** Kline-Fogleman (KFm) Airfoils - Building/Flying Discussion ** - Page 18 - RC Groups
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Nov 12, 2009, 11:34 AM
Lee's Avatar
If you haven't seen this walk along glider you ought to take a look and ask yourself is this a KF airfoil???

42 Second Flight of Surfer Paper Airplane (0 min 58 sec)
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Nov 12, 2009, 02:52 PM
High Altitude Flyer
viking60's Avatar
Originally Posted by Lee
If you haven't seen this walk along glider you ought to take a look and ask yourself is this a KF airfoil???


I have one of the Windrider "Ground Affect Controlled Glider",NO.W888; it is a singly layer of 3mm depron, 18" wing span, with an under-cambered airfoil, with a fair amount of sweep, and fairly heavily reflexed wing tips. It also has a fairly high dihedral angle on the center brace.

I have heard that Ming will include one of these if someone orders one of his other larger RC kits; he primarily designs injection-molded EPP slope aircraft, such as the BEE and the FOX:


Nov 12, 2009, 06:43 PM
Account Closed
Well, I took three wings out for a test run yesterday and earlier today. The winds were between 5-10mph yesterday and between 10-15mph today.

The three wings that went out were the KFm3, KFm4, and the KFm4(zigzag). All were flown without the aid of ailerons, and by not having ailerons, it hampered my turning abilities. Although, the zigzag won out over the other two with only elevator and rudder control. I was hoping that I would not have to use ailerons for control, but it appears that I will have to do so on future test flights.

All three wings have the same aspect ratio and weigh in between 5.2 and 5.6 oz. All seemed to provide adequate lift to carry around a +/-22 oz. plane. The ground take offs did not go so well. Non-power hand launches worked effectively for all three wings. Hand launching was the only way I could get the zigzag up and flying.

Here is a little info on the different wings and their performance.

  • Not a problem getting this one to take off from the ground. Hand launching was very easy.
  • Likes to fly straight and level and did not like to turn. It feels like something is attached to the wing tips when going into a turn. Once it breaks the hold it will continue with less effort in turning. Both flight tests came in second in regards to turning and did a horrible job in todays wind.
  • Floats, glides well, and provided the most lift. (nothing new here)

  • Anyone who has built this one knows how it performs. Built for speed!
  • Not a lifter airfoil and I never thought this one was ever going to take off from the ground. Hand launching not a problem.
  • Fast and straight, not a problem. I had a heck of a time getting this one to turn around and todays flight I had to keep it short. It needs ailerons.
  • Nice airfoil.
  • Keep the build/design light.


I'm liking this one. It was the only one I was able to control today in the wind, without the aid of ailerons. It wasn't great, but I did have some fun with this one. Both days, this one came in first with stability, yet failed on the ground take off. Could never get it to take off. Power off hand launching was fine and lifted much like the KFm3.
  • Extremely smooth level flight performance.
  • Best performer on turning. Although, something strange happens when turning. It always seems to want to climb as it turns, yet did not seem to show any signs of tip stalling. (more testing and video coming on this one)
  • Speed performance in the wind, much like the KFm3. Going with the wind... fast enough for my taste.
  • Does not seem to have the sticky feeling before going into a turn like the KFm3.
  • Needs to be tested with ailerons or tried out on an elevon setup.
  • Drag. Falls between the KFm3 and KFm4.

Overall all three fly and need more control surfaces. I was very surprised with the performance with the zigzag wing and will continue to test and video this one. This is a few highlights and I will try to get some video up in a day or two as the wings are built. I know some of this info is old news.

Viking and Steve, I will get into more step/aileron testing.

A few pictures of the wings.
Last edited by sharpewing; Sep 07, 2012 at 05:23 PM.
Nov 12, 2009, 07:13 PM
jackerbes's Avatar

Nice work on the builds and the testing.

I think the wings all being flat would account for their tendencies to not turning well or turning anything like normal in a RET configuration. If you could add dihedral to them I think you find that they all turn well.

If you combine dihedral and ailerons on any of the wings they will work against each other a little. Small amounts of dihedral on an aileron wing will really make for a good wing for someone that is transitioning from RET to four channels. Being able to let the plane self recover is good thing when you are learning to use ailerons and coordinate the use of the rudder with them.

But, as you probably know, an experienced four channel flier will not like an aileron wing with dihedral as much as a flat wing.

