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Thursday, October 6, 2011

Flyzone Micro Super Cub RTF (14") Flight Review

Updated the videos and expanded my comparison to the Hobbyzone Champ.

Can the new Hobbico Flyzone Micro Super Cub RTF knock off the venerable Hobbyzone Champ as the Z8RC top beginner RC airplane? The answer follows...
Hobbico packs the wings on the diagonal, making
their box size much smaller and more convenient 
and shippable than Horizon micros.
On the Ground:
My first impression of the Flyzone Super Cub is that it looks a little stretched in the longitudinal axis (or maybe the fuselage is squeezed a bit too thin along the lateral axis) and it seems to have ;dihedral.  The long snout could be promising, it might indicate a fairly light motor and prop in proportion to the airframe.

The SCub ships with two V-shaped struts equipped with three sticky pads to attach the ends to the wing and fuse.  There is a corresponding divot under the cabin, and the underside of the wings have recessed squares to accept the sticky tape from the struts. I left my struts off because they were a bit too long and too flexible, bowing them out and increasing main wing dihedral even more; I thought the uneven bend might adversely affect flight characteristics. The wing is plenty strong, so why add weight and induce asymmetric parasite drag?
The plane comes with stick-on wing struts (see 
unboxing photo, above).  I decided to save the 
drag and the wieght.
The landing gear is narrow, which might make ground operations a little difficult, but the wheels are large for a micro of this size and weight, which allows the mini Cub to handle some ground imperfections. Sadly, the tail wheel is fixed and does not turn with rudder movement.  On the ground engine torque is more than sufficient to turn left with rudder deflection, but there is not enough control to turn right, imputing full right rudder is only enough to go straight.
The tailwheel is stationary.
Nice paint scheme details for a micro, and the 
empennage looks great and is made of stronger 
and stiffer than Horizon micros even with no 
carbon reinforcement
The included battery is a 130 mAh 1S with Flyzone branding, but there is just enough room for a 150 mAh 1S stick.  The battery bay is designed so the connectors and excess wire can be slid inside the fuselage--kind of nifty--but the battery position is located well in front of the CG so changing battery capacity is going to affect flight characteristics substantially.
The battery compartment is just big enough to fit a 150 mAh 1S.

The propeller is very large with a beefy airfoil chord.  The motor and reduction gearing are well up to the task of spinning it, flight tests indicated that this tiny Cub has almost a 1:1 Thrust-to-Weight ratio.  Although hard to see clearly in the picture above, the motor shaft has no right thrust bias to redirect its plentiful power, leading to a lot of torque compensation by altering rudder position across the power band.

The included radio is smaller than it probably 
looks.  The Cub's wingspan is only 14".


In the Air:
If the design goal of this Super Cub was about light wing loading causing a wonderful flying experience, Hobbico did a sensational job!   The plane floats like crispy fall tree leaf, but with a 1:1 T:W power system to rocket skyward.

Speaking of engine power, the little Cub is demands full right rudder to roll straight on take off due to significant torque. This right stick input can be mostly released as soon as the airplane becomes airborne.  Again, the main reason is a stationary tail wheel. It's a bit tricky to roll straight, but at the same time the cub is forgiving enough to teach beginners the art of countering high throttle torque, without looming consequences.  As long as there isn't an obstacle between straight ahead and about 30 degrees left, take off is still pretty easy to accomplish even if not pretty.

Tossing the plane into the air is easier than a ground roll, because setting any throttle above 40% results in a strong, slightly left-spiraling climb as soon as the peppy yellow bird flies from your fingers.

With only 1 oz total weight, the power system is not stressed at all. Flight times are excellent at 10-12 minutes of battery life with mixed aerobatics (= full power loops and steep turns). The wing loading is so miniscule, that the plane can maintain level flight at 20-30% throttle, which if maintained, would extend the battery flight time to perhaps double or more the figure quoted above.
The Super Cub's paint scheme looks very nice, 
and there are some nice scale details like a 
gradient sticker windscreen and windows, reasonably 
tactful racing stripes, traditional Cub logos on the 
vertical stabilizer, and molded wing ribs for looks 
and strength.  The wing airfoil is flat with under-camber.
  Overall, the plane is very strong for its feather weight.
Once the plane is climbing away, you'll need half to almost full right rudder between 50% and 100% throttle respectively to track straight.  About 1/16th inch of right rudder deflection, as trimmed on the ground, is sufficient to track the airplane straight ahead at comfortable cruise power, around 40%.

The plane is very stable in level flight due to the pronounced dihedral, but rolling out of turns on a precise heading can be tricky due to some mild pendulum oscillations as the plane hunts for a wings level equilibrium.   Even with its very positive dynamic and static stability, keeping the plane tracking straight is a bit of balancing act due to the large draggy prop and plentiful thrust.  Any change in power setting produces a corresponding change is the Cub's desire to roll.  Adding just 10% more power above stabilized, straight and level flight will produce a positive climb rate and a mild left corkscrew skyward.  Reducing power 10% has the exact opposite effect, as the trim required for straight-ahead flight dictates a right corkscrew with a throttle reduction.  Since the mini SCub comes with a dedicated radio, there is no way that I know of to use a computer mixing radio to help straighten things out.

