ElectriFly Yak 55 Follow Up

In my original review, I described building the ElectriFly Yak 55 ARF, a flexible and durable ARF from Great Planes. So how has it held up over time?

The truth is, I have punished this plane quite a bit. It has survived countless hard landings, and has the hot glue repair seams to prove it. I've gone through four of the plastic spur gears, which get chewed up easily by the metal pinion gear. And the original foam nose has long since disintegrated. I bought spares, but it seemed that each crash pushed the stick mount a little more into the body, to the point where the propeller wouldn't clear the cowl. It was simpler to leave it off.

I made at least two major mistakes with this plane. The first was flying it with an older, non-computer radio, where I could only reduce the control surface throws mechanically at the servos. This still left the plane way too volatile for me to learn on, and resulted in more crashes than necessary. Since moving over to a Futaba 7C with dual rates and expo, I've found it significantly easier to control. This is still not a beginner plane though - it's small, fast, and easy to lose your orientation. I wish the bottom had more distinctive coloring from the top.

The second mistake was using such a heavy battery. I started with an 11 volt 1500 mah LiPo pack, which at 4.4 ounces did serious damage to the fuselage in crashes. The firewall completely shattered, and the floor of the fuselage (which is actually the top of the one-pice wing) crumpled. If you're sticking with the stock motor and gearbox, I'd start with a 3S, 950 mah battery instead. It may be tricky to get the center of gravity right, so try moving the receiver and ESC as far forward as possible. Another good idea is to put a spongy piece of foam behind the firewall, which will protect it and the battery in a nose-first crash.

My solution to the weight problem, and something I wanted to try anyway, was to upgrade to a brushless motor. I happened to have an ElectriFly RimFire 28-30-1450 outrunner on hand, which turns faster than I need, but actually worked out great. I found I was able to switch to a 7.4v 1500 mah battery, which both saved weight and slowed down the motor. Having temporarily run out of the original 11x47 props, I downgraded to a 10x4.5 with good results. Thrown from underneath with full throttle, this plane takes off fast!

The tricky part was how to mount the motor, given that ElectriFly doesn't make a stick mount for outrunners. By complete luck, it turns out the plastic housing for the factory motor/gearbox can be used. The two tabs which held the brushed motor line up with two of the RimFire's mounting holes. The third happens to line up with the tube used for the spur gear shaft. It just took a few seconds with a hobby knife to pare down the lip on the mount, and then fitting an extra long screw to run through the tube. The motor now sits flush with the old mount, and is mounted backwards for use with a prop saver. I used hot glue to attach the mount to the plywood stick, as well as the original side screw.

The result is more power than the factory setup, with much less weight. An added bonus is that the propeller turns freely now, which makes it even less likely to break on landing. The geared, brushed setup left the prop quite stiff, even without power (I didn't have the ESC programmed for brake accidentally). This added to the stress on the motor mount, which needed to be periodically reglued.

After several months of punishment, my Yak 55 had reached the point of barely flying anymore. I thought the last straw was getting stuck in a low tree, which took a direct shot with a football to retrieve. The tail had split again, and the bottom was starting to fall apart. I put the plane aside for a few weeks, then gave it one more shot. After an hour with the glue gun I was able to get it flight ready again, if barely. One more flying session though and the whole front was completely demolished.

The bad news is I'm going to have to retire this plane. The good news is that I'm buying another one and starting over with brushless power from day one. I'm also going to reinforce the tail with carbon rods from the old body to stiffen it. Knowing the weak points should help make the new one last, and using the smaller battery will make a big difference. I cant wait to get the new plane up in the air. The Yak is dead - long live the Yak!