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Extreme Flight Yak 54 68inch ARF Electrified Conversion Review!
By Steve H.
Nov 28, 2005, 02:09 AM
Introduction
Within the past couple of years, the Yak 54 airframe and the Extremeflight lineup have become two of the most popular in the R/C world. This review covers the electric conversion of their 68" Yak, one of their best sellers. Here is a little info on the full scale Yak 54...."The Yak-54 is a two-seater sporting and aerobatic trainer designed for training sport pilots in aerobatic flights and for participating in aircraft aerobatic competitions. The Yak-54 is a single-engine monoplane of conventional mid-wing aerodynamic configuration with non-retractable tailwheel landing gear and tapered empennage. The aircraft is powered by the nine-cylinder M-14X engine of 360 h.p. The Yak-54 is characterized by high thrust to weight ratio and good maneuverability that provides for the full set of aerobatic maneuvers. The aircraft offers simplicity in operation and maintenance with minimum of ground equipment and could be widely used in air clubs. The cost of this aircraft is less than other aircraft of similar class with comparable flight performance."
Kit Contents
Included in the box was:
The hardware was very complete, high quality Dubro components. There was also an extra set of Metric hardware that the manual mentioned were included by mistake. It told me to throw some of it out but who can do that? Mine went in my spare parts box with all the other metric stuff. :)
Assembly
The first thing I did, as with any ARF, was to go over everything with a covering iron. My kit did not have any major wrinkles but I noticed some after heating the covering.
Motor installation
To mount the Axi 5330/18 motor, I made a mount out of some aluminum rods and sheet I got at the local hardware store a while back. There were mounts available that I could have bought, but I decided to go this route as it was a little cheaper & I had the aluminum already. The Jeti 90A ESC is rated for fourteen to thirty-two regular cells, or five to ten LiPo cells, at 90 amps and was a perfect match to the large Axi outrunner.
Landing gear
I ordered a set of extended set of landing gear from TNT Landing gear, they gave plenty of clearance for the 20" prop. They were aluminum, but I used UltraCote paint and after a good cleaning with some acetone I painted them white. The wheelpants were installed with a 4-40 screw and I used some clear silicone to help hold them from rotating. The ARF's included tires were Dubro foam wheels and they were very flexible from side to side. On some landings I found that they rubbed against the wheelpant. Unfortunately these were the only wheels that would fit inside of the wheelpants...I tried to find some stronger ones but they were all too wide.
Canopy mod
I modified the canopy to have 2 dowels in the front and then two 4-40 bolts in the rear. The original mount was four 4-40 bolts all the way around. I also glued in a stick of balsa across the two mounting lugs to strengthen it up.
Completion
The completed Yak 54 turned out beautifully. All up weight with the battery in place was right around 10lbs. I hooked the system up to a whattmeter and to my surprise the setup pulled 3,000 watts for a few seconds before settling down a little bit. Thats about 300 watts per pound! I thought that would suffice!!
Flying
Every day that I took the Yak to the field, it seemed to be either cloudy or windy. Finally I got tired of it and flew anyway. The CG was perfect with the battery packs just behind the front former. The recommended CG range was from the front of the wing tube to 1/2" behind the wingtube, mine was right in the middle. I setup the control throws per the manual using the new Hangar 9 Incidence/control throw meter. The throws were setup as follows:
LowRates
High Rates
Taking Off and LandingI set it on the runway and after doing a thorough range check with the throttle on and off I was ready to fly. I eased into the throttle and it took off with the expected tiny bit of rudder correction. About 1/4 throttle was all that was needed to takeoff and fly around, anything more was extra. I did a few basic maneuvers to get a feel for the airplane and I could already tell it was a winner. The CG seemed to be a little bit noseheavy for my tastes but better that than tailheavy on a maiden flight.
Aerobatics/Special Flight Performance
This was what the Yak did best. Knife edge flight had almost no coupling and it tracked straight from one end of the runway to the other. Knife edge loops were no problem and didn't even require full rudder deflection. Aileron rolls and point rolls were very crisp and it stopped rotating as soon as the sticks were centered. The roll rate on high rates was unbelievable, it was almost a blur it rolled so fast. The Hitec 5645 servos had plenty of power and the precise centering was very nice. Snaps were pretty straight forward and they also stopped when I let go of the sticks, it had no tendency to over rotate. I did these on low rates most of the time. Harriers and Elevators were equally as nice. I had some wing rocking in an Elevator but with a little spoileron mixing it went away and I was able to Elevator all the way to the runway if I wanted.
