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Old Feb 22, 2012, 01:54 AM
Joined Aug 2011
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KFm4 50% Zephr II Flying Wing

I have a detailed step by step build log at:
http://www.rcgroups.com/forums/showthread.php?t=1626928

Many people have recommended that I try a KFm airfoil on my build/discussion threads. Well I finally did and am impressed. I had recently flown a Ritewing Zephr II and wanted to try a wing so I took the opportunity to experiment with the KFm4 configuration. I reduced the Zephr II planform by 50% and used 6mm Depron to build the KFm4 wing with 35% steps. I could not tell the difference between the handling qualities of the full size Zephr and my small KF4 version. Pitch around neutral was smooth and the wing just cut through the air. Here is a video and some pictures.

First Flight: KFm4 50 Percent Zephr II RC Flying Wing flown by Otto Dieffenbach (1 min 38 sec)


KFm4 24" Mini Zephr II Flying Wing Vertical Takeoff flown by Otto Dieffenbach (0 min 48 sec)
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Last edited by Otto Dieffenbach; Apr 04, 2012 at 01:39 AM. Reason: video
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Old Feb 22, 2012, 03:18 AM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
4,282 Posts
Nice build and flying Otto. Makes a change from your big Sea Dart. You are finding the same benefits that I found on my 610mm span KFm-4 Mini Wing. This was adapted from a hot wire cut airfoil design of the same physical size using 6mm depron.
http://www.rcgroups.com/forums/showt...0#post20769047
I've since made an EPP core with 3mm KFm-4 panels and under construction is a 6mm/3mm depron version that I'm building for a FB who liked flying mine on the weekend. His will use a 1500 blue wonder for starters rather than the 3000 kv that I'm running.
The design is super stable and can handle high winds without problem. I think you summed it up in your video -fly's on rails and cut through the air.
Now to specs! I guess your wingspan is around 700mm/28 ". Are you running 9 or 5 gram servo's and what lipo, motor, prop and esc are you using? Could you post some pictures of the underside as I'm not sure where you mounted the lipo.
Here's my Mini Wing in action using the BW 3000 kv on a 4.5 x4.5 prop which I think is a faster set up than the 4.75 x 4.75 -go figure!
Mini Wing KFm-4. 610 span. Shot with #16 HD Keycam (2 min 20 sec)

It's also very durable for just depron with packing tape. Just check out the crash - zero damage
Andy
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Last edited by headlessagain; Feb 22, 2012 at 03:43 AM.
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Old Feb 22, 2012, 05:45 AM
Watt Waster
Tsavah's Avatar
Joined Oct 2010
1,864 Posts
Nice Park Wing

Quote:
Originally Posted by headlessagain View Post
... You are finding the same benefits that I found on my 610mm span KFm-4 Mini Wing. ... The design is super stable and can handle high winds without problem. I think you summed it up in your video -fly's on rails and cut through the air.

Now to specs! I guess your wingspan is around 700mm/28 ". Are you running 9 or 5 gram servo's and what lipo, motor, prop and esc are you using? ... Here's my Mini Wing in action using the BW 3000 kv on a 4.5 x4.5 prop which I think is a faster set up than the 4.75 x 4.75 -go figure! ... It's also very durable for just depron with packing tape. Just check out the crash - zero damage
Andy
I like the design features. Thanks for sharing.
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Old Feb 22, 2012, 08:22 AM
Registered User
davereap's Avatar
Ashford. Kent. England
Joined Feb 2005
7,016 Posts
Nice wing...
KF sections do work well, don't they... and, best of all, they are an easy build and cheap
With the depron builds packing tape will strengthen the edges and make the wing tough. Ive hit metal posts with mine and only got creases.. they make for good combat jobs.. epp can further improve for combat but then you need CF spars to keep it stiff..
I stick with depron.. its cheaper...and so far Ive not wrecked any of my builds, a few creases is all..
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Last edited by davereap; May 08, 2012 at 03:44 AM.
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Old Feb 22, 2012, 09:03 AM
Jack
USA, ME, Ellsworth
Joined May 2008
17,215 Posts
Nice build and flight demo, Otto.

You have a nice opportunity here to provide an opinion on how the flying traits compare on flying wings abuilt with symmetrical and KFm4 airfoils. You're an experienced flyer so you can make a good subjective comparison. And if you're objective and don't let a personal preference sway your thinking it would be an objective comparison.

As other KFm2, KFm3, and KFm4 wings were "discovered" and being built, the following are some of the traits that were attributed to them (not to say that all are true or proven to be true).

1 - An improved slow flying ability (able to fly at lower speeds)

2 - Improved stall behaviors. Stalls at lower speeds and stalling less dramatically, easier to recover from stalls, and even showing sa tendency to self-recover better.

3 - Very stable power off glide.

4 - More inclined to stay stable in hands off flight or with a minimum of attention from the pilot.

5 - Easier for less experienced pilots to fly (less inclined to be "twitchy" or overly responsive).

And a couple of questions I have.

Did you find your KFM4 build to need any reflex to fly? That is not really a trait, just one of the needs that the KF wings either did not need or needed very little of.

