HobbyKing Yak 54 59inch!! - RC Groups
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Jul 27, 2010, 12:02 AM
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New Product

HobbyKing Yak 54 59inch!!

Just recieved my new yak from hobbyking today. Unboxed and started assembly. The plane looks Awsome! Hard to beat for the price. Got mine delivered to wisconsin from hong kong in only 6 days! And did i mention the price? $226 delivered PNP!! Can't wait to get this baby in the air!! Makes my FMS P-51 look tiny!!
Last edited by fatloser; Jul 27, 2010 at 12:21 AM.
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Jul 27, 2010, 12:26 AM
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Looks great. Let us know how she flies
Jul 29, 2010, 08:44 AM
Dirty low puller
GHFlyer's Avatar
I have this Yak from HobbyKing. It looked and flew great, until the motor burned up on the second battery pack. Had to dead stick it and when she landed she was smoking big time. The motor windings are all charred and the motor is trashed.
The motor is very poor quality and there is not sufficient cooling. The front looks large enough to cool, but there is not enough exit volume to allow the air to pass by the motor.
I also had to replace the elevator servos as it has a split elevator and one of the servos was bad. It would not center and was unresponsive at times.
On a good note, it will do everything you tell it to in the sky. Very responsive and easy to see. Might be a hand full for less experienced 3D pilots as the control surfaces are huge.
Easy to land. The foam is kinda weak though and dents very easy.
A good plane for the price, but don't be fooled. Replace the stock electronics if you want to make more than one flight.
Jul 29, 2010, 05:46 PM
It's over 9000!!!
Trexid's Avatar

Yak54 Monster

Hey thanks for starting this thread!

I received my Monster Yak54 last Friday and have done a little piecing together but not much progress so far. I am definitely not going to maiden this thing with the stock motor after all of the reports of failure and damage caused by the very low quality craftsmanship.

I've been looking at a couple of other motors on HK to replace the stock motor with but haven't decided on which one to grab yet.

I am almost sold on this one but some reviews complain about magnets coming loose after a couple of flights and the others report great performance out of these for many flights. Seems to be the best price for the most power though.

Jul 29, 2010, 07:02 PM
Registered User
Nice thread, and some nice build pics. I am also looking to purchase one of these birds from HK, but I am really concerned about the problems I've heard with the stock motor burning up. I was hoping that a new batch would be released with a different motor. If anyone replaces the motor and is successful let others know what worked for you, the electronics, battery capacity used, prop size and performance / flight times.
Jul 30, 2010, 12:42 AM
Registered User
Well, I finally found a battery to order and my new prop showed up 2day. Hopefully end of next week I will finally get this bird in the air. See if i can burn up that motor everbody is having trouble with. I will be running a Zippy flightmax 4000mah 20c 4s battery with a top flite 14x6 wood prop, optima 7 rx with my new aurora 9 tx. Im going to go ahead and add some extra cooling exits on the cowl and try and get some extra air flow also. I will post some pics soon as i can. To much work and no play makes jack a dull boy! Thanks for all the posts!! Glad to see this thread taken off....
Last edited by fatloser; Jul 30, 2010 at 01:04 AM.
Jul 30, 2010, 08:43 AM
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ukgroucho's Avatar

Flown mine a couple of times

Well I flew mine 4 or 5 short flights over the last couple of weeks. I'm not a particularly experienced plane flyer.. I have a bunch of hand launch stuff and I can fly basic aerobatics very well (but I'm really a heli flyer .

Anyway.. having something with landing gear that you have to have under the plane when it landed was a new experience. I flew initially with an APC 14x7 prop. Stock motor and ESC and Turnigy 3000Mah 20 - 30C 4S.

A ground test with a WattsUp was a little alarming as just over half throttle showed 68 amps... I elected to fly it but be careful not to go 'full throttle'. In hindsight (and after another ground test) I realised I had not trained the ESC what to expect from the Rx (AR7000) in terms of a throttle signal range. As a result all of the throttle 'comes in' in the lower part of the throttle stick movement. This had some repercussions on flying ...

Not sure how to retrain the ESC as there are NO instructions and it is completely unbranded so I did the only thing I know - power on at full throttle waited for the beeps to subside, and returned to zero throttle. Then powered off. Not flown since I did that so cannot report if it helped and I'm not going to do another static test without another set of hands.

Takes off beautifully, climbout was plenty, rolls very nicely. Loops are also easy and smooth... my problem was in trying to get stable level flight. It tended to porpoise. This looked like a CofG issue and I did try a little more weight in the nose on a later flight.

The level flight issue, coupled with a throttle that was more 'on/off' than progressive made landing a BEAR for me. I'd struggle to get a smooth approach as it was nose up / nose down and also to get airspeed right.. either way too much throttle so it's quickly accelerated past the speed I need or too slow and no throttle and starting to stall.
I thought it was just me and my newbie to LG perspective (although I can land my hand launched foamies easily).. so I gave the Tx to another guy who is a competent 3D flyer. He had two aborted landing passes and handed me the Tx back on the basis that I could crash it on landing.

Landing was HEAVY. On the second flight I tweaked the APC prop (flexi landing gear). Went back to the stock prop (which is fine for what I'm doing right now) and adjusted dual rates and expo to try to smooth out elevator. Did not really help.. still dodgy approaches and hard landings.

OK so I got to looking at how I'd built it (based on limited experience and crap instructions). Came to the conclusion I'd mounted the elevator pushrods too far out on the servo horns (in the last hole). I had LOADS of elevator travel.. had to tame it with dual rates - but I also think the quality of the servos shows up. They are not very refined, a bit notchy / steppy if that makes sense and I suspect that the minimum that they can move was resulting in a significant elevator change - hence the porpoise effect. I've now moved the pushrods in two holes and moved the connector on the elevator out to compensate for the more limited travel. Will see how that works out, I'm hoping it will smooth out elevator control and enable a more stable level flight.

