** Kline-Fogleman (KFm) Airfoils - Building/Flying Discussion ** - Page 324 - RC Groups
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Oct 17, 2012, 03:53 AM
Registered User
davereap's Avatar
Another good'n ... but a fair bit heavier... my radius 250 was 266gms AUW 5.3ozsqft with an 800 3 cell lipo...
Your extra weight and heavier wing loading at 6.5ozsqft will help it in the wind, and likely it will fly a lot faster than my lighter version..
Thanks for the design thomas.. its a sweet little model..

no flying here, wet and windy...yet again...so I think I will box in a fuz on my radius to cover my esc and rec.. they got a bit wet the other day when landing on the damp grass.. there was no problem, I had taped them over, but a proper fuz will do a better job
Last edited by davereap; Oct 17, 2012 at 04:24 AM.
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Oct 17, 2012, 11:39 AM
What could possibly go wrong?
nickchud's Avatar
Another good'n

What are your thoughts about the distance between the fins? On my 500mm variant, they are only 55mm apart. I like them like that, but I wonder at what point they start to interfere with each other, reducing their effectiveness. I haven't noticed any problem.


Oct 17, 2012, 03:15 PM
Thomas B.'s Avatar
The Radius weight of 400g includes a 1800mAH 3s battery which is 160g.
I maidened it this evening and it is great fun. It does everything the smaller version does but is more stable in flight and even faster.
The Kfm 4 wing works very well- neutral at high speed, good slow flight handling, gentle stall, excellent bad weather handling. Thank you for recommending it, Dave.
Will post a video soon.

Made a first attempt with sketchup, see attachment.

Nick, sorry, I have no experience with the distance between the fins. It is 20cm on the 55cm Radius and 15cm on the 40 cm Radius.
Oct 17, 2012, 05:14 PM
What could possibly go wrong?
nickchud's Avatar

Radius variant

With balsa, you can see there's a good structural reason for the fins to be the continuation of the fuselage sides. And I like the opportunity to have a waisted tail, with a more conventional tailplane. Certainly, I've had nothing but good behaviour from this version.

When I get home, I might try morphing the shape into something like a kestrel. As it is, I can get it to hover quite realistically.

Oct 18, 2012, 01:48 AM
Registered User
davereap's Avatar
If you are playing with gyros, have you seen the KK boards..used more for multi rotors they are 3 axis gyro boards and can be used for planes as well by flashing with aero software... best of all is they are quite cheap.. the latest is the easiest to use... a KK2 from hobbyking
do also remember to purchase the usb gadget for flashing at the same time..

here are some more pics of my radius 250
Last edited by davereap; Oct 18, 2012 at 03:28 AM.
Oct 18, 2012, 02:06 AM
What could possibly go wrong?
nickchud's Avatar
Good stuff Dave!

The gyro I got is this one from HobbyKing. Now that I've got it adjusted I'm pretty impressed with it. Just one channel, you put it between the servo and the RX. I reckon it's best to start low (p'raps set the gain adjuster to about 45 deg from zero) and build up till it starts to cause jittering. It seems to help on the aileron channel with high alpha flying.

Oct 18, 2012, 12:51 PM
Registered User
Dave -- nice plane!

Nick & Dave, I'm interested in gyros, but have not read up much on them yet. I assume that if a plane banks one way or the other, the gyro manipulates the elevons to bring it back to level flight.

Soooooo, how do you turn? If there IS an input from the Tx does that "over ride" the gyro?

Any references for a SIMPLE explanation of how to use gyros?

Oct 18, 2012, 01:01 PM
just Some Useless Geek
Guys, the fact that we're even having this discussion about gyros is indicative of a problem, is it not? There's something inherently off about this design if you have to use a gryo to get the thing stable.

I made something similar a while back when I was looking for a design for a very crashable airplane that I could market to the newbie crowd. That plane was awful and I dropped it after playing with it for a while. You might find that the Radius needs some more effort to make it look "standard" the way Nick did before the plane settles out. Don't know.
Oct 18, 2012, 01:10 PM
Sometimes it work some don't
RCSquale's Avatar
Well correct me if I'm wrong but the Gyros will help the plane to stabilize it back to a comfortable position where it can fly straight.