And have you tried the "elevator maneuver" yet? That is to have the elevons set up so that you have plenty of deflection (45 degrees or so) and to apply full up elevons from a power off descent. Done into the wind that puts the Zagnutz and Divinity and some other KF wings like those into a steep controlled descent. It is very controllable and the descent rate is slow enough for a pancake landing into weeds or grass. It is both entertaining and useful. It will let you land into some very small clearings or open areas.

And if you don't want to be bothered with any of this, that is fine too of course.

Jack
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Old Feb 22, 2012, 10:03 AM
Joined Aug 2011
2,810 Posts
KFm4 50% Zephr II Specs

My Mini Zephr II has a 28" wingspan, 14" length and weighs 6.3 oz. Wing area is 196 sqin. All construction is 6mm Depron. After flying into the tree and realizing this plane is a keeper, I did the repairs and dressed it up a bit. It is slippery at full power.

Equipment:

2 HXT900 servos
1 1806N 2500kv motor
1 10 amp ESC
1 Spektrum clone receiver
1 2s450mah, 25c battery
1 GWS 5 x 4.3 prop
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Last edited by Otto Dieffenbach; Feb 22, 2012 at 10:06 AM. Reason: addition
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Old Feb 22, 2012, 10:08 AM
Joined Aug 2011
2,810 Posts
Quote:
Originally Posted by headlessagain View Post
Nice build and flying Otto. Makes a change from your big Sea Dart. You are finding the same benefits that I found on my 610mm span KFm-4 Mini Wing. This was adapted from a hot wire cut airfoil design of the same physical size using 6mm depron.

Here's my Mini Wing in action using the BW 3000 kv on a 4.5 x4.5 prop which I think is a faster set up than the 4.75 x 4.75 -go figure!
http://www.youtube.com/watch?v=CFYAsUsAjOM
It's also very durable for just depron with packing tape. Just check out the crash - zero damage
Andy
That is a speed demon. WOW.
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Old Feb 22, 2012, 10:13 AM
Joined Aug 2011
2,810 Posts
Quote:
Originally Posted by jackerbes View Post
Nice build and flight demo, Otto.

You have a nice opportunity here to provide an opinion on how the flying traits compare on flying wings abuilt with symmetrical and KFm4 airfoils. You're an experienced flyer so you can make a good subjective comparison. And if you're objective and don't let a personal preference sway your thinking it would be an objective comparison.

As other KFm2, KFm3, and KFm4 wings were "discovered" and being built, the following are some of the traits that were attributed to them (not to say that all are true or proven to be true).

1 - An improved slow flying ability (able to fly at lower speeds)

2 - Improved stall behaviors. Stalls at lower speeds and stalling less dramatically, easier to recover from stalls, and even showing sa tendency to self-recover better.

3 - Very stable power off glide.

4 - More inclined to stay stable in hands off flight or with a minimum of attention from the pilot.

5 - Easier for less experienced pilots to fly (less inclined to be "twitchy" or overly responsive).

And a couple of questions I have.

Did you find your KFM4 build to need any reflex to fly? That is not really a trait, just one of the needs that the KF wings either did not need or needed very little of.

No. Mine is eyeballed at 0 reflex.

And have you tried the "elevator maneuver" yet? That is to have the elevons set up so that you have plenty of deflection (45 degrees or so) and to apply full up elevons from a power off descent. Done into the wind that puts the Zagnutz and Divinity and some other KF wings like those into a steep controlled descent. It is very controllable and the descent rate is slow enough for a pancake landing into weeds or grass. It is both entertaining and useful. It will let you land into some very small clearings or open areas.

No. Sounds like fun. On my list to try.

And if you don't want to be bothered with any of this, that is fine too of course.

Jack
I'm all about experimentation and advancing my knowledge. I like to stretch the limits as you may see from some of my threads. I was away from the hobby for 20 yrs and returned 2 yrs ago. A completely new playpen.
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Old Feb 22, 2012, 11:12 AM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
4,282 Posts
Hi Otto
Thanks for posting the additional pictures. I love the blue chequer pattern.
I've got a couple of those 1806N 2500kv motor's looking for a home and might try on in the new Mini Wing I'm finishing for my FB. It should go quite well on either a 4x4 or 5x3 prop on 3 cell's (all he's got)
Jack
My Mini Wing also fly's at zero reflex and is super stable in the windy conditions
Andy
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Old Feb 22, 2012, 11:21 AM
Joined Aug 2011
2,810 Posts
Quote:
Originally Posted by headlessagain View Post
Hi Otto
Thanks for posting the additional pictures. I love the blue chequer pattern.
I've got a couple of those 1806N 2500kv motor's looking for a home and might try on in the new Mini Wing I'm finishing for my FB. It should go quite well on either a 4x4 or 5x3 prop on 3 cell's (all he's got)
Jack
My Mini Wing also fly's at zero reflex and is super stable in the windy conditions
Andy
I just recently tried a GWS 5 x 4.3 cut to 4.5 at 3s on another project and all went well, so far. May even give you a little more speed.
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Old Feb 22, 2012, 11:22 AM
Fly it, edit it, post it.
tregtronics's Avatar
Joined Dec 2011
356 Posts
Otto! You amaze me with your building skills. One day you look at my Zephyr, the next day you are flying your own scratch built from your garage scraps. The next day! It took me about 3 weeks to get my Zephyr polished up. I also have to say that the EPO/EPP foam versions from Ritewing are really really tough (Otto you know you have seen me crash em). The value you get from Chris Klick's wings are amazing, and it is all American Made. I really support his company. That said....