And there are some fliers that will make almost any wing do almost anything regardless of the configuration. Those are the guys that wind up being the first flight test pilots for us newbies, the guys that can get almost anything back on the ground undamaged.

Nov 12, 2009, 08:44 PM
Lee's Avatar
This is a great site for airfoil research. As we look at the KF airfoils and try to compare them to airfoils already on the market we can compare them to these. I would love to get KF airfoils tested with the same precision that these airfoils have been.


Nov 12, 2009, 10:51 PM
Onward through the fog.
Cybernaught's Avatar
The Zigzag wing looks interesting. I wonder if the fact that there is more area to the back of the notch, with the increased actual length, plays a significant part in your findings? I also seem to remember that if a flat wing is mounted high, such as in a cabin type plane ie. Cub, it gives the equivalent of about 2 deg positive dihedral. Most of my early RET gliders had to have around 5 to 7 degrees of dihedral, if I remember correctly, to turn well.

A KFm4 Zigzag wing would make for a nice looking bird plane. Is your Zigzag wing notched on top or both top and bottom?
(KFm2 = top and KFm4 = both) Perhaps the correct designation would be KFm2-ZZ and KFm4-ZZ. Hmmmmmmm....


PS. Crashed 2 planes today. The Nifty may be a write-off and the Pagan cartwheeled. Too nose heavy and motor problems! I lost the Nifty in the sun on launch and it nosed in on the dirt road at full power. It requires major repairs and a complete new nose. It may be easier to just build another.

Edit: 11/14/09 14:42:00
New Nifty-ZZ ready for maiden. Pics and info on Nifty thread.
Started to repair the old one and it was a wasted effort. New bird was a lazy 1.5 day build.
Last edited by Cybernaught; Nov 14, 2009 at 01:44 AM.
Nov 14, 2009, 06:32 PM
Account Closed
Hey Guys,

The little KFm4 (Zigzag) birdy went up this morning with the aid of ailerons. Turns much better and seems to handle the wind very well. I did set the throws on the ailerons to 60% and the tail controls to max. I will tell you that both the KFm3 and this wing only need a little throw.

Could not really feel any drag on the wing tips this morning. Rolling was very easy to do, and it doesn't feel as heavy as the KFm3.

Steve, I may just have to build a Kline-Fogleman Pteranodon (big scary bird) after testing these wings out.

I saw your Nifty pictures. Very nice job with it... hope it maidens well.

Oh, and I'm guessing you figured out the ZZ pattern is on the top and the bottom. Symmetrical top and bottom.

Here is this mornings flight.

Last edited by sharpewing; Nov 15, 2009 at 09:26 PM. Reason: Update video link
Nov 14, 2009, 08:41 PM
jackerbes's Avatar
That's a very nice flying plane.

The flat wings and the ailerons, and the fact that you already know how to fly, really showed what that can do. It might have been a handful for a newbie because of the lack of inherent stability and the need to fly the plane full time.

And the winds were blowing pretty good and it handled those well too. The flat wings like the KFm3 really have good penetration and tracking as long as you have enough power to keep them driving into the wind.

You might have the world's best flying Sky Fly there.

Nov 15, 2009, 01:38 AM
Onward through the fog.
Cybernaught's Avatar
Went to the field today and flew the Pagan in the wind but didn't try the Nifty. The wind was quite strong and the Pagan Handled it with some effort but I didn't want to risk the new bird.
Just call me a chicken!

Trying t get your video now on Youtube but loading is slow with my provider on GPRS-wireless... They call it broadband but it's not. More like dial-up speeds.

Here's three screenshots from the Pagan vid-compilation. will try to upload the video when I can get to a cybercafe.

Glad your Zigzag is working out for you. I'll let you know how the new Nifty-ZZ does when I get to maiden it. Hopefully tomorrow. Still windy now at 2:30pm.
Got to see about 1.5 min of your video before the server hiccuped and dropped me. At 16oz/sq ft it's about 3 times higher wing loading than I like. I worry when I get close to 6oz/sq ft.


Edit: 11/16/00 19:02:00
Yesterday's flights Sunday 8am windy but OK.

Pagan11 15 09am (4 min 48 sec)
Last edited by Cybernaught; Nov 16, 2009 at 06:03 AM.
Nov 15, 2009, 07:27 AM
Registered User
davereap's Avatar
Good flying in the wind. A very pretty wing with the black and white zigzag..Nice and smooth...
Was it any different from the straight edge KFm4 in flight?

