Kwik-Fli Mk III for Reflex XTR - 40th anniversary edition - RC Groups
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Jun 24, 2007, 06:20 PM
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BurkhardE's Avatar

Kwik-Fli Mk III for Reflex XTR - 40th anniversary edition

Hi Reflexers, friends,

after celebrating the Ugly Stik anniversary last year with a virtual resurrection (see this thread), this year we can do the same for the Kwik-Fli. Forty years ago Phil Kraft was pattern world champion with the Mark III version. This is the other world famous Phil Kraft design, as well built all over the world from plans and kits.

Today it's only a sport model, but a very good one. Experts appreciating its characteristics can build it today from scratch using the plans still available, or from an American short kit, or even as an ARF ("enhanced" compared to the old original) recently offered by Graupner. REFLEX owners now can fly the old thing virtually (missing the joy to build it).

Rendering the original Phil Kraft model is now finished. The REFLEX model underwent thorough debugging so it should be pretty flawless regarding both appearance and flight characteristics. Enclosed in the installer and this post is an article about Kwik-Fli and the REFLEX model. Also enclosed is a demo flight which of course is only a demo and not a contest-winner.

Still found and fixed some very minor flaws. Added a completely new version with the original geometry but more powerful engine, neutral balance and retractable landing gear. More speed and sleeker looks!

Only recently I got a plan with dimensions. It says Mk III has 11" wing chord whereas I thought it were 12". All versions are corrected now, but virtually no difference in flight behavior, at least only marginal.

Replaced the square wing by a tapered one, giving the Mark IV. Otherwise it's the original Mark III version with a nearly neutral balance. Flick performance is better, which is the purpose of this modification.

Easy to do a Mark IV as well with more powerful engine and retractable landing gear.

Once again corrected the physical parameters, again virtually no difference in flight behavior, at least only marginal. But now finally all dimensions are really correct.

Replaced the conventional glow engine by a more lightweight and powerful rotary engine and made a new livery.

This last version was converted into a 'rocket' version with thinner wings and flaps;

The electric version based on the tapered-wing Mark IV is completed and already revised to be a nearly perfect configuration.

Now I finished the old Graupner version, and I rendered an O.S. 60F-SR from the 1970s for it.

The Flea Fli is a scaled-down (0.66) version of the Mark III for .20 engines. It was painted like the original presented by Phil Kraft in 1968.

Mark II and Mark I were made as true-to-reality as possible with the information available.

Bar-Fli has been added after the build articles with plan became available. Bar-Fli was Phil Kraft's alternate model for the 1967 World Champs. Its slightly different characteristics make a comparison to Kwik-Fli Mark III advisable.

Found out that Phil Kraft flew an enhanced Mark III in competitions. This version without canopy, a taller fuselage nose to accommodate a retractable landing gear, and a higher hatch has been added.

You may download the installer package (7.5 MB) from my website here. Simply run the installer and select model versions to install. You'll need Reflex version 5.03.0 or newer for the model. The installer will work properly also for the new Reflex version 5.05.0 or customized Reflex installations. The download and this post will still be updated when new versions are available.

There's an article about Kwik-Fli for REFLEX in an own pdf file which you may read or download here (3.2 MB) or after installation of the whole package.

You may just enjoy the model, but if you have any information, hints, suggestions, plans, articles or whatever for the Kwik-Fli, I would appreciate a message. And if you are an expert flyer you might record the 1967 pattern sequence in Reflex for demonstration (the schedule is depicted in the article).


Last edited by BurkhardE; Jan 02, 2016 at 08:24 AM. Reason: links corrected
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Jul 03, 2007, 04:30 PM
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BurkhardE's Avatar

original version finished

The Kwik-Fli Mk III package for REFLEX XTR has been released now (see post #1). There will be amendments later, but for now it's finished.

It contains a setup per plans with a rather forward c/g and some decalage. This "original" model version is neutral (flies straight and level) in upright flight but not inverted. There's a "crisp" version with a more backward c/g and only a tad decalage, flying nearly neutral both upright and inverted. It even snaps with only elevator and rudder, but reliably only at high speed.

