REFLECTOR: Exhaust noise

[nmflyer1 at aol.com]

Scott, 


My first plans were to put the exhaust out the aft cowl opening. Even though the Prop guy said it was OK, I just didn't like the proximity to the prop. I ended up running mine out the bottom near the very back of the cowl (pics on Facebook). 
How big is the diameter of your pipes? The other thing I did to mine is add some stainless steel cones to the inside of the pipe exit. 
I tried it with, and without them, and it definitely takes some of the edge off, but I didn't measure it, just listened. 
Here is the link to what I used: 


http://www.summitracing.com/parts/DTC-772-32520/ 


Kurt 



-----Original Message-----
From: Scott Derrick <scott at tnstaafl.net>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Sent: Fri, Jul 13, 2012 4:25 pm
Subject: Re: REFLECTOR: Exhaust noise


The tips of my pipes are cut at an angle see pic lowercowlremovedleft.jpg

Clinton at Custom Aircraft who made my exhaust recommends something like 
the second image. He says the bend will noticeably reduce the noise and 
have very little effect on back pressure.  It also will speed up the 
plane. That exhaust plume sticking straight out the bottom of the plane 
is like a huge stick.

It appears that more and more airports are going to be monitoring for 
noise. Which means we need an effective short pipe noise limiter or 
reducer.  Possibly modeled after a gun silencer, which I've heard 
reduces the noise as much as 60db!

Scott




-------- Original Message --------
Subject: Re: REFLECTOR: Exhaust noise
From: David Rene Dugas <renedugas at gmail.com>
To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
Date: 07/13/2012 01:48 PM

> Cutting the end of the exhaust stack at an angle on one half of the end so it 
is not square decreases the noise.  So half of the opening is at 90 degrees with 
the pipe and the other half is at some angle of at least 15 degrees off.  This 
is not optimal for tuned exhaust and power recovery but much less noisy.
>
>
>
>
> On Jul 13, 2012, at 11:17 AM, Scott Derrick wrote:
>
>> I'm using a Custom Aircraft exhaust which is fairly similar to the factory 
supplied exhaust. Basically a 3 into 1 stack for each side with the outlet pipe 
pointing straight down.  The factory exhaust joins  the 3 together under the 
forward cylinder. The Custom exhaust joins them under the middle cylinder.
>>
>> I got a noise ticket(warning) in the mail from the KSMO operating authority 
last month.  They have a 95db limit that they somehow monitor.  They said I put 
out 95.1 db on one of my departures that day.
>>
>> Anybody else experience this? Any solutions?
>>
>> Scott
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