HobbyKing Yak55 44.4" EP (new thread) - RC Groups
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Nov 10, 2012, 02:57 PM
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Build Log

HobbyKing Yak55 44.4" EP (new thread)

Hello all!

SkyCadet here. Looking at building a new HobbyKing Yak55 here in the upcoming few weeks. Just waiting for it to arrive!

Meanwhile, I plan to share here and on my blog the details of my build. I welcome all memeber who have an interest in or have currently this seemingly neat 3D-capable plane!

Here are the specs of HK's website...

Wing span: 44.4in (1120mm)
Length: 40in (1000mm)
Flying Weight: 32-35oz (about 900g)
Motor: 35-XXC 1100kv
Battery: 2200mah 3s 25C Lipoly
ESC: 40~50Amp
Servo: 4 x 15~20G park size

More to come shortly!

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Nov 10, 2012, 03:02 PM
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Power system for my Yak55...

I plan to use an RCTimer A3536-6 1250Kv motor. It fits into the firewall (mounting apparently with this unit is required to be internal/reversed with the can BEHIND the firewall.

3S with a Turnigy 45A ESC, 4xdigital servos (pics to come when arrive).

Nov 13, 2012, 10:35 AM
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Just waiting for the goodies!

Well, I expect the packages to arrive either the end of this week, or early next. Hopefully, I am still in pre-Christmas postal mode here in Canada!

Nov 15, 2012, 11:43 AM
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Yak goodies due to arrive either tomorrow or early next week!

Well I am very excited by the prospect of getting this plane into build mode!

I ordered a SECOND unit to have spare parts standing by, and also in the event the first unit has any issues.

Will shoot pix of the newly-arrived package when I get it!


Nov 16, 2012, 01:01 PM
The wind caused that!!
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that plane looks nice. been eyeballing this one myself. let us know what you think of it.
Nov 16, 2012, 02:02 PM
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Will do! It just arrived yesterday. On my blog I took some shots of the wings and cowling. Will do up more as the build progresses, here and on my blog.


PS - WORTH the money - nice model.
Nov 16, 2012, 02:30 PM
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First impressions...

The YAK55 arrived yesterday!

It came reasonably well-packed and arrived with no damage, save a very minor chip on the front of the fiberglass cowl - an easy fix.

IMO, a VERY nicely made product. Well put-together, all hardware is included.

Minor issues: manual is pretty plain, with poorly included pix, however, if one has worked on these models before (balsa ARFs), the construction is rather intuitive.

The slots for servos are marked, but due to the color of the covering in places, are a bit tricky to find. not too bad though... Covering is excellent, and fit of control surfaces on my sample is superb. I'm going to have to custom-fit some ply blocks ot mount my digital HD1810 servos (HKing) in order to fit them, but it's not a big deal. I'll also be color-matching the wood to the underside of the wings (see pic).

I also plan, once my motor/spinner come in from eBay (RCTimer motor, and 2" spinner), I'll be able to do up a custom vane system like the scale YAKs I've seen using a spare 46mm filter ring (photographic) and aluminum 1/8"x1/4" streamline tubing for detailing. The firewall will be blackened, and re-inforced using carbon rod (1/8") and the inner mains gear strut mount will also be reinforced.

More to come!

Nov 18, 2012, 01:44 AM
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Servo blocks fit!!!

Just finished epoxying the servo block inserts to fit my servos to the plane. Pix below. also have my cowling vanes cut and need to mount them. Next up, inserting the elevator wire, and make the slots for the CA hinges a bit larger for my slightly beefier than stock CA hinges.

Nov 20, 2012, 02:07 AM
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Horizontal stabilizer done, canopy detailing...

My horizontal stab has been affixed to the fuselage. It lined up nicely, but had a slight horizontal mis-alignment. I reclamped the fuse, top and bottom and the stab aligned nicely. Double checked with the wings test-fitted to make sure.

Detailed the canopy with 3M black vinyl. Cut two 4mm wide pieces to fit over the bubble to make look more scale. Also, I have on order a CF gear strut for the Yak! It will look more scale and is better suited to this model. HobbyKing HK280-148 --- this is a 15cc size gear, but the specs are perfect for this model. It will have a 3" wider wheel base on the mains, and the height will be around 1.3-1.4" taller than the kit gear. MUCH better for landing and better for my 11x7x3-blade propeller clearance.

Pix of canopy and CF gear below, tail is still drying - used Weldbon wood glue for the tail, as the CA or epoxy may not have been as well covered into the wood. I did this with my Pitts 12 15e tail and it worked VERY well.

