Durafly EFX racer

Recently came on sale late last year 2014, the latest fast model from Durafly that it is not a funjet but a conventional style aircraft.  The airframe has been engineered to be both rigid and lightweight, utilizing both glass and carbon fiber reinforcements throughout the model in combination using compressed EPO foam and a smooth surface finish to deliver performance in the air.   Looks good too on the ground!  This model is the PNP type we are getting used to .  In two colour variations so pilots can distinguish which model they are flying as I expect a few to purchase this model for the just "Chuck-n-Go" ease for instant fun.

 

At less than £100 in the UK this model comes in at just over half price compared to Eflite's Rare Bear in either of it's two versions, BNF and PNP.  The EFX Racer's wingspan is 43 inches so should be visible at long distances or height compared to the slightly smaller 39inch E-Flite Bear.  I would suggest that this is not a park flyer.  Obstacles and people do not mix with RC Aircraft especially fast models.

 Durafly EFX Racer    Let's see what is in the box, packing, etc.  Mine was delivered via Parcelforce next day from the UK Warehouse (total price £103.55) in a plain brown box about 48 inches long and inside was another box printed in black & white (colour is expensive) which held the EFX Racer.  Opening one end you have to drag the pre-formed packing out steadily to reveal the contents within.  Only a few bits!  Fuselage, Stabiliser, Wing and a bag of hardware and bit n bobs.   Oh, and a manual.  The latter being an A5 booklet.  It is written in clear English surprisingly although there is not much to do anyway.  So, after speed reading the booklet from start to end it was time to assemble.

 

As per the advertising the wing and fuselage are VERY smooth compressed EPO.  I wished a certain few other makers would take note of this when designing new models, ie; FMS take note.  In fact the wing is smoother than my E-Flite Habu II wings and fuselage!  However, being smooth makes gripping the fuselage a bit of a trial but I am not complaining.  Maybe sticky hands would help? lol.

Fuselage

The NTM 2836 2300Kv motor has good strong magnets.  The 50 amp, 5 amp 5.5v BEC ESC appearing a little small for a 50amp, more 30 amp size judging by the size of the heat sink, is positioned in a tunnel on the underside of the fuselage and is closed in once the wing is fitted.  Air exit holes are on either side of the fuselage just aft of the ESC for cooling air to exit.

The motor mount/firewall is plastic and the motor is held conventionally by a X Plate screwed to the plastic "firewall".  The cowling is plastic and prefitted to the fuselage.  The rudder and elevator servos are mounted inside the fuselage cockpit area towards the rear. A gap between them is for the ORX R620 receiver which is a neat sliding fit.  You could use another receiver where the connecting pins are facing backwards and physically the same size or smaller.  I cannot see any reason why a 4 channel wouldn't suffice.

Durafly use the Orange R620 6 channel which does have pins facing the right way, ie; not facing upwards as many Spektrum's do.  I am using the Orange receiver as recommended for purposes of this review.  After binding the receiver to my JR DSX9 I could now check the servos center and they work properly.  Access to the battery compartment is via a top hatch that locates at the front and is held down by a magnet at the rear.  A little clear tape acts as a pull up for the hatch.

Fitting the horizontal stabiliser is a no brainer.  Press down on the clip on the right hand stab and the two halves will come apart.  Next we insert the left half into the fuselage and then carefully slide the right on the plastic spigots, these reconnect the stabiliser and elevator until you feel or hear a definite click.  Thats it!  Simples!

Next job is to connect the ball links to the control arms.  Before doing this though I wiggled the control surfaces a few times to ensure they move freely.  They are not conventionally hinged but usual thinner EPO for flexing.  I may add 3M Blenderm tape at a later date to ensure the things don't become detached.  The ball links are screwed on to the piano wire rods and a little adjustment needed so that the ball links squeeze on when the control surfaces are at neutral.  I would recommend getting the settings right  first time as I would not like to keep pulling the links on and off to often, albiet use could undo the grub screws at the servo ends and adjust there but it would be rather a coarse setting.

