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Wednesday, November 30, 2011

E-Flite Cap 232 BP ARF - Flight Review

***** SAFETY WARNING *****
This product contains a manufacturing defect that makes it extremely dangerous to fly.  The hybrid carbon fiber/metal pushrod design is unsafe causing the binding between the metal and the carbon fiber to break loose under aerodynamic stress, causing the model to go out of control.  You MUST glue not only the clevis to the carbon fiber rod, as instructed in the manual, but also glue both ends of the black binding that holds the metal portion of the pushrod to the carbon fiber to prevent slippage in the air--which is not indicated in the manual. Horizon Hobby has been notified to pull the E-Flite Cap 232 off the shelves and recall all models until this unsafe defect is remedied.
At the 3 minute mark, a series of tight outside loops causes the factory supplied carbon/metal pushrod binding to slip (lengthening the pushrod in the air). I had to manually hold 95% down elevator + full down trim (indicated by the beeping in the video) to land the model. I erroneously thought the battery had slipped and moved the CG too far aft.  The manual calls for gluing the clevis to the carbon, but nowhere does it instruct one to glue this unsafe defective part.
-----End Update-----

I picked up this little "Cap 232" for $120 minus $25 in "store discounts" because Horizon Hobby forbids price competition.  ARF cost = $95. 
The E-Flite "Cap 232" is a proprietary, no-to-scale 
big wing RC 3D aerobat.  Sheeze, the cartoon 
canopy isn't even in the right place.
On the Ground:

The plane's name is in quotes 'cause it neither looks nor flies anything like a Cap 232.  Yeah, I know that there is a long tradition of naming proprietary RC airplanes after actual aircraft to which they bear little resemblance and share few major design features; usually they are minibats like this one, although the E-Flite Carbon Z Yak 54 set a new low standard for mos-characterizing larger airplanes.  Just because everyone does it, I don't accept it.  It's never worked for me, "but officer, surely you know that everyone speeds on this road."  It's lame to call an airplane something it is clearly not.
Real Cap 232's looks different and 
can accommodate 3D people
But I figured, hey, free motor, because E-flite boofed their Ascent's included 450 power system by including a way too heavy and strong 450 that also requires too much battery.  I replaced it with a drop-in 370.  450 now sitting in a drawer, and the Cap 232 recommended a 450, so you know, a lot like Charlie Brown charging Lucy holding a football, I skeptically bit.  
The plane turned out to be a great flyer.  The motor turned out to be another cludo recommendation - this time, too weak and/or too heavy on the denominator (T:W).

The informed might  be thinking, wait a second, the Cap 232 is lighter than the Ascent, so how can the motor be way too strong for a 19 oz motor glider and too weak for a 15 oz 3D aerobat.  Thing is, this isn't your average scale ultimate aerobat, the Cap 232 is a 425 sq in, 15 oz extreme machine.  Ok I know it is called a Cap 232, but lets get real, this unique RC design has wings, and that's where any serious resemblance to a Cap 232 ends.  The name is probably so E-flight can sell a few more airplanes to people who might like Cap 232s.  Fact is, this plane needs a 3D capable T:W, and it needs it bad.

That all said, this E-Flight thingamajobber is a super light, super low wingloading 3D'er.   The immoral Chinese sweatshop did a great job keeping the construction light and strong.  The plane comes with a beautifully covered single piece wing, incredibly light for the strength and stiffness.  The flat fuselage is built-up from balsa and plywood strips - it could have used some carbon fiber for strength and rigidity - it has some flex and seems a bit flimsy for the recommended power system.

The result of the skimpy fuselage and super light wing single-piece wing construction is an bare airframe weight of 8 oz.  That's not a typo, yes,  this plane manages 425 sq inches of wing area in an 8 oz balsa and ply airframe.  WCL = an eye popping 3.6 including a 7 min battery (but not the heavy E-flight 450; see below for more). 

That is an actual Wing Loading of 6.1 oz/sq inch.  Compare to a Precision Aerobatics RC Addiction X, which brags about achieving 8.1 oz Wing Loading and a WCL of 3.7.  The Cap 232 trounces the latest Addiction's numbers - except wingspan.

But wait, that's not the half of it.  The Cap 232 achieves that with a well designed .10 motor, not E-Flites brick 450.  Add a smallish 10x4.6 prop and you can eek out 10 minute flights using a 1300 mAh 3S.  T:W?  How about 2.1 to 1?
The Super Tigre .10 motor's high T:W ratio 
gives the Cap 232 astonishing 3D performance.
PNP cost for the model + motor + ESC + digital servos = $120 + $30 + $30 + $75 (minus $50 LHS discount) = $205.  Compare to $540 for the much lower spec PA Addiction X or $420 for the even lower spec Addiction.

In the Air:

As you've already seen, the maiden did not go well due to Horizon Hobby's dangerous negligence.  I decided not to ding the plane to an F, as I usually due when Horizon puts out an acutely dangerous model (far too often).  The reason is that E-Flite's incompetence is so easily fixed with a little upfront knowledge.  After reading this review, you will likely be safe.

Unfortunately, lethal design flaws are not the only thing wrong with the Cap 232.  The plane has areas of greatness: feather light WCL (much lighter than the Ascent motor glider!), superb power to weight as long as you ignore E-Flite's too-heavy motor recommendation, and nice large throws - but it also has major problems in the air:

  1. Stabilized inverted flight is overly affected by power setting
  2. The Cap 232 has great difficulty holding a knife edge
  3. Simple aileron rolls exhibit mild roll coupling
These two major issues share a single cause: the design thrust line is way off.  The stick motor mount is too high, and not coincident with the center line of the symmetrical wing airfoil.  This induces a severe nose down or up twisting moment whenever power is modulated.  While it is easily trimmed out for upright level flight, and tends to cancel increased lift from increasing airspeed, it works opposite (improperly) when inverted.

Worse, when on a knife edge, the plane wants to pitch down hard (nose away from canopy), exhibiting excessive pitch coupling.  Knife edge loops should be a piece of cake, but are instead onerous to pull off cleanly as the plane rolls out or bends the circle around the Z axis.

Simlarly, the off-axis engine placement creates some dumbbell effect and resultant roll coupling during maneuvers as simple as an aileron roll.  Uhg.

Lastly, high-alpha flight is fairly difficult to stabilize in a Harrier type attitude, though hovers are easy at less than half power (switched to an 11x3.8 for a better altitude connection to the throttle), as long as you can keep the Cap from effortlessly climbing.

All in all, this plane is a disappointment.  Not because of the all-to-common unsafe Horizon Hobby hardware (an unfortunate trend), and not because value is lacking, but simply because it the plane is poorly designed.  I am going to try to move the motor onto the longitudinal axis where it obviously belongs, but the basic structure makes that mod more difficult than it needs to be.

Sooooo much promise; so little reward.  Pretty sad.

Appearance: B-
Not bad for a contra-scale minibat

Airframe: C-
Incredible floater.  Untenable thrust vector placement.

Power System: B-
E-Flite's power system recommendation is too heavy and low T:W.

Build Quality/Durability: F
Lethal design flaw. Unsafe stock push-rods.

Value:  B+
Great performance:price ratio.  Sweet lightweight wing design.

Overall Grade:  C-
Could've been great!  Not aerodynamically pure.  Might be fixable.

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