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Monday, September 3, 2012

Quick Take: E-Flite UMX Carbon Cub SS BNF


As their all-time best customer, I usually get the inside scoop from my LHS.  Apparently, the new E-Flight UMX Carbon Cub is a retailer’s nightmare, attempted returns are rampant.  The problem seems to be caused by low quality linear servos in the Carbon Cub’s application. 

Wingspan:  24.0 in (610mm)
- Overall Length: 15.7 in (398mm)
- Wing Area: 83.5 sq. in. (540 sq. cm.)
- Flying Weight: 3.17 oz (90 g)

- Motor: 180-size, 2500Kv brushless outrunner
- Flaps

- DSM Radio

- $220 MSRP, $170 Street

- Floats Available: $30

While all Horizon micros use delicate, exposed gear linear servos with a few month half-life, it seems the Carbon Cubs problem is a lack of control surface throw requiring hyper extension of the servo.  When users set 100+% travel, the worm gear drives the servo’s wiper past the intended endpoints of the contact strip. 


This has been breaking elevator servos within a few flights, often catastrophically damaging/destroying the plane.  The alternative: not enough elevator throw, seems equally defective.

Given a rash of quality problems with Horizon UMs and their known bad linear servos in particular, I am putting out an immediate AVOID recommendation on the UMX (what is the X for, again?)Carbon Cub.

The dysfunctional UM Carbon Cub continues a long line of UMs with unacceptable component quality, coupled with unacceptable over-pricing.  Full sized PNP or RTF Cubs generally sell around $100.  

pr75374img1This 55” EPO Super Cub sells for $149 including a 2.4Ghz radio

1.5 to 2 meter balsa and ply ARF Super Cubs also run for less than the Carbon Cub. Z8RC’s recommended competitive target street price for the UMX Carbon Cub is $79 MSRP, $69 Street price.  I placed it on the high end of the current micro market price range, based on the inclusion of flaps and a decent motor.  

Appearance: B- 
Funky windscreen.  Lines slightly off.  Ok, but not quite right.

Aerodynamics: Untested 

Power System: C-
E-Flight 180 2500 kV = good, expensive motor.  Predicted reliability of integral ESC and E-Flight batteries:  Very poor. 

Build Quality/Durability: F
Cheap Styrofoam micro at a giant scale scale balsa and ply ARF price.  Cheap linear servo failures are rampant.  Weak tail.

Value:  F
Low end micro components at a giant scale price.  Poor, non digital servos with exposed gears.   Low amp, integral ESC.  DSM Rx.

Overall Grade: F
Rip off pricing.  Non-competitive component quality.

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