I had an idea based on the simple tangential muffler to maybe drop a
few more dBs. I like the simplicity and compactness of the design
even if it's not the most effective at making a rotary quiet. Summit
and Jegs both carry an affordable selection of stainless exhaust
bends. I thought it might look kinda cool having an exhaust bend
come out the side of the cowling like a turboprop would have. If the
exit was made from a 3" bend and perforated with a drill press, it
could be fitted with a 4" outer sleeve and packed with high heat
muffler packing materials acting as a glass pack or resonator. The
muffler packing would also slightly reduce the outer sleeve
temperature protecting the cowling from high heat. If anyone is
interested I'll try to post some concept sketches. Waiting to hear
back from a guy on craigslist who is selling a 13B with transmission
so i can build a prototype.
Chad Peterson
The trouble with rotary mufflers in aircraft heavy duty service is
they melt :)
This is the way to go as it is both cooled and it adds a bit of
thrust like the
P51 cooling system.
http://www.rotaryeng.net/exhaust.html
<http://www.rotaryeng.net/exhaust.html>
Paul Lamar
Unfortunately, building a wooden aircraft, i just can't use the coax
underneath the fuselage. Compactness is my main priority, and since i
will be peripheral porting i will still be able to reach my goal of
190-210 with a tangential, although noise reduction will not be as good.
Race applications have had good results with 316 and 321 stainless and
they run 4000+ rpm higher than i would need for aircraft use. Inconel,
while much more expensive is available too.
Getting a thrust vector and effective sound attenuation at the same time
is awesome, but the coax just isn't right for my 4 place wooden jodel
variant.
Chad Peterson
It is not the RPM but the sustained high power for aircraft applications.
Best use inconel to be safe.
Paul Lamar
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