Here is another fail safe design. The Brits invented it almost
100 years ago. It was used on Brooklands race cars. It is called
the Fishtail muffler.

The flat panels must be beefed up or they will resonate and crack.

The last one is a tuned tangential with Fishtail.

Paul Lamar ...No rotor no motor.


Ed Anderson tried a fish tail muffler on his RV 6 about 5 years back.
Said it disintegrated within a couple of flights. I don't remember
whether he reinforced the panels though.

Mark Wrathall

Ed just squashed the exhaust pipe flat. See the last two jpg's.
That is not a true fish tail muffler as the exit area is reduced
compared to the cross sectional area of the exhaust pipe.
That speeds up the exit air velocity and adds more back pressure.

Also it was not reinforced and one or more designs
had holes drilled near the squashed ends.
Consequently it failed where the pipe was over stressed in the bend and
the flat parts probably resonated.