Kris' GP Yak-54 buld thread

[Pappy]

Well, now that I've got my CG issue squared away, I thought I'd post a few pics and add some commentary about the build.


This has been a fantastic thread with lots of great advise. I read it through a couple of times before and during the build and incorporated some of the advise and hints given.

All up weight with the CG at 5 5/8" aft of the LE is 15lbs 4.3 oz. Heavier than the ideal but I can work on that later

Gear
Brillelli 46
CH Auto-Advance Ignition
Single cell Li-Po pack
Xoar 21x8 prop
JR / Spektrum
Spektrum DX7 Tx
JR921 with one satelite receiver
JR Data logger
5 JR8611a high torque servos
1 JR821 digital servo
Fromeco
2600mAh Li-Ion receiver battery
Regulator w/ two power outputs
Swtich harness
SWB control horns all around except rudder
Jersey Modeler fueling system

[Pappy]

Landing Gear Reinforcement

I noted some issues with the strength of the langing gear mounts and was proactive.

I fabricated one triangular brace for each side and one beam brace to oppose it. These were epoxied in place with on 2-56 bolt and blind-nut for reinforcement. The install leaves a gap of about 1/16" to allow the gear to flex under normal landing loads but a hard one will land on the brace and distribute the load more efficiently into the structure.

Though I was overall very satisfied with the kit, this issue, the use of large amounts of gasoline-soluble foam, and the stab mounting method - which I'll discuss later - were my only complaints. The plywood they used in this area should have been the higher-strenght 5-ply variety, not the 3-ply light stuff.

[Pappy]

Stabilizer Attachment
I didn't take any photos (all I have is one grainy image from the manual) when I did this but here's my commentary:

The instructions, which are very well done in nearly every way, are surprisingly limited with respect to this one very important step. In effect, after a detailed series of steps to ensure accurate alignment, all it says is basically "apply epoxy and glue in place." The issue is twofold:

First, a fundamental "How do I do that?!?" question:
The stab slides through close-tolerance, airfoil-shaped openings in the fuselage side. How, exactly, do I apply epoxy to the fuse and the stab center section without, a) getting glue all over everything while simultaneously leaving enough in the joint to result in a strong, durable bond, and b) clean-up the excess glue without ruining the alignment?

Second, will the joint between the stab and the 1/8" thick balsa fuselage sides be strong enough to withstand the pounding they're going to get from a gas motor?

I ended up aligning the stab per the instructions and used copious amounts of thin CA to glue it in place. Later, since there's no other way to access the area, I cut open the fuse bottom at the nearest open bay to give me access to the bottom of the fuse-stab joint. Next, I epoxied 2 pieces of 5/8" balsa triangle stock to the interior of the fuselage. Each piece was custom-cut to clear stringers, and since the stab is airfoiled and curves away, I kerfed the forward-half of each piece. There is no way to access the top of the stab joint.

Once the epoxy set, I ended up with an incredibly strong joint that I feel much better about and didn't have to clean up a bunch of smeared epoxy. Since the plane ended up tail heavy, I would recommend going with a slightly smaller stock size but still believe the joint needs to be reinforced.