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Looks like it may have some merit in muting the exhaust a bit. The problem I had when experimenting with exhaust was that anything which presented a flat surface to the exhaust pulse simply did not live long. Even 1/8" thick stainless steel plates were destroyed. Now a cone or some shape that deflected rather than brute force tried to break up the exhaust pulse may well survive quite a bit longer.
I finally got tired to almost having success - the disks fabricated to look like a pin wheel came the closest to being successful. It really muted the exhaust, but the disks soon broke loose and beginning to spin like a turbine wheel in that exhaust and like a wind milling prop resisted the exhaust flow. I ended up with EGT 150-200 deg higher than normal and rpm limited to 6000.
The first (ignored) clue that the disks were spinning, was when I was told by a hangar mate that on take off it sounded like I had a turbine under the cowl. Yeah, Yeah a poor man's turbine - a rotary, well it turned out he was right, it sounded like a turbine because the exhaust flow was being broken up by the spinning discs (and they were really spinning) at a very high rpm.
So I am now flying with HushPower II mufflers and I'll leave further experimenting with exhaust to a new spirit {:>)
ED
----- Original Message ----- From: "Charlie England" <ceengland@bellsouth.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, November 25, 2007 10:16 PM
Subject: [FlyRotary] exhausting work
While re-perusing an old article to answer a question on another list, I noticed something about coanda nozzles that might be of interest to rotary fans. It mentions that while there is no performance increase, it does seem to 'mellow' the exhaust sound. I wonder if this might survive the rotary pulses better than other pulse breaking techniques & help take the edge off the rotary bark. (Although it might be a moot point if everyone adopts Dennis Haverlauh's system for the Renesis.)
http://cafefoundation.org/v2/pdf_cafe_reports/EPG%20PART%20IV.pdf
Charlie
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