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Jan 11, 2010, 06:44 PM
bobskinner's Avatar

16" KFm4 wing, David (+ Free Plans)

Well, I have posted this little wing in a couple of different threads, but have decided to give it a thread of it's own. I have included the single letter sized page of 1/2 of the wing plan below. If there are any suggestions on how I can clean up or improve the plan please let me know and I'll make the changes. This thread will also allow for a place to do a build log for when I build another one just as soon as I have some more 3mm depron.

A few weeks ago I drew and built a little 14" wing, my first wing. It was a handful but I got it flying and then decided to retire it as it was a little too much to handle. Inspired by the Goliath from Sylvanaircraft I drew this little 16" wing.

Wing Span: 16"
Wing Area: ~86sq Inches
Weight: ~66grams (~2.32oz)
Wing Loading: ~3.9oz/sqft
KFm4 Airfoil, 50% steps top and bottom (Entire wing consists of 3 layers of 3mm depron)

Motor: 5g Turnigy 1400 4500Kv from HobbyKing with GWS 3x3 prop (possibly a little too much for this motor and the battery but have not had any issues yet, am trying to track down a 3x2)
ESC: Pentium/Turnigy 6A
Battery: 230mAh 2s lipo
Sevos: 2x "3.7gram"
RX: Berg 4l

This wing is truly a pleasure to fly. It feels very stable and it slows down nicely, the 2nd video below I tried to slow it down some to give an idea. It has no tip plates and I have not had any surprise stalls. Power off it glides reasonably gently down.

I had no idea what color scheme to go with so I decided the copy someones. Well at least attempt to copy it. Since Laine's SRT-10 13ft wing saga was what first drew my attention to and got me interested in trying flying wings, I decided to do a rough Sharpie approximation of his SRT-10 color scheme (Hope you don't mind Laine, thanks for the inspiration)

16" Flying Wing, David (3 min 14 sec)

After some coloring:
David got some color (4 min 20 sec)
Last edited by bobskinner; Aug 10, 2011 at 09:26 AM. Reason: Cleaned up accidental double posting of info... oops
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Jan 11, 2010, 09:18 PM
John 3:16
Daddy-O's Avatar
This looks like a great little wing! Congratulations, and thank you for the plans.
Jan 13, 2010, 04:45 AM
Registered User
Very cute.
Jan 13, 2010, 08:19 AM
bobskinner's Avatar
Thanks chalermkiat. It is really a lot of fun to fly too.

Jan 15, 2010, 12:30 AM
Registered User
That motor and batt pack really makes a difference. We have that motor and a wing for it ,too, but still missing most of the other lighter stuff. Need to catch up first.
Jan 15, 2010, 10:51 AM
Registered User
jdmech's Avatar
This looks like it's going to be my first Wing project - very cool!
I'm on a very tight budget so it looks like it also might be very cheap to build.
Haven't gotten into Depron yet but looking to pick up a piece soon and play with it.
Thanks for including the plans and parts specs. I need to ask though, on your plans, what is the term 'Mac' referring to?
Jan 15, 2010, 04:13 PM
bobskinner's Avatar
jdmec, thanks for the comment. I appreciate you considering building one. All the gear used is pretty inexpensive and I had it lying around so definitely didn't cost much at all to get little David in the air. I would love to see some pictures and get some feedback if you do get around to building one. (Same goes for anyone that might consider building this wing, please post some pics and give some thoguhts on how it can be changed or improved)

(Don't quote me on any of this) MAC refers to "Mean Aerodynamic Chord" I believe. I could be horribly wrong but I think it is what the chord of your wing would be if you were to make a rectangular wing shape with the same wing area as the actual wing. I believe it also divides the area of one wing half in 2 so that the area to either side of the MAC is equal. I hope that makes some sense. If someone more informed wants to explain it please do so.

Ultimately, it gets used to determine where you should balance the wing. At least that is what I've seen it used for I'm sure it has more technical purposes also.

Since I don't have any more 3mm depron, but I do have some cheap $1 poster board, I decided to scale up the wingspan according to the difference in thickness and am working on a 20" David. I will post the build process here as it is identical to the 16" version.

Jan 15, 2010, 07:35 PM
John 3:16
Daddy-O's Avatar
Here are two illustrations that I have found describing the MAC. I hope it helps someone. There is so much to learn in this hobby.

I love this little wing, and plan on building one. I don't have a 5 gram motor, but do have a little 10g motor from HC that I am going to try to use.

Jan 15, 2010, 08:35 PM
Huh?! well waddayouknow!?
Nice work Bob.. just watched the vids... did I see that correctly?..No winglets?
I have a bum 5 grammer layin around and some scraps of foam as well.Probably take me longer to wind the motor than to build the wing? I like that idea!
I know... cut the pieces ...lay the glue throw it all under the mattress for drying ...wind the motor...take the wing out n fly it.
Shouldnt be more than a couple of hours.
Stay tuned.
Jan 16, 2010, 07:01 AM
A real WingNut
j4ck4's Avatar
Cool Bo if I ever get caught up with building I'll have to put one of these on the bench.
Jan 26, 2010, 01:58 AM
Registered User
jdmech's Avatar

Need help with finding the battery -

Bob -
I'm a bit of a newbie to the brushless world.
I'm trying to price out the motor, esc, battery, but I can't seem to locate your battery.
At least nothing in the 230 mah 2S style as stated in your first post above. Any hints where i can find it? I looked in Hobby King and Grayson but nothing seems to fit those specs.

Thanks bud - JD
Jan 26, 2010, 04:52 AM
John 3:16
Daddy-O's Avatar
This is my next build. I love wings and this small wing really looks great! I don't have a finless wing, and am amazed that it handles so well. I am finishing up my BowStick, then I will get after this little wing. It looks like it will only take a couple of hours from start to finish.
Jan 28, 2010, 08:09 PM
John 3:16
Daddy-O's Avatar
How is your David Wing going? I am building it, but I thought since you were using your 5g motor, and built it so light, that mine might fly like a brick with my 10g motor and 3s 360mah batteries. I extended mine to 24" and built out of 3mm depron. I've got it all glued together and the motor mount is drying right now. It is extremely light. Now that I am thinking about it, I should have built it out of my 3mm epp to make it more durable. Maybe I will just fly this one until it can't be flown anymore, then transfer everything to an epp 24" David.
I went with a black KFm step on the bottom and elevons, and everything else in white. It will be ready to fly tomorrow evening. I might get to maiden it early Saturday morning. Thank you for the plans.
Jan 28, 2010, 09:16 PM
bobskinner's Avatar
Hey Daddy-O Sorry I have not been very responsive on this thread as of late. I am honored that you would build this wing, thank you! Post some pics and a flight report when/if you get a chance. I am interested to hear how scaling it up but keeping the thickness the same works out. All the best with the maiden!

jdmtech, I am truly sorry I completely missed your comment. From HobbyKing, you could possibly get 2 of these and then solder up your own 2s pack. Otherwise, perhaps one of these or these might work but they are slightly heavier and will most likely need to be place further back from the nose to get the correct balance.

I have finished cutting the 20" version (scaled up by hand) and need to get it done. I plan on using a 10gram motor on it. I have been taking pictures of the process to post here, but seem to have misplaced my memory card with them on...

I have also since I last posted purchased for myself a GWS 3x2 prop and if flies very similarly to the 3x3 on the vertical but a teeny bit slower in a level pass. The current draw is significantly lower though so I think the battery and motor are both a little happier.


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