UltraFly Radix ARF with stock brushless power package Review - RC Groups
Shop our Airplanes Products Drone Products Sales

UltraFly Radix ARF with stock brushless power package Review

Nick Maxwell explores this good looking fuselaged foamie, and finds it to be an easy build and a VERY strong 3D performer with the included brushless power package.

Article Thumbnail


We can hang...alll day long!
We can hang...alll day long!
Wing Area:313.1 sq. in.
Weight:8 oz.
Wing Loading:4 oz/sq. ft.
Servos:3 Futaba S3108
Transmitter:Futaba 9C
Receiver:ElectriFly 4ch FM
Battery:3C 640mAh Electrifly Lipo
Motor:Brushless Ultrafly, Incl.
ESC:Silver Series SS8 8A
Available Online From:Tower Hobbies

Ultrafly has come out with a great model once again! What separates this model apart from most? I would say that the lightweight full fuselage design, plus the rigidity and ease of building of this model sets a good example. Radix was unique in that it was made from 1.3 mm foam! As most foam models are made from 3mm foam, which is much less flexible during a crash, the 1.3 mm was rigid, plus the added fact that during minor hard landing nothing was damaged!

Kit Contents

The Power Included Package Includes:

  • Radix pre-printed foam components
  • Brushless Ultrafly B/06/12
  • complete hardware package
  • photo manual

Equipment Used:

  • Radio: Futaba 9c
  • Servos: (3) Futaba 3108 Micro Servos
  • Receiver: Eletrifly 4 channel FM
  • Speed Control: ElectriFly 8-amp SS-8 Silver Series Brushless ESC
  • Battery: 3-cell 640 mAh ElectriFly lithium-polymer (Li-Po) battery

Upon receiving this model, I skimmed over the model’s parts and manual. I then laid out the all the parts and started to follow the instructions. This model can be built in about 7-8 hours and is very strait forward.

There are no words in the manual, photos only, which makes it a bit more of a challenge to assemble.



Even though there were no words in the manual, just pictures, the fuse went together easily.

Wing and Tail

Next stage was to hinge the wing and tail. It was done very easily. The parts needed to be beveled before attaching -- I took some very light sand paper and sanded the depron until the foam had a 45 degree angle. I was careful not to sand too much as it was only 1.3 mm foam and didn't take much at all. To apply the 1/2" tape, I started at one end and slowly worked my way to the other. I taped the top and the bottom for a very strong hinge. It worked out very well, and made for a nice clean set-up.

Next was to apply the carbon spars. This was easily done by lying them on top of the wing and just foam safe CA’ing them down.

Then I needed to attach the wing and tail to the fuselage. It was made easy as everything locked together. So all I needed to do was measure from wingtip to tail to make sure they were perfectly centered, then glued them into place, and I was ready to move on!

Radio Installation

The radio gear installation was very well thought out. Because at this point the fuselage was still open, I still had access to the servo holes. After I added the doublers, I needed to mount the servos. The manual recommended CA for this, but, as most people move radio equipment from one airplane to another, I used hot glue that could be peeled off.

Control Throws and the Center of Gravity:
Control Surface: Low Rate Travel / Expo: High Rate Travel / Expo:
Aileron: 25-degrees / 0% Expo 55-degrees / -35% Expo
Elevator: 25-degrees / 0% Expo 55-degrees / -35% Expo
Rudder: 25-degrees / 0% Expo 60-degrees / -45% Expo

Motor and Battery Installation

Motor and battery installation was made very simple by using a second firewall. It screwed to the motor, which then screwed to the mount. The motor was mounted in the fuselage which gave the model very nice looks. The battery fit nicely right up in the compartment behind the motor. I used Velcro to attach it.

After the model was fully completed, I checked the Center of Gravity to determine the location of the battery pack. When all was said and done, and after the model was flown, I settled on mounting the battery right behind the motor mount. I found that with the battery in this location, the model was extremely maneuverable in 3D flight while maintaining good forward flight & non-stalled (non-3D) flight conditions.


A calm day was chosen for the initial test flights for the Radix. After the final check was completed, I plugged in the 640mAh 3-cell electrify battery, checked controls, and was ready to take off.

For the first few flights I was very gentle. I had a patch of cement to take off from, which made it much easier. As I slowly applied power, it rolled very briskly. I hit about quarter throttle and it jumped into the air and flew straight away. A few circuits were completed to get the feel of the model and then it was time to make small trim adjustments.

Trimming was a breeze! It only took a few right clicks of aileron to make this model fly like a dream! Over several flights, I played around with the center of gravity to find what it liked the best. It really liked to fly a bit on the nose heavy side and was just as stable in a hover as when it was tail heavy!