Kwik-Fli Mk III turns out to be the prototype of a low-wing sport model even today – simple, easily built, good-looking, good pattern ability, honest flyer. It’s just the most basic design of a pattern model. So it’s a modern model as well and worth to be used in the simulator.
Last edited by BurkhardE; Jul 09, 2007 at 04:51 AM.
Jul 07, 2007, 10:52 AM
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BurkhardE's Avatar

retracts version added

A completely new version with more powerful engine and retractable landing gear was added to the package (link see post #1 above). It is completely neutral and a bit faster and looks better in-flight. Even though there’s not really much changed in the “retracts” version compared to the “original”, this is just a considerably more powerful, faster, and sleeker airplane. You may knock it around just for fun without risk because it’s still not vicious. But you may just as well fly serious aerobatics and even fly snap rolls the old-school method. This version already gives an idea of the even sleeker and faster pattern ships which came after the Kwik-Fli.
Last edited by BurkhardE; Jul 09, 2007 at 04:54 AM.
Jul 09, 2007, 06:45 PM
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tapered-wing version added

Phil Kraft himself designed a simple tapered variant of the Mark III wing and combined it with the rest of the model giving the Mark IV. Though he didn't use it, others adopted this modification for it's better flick performance. All other characteristics are unchanged and the model is still not vicious. The REFLEX model is basically the original version with the new wing, again with a stable and a slightly more neutral balance.

Of course, also the Mark IV was equipped with retractable landing gear, making it a model quite different from the original Mark III, but you'll still recognize it.
Last edited by BurkhardE; Jul 15, 2007 at 12:52 PM.
Jul 15, 2007, 01:07 PM
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rotary-engine version added

The Graupner/O.S. 49-PI rotary engine is small and lightweight but powerful. It fits into the Kwik-Fly by size and weight. A completely enclosing engine cowl and wing fillets substantially reduce the model's drag. Though still no "rocket ship", this version already gives an idea of "ballistic" pattern flying, so it required a modern and pertinent paint scheme.

The same paint scheme, now red instead of blue, was used for just another version. The powerful and already fast (95 mph) rotary/retracts version was fitted with a matching thinner wing. Now it's really a rocket ship (105 mph) and was hard to land, but big flaps make landings easy.
Last edited by BurkhardE; Jul 21, 2007 at 07:40 AM.
Jul 23, 2007, 02:13 AM
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electric-drive version added

The electric Kwik-Fli is just the tapered-wing Mark IV with an AXI 4220/14 brushless outrunner motor, a 12x8" propeller, and a 5-cell 6000 mAh LiPo battery. It weighs about as much as the glow powered version, and the electric drive pulls it with just as much authority and speed as the glow engine. Aerobatic performance seems even slightly better due to more thrust at lower speeds. Landing speed is only a bit higher.

The remarkably steady and smooth flight behavior of the original is still there, so this version really is a modern sport aerobat. The modern paint scheme features a silver-metal shiny grey. The model is embellished by a rounded motor cowl and wing fairings, which also reduce drag and thus help to reach the speed goal.
Last edited by BurkhardE; Jul 23, 2007 at 03:04 AM.
Aug 09, 2007, 09:03 AM
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Graupner version added

Just for nostalgia, the old Graupner version was made. The kit was brought out already 1968 and offered for several years. Recently, Graupner even brought out a new ARF version, though it's not as nice as the old one.

It must have been a lucky chance for Graupner: a model that everybody wants to have because it was world champion, that is still so well-behaved that everybody is able to handle it, and that is even easy to build.

Especially for this model, an O.S. MAX 60F-SR from the 1970s was rendered in REFLEX. With this engine, the model has a bit more weight but also more power than the original.
Mar 21, 2008, 11:16 AM
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BurkhardE's Avatar

Mark I and Mark II added (and Flea Fli)

Just out of curiosity and historical interest, other Kwik-Fli versions and variants were made for REFLEX. It's amazing to have the look and feel of these old birds today, at least in the simulator.

After the 1967 world championship, Phil Kraft brought out the Flea Fli, a 0.66 scale Mark III for .20 engines. Maybe it was meant as poor man's Kwik-Fli, but nevertheless it's a vivid flyer just as good as the full-size Mark III and much fun.

Mark I was the first Kwik-Fli of all, called Mark I only after Mark II appeared. It's a big bird (66x12" wing) and flies just great in calm air. Mark II is actually a slightly smaller version (60x11" wing) for the smaller (and cheaper) .45 engines. Even though its wing loading is the same it's said to be better in gusty wind. (Makes sense: same wing loading = same absolute airspeed, but more speed relative to the smaller size.) Using a .60 engine on the smaller model makes pattern flying even easier and better. Mark II was a successful competition model.

Mark I and II both have not only the typical smoothness on ailerons but are remarkably smooth also on elevator. Due to a quite short tail moment arm, they are lacking some tail authority, though, and the small vertical tail on an even shorter moment arm is barely sufficient. That was completely o.k. in the mid-1960s when flying pattern with models was a big achievement. But when spins and snap rolls were included in the pattern competition schedule, more tail authority was imperative and some smoothness had to be sacrificed.

