KFm3 airfoiled wing - RC Groups
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Aug 01, 2009, 09:28 AM
Is it supposed to do that?
SimonP.'s Avatar

KFm3 airfoiled wing

Howdy! I've decided I'm gonna make a real (ish) sloper to fly along with my little Fling but i want to make something easy and cheap for if (when) I destroy it. So I spent a few hours on here and sketchup making it.

http://sketchup.google.com/3dwarehou...dd&prevstart=0 Anyone with sketchup can check it out here. I'll be building it out of 1/4" blucore with carbon spars and plywoood for the elevons. Any suggestions on how to make it better or if something is horribly wrong with it would be much appreciated.

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Aug 01, 2009, 10:36 AM
The Predator
The Predator's Avatar
I'm going to guess it will waggle a bit much in yaw because the winglets are quite close to the CG leaving them with little leverage to stabilize it enough. I use more sweep to get the verts further back. You could use a CF on a boom or tip lets on booms but, those break lots easier. I'm quite familiar with this issue.
Aug 01, 2009, 10:45 AM
Mark Robbins
Predator, You must have built one that looks like that?
Aug 01, 2009, 10:46 AM
The Predator
The Predator's Avatar
Not just one . . . . . LOL
Aug 01, 2009, 11:40 AM
Is it supposed to do that?
SimonP.'s Avatar
this one here http://sketchup.google.com/3dwarehou...dd&prevstart=0 is a little fatter and has the same swwep as the other one. I made it a bit bigger so the airfoil is almost excatly 10%. The winglets are farther back to hopefully neutralize the "waggle". I know this wont be a beautiful flyer by any means.. just something a but more extreme.
Aug 01, 2009, 02:18 PM
Biting ankles since '53
Ply may be heavy for the elevons...

Seen this? REVERT
Aug 01, 2009, 03:43 PM
Is it supposed to do that?
SimonP.'s Avatar
in the sketchup the stuff painted as particle board is 1/8 balsa. Yeah, I've seen the revert. I figure if he can do it in 20 minutes i can do in in a few weeks :P I made a mini version without any airfoil and it tracks dead strait so I may start drawing and slicing tomorrow.
Last edited by SimonP.; Aug 01, 2009 at 03:44 PM. Reason: Apparently I can't spell
Aug 12, 2009, 07:56 AM
Registered User
davereap's Avatar
check out the main KF thread here https://www.rcgroups.com/forums/showthread.php?t=558321 for any of the KFm2,3 or 4 designs .. keep the gear inside the wing as much as posible to lower the drag.

heres a KFm2 I flew the other day, a horton shape rather than zagi, but it went ok..first few launches were part of a lot where I was trimming the COG.. the last launch was on a slightly steeper slope and soared ok..
MY first sloping in 30yrs
the basic zagnutz shape is more similar to yours and would have been a simpler build

ho229 KFm2 flying wing shape on The Slope (2 min 59 sec)
Aug 13, 2009, 09:54 AM
IFO's are planes too
atone1's Avatar
HI Dave,
Great flying wing video you have there, I liked the first couple of launches. In the end you went with the old wing tip launch and that looks like the way to go. That's the way I launch my wing and all my kites.
What's the weight and wingspan on that wing?
Keep up the good work guys.
Aug 16, 2009, 05:26 PM
Is it supposed to do that?
SimonP.'s Avatar
I did some testing just with a single step on the second platform I posted. it was at 50% chord and about 9% thickness. When I tossed it with the KF on the top it took very little weight to even out the cg but it was VERY unpredictable. I set it up with no control so I could just see how it flies. With the KF on the top it would nosedive at the slightest drop in windspeed or climb and stall with little gusts. when i flipped it over to make it the KF1 on the bottom It took a TON more weight to even out the CG, flew straighter, the weight made the wind unnoticeable, and surprisingly, flew only a tiny bit faster than the KF2. I deffinately need to change my drawings cause the KF1 rocks!
Oct 20, 2009, 08:35 AM
Registered User
davereap's Avatar
The baby ho229 is 36" and about 4oz 1.66sqft
the upright fins are removable and were only for the initial flight trials..

Its not flown that model since then, the winds have not been favorable for that slope
Ive been thinking about going bigger with a slotted prop..KFm4 works well
Last edited by davereap; Oct 20, 2009 at 09:06 AM.

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