Last edited by SkyCadet; Nov 20, 2012 at 02:13 AM.
Nov 24, 2012, 11:54 AM
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Starting to look like a YAK!

Well, we've got the tail section done, the cowling trimmed, the firewall, painted and reinforced, and the canopy done!

Waiting on the motor and CF mains gear to arrive, so I am finishing th eailerons today, and then mounting the servos and control horns. I've taken a few shots with the cowling on the unit, with it over the firewall. There's lots of airflow, so cooling will be a non-issue.

Something occured when test-fitting the cowling: the firewall is LONG - about 4"/100mm. the cowl as the kit stock arrangement suggests, sits on four screws, all in a ~60 degree angle, about 30 degrees from horizontal. This leaves nothing holding the cowl on at the top and bottom, save ~1/4" or so of firewall to the front fuselage! It also won't withstand much damage insofar as a noseover, or inadvertent bump during transport, IMO!

I will be placing two blocks top and bottom to assist in guiding the cowl into position, and use some CF rod on the motor mount to act as both guides and supports for the firewall. Otherwise, I think that this plane will have cowl issues.

My front cowl on the intake is planning to have a ring of 1/8"x1/4" aluminum streamline to make the plane look like scale, but I'll have to wait until the motor gets here so I can test fit everything first to adjust for cowl clearance and prop location on the motor shaft.

There is no specific location for a radio tray in the plans! I thought that sort of odd... So, I made a piece to fit on the bottom of the plane next to the battery tray to fit the RX and tie off any servos wires.

More pics and info to come during the build!


Other than this issue, I think that the kit is really nice.
Nov 27, 2012, 02:13 AM
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Starting to look like a Yak!

Well, I finished the Aileron hinges, and am ready to mount the servos. Still waiting on the motor and spinner.

Something I realized when putting the wings back on for a look at the plane is that this model is bigger than I thought! Nice!

However, the wings (and manual also does not cover this!) don't go onto the plane with any accomodation for the servo wires! So, I'll put in a 1/32" ply insert and cut some small slots large enough to permit this. I have to add the radio tray as well, and also some mains reinforcements in the fuselage anyway, so I can do all the inner airframe mods in one go. Then, servos and horns.

The kit looks pretty sweet so far, I am having fun getting this all spec'd out...

Pix below...

Last edited by SkyCadet; Nov 27, 2012 at 01:38 PM.
Nov 29, 2012, 12:41 AM
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Servos installed, RX tray and fuselage innersides done!

I finished installing the servos, into both the wings and tail. Ran a 12" extension on the servos in the tail, and will be using HK servo wire clips on the wings so that a Y harness can affix the wing servo connections.

Also paint-tinted the outer fuselage front and epoxied the RX tray onto the rear runner behind the battery tray.

I used CF rod/1" balsa blocks on the mains for reinforcement, pictures shown below... Now, just motor, setting the horn throws, and then connecting the electronics!

Sky Cadet
Dec 04, 2012, 02:13 PM
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Motor mounted, ESC wired up, test fit cowl, and gear done!

Well, My gear (CF) and motor arrived in the mail late on Friday.

This weekend, I installed the motor, wired the ESC to be ready, and fnished the mains CF Struts, plus did a test fitting of the cowl, vane, and prop. PERFECT!

Everything is coming together nicely. See pictures below...

I am still awaiting the spinner, but otherwise, it's now just a few hours away from being ready to fly...

Only control horns, thorw settings, and final cowl install and electronics affixing in the plane to be done!

Dec 06, 2012, 12:13 PM
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Servos done, final assmebly underway!

I finished my servos and have everything pretty much ready to assemble. I still have to finish mounting the cowling, and the radio/electronics inside the plane, but it's off to the final stretch!

I shot two pix of the plane without the wings attached (easier to work on electronics placement without them on there for now), and have the cowling test fit one final time with the prop. It loos great with the vanes in there!

My tests of the motor system (an A3536-6 or 1250Kv/500W RCtimer unit with MAS 11x7x3 propeller, 45A Turnigy ESC) running 3S was as follows:

WOT: 325Wp, 37Ap; 50%: 130-140W, ~11.5A nominal
(battery had been test run for 1 minute over some settings prior to WOT, so normally, this would be in the 360-380W range on a full battery)

Since my ESC can handle 45A nominal, and over 55 peak, I am fine. Also the motor is rated at 500W, so the extra 100-120W of tolerance is most likely fine too. I can even prop up to a 12x6x3 before getting into the red zone, apparently.

I'll run it like this for now, to see how she flies. It is certainly in the regime I was targeting fo rwiht this power system...


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