Ed Anderson wrote:

 Here are a couple of photos of my under the fuselage exhaust/muffler
system.  The mufflers are two 36" long 3 1/4" dia Bolra Stainless Steel
Straight Throughs (old glass pack except using stainless steel wool instead
of fiberglass).  Mufflers are mounted to the fuselage at each end  using a
piece of rectangular tubing cut in half with the back side against the
fuselage and a curve cut into the other side to accommodate the tube.  A
strap of stainless steel is rivet on one side of the channel wraps under the
tube and is bolted to the other side of the channel.  So only takes two
pieces to mount the tube (not counting the bolts)  two bolts hold each end
to the fuselage (nut plates on hard points inside fuselage).  There is
approx 3/4" between tube and fuselage and I have repeated felt the floor and
it only gets warm on the ground never hot and is cool in the air.  I've
flown with the fuselage painted and no indication the paint suffered.  Total
weight for the mufflers and mounts is 16 lbs.

  At least on my installation there are two things that are less than ideal.
I had not yet installed any uphostery and the viberation of the engine is
transmitted through to the fuselage.  I should have taken more care (rubber
exhaust dounts perhaps?) to insulate the fuselage from the viberation.  With
the Rv-6 being a tin can and without any uphostery it can at times get
noisy.

  The second is that the Borla mufflers mute the high frequency raspy sounds
but it is still quite loud at full throttle although at idle and low power
it does OK.  I suspect that the packing in the Borla mufflers is not quite
as sound absorbing as it could be.  In any case, it does remove the muffler
and heat from under the cowl.

   I have removed the mufflers to try the ole slotted holes in a 18" length
of pipe with the end of the pipe pinched into a fishtail.  This arrangement
is much lighter and will probably not be any lounder.  Good results have
been reported in aviation circles and in a book I have on exhaust system
design.

Ed Anderson

 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.

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