Example if you have a plane without Gyros and you apply left or right ailerons, the plane will bank and stay in that last position where you place it into... (That is when you leave the control of the TX after the action) with Gyros the plane will auto stabilize itself when you take of your hand of the control, when you'll apply right or left ailerons and you leave your control the Gyros will take over to place the plane straight back without having to do it yourself by applying invert imput.

You apply left ailerons and without apply right ailerons to stabilize your plane back again the Gyros will do it for you. This is how it works.
Oct 18, 2012, 01:26 PM
Reap the wild wind
headlessagain's Avatar
I don't think everybody is using giros on the Radius and I think Nick is just experimenting. There are basically giros that will adjust for any unwanted model deflection caused say by a gust of wind and other more sophisticated ones that will return the model to level flight.
The basic ones can be single to 3 axis such as this HK one http://www.hobbyking.com/hobbyking/s...tabilizer.html. My brother use this in his Super Bandit Parkjet and there is now zero torque roll on take off.
Oct 18, 2012, 01:39 PM
What could possibly go wrong?
nickchud's Avatar
I don't think everybody is using giros on the Radius and I think Nick is just experimenting.
. Yes exactly. Nothing at all wrong with the Radius. In fact, if you're going to learn something new, do it where you know the other variables are reliable.

Mine is a simple, single channel gyro. The instructions are next to useless. To use it with ailerons, you mount it along the line between the ailerons. Then switch on, hold the plane level, don't touch the TX. Give it a little rock to the left and you should see the servo make a little move to push it back again to the right. These movements should only by just noticeable. If the gyro moves the control panels in the wrong direction, turn it around.

Any input via the TX should work exactly as it always did - the gyro lets that signal pass straight through to the servo.

I was flying at the beach this morning in winds of about 10mph and I could hover rock steady heading into the wind. Easy!

Oct 18, 2012, 03:29 PM
Thomas B.'s Avatar
Marty, the Radius does not need a gyro, Nick is just experimenting to get used to the technology.
If cg and control throws are set up properly it flies stable and nice.

Here is a video of second and third flight of Radius 275. Wingspan is 55 cm, Kfm 4, 400 g, Turnigy d 2826 /6 / 2200, 3s 1800 lipo. It was intended to be a speed model and it is. It is really fast, good slow flight handling, too. I guess it would be great with less power and lighter battery for park flying:

Radius 275 Speed (3 min 5 sec)

Dave, i see the front part of your radius has a glossy finish - how did you do it?
Last edited by Thomas B.; Oct 18, 2012 at 04:19 PM.
Oct 18, 2012, 05:06 PM
Reap the wild wind
headlessagain's Avatar
White packing tape I think.
Nice video Thomas. Now to try it on a 4S 1300 pack
Oct 18, 2012, 05:26 PM
Registered User
Dickeroo's Avatar

Another great video from Trond.

Here is the footage from his first KFm4 platform. Stunning and stable. Visually quite beautiful. He does outstanding work.

FPV49v3 Onboard HD Camera (10 min 25 sec)
Oct 19, 2012, 03:26 AM
Registered User
davereap's Avatar
headless is correct at post 4855... gyros are used to prevent unwanted model movements.. stick movements put the model as you want it and the gyros keep that position from being knocked about by wind etc..
Some of the boards like the KK2 I mentioned before, will do auto level as well...
A usefull gadget to smooth out any model plane for fpv or camera work.. also good in windy locations ... definately needed on the multi rotor platforms..

They are not needed on the radius, with the KF section it is steady in flight as can be seen from my last video ..the first hand launch went away hands off..
Thomas's nice video above also shows its smooth speedy flight characteristics... your motor there has 4x the power I am using.. lol. no wonder it goes so well..
I am setting mine up , less for speed, more park fly.. but I am still waiting for it to stop raining...
The decor is 2" packing tape, I use it on all my models.....clear, white and colored, it makes depron significantly tougher, and when you've three layers of depron and then the packing tape, it takes big hits with little damage.. I use it both on leading edges and trailing edges and anywhere that will be abraded..at the leading edge it prevents hit damage, at the trailing edge it stops stress tears and makes the hinges..I also fully cover all my control surfaces to stiffen them up..
Last edited by davereap; Oct 19, 2012 at 04:03 AM.

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