This model flew extremely slowly in 3D flight. It performed harriers, both upright and inverted, extremely well. When in a hover attitude, I could perform a torque roll by either naturally letting the effects of torque take their place (resulting in a left torque roll) or apply right aileron and perform an “anti-torque roll.” Anti-torque rolls can only be performed with airplanes with great aileron authority and the Radix was capable of doing that. High-alpha rolls were performed with minimal rudder. I noticed I did need to be on the elevator more than the rudder with this model. Knife edge was very nice and used almost no rudder. I did not notice any coupling during knife edge flight, unless I entered high alpha, then it tended to pitch to the canopy.

This model did require a lot of rudder in turns. It would not turn with aileron, or elevator alone. It is a good habit to get into with profile foam models as it will help with your abilities to use rudder in a hover.

Aerobatics/Special Flight Performance
Maneuver Grade Notes
Hover A+ Model hovers very stable, and can very easily be left hands off for a minimal amount of time!
Torque Roll A The Radix torque rolls very nice, anti-toque rolls require a little more work but can be performed.
High Alpha Flight A- Rock solid upright and inverted! But does need a bit more elevator for inverted.
Waterfalls (high alpha half loops) A This model can waterfall / flip end-over-end within a 5-10 foot radius.
High Alpha Rolling A+ The Radix performs this really well. It needs almost no rudder, but does need a bit of elevator, very controllable.
High Alpha Knife Edge B If in a simple knife edge (not high alpha), this model will not pitch to the canopy. However, if the model is slowed down for a high alpha knife edge, it will pitch to the canopy slightly.
Stall Turns A The Radix performs this with ease.
Knife-edge-to-knife-edge turns A The Radix can perform this maneuver great. It does take full rudder to make the full transition.
Wall A- When the wall is performed, the Radix really pulls up strait, but watch as sometimes it will snap out with enough speed.
Flat-Spin B+ The Radix will flat-spin, but is hard to get to completely flatten out.
Pinwheel B With full throw, the Radix will pinwheel, but really doesn’t have enough rudder to do multiple pinwheels in a confined area.

Editor's Note: Unfortunately, the flight video attempts were unsuccessful, with a series of equipment problems, so we have no flight video for you at this time. If it becomes available at a later time, we'll sure add it here! Hobbico's flight video of the Radix shows her well.


I can say this model is on the top of my list! It flies super smooth and hovers very stable! It is light weight, but can still handle 5-8 MPH winds! It also is very rigid and makes for a super strong model. Over all, this has been a great model to review and I am sure everyone would be happy with their Radix!

Thread Tools
Jul 14, 2006, 03:28 PM
FUT/RealFlight Marketing
Hello Jim. Good article Nick. It is a good little foamy.
Jul 20, 2006, 08:57 AM
Registered User


Lets be honest If a plane will not turn without adding rudder
it is a very bad designed plane. Lets not try to sell junk when
there are better flying planes out there.
Jul 29, 2006, 05:56 PM
Brandon Evers
bevers01's Avatar
I highly disagree. Most, if not all, aerobatic planes require rudder in coordination with both ailerons and elevator (i.e a coordinated turn) to turn. Ailerons only result in a roll, causing "goes where you point it" precision. This is not a "very bad design," since even full-scale aerobats like the Edge 540 behave in exactly the same manner. Flying these highly maneuverable aircraft with precision always requires rudder correction, and it is this proficiency with rudder use that often separates better pilots from the rest. BTW, I don't own the Radix, it just struck me as odd that someone would condemn a plane as "junk" without obviously understanding the nature of aerobatic planes and the flying style needed to pilot them (Hint- it's not bank and yank)

Jul 30, 2006, 09:07 AM
Registered User

Rudder Turns

I must be doing something wrong having been flying stunt planes
for 45+ years. I have 16 foam planes now and all of them do not
need rudder with aierons to make turns. If I build a plane and find
that it needs rudder to turn I give it away or burn it. Some of us
older flyers just want a plane to fly easy and right and we use rudder
for Knife edge, Hammer heads, Snaps + others. Why put over size
aierons on foames if then you have to couple in rudder to get it to
turn. Is it not funny that all planes in the mags. are all perfect and
fly with no problems. So much for truth in advertizing, lets just make
Aug 06, 2006, 12:29 AM
R/C Airplane Executioner
I agree with bevers %100. Profile planes use ailerons for precision roll authority, not for turns. Rudder needs to be applied since the plane has no airfoil, this means rolling it to an angle doesnt cause it to turn, it just keeps tracking straight. This also gives crisp rolls, the plane will not move to one side when rolling, it will roll straight. Great designed plane. I hope to order one soon, theres a combo on modelflight.
Aug 06, 2006, 10:08 PM
Registered User

Rudder Turns

There must be a lot of would be flyers out there that believe what
others say because they have not flown a good 3D flat wing foamie.
Of the 15 planes that I have 11 of them are flat wing and they all
turn very good without rudder. If I build a plane that needs rudder
with aierons to turn, I get rid of it very fast.
Sep 05, 2006, 02:03 PM
Registered User

RADIX 3D Flies great!

