REFLECTOR:TUNE, STRAIGHT EXHAUST PIPES

[Jim Sower]

Pat,
I didn't mean to imply that vibration was the central issue.  I believe "rooster tail"
drag is pretty well documented (I'll try and find you some references).  I am
suggesting that straight back pipes would increase performance and that perhaps if we
focused on the soot-on-prop problem we might find a solution that doesn't have such a
big performance penalty.  Just off the top of my head, extractors would enhance
cooling of a downdraft airplane and should mitigate the exit temps from the cowl).

But in the end, it all turns on what you're willing to give for what you get .... Jim
S.

Pat Shea wrote:

> Jim,
>
> What you would NEVER do is exactly what most, if not
> all, of the XL drivers are doing. Virtually all of the
> pipes (factory stacks, 3-into-1 Y stacks, 6 separate
> pipes...) for the for the lyc or cont 6 cylinders exit
> down out the bottom cowl. No vibrations reported. As
> has been previously discussed, the guy who had the two
> 3-into-1 stacks running out the back couldn't get them
> to work w/ 6 cyl lyc and a three blade prop - heat
> damage to the prop.
>
> Pat
>
> --- Jim Sower <canarder@frontiernet.net> wrote:
> > Tom,
> > By straight "tuned" exhaust pipes do you mean
> > sticking straight
> > out the cowl?  I saw pictures of a Velocity with
> > what appeared
> > to be a pipe from a 3-into-1 header sticking
> > straight out of the
> > cowl.  I would NEVER do that.  Exhaust exiting the
> > airplane that
> > way creates "rooster tail" drag that is the rough
> > equivalent of
> > having the pipe sticking out a foot or two from the
> > airplane.
> > That's a LOT of drag.  I would be inclined to find
> > out if the
> > guy who made the 3-into-1 pipes that went out the
> > back still had
> > his jigs and get some of those.  Shirl Dickey went
> > NUTS for over
> > a year trying to track down some hideous vibration
> > in his
> > E-Racer and found out it was exhaust pulses from the
> > stub pipes
> > from his V-8 routed straight through the cowl going
> > through the
> > prop.
>
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--
Jim Sower ... Destiny's Plaything
Crossville, TN; Chapter 5
Long-EZ N83RT, Velocity N4095T