Mark III is not much more than a Mark I fuselage with the smaller Mark II wing. The elevator was a bit enlarged and divided in two halves. That made room for a big rudder going a bit below the stabilizer, where the fuselage was lowered as part of a big fin on a longer moment arm. The model is still smooth on rudder and elevator if small deflections are used, but 30 degrees deflection have much effect to reliably enable spins and snaps to be done. Not only the vertical tail's aerodynamic center was lowered, but also the engine thrust line was lowered to the center of drag. The fuselage nose was elongated a bit to balance the bigger tail. As a side effect, Mark III is a quite sleek and good-looking airplane.

But hold the ancestors in honor! Flying Mark II and especially Mark I is quite appealing to me and maybe to you, too.
Mar 23, 2008, 08:16 AM
Registered User
OOOO, I just got Reflex and you guys have created things I must have! I had no idea! Where else are there flying things for those of us well over 21?
Mar 23, 2008, 07:04 PM
Reflex sim model builder
BurkhardE's Avatar
There were no such things for Reflex so I had to DIY. Otherwise I'm working hard to prove that Reflex is good also for airplanes and not only for helis. Suppose you saw my download page and W3 Group's.

There are a few guys belonging to the metal generation as well building oldtimers for AFPD (see RC-Sim).
Mar 23, 2008, 09:59 PM
Registered User
Originally Posted by BurkhardE
There were no such things for Reflex so I had to DIY. Otherwise I'm working hard to prove that Reflex is good also for airplanes and not only for helis. Suppose you saw my download page and W3 Group's.

There are a few guys belonging to the metal generation as well building oldtimers for AFPD (see RC-Sim).
Thank you for your time in creating these wonderful aircraft!
Jan 31, 2010, 10:42 AM
Edubarca's Avatar

Kwik-Fli MK. III a classic!!

So nice to hear about the Kwik Fli Mk.III. It is for me one of the finest, if not the finest airplane of this type ever designed. I learned to fly aerobatics with mine built from MAN plans way back in 1970. I still have the model in flyable condition. At that time I had an EK Logictrol and a Webra Blackhead engine. Despite Bogotá's (Colombia) elevation of over 8.650 feet above sea level, the plane performed beautifully as long as it was kept light!!! Mine weighs only 5.5 pounds using MonoKote. Nowadays I fly my Kwik Fli with an old Webra Speed .61 and my trusty Futaba 6Xas with small servos to keep weight down. I am at the present time building the Flea Fli also from MAN plans but with miniature Chinese servos and a HobbyKing 2.4GHz radio. Engine is ASP .21. It will be ready to fly in about two weeks and I will tell you all about its performance.
Aug 05, 2010, 12:54 PM
Reflex sim model builder
BurkhardE's Avatar

Bar-Fli added

Of course, Bar-Fli isn't really a Kwik-Fli, but it is rather similar and it was Phil Kraft's alternate model for the 1967 world championship.

Obviously, the model had been designed and built just for a change from the Kwik-Fli Mk II and just for sport flying. It was made a bit smaller (58 x 10 in wing instead of 60 x 11 in), got a thinner airfoil (15% instead of 19%) and a deep fuselage with much side area as well as a large rudder like that of the Kwik-Fli Mk III. Bar-Fli is lighter than Kwik-Fli Mk III but has the same wing loading and the same powerful .60 engine, so it's the faster and more powerful machine. The thrust/weight ratio is increased from 0.8 to 0.91, what is quite spectacular for the time.

Unexpectedly and despite being a bit small, Bar-Fli turned out to be a very good pattern ship, especially in high winds and turbulence. So the reason why it was chosen as the secondary model for the world champion­ship was only the mild weather forecasted for Corsica. Being a bit smoother in such conditions due to slightly bigger size and thicker wing section, Kwik-Fli Mk III was preferred as the primary model. Actually, it was a tie.

Please see post #1.
Aug 15, 2010, 03:35 PM
Registered User
Terry Rigden's Avatar

Thank you


Thank you very much for making the kwik fli model and sharing it. I've really enjoyed flying it. It takes me back to the days of my youth when I was learning to fly and teh ace pilots in teh club all flew them


Aug 21, 2010, 08:14 AM
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BurkhardE's Avatar

enhanced Mark III added

Thanks Terry, much appreciated!

Only now I found out that Phil Kraft obviously flew an enhanced Kwik-Fli Mk III in competitions after the 1967 world championship and till about 1970. Even though he tried newer designs, he was very fond of the smooth-flying Kwik-Fli, especially the square wing.

He just omitted the canopy, installed one of the newer, more powerful .60 engines with muffler, and made the fuselage nose taller to accommodate one of his retractable landing gears. Engine and retracts considerably added to weight and wing loading. That gave a noticeably different model, more suited to the evolving fast and acrobatic flying style, but still retaining the smoothness and control precision of the original Mark III design. A simplistic approach, typically Phil Kraft (I believe).

For picture and download please see post #1.

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