Incidentally I split the elevators onto two channels and mixed in the DX7. I could not get them to center the same with a Y cable (as shipped).

Other notes... if you choose to use the stock motor then CHECK the screws holding to the mount. Mine were hand tight with no blue loctite.
My model had a couple of minor dings on it... from the factory (no way they happened in transit). Disappointing that they would ship it out like that but I'm not surprised.

If anyone has any guidance on ho much the throws should be on this beast (elev, Aile and rudd) I'd appreciate the info.
Jul 30, 2010, 06:19 PM
It's over 9000!!!
Trexid's Avatar
Thank you for posting your flying experience ukgroucho, it was very detailed! I am definitely interested in hearing more from you on your next trials with this beast! I am surprised that your stock motor had no issues after reading about all the problems other people have been having.

I took some pictures and measurements of the stock motor for anyone that is interested in what it looks like and the dimensions for replacement.

My friend has the TR 42-50A 700kv Brushless Outrunner / 720W motor that he hasn't used yet so I'm going to fit it onto the Yak54 tonight probably and see if it has enough clearance on the cowl.

I'll post my results and pictures later. I'll also try to borrow his Watt meter so I can get some readings with the stock prop.

Physical Measurements.

Physical Specs are:

Weight (g) 147.4
Max Current (A) 60 (assuming this spec since the stock ESC is 60A)
Shaft A (mm) 5
Length B (mm) 45
Diameter C (mm) 37
Can Length D (mm) 20
Total Length E (mm) 65

Battery Compartment measurement of the Yak54:

Last edited by Trexid; Aug 02, 2010 at 07:49 PM.
Jul 30, 2010, 10:11 PM
Registered User
ukgroucho's Avatar
I suspect that 720 watts will be too little. Given that a ground test with a pack that had done a flight showed 68 amps, I suspect the stock motor is delivering 1000 watts or more.

To be clear I have done 4 (or 5.. takeoff and land in the same pack for one flight) flights of around 5 mins... but VERY gentle. Yes some rolls and loops and some climbouts but I was mainly trying to sort out the instability in level flight.
In other words.. the motor could still go BOOM .. or not - I really have not pushed it that hard.

On a more positive note. The Yak looks GREAT in the air.. and actually on the ground. I've had a bunch of folks say "NICE... ohh is it foam?" Folks are generally impressed with it (and it does look good). I also had a gas plane flyer comment on how smartly it got off the ground.. you have to qualify that with the fact that I'm a beginner to moderate plane flyer and I was not consciously goosing it as I was worried about possible over-ammping it ( because of the non-linear T response from the ESC).

I also have to say that it makes a great sound as it comes past on low throttle.. you get that lovely err "hum / buzz" that you get from bigger planes.
Jul 30, 2010, 11:29 PM
Registered User
UKGroucho i would definately check your cg and also make sure your ailerons are set perfectly in line with your wings. If you have a little down(hence up) on them your plane will be awfully unstable in flite to. btw excellent flite report, cant wait to get mine up!!
Aug 01, 2010, 12:40 AM
It's over 9000!!!
Trexid's Avatar

build progress

Originally Posted by ukgroucho
I suspect that 720 watts will be too little. Given that a ground test with a pack that had done a flight showed 68 amps, I suspect the stock motor is delivering 1000 watts or more.
Yeah I've actually fitted that 720 watt motor into the cowl and it is snug in there. The diameter on the motor port on the front is definitely exactly 42mm. I'll post a picture below.

I've also got some other photos from my build progress today. After showing my roommate how the 4250 720w motor looked he suggested that I just cut out the black area on the front of the plane so that I can fit a motor with the right amount of power in there. I'm thinking I might just do that so I can get enough thrust to 3D this beaut effectively and not have to worry about smoke, explosions or melting foam if the stock motor were to fail mid flight.

Maybe I can even just shave off enough clearance for what ever motor I end up going with.

I've also added a couple more rare earth magnets to the canopy section to keep it on during aero stunts when that time comes. They are pretty cheap from DX
Last edited by Trexid; Aug 01, 2010 at 01:53 AM. Reason: Grammar and Spelling
Aug 01, 2010, 01:35 AM
Registered User
Well 2moro is d-day!! My new battery is not here yet, but i have a 4s 20c 2200 on hand i will give a try. I opened up the air hole a little more under the cowl for extra cooling. The hole under the cowl is way to small for the amount of air entering the fuslage to exit. I believe that is why canopy pops off. Very good idea to add extra magnet, as the areas for 1 are already in place. Also i opted to change out the spinner to a smaller 1 for more air across the windings.
Aug 01, 2010, 03:05 AM
It's over 9000!!!
Trexid's Avatar
Very cool prop and spinner fatloser! What are the specs of the prop?

Also, could you take a picture of your exhaust modification? I may copy your idea.

Please post your maiden report tomorrow.
Aug 01, 2010, 04:13 AM
Registered User
Very nice guys, are you going to modify/strengthen/replace the flimsy landing gear?
Aug 01, 2010, 04:09 PM
Registered User
Hey Trexid, anxious to hear of the results of the 720W motor. If it works efficiently, pulling verticals etc this might be a good alternative to the stock. What material is the black fins in the front inside of the cowl? Rather than remove it completely can't you use a dremel or something to open it sufficiently to support the larger C4250 800KV motor, or are there other variables involved?

I feel the 720 might be a bit underpowered, but we have to wait and see the results. I'm pleased that we at least have an alternative.

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