E-Flite Eratix 3D 25e

The E-Flite Eratix  is a 54" wingspan electric plane, made with ultracote-covered balsa; sold by Horizon Hobby for $170. (Ultimate Hobbies used to have it for less money, but they don't seem to carry it anymore.) It flies like a mix of a balsa plane and a good foamie. Very responsive; handles wind well; very fun to fly. The power setup described below is much less expensive than the recommended setup, while still providing excellent performance. It's a really great way to get into a larger-sized electric.

The recommended power setup is to use an E-Flite Power 25 or Power 32 brushless outrunner motor, 60-Amp speed controller, and a 3S 11.1V 4200mAh or 4S 14.8V 3850mAh Li-Po battery. To bring the cost down, I'm using a $38 BP Hobbies A3520-6 motor, a $25 BP 60A speed controller, and I'm powering it with two 3S 2200mAh Li-Po batteries wired in parallel. With an APC 14x7 Thin Electric prop, the current draw tops out at about 50 amps (which is the recommended maximum for the motor). I've found that an APC 15x6 Thin Electric prop works well, providing good thrust and speed.

As per the note on the BP Hobbies page for the speed controller, I set it up with 15° timing and 16Khz PWM. From what I've read, the Eratix cowl and spinner will fit well with the Power 25 motor, but need adjusting with the Power 32 motor (which is 0.2" shorter). I ran into the same issue with the BP A3520-6 motor, so I put a 0.25" nylon spacer and a washer on each bolt to move the motor out a bit. (Longer 4-40 bolts were also needed.) Other than that, the BP motor mounted just fine. I used the prop adapter that came with motor, and mounted the spinner adapter plate right under the prop. Both the prop and spinner adapter had to be reamed out to 8 mm. Here is a pic of the motor mount:
I used the recommended Hitec HS-225MG (metal gear) servos (4), and the two-piece servo arms that came with the HS-255MG servos to get a longer arm length (and throw). One of the aileron arms had a habit of loosening up, so I painted epoxy around the arms and the outside of the mounting screws on all of them -- enough to prevent any loosening, but not so much that it couldn't be disassembled if need be. Haven't had any problems with the servo arms since.

The build was quick and easy; the fuselage and wings come pre-built and covered. It was just a matter of hinging the control surfaces and gluing everything together (mostly with thin CA). The pre-built components can be purchased separately as parts, which is nice.

The plane balances well with the batteries pushed towards the front a bit; with maybe an inch or two of battery hanging over the mount. I put velcro on the mount and in between the two batteries, and then a velcro strap around them and through the mount. After breaking some of the thin balsa of the battery mount, I reinforced it by epoxying in a couple of carbon fiber strips.

I use a separate 3A 5V/6V Switch-Mode UBEC, setup to run at 6V. (The BP 60A speed controller has no BEC, so a separate one is mandatory.) As with all my Li-Po powered planes, I use the HRPoly-X Visual/Audio Lipo Low Voltage Warning Device to monitor the battery in-flight. Here is the home site for the product (UK). I have the HRPoly-X set to voltage level #8 (9.6V), so it starts beeping at 9.9V.

The main landing gear has a very nice amount of spring to it, allowing it to absorb a lot of bounce in a landing (which I've tested while bringing the Eratix down in some pretty strong, gusty winds). After a while, the bracket holding the tail wheel on my Eratix loosened up. So, to get it really solid, I opened up the end of the balsa, put in a lot of epoxy and then some strapping tape. After that I attached the ultracote back in place with clear hinge tape. If you're putting one of these together, I'd recommend pushing as much epoxy into there as possible.

Other E-Flite planes that I'd expect could use the power setup described above are the Ultra Stick 25e ARF and the AT-6 Texan 25 ARF. Anything that calls for a 3-cell 4200mAh Li-Po, really.

Click here to view a gallery of pics of my Eratix.

Eratix reviews:

Eratix thread on RCGroups:

(Eratix in sky photo by Erin Dack)

Eratix on Skis

The Eratix is a great ski plane; a real joy to taxi, take-off and land.  I have Dubro Snowbird Skis (#825) on the front and a Dubro Park Flyer Ski (#830) on the rear.  The #825 snowbird skis are well made, constructed from high-quality plastic.


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