I have some other requests for testing, can we try some different sized winglets to see the effect? I have been researching the different mods Chris Klick from Ritewing has been putting on his Zephyr's, and one thing I have noticed is a bigger winglets on his latest FPV platform.

Having just snapped my Zephyr II in high winds, rough landing, shearing the two glass rods, what kind of wing sparring are you putting in this plane?

If I buy the foam would you make a full sized FPV version we can test... maybe even a bit oversized?

I also have to admit that I dropped my broken in half Ritewing Zephyr II off with Otto to see what he could do to salvage the wing. I have some building skills, but Otto's level is somewhere between Jupiter and Pluto.

Also, you have to rename it, the Zephyr is Ritewing's (http://www.ritewingrc.com/) name, and is cut from a solid foam block. It's an FPV platform, where your plane is a light speed demon, more like Chris Click's, well, Demon! I think it feels like (not looks like) a Cylon raider going through the sky, so I say call it the Cylon.

That would be my final request, is to make a flying wing that actually looks like a Cylon Raider.



I also had no idea what you meant by KFm, so I looked it up, and I liked this link so I share:
Kool Article about Kline
Very cool to read about him.
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Last edited by tregtronics; Feb 22, 2012 at 11:29 AM.
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Old Feb 22, 2012, 11:32 AM
Jack
USA, ME, Ellsworth
Joined May 2008
17,215 Posts
Thanks for the details, guys.

My smallest wing so far has been a Divinity 42 scaled down to 32". That was built with Dollar Tree foam board (3mm nominally) and was a real light build and a lovely flyer too. A little on the too fast and twitchy side for my old hands and eyes but I didn't have it power or propped for speed and it was a lot of fun.

If any of your have occasion to do comparison builds with one being a KF airfoil, your impressions and comments or a link to the results would be welcome over on the ** Kline-Fogleman (KFm) Airfoils - Building/Flying Discussion ** thread if you post them there.

There has been a lot of misleading claims made for the KF airfoils. But, as a group, the crowd over there is objective, polite, and thoughtful. And they like to hear more about the comparisons.

Jack
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Old Feb 22, 2012, 11:33 AM
Joined Aug 2011
2,810 Posts
Quote:
Originally Posted by tregtronics View Post
Otto! You amaze me with your building skills. One day you look at my Zephyr, the next day you are flying your own scratch built from your garage scraps. The next day! It took me about 3 weeks to get my Zephyr polished up. I also have to say that the EPO/EPP foam versions from Ritewing are really really tough (Otto you know you have seen me crash em). The value you get from Chris Klick's wings are amazing, and it is all American Made. I really support his company. That said....

I have some other requests for testing, can we try some different sized winglets to see the effect? I have been researching the different mods Chris Klick from Ritewing has been putting on his Zephyr's, and one thing I have noticed is a bigger winglets on his latest FPV platform.

We can, but I like mine the way it is.

Having just snapped my Zephyr II in high winds, rough landing, shearing the two glass rods, what kind of wing sparring are you putting in this plane?

1/4" ply.

If I buy the foam would you make a full sized FPV version we can test... maybe even a bit oversized?

How much bigger? If I use R-Tech, it will not stand up to the abuse but I can make it half the weight.

I also have to admit that I dropped my broken in half Ritewing Zephyr II off with Otto to see what he could do to salvage the wing. I have some building skills, but Otto's level is somewhere between Jupiter and Pluto.

Also, you have to rename it, the Zephyr is Ritewing's (http://www.ritewingrc.com/) name, and is cut from a solid foam block. It's an FPV platform, where your plane is a light speed demon, more like Chris Click's, well, Demon! I think it feels like (not looks like) a Cylon raider going through the sky, so I say call it the Cylon.

I want to make sure everybody understands that the planform is the Zephr II, Chris's design (and how highly I think of it).

That would be my final request, is to make a flying wing that actually looks like a Cylon Raider.

That is well beyond Pluto.

From what I've seen, wing planforms do not vary much.
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Old Feb 22, 2012, 04:17 PM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
4,282 Posts
Well, I can't promise you a Cylon Raider but here is a video of a model where the thin wings were swept forward in a semi circular shape.
Crescent RC flying electric homemade rc depron plane by Baddad (4 min 21 sec)

Andy
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Last edited by headlessagain; Feb 23, 2012 at 02:25 AM.
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Old Feb 22, 2012, 07:07 PM
Went to mow a meadow
frank48's Avatar
Joined Feb 2007
1,459 Posts
Great flyer Otto This ones on my next to do list

Can you please confirm some measurements for me as on attached drawing and what width are the elevons?

That would be great

Thanks
Frank
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