it???

Not easy to divorce the two for most of us.

You make a good point Bruce. Seems like in one thread we have "Practical" with a bit of theory and in the other we have "Theory" with a bit of practical.

Personally I like the "do" but also want to know the "why".

Sep 18, 2010, 11:19 AM
just Some Useless Geek
Bruce and others are experimenting with reducing step height on KFs that approach surface turbulator values. Has anybody got anything on that?
Sep 18, 2010, 11:58 AM
fix-it-up chappie
tolladay's Avatar
Originally Posted by A Useless Geek
Bruce and others are experimenting with reducing step height on KFs that approach surface turbulator values. Has anybody got anything on that?
I always assumed that turbulators were placed on the front part of the airfoil, but I guess I just misunderstood.
Sep 18, 2010, 01:01 PM
High Altitude Flyer
viking60's Avatar
I'm primarily reporting on the experimental wing testing in the "Building & Flying" thread for now, since it focuses on the flight testing of the variations. I won't duplicate those on-going postings here for now; eventually the DANCER III web page will be put up on my web site with all of the extensive information and a wrap-up analysis there. (Another generation wing prototype is already planned.)

(Turbulating structures are sometimes used back to ~70% to 75% of chord; Phil Alvirez has posted about this in his blog.)

Last edited by viking60; Sep 18, 2010 at 05:53 PM.
Sep 18, 2010, 01:34 PM
just Some Useless Geek
Yeah, there's a lot to be had on Phil Alvirez's blog. It's worth a visit. Be prepared to spend some time reading.
Sep 27, 2010, 11:35 AM
High Altitude Flyer
viking60's Avatar

DANCER III with new KF3P wing now has it's own thread


I know that some of you have expressed interest in the ongoing design and testing process of what I'm referring to as the new KF3P wings. I finally spent a few hours to compile all of the information on these new wing designs, and added a lot more detailed photos to help with the build process. Rather than overloading this technical discussion thread with all of the extensive 'building and test flying' aspects of the advanced KF3P glider wing / DANCER III design project, I've decided to get all of the associated discussion, photos, and flight testing reports collected in a more appropriate thread.

So I've now collected and placed all of the material on the DANCER SERIES discussion thread, starting on page 2 with post #26. From there, I complied all of the material from the last 4-1/2 weeks which had been scattered across three different discussion threads, so it's now all accessible in one place.


I'll still be following & contributing to this great discussion thread, too, of course- but the sheer amount of divergent topic material should have it's own place, too!

Keep up the great work!!

Sep 27, 2010, 12:10 PM
OpenTX University Staff
maguro's Avatar
Viking, you have been doing great work. I suppose it is the nature of the folded foam, that my airfoils come out looking like yours. That is to say they they both resemble the MH32 without under camber. My airfoils came out with a blunter leading edge, because I used a single piece of foam scored at the fold. I plan to do my tests using the "pointier" airfoils obtained with two pieces of foam cut at 45 degrees.

In order to obtain comparison data I will be constructing a two piece airfoil with no step. The upper surface will continue to the trailing edge. This will require tapering the foam to obtain a sharp TE. If all goes well maybe I can test using your latest mod to the KFM3.

I made a KFm1/2 mock-up to enable testing of mounting methods. I decided to use bamboo skewers through the LE and TE just above the bottom layer of foam. The skewers rest on the wing mounts, enabling me to mount the wing step side up and step side down. The same technique allows mounting of a KFM4 wing to the same fuselage with no changes.

Viking I wish I could whip out drawings of my airfoils the way you do. It sure would make it easier to explain what I'm trying to do.

Sep 27, 2010, 01:06 PM
High Altitude Flyer
viking60's Avatar

Thanks! As far as the drawings, there are lots of 'craftier' guys using the CAD software out there; I'm not up to speed on that, so I do what I can. I end up back to the basic "Pencil 2.0" technique many times, too.

