With all of this talk about exhaust system materials I've got to chip 
in with my concerns. First of all, it's been said here before and I 
agree that an exhaust system failure would be one of the most likely 
things that could happen to one of us flying to ruin our day. Right 
now the first 8 inches or so of my exhaust system consists of (2) 
square four hole flanges with  2 inch dia .049 321 bends. These are 
bent on a 5 or 6 inch radius IIRC.  Pretty tight bend, so I'm concerned 
that the outside of the bend is somewhat thinner than the original 
.049 material.  The rest of the exhaust system will be a slip fit 
over these two pipes.The first couple of inches of the system 
take the most abuse, and the tightness of the bends concerns me. 
Here are a few thoughts:

Ceramic coat the first two pieces of the exhaust system.

Have the first two pieces of the exhaust system made out of something like Inconel.

Make the first two pieces out of .065 [.140] like Ed Anderson's exhaust.

In any case, I am going to build baffling around my exhaust 
system out of .018 304 stainless, with a small NACA duct ducting 
air into it and louvers taking air away from it. The cowl skin 
that is part of this baffle arrangement will also be made from 
the .018 304 stainless with louvers in it. The idea here is to 
isolate the rest of the engine area from the exhaust to keep it 
cooler, and in the event of a hole or crack in the exhasut system , 
the baffling will mitigate the seriousness of the failure, allowing 
more time for an emergency landing.

Just my .02 worth.

Brian Trubee

Fabricate those pieces from flat stock, in .063

Minimum.put in a littleblast

tube for airflow. Never a problem.

Lynn E. Hanover

I've got the facilities to weld this stuff, but I'm not sure exactly 
how to fabricate a tight bend like this out of flat stock. I'll have 
to take a look at it. I will have air cooling the exhaust system.

Brian Trubee

Brian, clarify something for me. Are you going to make square tubes
coming off the square exhaust flanges? Like your originally square
tube tuned muffler? If so I would like to test it on the dyno for noise
and power  if you don't mind.  I think it is a good idea worth testing.
Don't forget to purge the inside of the SS tubes with inert gas when you
are welding them. Keeps the flash down.

Paul Lamar

 
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