Slow flight is absolute impressive in absolute terms--the plane is so small and stable that adding about 75% back stick under gentle power slows the airplane near walking speed.  That said, stall characteristics of the undercambered airfoil are unrefined.  Pull back more than about 75% on the elevator and the plane will slip off to one side as one wing drops, tugging the nose down with it.  Recovery altitude varies with stall severity, but its never a whole lot due to the super light airframe's desire to start flying as soon as possible.

The only exception to the stall sequence discussed above is when the plane is already established in a steep turn.  If smoothly entered, the Super Cub will stabilize in a steep turn in either direction, with full left or right rudder (which is mapped to the aileron stick) plus full up elevator.  Jamming the stick in either rear corner of the radio gimbal, with anywhere from half to full throttle produces an easily sustained min-radius turn.  The plane turns tighter to the left due to additive motor torque.  The tightest (left) turn circle is about 8 feet in diameter.  The plane can reverse course in even less lateral space than 8 feet if you add a little vertical spaghetti; perhaps 3 feet, wall to wall.

1:32 - Slow flight to stalling speed                  
1:42 - Full stall, wing drop                             
1:50 - Stick planted in bottom left corner        
3:40 - Thrust demonstration                            
4:30 - Climbing at 5% throttle (throttle shown)
5:30 - Min-radius turns                                   
5:38 - Stick planted in back right                     
corner (torque pulls plane out left)
5:55 - Sweet landing                                       
Speaking of turning, the SCub is light on rudder throw as shipped, even beginners will want to move the push-rod to the inner most hole on the rudder control horn.  Still, there is not quite enough rudder throw for my liking.  The elevator is just the opposite--a tad touchy--so while you are adjusting the rudder horn, move the elevator push-rod to the outter most hole on the control horn.  Much better.  But there still is not enough rudder authority, or too much dihedral, to accomplish anything resembling a barrel roll.  Inverted flight is unsustainable.

Spins are as benign as they come, but if you keep full power or down elevator in, the plane can bee-line for the ground.

Lastly, the included radio is worth comment.  I prefer the form factor of the SCub radio to the cheap Horizon Hobby equivalent.  The trim buttons function well compared to the sub-standard Flyzone Albatross radio.  That said, my radio developed noticeable binding between the dome shaped gimball covers and the stick frame, and while it didn't ever result in diminished control, it was quite distracting.

Tooling around on a windless morning (don't fly this little yellow feather in any wind) with this miniature kite with a tiny rocket motor could not be more fun.  Though not as refined as the Hobbyzone Champ, the Flyzone Micro Super Cub is an endearing trainer.  In a way, it is a better trainer than the Champ because it brings many of the same vices as it's big brothers, but without the wing loading to create sustained momentum in a bad direction, or the mass to do any damage during a crash.  Without any experience or assistance, one could learn to fly the SCub as long as you stay over grass and spend 30 minutes in ground school, first.

Flyzone Super Cub advantages over the Hobbyzone Champ:
  1. Smaller flying area requirement
  2. Slower minimum speed
  3. Rough runway ops
  4. More benign spins and hands-off landings
  5. Thrust-to-Weight Ratio
  6. Feather light wing loading
Hobbyzone Champ advantages over the Flyzone Super Cub:
  1. More refined slow flight and stall behavior
  2. Proper thrust vector; less need to compensate for torque
  3. The right mix of stability and agility from less dihedral
  4. Top speed
  5. Better ground handling and controlability during Touch and Goes
  6. Flightpath precision
Due to its slower flying speed, the Flyzone Super Cub is a easier to handle than a Champ in smaller spaces, or to stay ahead of, even in a larger space.  As long as you stay away from the Cub's absolute  air speed limits (no full throttle or full stalls) this Super Cub is quite possibly the easiest first trainer to keep aloft.

That said, the SCub strongly displays and even exaggerates the traditional vices of a stereotypical single engine airplane--it has an affinity for torque roll to the left under mild to moderate power, correspondingly, it spirals right in idle, and it slides into a sharp bank with a nose drop as a wingtip stalls.  Flyzone's floaty micro trainer has outstanding power for its weight, with an almost magical ability to callously yank the airy foamie out of square corners.

I see conflicting attributes and redemptions with Flyzone's excellent little Super Cub as a practical RC trainer.  One one hand, with superb power and a centered thrust line, is it an excellent little torque trainer because throttle and airspeed and rudder are a constant balancing act.  Learning the skills to cope with torque as a function of engine power an airflow over the rudder will serve students very well as they progress to larger, more powerful single engine RC models. 

On the other hand, the combination of very strong power and feather light wing loading defies real world concerns when it comes to managing flight path momentum.  This paper-weight Cub is unrealistic in its ability to instantly power out of tricky situations, and probably not the best trainer as a means to an end beyond guiding a feather.

Overall, the refined flight characteristics, larger scale and aircraft feel, and the slow speed precision of the Champ are well worth the extra $10.  The Champ is a more realistic and satisfying first-step into the realm of RC flight and is just as easy to fly, given double the airspace.

Appearance: A-
A little cartoony.  Very nice paint scheme.  Vibrant visibility.

Airframe: B-
Strong.  Unrefined slow speed wing.  Unsteerable tailwheel.

Power System: A
Gobs of power.  Little loud.  Great battery efficiency.

Build Quality/Durability: B+
Strong tail.  Light mass has a hard time sustaining damage.

Value:  A
$79 RTF - one of the best trainer deals.  Not bindable.

Overall Grade:  A-
Very easy to fly! Hard to balance motor torque.  A few rough edges.
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