 With this done that is virtually it!  Inside the battery area is a velcro tape to secure the pack and located either side with some wooden sections similar to large lollipop sticks.  I assume they stiffen the fuselage at this point and secondly hold the velcro tape in place.  Durafly state you can use a 2200 maH 3 cell 30C minimum for sport use or for speed a 1800 maH 4 cell 30C set up.  They supply two plasticky props (I will change these for APC-e later no doubt).  6x4 for sport use on the 3 cell and 5x5 for 4 cell.  I am going the 4 cell option so when fitting prop spinner I will leave off the spinner tip to allow more air to flow through the motor and fuselage.  This is recommended in the manual.

Back the battery options I have found that either choice is a close fit inside the fuselage.  Even when pushed fully forward there is not much room for the connecting cables and to make sure that they don't foul the servo arms/rods.  I tried various makes of LiPo in 3 cell and 4 cell config and not found anything perfect.  Another 18mm of space would've helped maybe?

Found also in the hardware bag is a preformed clear PVC protector.  This has two self adhesive strips.  If you have rather a coarse, rough landing area then you have the option to apply this PVC strip to help protect the underside of the fuselage between the cowl and the wing leading edge. I land on well kept grass but I fitted anyway,maybe to avoid green grass stains!  The tail of the fuselage has a plastic fin to keep the rearof the  fuselage off the landing surface.  

Wing

The wing is fully made up in one piece and is stiffened with carbon rod and a grp strip.  The ailerons also have carbon rods embedded during molding.  All in all these simple items really make the wing rigid.  Control arm are fitted, glued I suspect so keeping an eye on these that they do not come loose.  A drop of epoxy will rectify that.

The metal gear servos are prefitted and the arms appear on the top side.  Plastic servo covers are supplied in the hardware bag and are self adhesive.  Also found in the hardware bag are the connectors for the ailerons, ball link one end and the servo end is a bend and secured with swing keepers.  After centering the aileron sevos all that is required is to do is to screw in or out the ball link so that it drops on to the control arms with the aileron's edges level with the wing's trailing edge.  Now you can clip back on the swing keepers and stick the servo covers on.  The wings have little plastic pods on the underside at the wing tips.  These help to keep the wings from getting damaged when landing on rough areas or surfaces.

The wing locates by a protrusion on the forward leading edge, beefed up with two strips of 4mm ply built into the wing.  Two screws 25mm x 3mm pull down the back edge.  By it's convenient size I would suggest leaving the model assembled as putting the wing on is a bit of trial with regards to ensuring the servo wires do not become trapped when fitting.

 

Before the next step, I opted to test the power train and to check the "real world" actual current and input power (wattage) being used rather than relying on Durafly's figures.

See Finalising below

In the hardware bag is a Y lead which will connect the two aileron servo leads to the receiver.  Ensuring that the cables and servo leads on the bottom of the fuselage are settled in the wide groove the fitting of the wing can be performed. This entails simply to engage the forward spigot into the fuselage and secore the trailing side with the two 3mm x 20mm screws.  Verifying that no servo leads have become trapped which usually they do in this sort of set-up.  Because of it's convenient wing span, 43 inches it is quite possible to leave the whole model assembled.

Finalising

Temporarily connecting a 4 cell LiPo I checked the direction of motor rotation which was correct.  However, continuous beeps tells me the throttle needs reversing on my transmitter. Unplugging the power I changed this on the transmitter and rechecked again.  All's well now.  A little nudge of the throttle stick and the motor screamed into life.

For the control throws I followed the manual's guidance as a starting point.  They are:

  • Elevator Rates: Low 6mm / High 10mm
  • Rudder Rates: Low 8mm / High 14mm
  • Aileron Rates: Low 12mm / High 16mm

Centre of Gravity is 50 - 55mm from leading edge

Static Power Test

NanoTec 4 Cell 25 - 50C 2200maH Fully charged voltage:    OEM Prop: 5x5.

  • Idle: amps 0.7   voltage 16.74v  watts 1.1w
  • 50% Throttle (10 secs): amps 8.1  voltage 16.59v  watts 130w
  • Full Throttle (10 secs):  amps 27.3   voltage 16.36v  watts  503w
  • Ambient Air Temperature 8 deg C,  ESC remained cool to touch
  • Battery drop during test: 8%

From the above figures it appears, depending on wind conditions the ability to fly for a decent time at 50% throttle.  At WOT the figures suggest 3/4 hp on tap and for a model weighing in at less than a bag of sugar some speed should be attainable.  The maiden flights will confirm this and flight times.

