Originally Posted by kbailey45us

Yep those Yak 55's are so ugly I almost had to have one.

If you have ever flown one,you would SEE how beautiful they really are.

Going to be building a lot tomorrow on my yak 54. Do you guys find the 2 degrees of right thrust to be enough or does it need more? I may just start with two and go from there to keep it simple. The way I fly I probably wouldn't know the difference lol. Other than the firewall everything else is just radio and setup. May be able to get it done tomorrow or close anyways.

Oh yea I forgot to post my findings. My Yak -54 has 3 deg rt thrust and found it could use a little more. I just added a washer under my left side standoffs to give it more. I will be flying it in the morning and let you know the results. I'm now at just shy of 4 deg. 3.85 is what I'm coming up with.

I had a surprise with the M55 Yak.It is nose heavy to the point it takes the a123 battery resting on the rear stab to balance it to the recommended CG.
If I mount two 7955's under the rear stab it balances to the recommended CG.So I am going to use a push pull set up.I have read that it does come out nose heavy,but this is a little much.I am using a heavier engine than it was design for but not by that much for a GP61.

I'm curious what test you guys are using to determine adequate right thrust. four degrees seems a bit much.

Well its official. I will take gluing hinges over putting a firewall on any day. This thing is supposed to be designed for a dle55. I've got one and measured and even it won't fit without cutting. I'm using a gp61

I had to cut my sidewalls using the GP61,but mine is a M55 Yak don't know if there is a difference?
I think you will have to set the firewall back using most any engine.Most engines are set close to a 6-3/4 to 7" length.
I remove 5/8" from the sidewalls and set my firewall flush at that point.That gave me 1" prop to cowl clearance.The plans called for a 1/4",but I like more on a Yak.
Its not that hard just a pain in the ass, do it and get past it.It has it good and bad points in setting the firewall distance.

Well I got it done. Whether it's right or not is still up in the air lol. Gotta go get some bolts tomorrow to mount engine. The stand offs I have aren't threaded they are straight through so I gotta find some 3 inch bolts. I did notice their isn't a lot of room in this plane to move things around without adding some wood. I may need to mount battery more rearward considering the 61 and pitts muffler. One thing that may help me out is I used savox 1230s and they are a little heavier than most standard servos. I didn't cut the sidewalls yet just bottom and tristock. May end up taking a little off later.

Well one more thing to spend too much time on. The firewall is drilled in the premarked spotbut the left hole is so cles to the bolt heads that hold it on I am going to have to trim the side of stand off so it clears. Do not think about this stuff when designing a plane? This is the kind of things that makes the 10 hour assembly go to 40 hours lol

A die grinder will make short work of aluminum standoffs.

I got my stand offs ready and low and behold ran into another problem. The casing on the motor wont let me use the 1/4 inch bolts because their isnt enough room for the bolt heads on the bottom for them to slide all the way in. Rather than grind on the case I decided to call it a day and ordered some 5mm bolts. There isnt anywhere around here to get 5mm by 70mm bolts. I wish everything would just use the metric system it is so much easier and would make the rc hobby less stressful when needing something and being able to find it. Once I get the motor mounted and cowl cut should be done fairly fast. Probably gonna have the manual choke come out the side of fuse on the gp61. Been getting a little ill at this whole project so I just stopped for a few. May put the switch in and stuff but until I get the motor mounted Im at a standstill pretty much, Time to drink some beer and hop on the lawnmower.

I figured I would post what I was running in to. One of the bolts, well two really but I can work with the other one, I have no idea how I am going to get it in. Basically, when inverted, the two bottom bolts head wont clear the casing. On one side I can barely grind the bolt head and tighten on the nut side and be fine. On the other side the nut is too close to the firewall mounting bolt to do that. The hole on the mounting flange goes almost all the way to the casing. I hate to grind all the way around the the bolt head to tighten. I had to use 1/4 in bolts because the 6mm have even bigger heads. My firewall has already been drilled with 1/4 holes and I hate to have to redo that and even then it might not work out all that good. Also as I said before the nut and washer on the inside is going to hit the "L" bracket that holds the firewall. I have no idea why this motor is made this way. Any help would be great. thanks

Edit: Well after looking at my post and pics i think the best thing I can do is remove that one firewall bolt and move it enough to where the nut will clear enough to be tightened. Let me know if that sounds good or if you have another opinion. Thanks

Here is mine just finish.One a123 battery ended up on the rudder pull-pull tray for the correct CG.Along with moving two rudder servos to the rear.
Now how can you call a plane that looks so good ugly.LOL

just a note on set with rear mounted servos. at neutral, the arm should be perpendicular to the control rod, not to the servo.

I always try to set them up at full deflection the control rod is level with the servo, that's the correct way.
None of the control surfaces were at neutral when taking pictures.But you probably didn't think of that.