Paul, I have Chris Harris of planexhaust rebuilding my exhaust system and he called me
 to ask if this muffler of yours actually worked?? I told him that Paul Lamar designed it
 and he was suddenly interested. I have already sent him the plan, but he wanted your
 official design and if possible the Y tube recording of the muffler in action. Can you
 forward both to him at sales@planexhaust.net please. He says he either knows you or has
 a mate that knows you very well, so he can ask you any questions direct which stops me
 from any misinterpretation. Not only that but you are all awake 8 hours before me here in
 Oz, so by the time I get to ring him tomorrow he should know all.

 Thanks Paul, Neil.

 It amazed me it worked :)

 I was thinking about it today. If we can get 10 pounds
 of thrust at 300 feet per second (204 MPH) 3000 foot pound
 per second HP or 5.45 HP is for free :) However most of the benefit
 I suspect is lower back pressure.

 That is not much increase in speed.

 I hope you are still flying while the new muffler is being made.

 I have got to get over there and go for ride when
 I get this turbo compound project done.

 My AN24 SS hose coupling idea did not work out. The SS wrinkled at about
 30 foot pounds.

 The rotary accelerates rapidly when it starts.
 It goes from cranking rpm to 2000 in flash.
 That could put a lot of transient torque load on the coupling
 due to the power recovery turbine inertia so I figure I need about
 100 foot pounds.

 I am going to try two one inch steering gear u-joints back to back.

 Paul Lamar
 --

I am finishing the bottom skin on my RV-4 with this exhaust system in mind. Can anyone suggest how to attach the muffler to the airframe after it leaves the engine compartment? Can I rivet brackets to the bottom skin, or should I grab one or more of the bulkheads and the skin?

How many attach points, and at what positions? Thanks for the help.

David Walker

About a 1/2 a foot apart. Use a U shaped outer tube with a .5 inch wide flange.
It will have to be contoured to fit the curved bottom skin. Continue it back to the trailing edge
of the wing. Make the outer U tube out of .032" thick  304 SS. The top can be flat .032" thick  SS sheet with a
layer of fiber frax between it and the bottom skin. Use 6-32 or 8-32 SS riv nuts to hold it to the bottom skin about
a 1/2 a foot or so apart.

Here are some pictures of mine.

Paul Lamar





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