Muffler positioning - cowl opening for exhaust pipe

[Peterk]

Originally Posted by BigJohn

Hi Joe, good to hear from you on this. And good to know I am not alone with this issue. Tony T. reports he had to enlarge his opening as well. I'd be curious to get Scott's take on this, as apparently all mufflers or cowls are not created equal. Actually, I am suspecting that there is just not enough bend in some of the muffer pipes. I can see that if the pipe was bent inward just a tad more, it would line up perfectly. I don't suppose there is any way to bend it (stainless) in the field. John

John,

I had a similar problem with my tunnel rubbing on one of the covers. Its easy to cut out a piece of the tunnel and lay in a couple pieces of "indented" glass. Then maybe you wouldn't have to make the pipe hole larger.

[rvbuilder2002]

Originally Posted by BigJohn

So here is what I am going to do:

1. Proceed with installing the cooling shroud inside the cowl.
2. Test install the cowl and reposition the muffler to center the pipe in the existing hole.
3. Check to see if I still have enough clearance for the pipe and springs on the left side.
4. If all clearances look good I torque the mounting nuts and be done.
5. If not enough clearance on left side enlarge the cowl opening and position the muffler for best clearances all around.

I'll let you know how this goes in a few days. Once again, thanks for all the advice. I thnk if I ever get this airplane done I will have to add a plaque giving credit to all the VAF members!

John

Originally Posted by BigJohn

Hi Joe, good to hear from you on this. And good to know I am not alone with this issue. Tony T. reports he had to enlarge his opening as well. I'd be curious to get Scott's take on this, as apparently all mufflers or cowls are not created equal. Actually, I am suspecting that there is just not enough bend in some of the muffer pipes. I can see that if the pipe was bent inward just a tad more, it would line up perfectly. I don't suppose there is any way to bend it (stainless) in the field. John

I mentioned it was designed for the muffler to be centered with the exhaust pipe centered in the opening. The opening location is consistent because it is marked in the mold. There is likely a slight variation with the mufflers. Considering the length of the pipe, a very small change in the angle of it relative to the muffler would move it laterally enough to make it close to the edge of the cowl opening. Enlarging the cowl opening is totally acceptable.
John, you plan sounds like a good way to deal with it.

[MartySantic]

John,

I did the same as you. Centered the muffler as best I could with respect to the engine and then ended up with the pipe exiting the cowl as yours does. I removed a bit of material on one side and the aft side of the hole.

[Jetguy]

Mine was the same way. John did you already install the tunnel shroud on the the outer cowl yet?

John
RV12 N1212K

[N223JH]

There is *no way* my lower cowl fits over the tailpipe. How much did you folks cut off and how did you accomplish this? Will I need a metal cutting band saw or can it be done acceptably with a Sawzall?

[MartySantic]

Originally Posted by N223JH

There is *no way* my lower cowl fits over the tailpipe. How much did you folks cut off and how did you accomplish this? Will I need a metal cutting band saw or can it be done acceptably with a Sawzall?

I did it with a metal cutting blade in the Sawzall with the muffler mounted, then cleaned up the end with a 1" scotchbrite wheel in the die grinder.

[Mich48041]

I put the tailpipe in a vise and used a hacksaw. It cut easily. I cut it at an angle like Larry did and took off about an inch and a half. The extra thrust from the aft facing exhaust might put the RV-12 over the 120 knot speed limit. LOL
Joe

[BigJohn]

.... has a power hacksaw (horizontal bandsaw). We just marked the pipe 4" from the cowl, clamped into the saw, and let it do it's work. Cut it straight across.

I have not mounted the cooling shroud yet, just laid it in the cowl to get an idea of fit.

[Jamesey]

1. I have measured the 4" vertically from the bottom of the cowling to the top of the exhaust pipe. Actually 41/2" on mine. 4" from the cowling following the exhaust slant looks far to close to the bottom of the plane for comfort. No cutting required.
2. One thing I cannot find is mention of the fact that unless the muffler is central the exhaust (L or R) is going to touch the cylinder head cooling hoses. The clearance is minimal anyway. Is there any recommendation on the clearance exhaust pipe to cooling hoses??

Jim D

[John-G]

Originally Posted by Jamesey

One thing I cannot find is mention of the fact that unless the muffler is central the exhaust (L or R) is going to touch the cylinder head cooling hoses. The clearance is minimal anyway. Is there any recommendation on the clearance exhaust pipe to cooling hoses?? Jim D

Jim- My powerplant kit was one of the very first kits shipped after Van's made the change to the exhaust system that moved the muffler a little further from the oil cooler. Kits shipped prior to mine have the exhaust pipe exiting the muffler canted at an aft angle whereas with the new design the mufflers now have an exhaust pipe that exits the muffler pointing straight down. At first I tried to skew the muffler to the left side of the aircraft so the exhaust pipe would fit into the cutout in the lower cowl .... but that begins to interfere with the other hoses already in place.

I resigned to the fact the muffler should be centered even though the cutout scribed in the cowl (which was already cut to the scribe lines) was not quite right. It required making a half moon cut to obtain the necessary clearances as can be seen in the photos below.
https://1.bp.blogspot.com/-w3DOH8djQ...0/DSC01848.JPG

https://1.bp.blogspot.com/-9xVVsXJUa...0/DSC01846.JPG
Happy Building,