An excellent follow on wing for anyone with that sort of molded body still in one bit...
Last edited by davereap; Nov 16, 2009 at 04:23 AM.
Nov 15, 2009, 11:43 AM
High Altitude Flyer
viking60's Avatar
In the SKYRAY discussion thread, Trooper8 wrote the following about his 26" wingspan Skyray which he had origionally built with a KFm4 wing:

"In a quest for more speed from the 26" ray with kf4 I covered the wings in packing tape to smooth the flow off the trailing edges of the steps.

It picked up a noticiable bump in speed but the interesting thing is that it made the Ray even MORE rock-solid. It was great before but now it seems eerie solid like it's not even a "model". Pilots at the field that have seen her before even commented how it just looked so very solid like on rails!"

This caught my attention, so I thought I'd mention it in this thread for possible discussion. The video on Youtube briefly shows the tape. The ouboard ends of the added top & bottom panels were very close to the ailerons, but the tape was added to the inboard sections of the doubler panels; the photo below does offer a look as to how the parts were cut.

This comment was made in post 1530 on this page:


Last edited by viking60; Nov 16, 2009 at 04:38 PM.
Nov 15, 2009, 09:49 PM
Onward through the fog.
Cybernaught's Avatar

Question for the group.

Went out this morning, Monday, to maiden the zigzag Nifty and re-fly the Pagan after repairs. It was windy and the Nifty was just a tiny bit tail heavy! I have minor damage to both planes.

The question:
Why do we fly when we know we shouldn't?

Nov 16, 2009, 12:57 AM
Account Closed
Guys, thanks for the kind reviews...

Dave, I got the right video link copied over. I noticed the video didn't show up when I did the post and I wasn't sure what I had done.

The KFm4 testing has been short right now. After I put ailerons on the wing I will update my findings and put up a video. It seemed to fly pretty good, except for turning and it did feel lighter than the other two wings.

Jack, I'm still learning to fly. I enjoy experimenting with my planes and I seem to experience something new everytime I go to the field to fly.

The zigzag video was taken at a field I do almost all of my first test flights. Did you see the large bush in the video? That is just one of several that like to catch my planes. One actually saved my foam B-2 from destruction. True story.

I may try out KFm7 or 8 after working on the KFm4. I don't think 1 and 2 can take the weight of the plane. I 'm putting an updated picture showing the aileron size for the first two.

Last edited by sharpewing; Sep 07, 2012 at 05:23 PM.
Nov 16, 2009, 04:53 AM
Registered User
davereap's Avatar
It just goes to show the KF steps work even if they dont follow our normal guidlines...
Weve all done it in moving the steps a bit, but Bill has gone away from convention.

sorry bill, this is not a criticism because the plane is going well..the zig zag in my eyes is too far back.you have it starting from 50% with the points at 75%..
Our normal steps are at 50% so I personaly would have put the steps so a line through the centre of the zigzag was on the 50% mark..
Still, even so, the steps are working well like that, cause the plane is wizzing around very nicely..Bill flys it smoothly and it is really cutting through the windy conditions
As I said, it just goes to show..... well done bill...another successfull experiment..

Bill If you want a slower plane, increase the span and chord of the wing, if you double the wing area you will half the wing loading and slow the plane to half the speed..
If you want to bank using rudder the wing should have dihedral, a couple of inches under each tip will work..
Again personally I would keep the wing flat, its easier to build, and you are easily capable of flying ailerons as you have shown. Keep the rudder for yawing rather than banking..
Joining wings at the centre always makes for the problem of reinforcing that weak spot in your build..
Last edited by davereap; Nov 16, 2009 at 05:05 AM.
Nov 16, 2009, 02:26 PM
just Some Useless Geek
Originally Posted by davereap
Joining wings at the centre always makes for the problem of reinforcing that weak spot in your build.
Not necessarily. Take a quick look at my Smart Dart XS or any of my Smart Dart builds to see how the wing root joint can actually increase the rigidity of the plane's longitudinal axis. This depends on the wing having a dihedral, of course.

For dihedral wings with longer spans I use a wing-to-wing brace as I did on my Yardarm. The bamboo brace represents a small frontal area and low drag.

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