The Yak did an awesome blender and transitioned into a inverted flat spin very nicely. The inverted flat spin could be slowed way down, and it almost seemed to hang there. This was a very violent maneuver so I made sure my wing and canopy bolts were tight. Rolling circles could be stretched out over the whole flying field and the Yak looked very graceful while doing them. The Axi provided more than enough power to hover. It pulled out of a hover with ease, and accelerated while doing it! With the large prop it performed torque rolls very easily. There was so much power after liftoff that I could point the nose straight up and it would accelerate while climbing! A perfect Wall could be done and I found that a little spoileron mixing helped to keep it from snapping out.
Flight Video
Conclusion
The 68" Yak 54 is a great airplane, and I would recommend it highly. I am sorry to say that I have been informed by Chris Hinson at Extremeflight that, for now at least, these may no longer be available. However, he has lots of other great planes on his site at http://www.extremeflightrc.com for sale and they can all be converted to electric if you want them that way. I have seen the 87" version converted and it flew just as well as its gasoline counterpart. The parkflyer Yak also flies very well. |
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Nov 29, 2005, 12:57 PM
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#2 |
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Use the 4S Luke
Join Date: Aug 2003
Location: Euless, Tx
Posts: 7,824
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Great info. I just bought that very AXI and was wondering how it would do with those Tanics. It's amazing they can deliver 90A!
So what is the all up weight? |
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Nov 29, 2005, 03:10 PM
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#3 |
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"Fly It Like Ya Stole It"
Join Date: Jul 2004
Location: San Bernardino, Ca
Posts: 768
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He said it was right at 10lbs
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Nov 30, 2005, 10:50 AM
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#4 |
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Forgot how to fly
Join Date: Oct 2002
Location: Atlanta, Georgia
Posts: 10,142
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Nice Job Steve.
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Dec 05, 2005, 09:37 PM
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#5 |
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Registered User
Join Date: Mar 2001
Location: Palm Harbor, FL, USA
Posts: 350
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Wouldn't the plane fly better with a lighter power package like a smaller motor and fewer cells?
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Dec 05, 2005, 10:10 PM
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#6 |
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Forgot how to fly
Join Date: Oct 2002
Location: Atlanta, Georgia
Posts: 10,142
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Depends on the setup I suppose. I ran mine on a Hacker C50 12Xl and 8S. However, it was still about the same weight. I know of another pilot that ran a 4130 on 10S. Ended up smoking the motor.
There is still a power to weight ratio needed to match the glow setup and sometimes you can gain by running fewer cells and a deeper gearing, but sometimes not. -Mike |
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Dec 06, 2005, 12:28 PM
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#7 |
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Registered User
Join Date: Jul 2003
Location: marshall , va
Posts: 773
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It will be interesting to see how well these cells hold up running a 10s1p setup like this
at high amps. I use polyquest xp3700 cells at 60 amps and they seem ok so far. It does help keep the cost and AUW down to go 1p instead of 2 or 3p. Kevin |
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Dec 06, 2005, 02:34 PM
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#8 |
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IAN!
Join Date: Oct 2003
Location: Just south of Cambridge, UK
Posts: 937
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do you think the snapping out could be due to the larger gyroscopic forces of the prop? ive found i get no snapping running a 18" prop.
Ian |
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Dec 06, 2005, 03:22 PM
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#9 |
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Registered User
Join Date: Aug 2000
Location: Raleigh/Durham Intl, North Carolina, United States
Posts: 5,013
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Just found this discussion. Thanks for the compliments.
 The setup pulls about 75 amps at full throttle but as you know on a 3d plane you are not at full throttle very much at all, and when you are it is in short bursts. The packs are rated for 15-20 C so this is just at the top of their limit for the full throttle bursts. I am sure it could be flown on many setups, but this is the one I chose. I have the packs pretty far forward and the Axi is a little heavier than the Hacker I think so a much lighter setup (if there is one?) may have balance issues, plus these packs are pretty light. |
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