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        Discussion KFm4-Epp-Swift-Like (KESL) 32" Wing

#1 rdjay Apr 27, 2009 01:42 PM

KFm4-Epp-Swift-Like (KESL) 32" Wing
1 Attachment(s)
So I wanted to try a wing but being too "thrifty" to buy one I built a 32" wing based on the Swift II that I've read a lot of good things about.

My only "wing" experience is a Superfly (close) so I don't have much to compare to. This thing isn't overly fast but I think with the right motor and better batteries it will be all I can handle.

Right now with a 1300kW BW motor and tired 800mah 3cells it moves along nice. Handles well and slows way down.

If there is any interest let me know and I can post more pictures and a layout drawing.


#2 dekan Apr 27, 2009 02:31 PM

RD It looks promising... A smaller version 22" - 24" would be a bit quicker...With an Ele C20.....

#3 rdjay Apr 27, 2009 02:33 PM


Originally Posted by dekan
RD It looks promising... A smaller version 22" - 24" would be a bit quicker...

For sure. I was looking for slow/floaty. Could easily be scaled to any size.

#4 rdjay Apr 28, 2009 09:25 AM

8 Attachment(s)
Here's the layout drawing and a few of the pictures of the build. Sorry about the black/white pictures, didn't realize my camera could even do that.

I used Scotch Extreme tape for the LE with a small (~1/8") wood dowel, carbon fiber if you've got it. Did the laminating with 3M 77 (works great) and used a bead of Gorilla down the LE.

Elevons are two laminated layers of Dollar Store foam board (paper removed. EPP would probably work well, I just wanted a little stiffer surfaces.

Edit - Tiled plans added on Post 26 - Thanks Meistertek!

Edit - Mini (20" wing span) version plan on Post 309

#5 rdjay Apr 28, 2009 09:37 AM

7 Attachment(s)
I cut the servos just in front of where the middle layer is, poked the wires through the gap. Added a doubler of EPP on the top around the motor, glued (Welders) a piece of plastic under the motor mount on the bottom and a strip of Extreme tape both top/bottom make the motor mount area pretty strong.

I cut a battery/rx bay hole all the way through the wing. On the bottom covered it with thin plastic and tape. Used a piece of coroplast on top to make a "door". Wing tips are about 3-1/2" wide by 11" long centered.

Power is a 1300kv Blue Wonder. I've got a 1500 on order to give a try. Prop is 7 x 6 "APC Style". The only batteries I've got are 800mah, 3 cell that are real "tired". Voltage drops under 10 at about 5 amps. New batteries are on order with the 1500 from HC.

12A ESC, servos are HXT500 but I may change them to HXT900's when my order gets here. EDIT - Stripped out the 500's, switched to 900's.

Pretty simple build and flies great.


#6 Dickeroo Apr 28, 2009 05:00 PM

Any chance you could get a video of your wing in the air?
Is there any chance of getting someone to video it? If you do, try to keep it fairly close in because it is so easy to lose in the sky when its far away. You've done a fine job with this build.

#7 rdjay Apr 28, 2009 05:39 PM

Thank you for the compliment. I'm amazed by how nice this wing flies. And thanks for all you've done for our hobby!

I usually fly alone so video is a little tough. I can try the "hat cam" but as you say it's kinda tough to follow. If I can get something decent I'll post it.


#8 rdjay Apr 29, 2009 09:28 AM

A few details I forgot;

Weighs 8 oz without battery, ~10 oz AUW.

With a 800mah battery the cg is 7-3/4" from the nose. Power off glide is constant, slight "down" elevator when inverted to stay level. With a 500mah battery the cg is 8-1/2" from the nose. Glide tucks under pretty severely, inverted takes almost no "down". Floats with power off great.

EDIT - After a bit more flying I'm liking the cg at 8-1/2". Seems pretty forgiving which is not supposed to be "normal" for wings. Another KFm4 property maybe??


#9 rdjay Apr 30, 2009 12:55 PM

KESL Video
YouTube Video of wing. Quality not great, used my "hat cam". YouTube muted my audio (song), switched to Vimeo.


KESL, 32" RC Wing (4 min 21 sec)

#10 Dickeroo Apr 30, 2009 01:00 PM

Rdjay... that is outstanding. What a great demo of the KFm4 airfoil. She's smooth as silk. Congratulations!

#11 rdjay Apr 30, 2009 01:12 PM

Thank you, it (KFm4) is a great design for this wing. There was a bit of wind, maybe 6 - 8 mph kind of swirling around some of those big trees, barely even noticed it.

I'm waiting for new batteries and an 1500kV motor to speed it up just a bit. Also think the cg could go back just a touch, will test some more.

This one will stay in my car for quite awhile (or until I kill it!).


#12 High Flyin' Apr 30, 2009 02:42 PM


I really like your parts bay area! It looks like it would solve a lot of problems. Also like the idea of the reinforced leading edge...I will need that the way I fly! What thickness of EPP did you use for the wing? It sure looks nice and smooth flying. I have not built a aileron airplane before but have been pretty successful with the old RET builds. Do you think this would be a good step up or should I try something more standard? The EPP, quick build and I have a "Blue Wonder" just setting around makes it look tempting!

Thanks for all of the information, you have used a lot of good ideas on your build.


#13 rdjay Apr 30, 2009 03:05 PM


The EPP is 9mm, 1.3#. It actually measures closer to 8mm.

When the cg is right this thing will fly very slow and "goes where you point it". It tracks well and I think will be durable (haven't done much testing of that yet!). Wings/Deltas (elevon control) fly a bit different than RET but for a pretty small investment in both time and $$ you will be heading around that learning curve.


#14 rdjay May 01, 2009 11:12 AM

Some good news, and some bad.

Good news is that this wing flies great and continues to exceed my expectations. It's also quite strong, surviving (mostly) acting as a lawn dart.

Bad news is a major crash. Damage is pretty minor needing only about 30 minutes to repair. Both vertical wing tips snapped in two and the prop (held with prop saver) caught the back edge and broke a small 1/2" x 1" piece out and also a rip of about 4" into the wing. All glued back up with Welder and almost as good as new.

The nose/leading edge suffered no damage. The two pieces of epp jointed with Extreme tape, 1/8" dowel and Gorilla glue are really strong.

Cause of crash was both servos stripped. I was going up high and checking out handling while diving at full throttle. First couple of times it was ok. Last time tried to roll, nothing, tried to pull up, doink. Amazing how fast it can happen. I had a feeling when building and looking at the size of the elevons that the 5gr servos were too small but they were all I had. Some 9gr are on the "slow boat" from HC, should be here soon and will be an easy swap.


#15 Daddy-O May 03, 2009 08:48 PM

I was looking for this build thread after seeing the video (linked to the KFm thread by Dickeroo). I absolutely love your video, and have been wanting the Swift II also, so I have to build this wing. Thank you for posting the plans and the great pictures of your build. They are very helpful. It looks like you have made a great flying wing. Congratulations.

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