Tangential muffler and fishtail muffler

I had completely forgotten about that old fish mouth drawing. It has
a major problem that I was unaware of at the time in that the exhaust
ports can "see" the opening into the fish mouth. Exhaust gases,
instead of tumbling as we would want in a tangential, will dive
straight into that large 3" diameter exhaust pipe. Lots of noise and
heavy pulses. A possible solution might be to extend the 3 inch pipe
much further into the muffler so that the exhaust gases by pass it.
Maybe extend the exhaust ports too. Also, I think a six inch
muffler might work better. Jerry

On Jan 15, 2009, at 4:23 PM, Rotary Engine wrote:

Hello Paul,

I've moved on to an exhaust system, now. I live on a lake surrounded by
neighbors so my operating area is somewhat noise sensitive. I like the
combination of the tangential muffler and a fishtail muffler that you
show on your site. They seem very simple to construct. I've attached a
drawing to illustrate how they could be installed in my airplane. I
could only get 8" on the fishtail rather than the 16" you show. I might
be able to get a few more inches out of it.

Q1: How does this look to you? Do I need all 16", or do I adjust the
exit area?

Q2: You show the exit to be 9.5" x 3/8". The area of a 3" pipe is closer
to 9.5" x 3/4" or about twice what you are calling out. What's happening
there with the smaller opening?

Thanks,

Sandy McNabb
Renesis in a Glass Goose

Looks pretty good.
Q2 it speeds up the exhaust air and provides a bit of thrust.
Sort of a poor man's turbo compounding. Worth about 400 HP
on the P51 at 400 MPH. Not much HP at 100 MPH however.
In your case probably not a good idea for a slow airplane.

Great minds work in similar fashion. I was just thinking about
that for the side mounted rad in the RV8 mount I just completed.
It too will fit in the cowl under the engine. The exhaust can then
be made to extract air through the cooling system.

The thing about fish tails is they have to be beefed up because
the flat panels are resonated by the exhaust pulses.
Figure on .062 inch thick 321 SS with stiffening ribs welded
on here and there.

All and all a positive thing.

Paul Lamar