Maiden Flight

Maiden Flights was completed on the 14th March 2015 - Cashmoor Field.  Wind was a blustery NorEasterly with air temps around 8 degrees C.  Our Dave Bright was tasked to maiden this new model which as you all know would take no arm bending.  Many club members know that Dave only knows idle and full up so you would be maybe a little concerned at lettting him have the sticks.  Not really because if the EFX is to stand by it's claim then it must be subject to what's advertised and some reasonable abuse.

The flight battery was 1600maH 35C 4 cell Zippy Compact.  This little bundle is 100mm long so fit s neatly into the tight battery space provided.  The Durafly recommended Lipo is a Turnigy 1800maH 4 cell 35C minimum A Spec but as usual was on backorder hence the maiden battery choice.

Gently launched into the wind Dave climbed it at 45 before banking round and levelling out at about 100 feet.  Some trim was needed to elevator (which could be adjusted mechanically at the control rod later) and now given some tight circuits, figure of eights, varying between half and full throttle. All seems well so now verticals were initiated and no problem here, it just keeps going.

When power started to reduce after about 4 1/2 minutes Dave brought it in and the battery pack was checked.  Um!  4%.  Warm but not hot which was to be expected.  The next flight will be done reducing the flight time to 3 mins and more upper throttle use with some power off glides to watch for stall.

With a charged pack inserted the EFX was launched again and Dave brough tit up to vertical for a couple of hundred feet before rolling back down into a 45 and skimming the field centre, a distinctive whistle as it passed us before climbing back up high again.  A lot more full throttle was used with some power off glides.  Glide it did easily and no sudden dip of a wing.  This was done a couple of times before some more WOT loops and a fabulously clean 16 point roll with no obvious loss of height.  Then power dropped out and time to glide it back on a slight idle.  Just before touchdown flicking throttle to move prop to the horizontal.  I suggested this to try and save a possible broken blade.  Battery again was retreived and checked. 5% capacity and a bit warmer this time.

So, on this basis a good 4 minute race around definitely needs a 1800mah Lipo pack which is the biggest your going to fit in the tight space.  Centre of Gravity is fine with pack pushed fully forward.  Battery space suggests maximum of a 110 mm long pack.

Speed?  Well appears very quick but we had no checking equipment and we were unable to compare it with last years group build "Impressivo"

Dave Bright likes it and approves it.  Would be good for more Club members to get one for an all out "Scramble"  It also survived Dave's flying and I would like to sincerely thank Dave for the maiden and subsequent flight.

Update: April 11th 2015, a sunny day but gusting NorNorEasterly crosswind at Cashmoor.  The big gas engine models were mainly grounded although some did venture out when the wind settled back a little. IMAC practice!  But landings were interesting.  So, lets see how the EFX fares.

Jon Tappin piloted and yours truly launched.  Flew clean and precise.  Jon was impressed so another battery and another flight.  Multipoint rolls, verticals. all nicely executed.

 

Declared Specifications

  • Wingspan: 1100mm = 43ins
  • Length: 760mm = 30ins
  • Flying Weight: 720g
  • 4 channel control
  • ESC: Durafly 50 amp
  • Motor: NTM 2836 2300kv
  • Props: 6X4 & 5X5
  • Recommended Battery: 1800maH 4Cell 30C<   or 2200maH 3 cell 30C<
  • Minimum 6 Channel receiver

 

 Conclusions

For the price good value at less than the £100 mark delivered (UK)  Well thought out design.  Good fitting of components and excellent finish.  Spare parts available at time of review.  From earlier reports it appears that the ESC has been upgraded as the initial version was only 30 amp.  No burst value has been indicated on either ESCs.  The manual is well written although I am a little concerned that they have described what sticks control pitch, yaw and roll.  Anyone purchasing something like this should have some experience of RC flying and would know these basics. I hope resellers don't sell this model to people as a toy, which it is not.  Especially with a prop turning at 30,000 rpm!

This model has only been available since October 2014 and there are already some mods being carried out. These vary from swopping out motor for similar size but 3000Kv and other have squeezed a 6 cell 1300maH in to model.  So, it could be open house on possible mods to this capable model from Durafly.

 

 

 

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