REFLECTOR: turning the exhaust exit

Velocity velocityxl at fastmail.fm
Fri Nov 23 09:21:14 CST 2012


Thanks for the picture I like what you have done. I will try it also . 
One reason I keep telling my self
why I have not painted my plane yet still experimenting!

Ron
On 11/23/2012 9:11 AM, Scott Derrick wrote:
> It does work,
>
> I think I increased my top end by 3-5 knots by adding the 90's to my 
> exhaust. I have 3-into-1's, one on each side.  See attached photo.
>
> The ramps in front of the exhaust exit on the cowl were to prevent air 
> from entering the lower cowling through the two holes(port & 
> starboard) and thus reduce my cooling by raising the ambient lower 
> cowl pressure, they also worked well.
>
> I don;t think you loose 10 knots by straight down exhaust, but you do 
> loose something.
>
> Scott
>
> -------- Original Message --------
> Subject: Re: REFLECTOR: Reflector Digest, Vol 92, Issue 64
> From: Brian Michalk <michalk at awpi.com>
> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> Date: 11/23/2012 07:27 AM
>> I've heard the 90 degree exhaust so many times, but I can't help 
>> think that its an old wives tale.  Does anyone have any research that 
>> describes the phenomena?
>>
>> Logically, it doesn't make any sense to me that it should be a 
>> problem with drag.
>>
>> On 11/22/2012 09:40 AM, Dave T Nelson wrote:
>>>
>>> Hi Richard.  Your friend is exactly right - you do need to have slip 
>>> joints of some type on each cylinder of your exhaust.  You should 
>>> also check to make sure that they are free to move - I do that as a 
>>> part of my preflight.  If you don't, any exhaust will eventually 
>>> fail, and it can go through the prop.  That's not true of just "in 
>>> the cowl" exhaust systems - that's true of _every_ exhaust system. 
>>>  A safety of some type is also a requirement of any exhaust on a 
>>> pusher.  Remember - you have to consider _anything_ aft of the 
>>> firewall as a direct threat to your prop and make sure it's safetied...
>>>
>>> I had the two into one exhaust exiting the bottom of the cowl for 
>>> awhile.  The drag penalty was 8-10 knots.  Shooting the exhaust 
>>> straight out of the bottom creates a huge plume of flat plate drag....
>>>
>>> Happy Thanksgiving!
>>>
>>> Dave
>>>
>>> Dave T. Nelson
>>> T/L 553-4327, Voice 507-253-4327, Fax 507-253-3648
>>> Program Director, ISC ECAT NPI & Test Engineering
>>>
>>>
>>>
>>>   1. Re:  STG-RG Performance (Richard J. Gentil)
>>>
>>>
>>> ----- Message from "Richard J. Gentil" 
>>> <richard at naples-air-center.com> on Thu, 22 Nov 2012 08:00:21 -0500 -----
>>> *To:*
>>> 	
>>> Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
>>> *Subject:*
>>> 	
>>> Re: REFLECTOR: STG-RG Performance
>>>
>>> I had the help and advise of a long time builder who had built 
>>> several EZ's among his long list of aircraft.
>>>
>>> I was thinking of a EZ style exhaust for my SERG but he recommended 
>>> against it because of complexity.
>>>
>>> His primary concern was that you need springs, brackets, hardware, 
>>> etc to hold the exhaust in place and many an EZ owner have had those 
>>> part break off and go right through the prop.
>>>
>>> For that reason I went with 2 to 1 exhausts that I cut flush with 
>>> the bottom of my cowling safety wired to the engine mount.
>>>
>>> With as fragile as MT props are I wanted to eliminate as best as 
>>> possible anything going through the prop.
>>>
>>> Richard
>>>
>>> Sent from my iPhone 5
>>>
>>> On Nov 21, 2012, at 9:31 AM, Dave T Nelson <_dtnelson at us.ibm.com_ 
>>> <mailto:dtnelson at us.ibm.com>> wrote:
>>>
>>>
>>>     Hi Grover,
>>>
>>>     Yes, you absolutely need to be concerned with your prop -
>>>     anything and everything that can affect your prop you should be
>>>     concerned about!  In this case, I am a follower, not a leader.
>>>      I'm still very connected with the EZ crowd (I built a Varieze
>>>     first and flew it for many years).  The EZ guys were the first
>>>     to try this kind of exhaust.  Prop heating is for sure the
>>>     biggest concern.
>>>
>>>     For the first hundred hours I flew this exhaust I very carefully
>>>     monitored it for any signs of degridation.  There are specific
>>>     things you look for (surface cracks, a distinctive "burnt
>>>     orange" smell, etc.).  I have had no issues (200 - 300 hours on
>>>     it now).
>>>
>>>     I'm certainly not recommending this to anyone - I'm merely
>>>     showing what I've done and sharing results.  Your results may vary.
>>>
>>>     After many years and hours of use now, the biggest problem I
>>>     have with this setup is that a three blade prop can't be clocked
>>>     to avoid the exhaust pulse, and so I get soot on the blades.
>>>      I've found that "goof off" is the best at removing the soot.
>>>
>>>     I haven't observed any paint coming off the prop at all.  Yes,
>>>     it's an MT (MTV - 18B (if memory serves)).  I'd have to check,
>>>     but I believe there's maybe 8 - 10 inches or so from the exhaust
>>>     exit to the prop blade.
>>>
>>>     Good luck - let me know if you have questions.
>>>
>>>     Dave
>>>
>>>     Dave T. Nelson
>>>     T/L 553-4327, Voice 507-253-4327, Fax 507-253-3648
>>>     Program Director, ISC ECAT NPI & Test Engineering
>>>
>>>
>>>
>>>
>>>
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>>
>>
>>
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>
> -- 
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> Bible, 1 John iv. 18.
>
>
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