I have just finished test flying my new RADIX 3-D. I have at least 10 flights on it now and feel I can speak factually on the model. The plane was built as the instructions illustrated. I am using the Ultrafly B/06/12 brushless motor W/ 9x4.7 slow flyer prop, Electrifly SS-12 Silver Series ESC, Electrifly 7.4V. 350 mAh Li-Po battery, GWS Nano 6 Ch receiver and (3) Hitec HS-50 micro servos.

I have to admit this is a super fun airplane to fly. It does about anything you can think of. It is very easy to fly and very forgiving. YES, it does turn with aileron applied to achieve bank angle and using the elevator to complete the turn. If you don't apply elevator it will remain in a knife edge. A little rudder applied does add a touch of finesse to your turns, but it's not required! This model was designed to be a 3-D aerobatic model and that's exactly what it is. It is NOT designed to be a trainer with inherit stability. It does not right itself. It goes where you point it and it stays there! I have flown it in 8-10 mph winds. It does bounce around a lot in wind, but is totally controllable, but you want to be sure and stay upwind.

With the 7.4V 2-cell 350 mAh Li-Po battery gives flight times around 7 minutes. While vertical performance isn't awe inspiring on the 2-cell pack, it does climb vertical and does hover. I have ordered the Electrifly 3-cell 11.1v 640 mAh pack to give better duration and performance. I am also changing the aileron servo. The Hitec HS-50 servo has only 8 oz/in torque and doesn't have enough power to overcome the wind friction and the mechanical friction of hinges and linkages of 4 ailerons, making roll rate slower than I would like. I am replacing it with the Hitec HS-55 servo that has 15 oz/in torque and weighs only 1 gram more. The rudder and elevator does fine with the HS-50's.

The only complaint I have about the assembly is the lack of written instructions. Some details are somewhat vague and required a little study, but nothing that can't be reasoned out.

The RealFlight G3 simulator has a new add-on G3 volume #2. It has the RADIX 3-D airplane in it. If you get a chance, give it a try. The model flies EXACTLY the same as the simulator does!

OK.....So what is my final opinion? I love it! Everyone who has flown it at the field loves it, 2 people are now going to order one!

How much experience do I have? 45 years building and flying model airplanes, 33 years building and flying model helicopters, 42 years flying full scale, rated single-engine land, multi-engine land, glider, helicopter, instrument rated with 5000 hours. I have flown planes from ultralights to a Pitts special to a B-17 bomber.

SO THERE! Get one...you won't be sorry! Heli_Rod
Last edited by heli_rod; Sep 06, 2006 at 08:57 AM.
Oct 23, 2006, 05:53 PM
Registered User
the radix 3d is a piece of sh^*^*
the kit is very hard to build and structural integrity of the controls
is very fragile it sis not true it will resist a hard landing
i could never make it fly right like my other foamys
it was a disapointment and awaist of time
its low quality kit and definitivly not an arf
need to know all the tricks of the trade to be able
to complete the kit none of the carbon sprs are cut to size
and almost no hard ware if you get to complete it it will
probably brake control horns in the first flight and crash
just as hapend in my 3rd flight after varius repairs because
of fatige in the control points it is definitively not worth
the efort Ill just stay with simpler and beter built foamys
like graet planes or foam z
Nov 28, 2006, 09:37 AM
RC Player
Please look at this thread to know more about the RADIX 3D


I believe there will be more info for you to judge if this is a junk or not!
Jun 22, 2007, 11:15 PM
Registered User
pval3's Avatar

fly what ya brung!

Hey folks

OK, I am an experienced newbie!

I only have about 32 years of doing this crud . . .

I always tell the folks I fly with - aint a good day unless I learn something new!

This week was no exception. I had this same discussion with a fellow flier at work regarding the use of rudder and the design application of rudder in 3d in relation to several flat foam foamies that I have and use regularly. . some fly normal and some you have to work at . . . . . . .

The proof in the poodin' for me came when I applied the logic to my T3D this weekend.

I started flying using the rudder both as a "normal pilot" - that was me before my ejumication
and as an "indoor/3D pilot" - that was me after my ejumication

When you start really using the rudder to turn you find yourself with a whole heck of a lot more room to fly your plane and a whole heck of a lot less "dead space" in your flying area.

I fly in my street / culdesac and found that flying with heavy rudder to guide the plane through the turns made my flying much more rewarding and efficient for the purpose of flying 3d type stuff.

I am planning on ordering a radix simply because it is priced at a point where you really cant go wrong right now . . . AND I have seen one fly (using the proper technique) and was really impressed - now that I understand the rational behind the heavy rudder use for guiding the airplane through flat turns in a tight space.

If you want fun flyers - buy a fun flier . . . if you want a precision indoor or indoor/outdoor 3d bird . . . buy one . . . just realize that you are not going to be happy with this plane if you are not buying for precision tight spaced 3D flying.

Ya got to buy the right plane for the right application or you will not be happy . .and it will be a piece of bovine colloid for you.


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
E3D brushless power package TorkRollN Aircraft - Electric - Airplanes (FS/W) 0 Jun 13, 2003 05:57 PM