REFLECTOR: Reflector Digest, Vol 92, Issue 64

[Brian Michalk]

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
>
>
>
>
>
> _______________________________________________
> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.tvbf.org/mailman/private/reflector/attachments/20121123/e409336a/attachment-0001.html>