I know have 260 1/8" dia holes in a 36" length of 4' tubing.

One

for

each exhaust.  The fishtail is squeezed down to 1/4" slot.  So we

will

see

if it lives when next I fly.

Ed

Are you beefing up your fish tails Ed?

Paul Lamar

I have not done so as yet, Paul.

    Not having any welding equipment, I just fashioned two more

"expendable"

fishtails and stuck them on the end of 4 foot length of tubing.  That

puts

them over twice the distance from the exhaust port as the previous set.
Will be interesting to see if they live any longer or not.

   When I get back from Sun & Fun I will see about getting some nicer
looking fishtails crafted and reinforced.  I was busy creating brackets

to

hang the pipes from and getting other things ready for S&F.

   See attached photo of the cracks in the 2" 0.035 SS pipe.  The hole

sizes

are 5/16" dia but apparently did little to dissipate the energy of the
exhaust pulse.

Ed

A fish tail is not a true fish tail unless the area of the slot is the

same

as the area of the round pipe. Merely squishing the pipe does not meet
this criteria. We need to make this clear so we all know what we are

talking

about. If it is a true fish tail it is
supposed to reduce the noise all by itself. No holes needed. It does

however

need to be beefed up to deal with the sonic induced vibrations.

Paul Lamar

Well, the first one certainly did not meet that criteria.  The slot was 1/8"
and approx 3.5" wide so nowhere near the 3.14 sq in of the 2" dia tube.
Even with a 1/2" slot at 3" wide it is only 1/2 of the needed area.

However, I believe the 260 1/8" holes, area = 3.19 sq inch may help
dissipate the shock wave before it gets to the "quishtail" (as opposed to
theoretical Fishtail {:>).)  Plan on flying tomorrow to see.

Best Regards

Ed

I like that Ed. "squishtail" One theoretical advantage of the true fish tail
is it generates a bit of thrust. As I recall about 100 HP worth at 400 MPH 
in the P51.

Paul Lamar
 
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