Mailing List Message #65374
From: Andrew Martin <>
Subject: Re: [FlyRotary] Re: Mufflers
Date: Wed, 20 Nov 2019 10:07:52 +0800
To: Rotary motors in aircraft <>
Matt, Mine is not like Gary's final design, he was striving for a silent exhaust, where he combined different ideas. whereas I'm ok with just not too loud, and I think the original Schwarzpipe design is good and easy to make. Just seems hard for people to visualize how it works.
Finn. Yours looks like it would be very easy to experiment with, just add more holes and an outer pipe to your perforated section of pipe, both rear ends blocked off, with outlet only at front end. I reckon you could then do away with your muffler and save some weight.

On Wed, Nov 20, 2019 at 1:30 AM Matt Boiteau <> wrote:
Disregard the previous email. I was still reading the whole thread. From Gary's thread, I attached the only picture that shows the Rotary.

Above link breaks down the install Gary did on a rototiller. Basically the header pipes enter a larger pipe (4inch in our case) from the side, close to the top or bottom (not pointed to the middle) so exhaust swirls around. Inside in the middle, is a perforated smaller pipe (2.5inch) that exits out one end. You want the holes to double the volume of exit pipe. The start of the perforated pipe is capped off, so the gasses are forced to enter through the small holes. The end pipe is up to your design. I'll probably go back to the coax style, or maybe swiss if I need to quite it down even more.

The 3d picture is one from Paul's newsletter. I think they had an air opening at the front to try to decrease temperatures. Not sure, but basically similar. Andrew, you said you had the inlet and outlet on the same end, how does that look ?

My first problem was I didn't cap off both ends of the perforated pipe. I like the muffler idea using the stock manifold. Sadly I won't be back for 2 months to the plane to weld new exhaust. Now to go find some 321 SS piping in the meanwhile.

- Matt Boiteau

On 2019-11-19 10:37:04 AM, Matt Boiteau <> wrote:

Here is the picture from Andrew's email. 

My exhaust is stupid loud. I've tried a few things which didn't work. Getting noise complaints around the airport while testing.

Just reading this Gary Schwarz's link, looks promising. Andrew, did you fit yours inside the cowl? I'm surprised 5mm endplates are holding up.

- Matt Boiteau

On 2019-11-19 12:57:36 AM, Andrew Martin <> wrote:

Kelly, I would if I had some, really did not expect it to work as I deviated from the design a bit. Will be back at airport on weekend to take photo, too late for construction photo. But nothing to it.

I read about the idea by Gary Schwarz in this thread, post #7 , post #58 for his testing and post #142 sums up his findings.
Someone on here may know him as he was doing it for a rotary. Mine is much shorter than his drawing below due to space constraints but the theory works.
edit: Ahh!!! deleted his picture as too big to post. it is in his post #7 mentioned above though.

Archive and UnSub:
Subscribe (FEED) Subscribe (DIGEST) Subscribe (INDEX) Unsubscribe Mail to Listmaster