"Bass, Jerry" wrote:

I just tried two short (4.5") fishtails with 3/16 slot and 4.31 wide.  86
i/8" holes.  No apparent improvement.  I could hear some Wiz-ing under my
feet, though.  The extensions apparently cause some buzzing.

Jerry Bass

That is interesting. Are the lips on the fish tail vibrating? The P51's have beefed up lips.
Are the holes in the fish tails themselves or in a pipe leading up to the fish tails?

Jerry, are you willing to pop $80 for a Radio Shack sound (db) meter?
If you get one stand 30 feet away along side the engine while running it
up to static RPM and let us know what the RPM and the reading is on the
"slow" A scale (as I recall). I published some numbers back in
December for Tracy's airplane before his bullet muffler failed.

I'll be sure to bring my db meter to Sun & Fun so we can have
a little muffler competition :-)

Paul Lamar

Finn Lassen wrote:

RadioShack has their analog sound level meter for sale at the moment. $30.

Finn

Good news.  Cheap enough for everybody to get one, essential tool if we are going
to make progress on this muffler problem.

Paul Lamar
 
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