Sep 29, 2010, 11:24 AM
High Altitude Flyer
viking60's Avatar
The DANCER III glider with it's 62" span KF3P wing is flying superbly. (I have two great KF3P wings, and I'm thinking about another fuselage which will be designed to carry the battery within the structure, further minimizing drag in the fuselage, and thereby allowing these wings to perform at their optimum.)

I've tested a few variations along the way over the last 5 weeks. Primarily, I had wanted to investigate the affects on in-flight handling, stability, and performance when the height and position of the KF3 stepped discontinuities were changed from what I & others had commonly been using on the fun-fly foamies.

One question was, "Can the stepped discontinuities be implemented at a shallower depth, while retaining the positive influences on the wing's stability and stall characteristics?"

The second question dealt with the placement and height of the secondary step; "Can the depth and placement of the secondary step be changed in ways which allow the wing to glide more efficiently, while having precise response at all air speeds to slight aileron control inputs?"

The third question dealt with verifying aspects of airflow dynamics over the wing structure ahead of the placement location of the stepped discontinuities: " Can the glide performance and wind penetration capability of the wing be improved through more careful shaping of the airfoil surface contours of the forward ~half of the wing structure? And in doing so, will the stepped discontinuities implemented in the aft half of the wing's structure be able to more efficiently function in controlling airflow over the aft half of the wing and control surfaces, while minimizing drag in the process?" (Quite a loaded question, with many complex aerodynamic interactions to consider, I admit!)

The fourth question dealt with wing tip airflow dynamics, on which I've been experimenting with all of the Dancer series wings, as well as on the Me163-e Komet, and on the Soarbird 4 wing. It's too broad of a subject to try to summarize in one simple "question" right now... I'll just say that the 62" KF3P wing's extended wing tip structures are working superbly to add 'virtual dihedral' stability, while controlling the wing's upper surface airflow at the wing's outer end, allowing it to flow up & away from the upper and lower wing surface in the wing tip area with very minimal drag.

Minimizing drag while retaining the 'almost un-noticeable stall' is another characteristic of the KF3P wing design.

Bottom line- it's REALLY working!!

Thanks again to Dick Kline & everyone involved in these discussions for all of your inspiration and support along the way!

Last edited by viking60; Sep 29, 2010 at 11:31 AM.
Sep 29, 2010, 12:12 PM
just Some Useless Geek
Bruce, you've done a superb job of identifying, isolating, and resolving a lot of the specific questions we needed to examine in dealing with the KF step action. Hats off to you all around. If you ever get out to western Chicagoland I owe you a tall one.

Now, perhaps I can pose some new, slightly less heady (but certainly equally pragmatic) questions for some other enterprising builder/tester to tackle: taking the work that Bruce has done, is it possible to reduce some of the effort involved in making effective KF wings and distill that down to a set of building rules that can be easily implemented for foam builds?

I realize that, Yet Again, we are starting to blur the distinction between build and research. However, I think this question can't be abandoned because of the nature of what we are working with here. Bruce's work is art in flight. My stuff is hacked out FFF, Gorilla Glue, and tape. How can we apply what Bruce has learned to how ordinary slackers such as myself put out on a weekly (or, in Steve's case, daily) basis?
Sep 30, 2010, 08:56 AM
Registered User
splitpilot's Avatar
Sep 30, 2010, 09:32 AM
That Guy Who Flies Wings.
Here's my KF wing project page. I even got to fly this indoors at the UniDome in Cedar Falls, IA!
Sep 30, 2010, 10:07 AM
Flazo's Avatar
I would like to learn...thank you.

Sep 30, 2010, 10:09 AM
Addicted to building...
Freddie B's Avatar
Originally Posted by frednjess
Here's my KF wing project page. I even got to fly this indoors at the UniDome in Cedar Falls, IA!
Cool project, simple and BIG! Don't take any of those Heli dudes at the La Vista field or they will ban you forever! Your video looked like the B-2 doing a flyby! LOL. Back to KFm discussions, sorry!


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