3D Restoring The Yak

[stangflyer]

Why not split it like we discussed? That way, it is 4 smaller holes, than 2 slots that are long. But, what you could do is get some of out narrow chrome louvers and cover up alot of the slot. I'm putting that trick to work on my EG Extra, since I'm running pipes in it, and trimmed the cowl to fit a DA 120 and 3W 106 stock exhaust system.

So I have taken a lot of time to think about this situation. I worked very hard and suffered many cold days working out of town to get that Red Headed four cylinder. I know I have gotten exasperated at times. And even to the point of nearly giving up on the idea of having that beast up front. I also realize some of you may have been disappointed with my initial reaction and decision to sell the 212 and go a different route. For that I apologize. I had just felt I reached an impasse and really got burned out on trying to figure out what I wanted or "needed" to do. I seriously contemplated splitting the cowl to allow for baffling and ease of exhaust installation. I had also thought I could stuff some Greeves pipes up the tunnel and get away with it. Problem for me in splitting the cowl is this. I feel comfortable doing a rebuild or restore on an airframe. But when it comes to a 180 dollar cowl and splitting it....yeah, not so much. However, here is what I have come up with. And I will be the first to admit if I have errored. Which it turns out I have.

There is physically zero possibility of me putting "ANY" type of can, muffler or pipe down the tunnel of the Yak simply because there just simply is no clearance available.

As you can all see, the headers are a 2.5" drop header. The shortest drop offered by 3w. The end of the header leaves me about 1/4" to play with at the can tunnel entrance. Which is far from enough for any cans/pipes available.

Unless......I have special headers built for the 212. Which, I may end up doing. I spoke with Kevin from Jtec. He has told me that what ever I need, they will do their best to help me figure out a way to make it work. I did some measuring again inside the cowl and I really don't know how I missed it. (This is the part where I admit my error)

The mounting offset of the JA mufflers (E) is .50 inches. The chamber diameter (B) is 2.0 inches. The down stack (C) is 4.0 inches. For a total of 6.5 inches from the cylinders of the motor. Inside...and I measured three times with a tape this time, is precisely 6.75 inches. Hence, the JA mufflers will "INDEED" fit inside the big round cowl of the Yak. Without cutting one bit of the bottom of it out as I feared. In fact, the two rear cylinder stacks will drop right down the air exit in the bottom of the cowl. Which needs to be removed for airflow anyway. The two front will need to have two 1.25" diameter holes drilled in the cowl and then short extensions added to exit the exhaust. "THIS", this I can deal with. Along with this design, I have come up with a really easy and straight forward way of baffling the motor "WITHOUT" having to split the cowl. Whew....been sweating that one.

So my options are now reduced to a simple decision. Do I have Jtec build me some custom headers to give me the clearance for Greeves pipes, Like I really really want? (That motor just wails on Greeves Pipes) I am sure they will with the new Slimline offered by DA as well. I still don't believe there will ever be any way of getting enough clearance to put a standard muffler down the tunnel. Or, do I simply buy the JA mufflers from Aircraft International and be done with it? I have weighed also the consequences of the JA mufflers verses the Greeves pipes. The JA mufflers are about 13.75 ounces for a set. (According to AI's website) Bringing the total weight "ON" the nose to a whopping 27.50 ounces. (The extra noise from the four stacks won't be too unbearable.) That is an extra pound and a half I do not want up there. While the Greeves pipes weigh about the same, maybe a tick less...the weight will be more evenly distributed through the CG span. I'm leaning no particular direction at this time. I sometimes get really anal about making the best decision. Maybe I overthink things too much. Afterall, it's just a toy plane right?

So what do you all think? What are your opinions? I am definite about one thing for sure. I will not sell that in which I worked so hard to achieve. Again, I apologize to all those that have been so loyal and diligent in following this build/restore thread. I just want it right, clean and to be what I was hoping for.

 

[HRRC Flyer]

Hey Rob,

First of all, you don't have to apologize for ANYTHING. It is your plane and believe me when I tell you, if I had put the time and investment into an airplane like this, I would be more anal about things than you will ever be. . . . . . Your BIG Yak is going to be INCREDIBLE wit that 212 bolted to the firewall. I also think after you fly it for the first time, you will forget ALL about the trials and tribulations of your journey to this point. . . . . . After watching what @49dimes has done with that awesome muffler for his DA70, I wonder if it would be possible to take the headers you have and make a 4 into 1 muffler. It would have to be a fairly good size muffler, but I think it would be less weight than the four individual stock mufflers.

 

[WMcNabb]

From a head on view, is there enough room for a Pitts style muffler? Borrowing on David's suggestion, 4 into 2, with your headers, into a muffler can, and out?

 

[stangflyer]

Hey Rob,

First of all, you don't have to apologize for ANYTHING. It is your plane and believe me when I tell you, if I had put the time and investment into an airplane like this, I would be more anal about things than you will ever be. . . . . . Your BIG Yak is going to be INCREDIBLE wit that 212 bolted to the firewall. I also think after you fly it for the first time, you will forget ALL about the trials and tribulations of your journey to this point. . . . . . After watching what @49dimes has done with that awesome muffler for his DA70, I wonder if it would be possible to take the headers you have and make a 4 into 1 muffler. It would have to be a fairly good size muffler, but I think it would be less weight than the four individual stock mufflers.

From a head on view, is there enough room for a Pitts style muffler? Borrowing on David's suggestion, 4 into 2, with your headers, into a muffler can, and out?

Actually there is. And as I was attempting to lay down last night, that very thought crossed my mind. Would make life pretty simple and would look hella cool. I need to call Jtec back.

 

[49dimes]

Jtec to the RESCUE! Dial 4-n-2.

 

[BillVargas]

Go stock mufflers. Fly and have fun.

 

[stangflyer]

Go stock mufflers. Fly and have fun.

Heard you have a set of stock mufflers for the 212. Interested in selling them?

 

[stangflyer]

Ah ha!!! Went back to the drawing board and came up with a new resolution. Decisions, decisions, decisions! Admittedly too anal on the Yak. But!!! In my defense, I want it clean, functional, quiet and most of all my design.
Sneak peak:

This is an extremely trial fit.

 

[stangflyer]

So I now have the throttle servo in place and set up. I really don't think I've ever had a linkage as linear as this one. With each little incremental movement of the gas pedal stick, the linkage on the twin Tillotson carbs kept perfect time and equal movement.

Now with the test exhaust system in place, ignition batteries temp'd in the fuse, temporary fuel tank inside, (new TDRC tank due to arrive in the next couple of days) and the Falcon 34x12 torqued on the front hub...the moment for a test run is rapidly approaching. Weather permitting, I will fuel the big Yakster up and lay my hands generously upon that red headed beauty. Looking forward to tomorrow for sure.

 

[pawnshopmike]

Looking good bro. That's a pretty sweet setup.