REFLECTOR: Reflector Digest, Vol 98, Issue 29

Fri May 10 07:34:42 CDT 2013

Maybe that was a different one.  This guy had the exhaust just straight 
back, not through the wings.  He also did several other things which 
added up to an astounding 60+ kn increase, IIRC.

John

On 5/10/2013 6:52 AM, Dave T Nelson wrote:
>
> Yes, I remember seeing that too at Oshkosh.  The builder had created a 
> channel through the wing for the exhaust.  I can't remember if it was 
> two or one pipes - but I do remember thinking... Jeez, do I really 
> want that hot exhaust gas going through my wing???  What happens if 
> that long (Long!) pipe breaks???  Just sayin'....
>
> Dave
>
> Dave T. Nelson
> T/L 553-4327, Voice 507-253-4327, Fax 507-253-3648
> Program Director, ISC ECAT NPI & Test Engineering
>
> ----- Message from Dave Philipsen <velocity at davebiz.com> on Fri, 10 
> May 2013 02:04:02 -0500 -----
> *To:*
> 	
>
>     Velocity Aircraft Owners and Builders list <reflector at tvbf.org> 
>
> *Subject:*
> 	
>
>     Re: REFLECTOR: Performance 
>
> Wow! That is amazing!  Did you also convert from a 4/2 exhaust to a 
> 4/4?  Is your new exhaust simply one pipe from each cylinder or 
> exactly what is the configuration?
>
> I don't remember if it was a Velocity or a Cozy but I remember seeing 
> a photo of someone's plane with the exhausts being routed out to the 
> trailing edges of the wings.  Does anyone else remember seeing that?
> Dave Philipsen
> Velocity STD FG
> N83DP
> On 5/9/2013 4:15 PM, Dave T Nelson wrote:
>
>
>     Richard, I can't point at any NACA or other research, but I
>     changed from a "straight out the bottom" to an enclosed aft firing
>     exhaust on my 200 HP STD-RG.  I picked up at least 10 knots,
>     really more like 15.  I did it because all of my EZ friends, and
>     especially the guys I know that race, had done it and claimed
>     great results.
>
>     Clearly shooting the exhaust out the bottom creates a big plume of
>     disturbed air... I've struggled as to exactly how the force of
>     that "drag plume" is translated back to the aircraft... but it
>     sure worked for me.
>
>     Here's a picture of my exhaust.  Yes, I do get soot on my three
>     bladed prop.  No, I've never seen any damage issue to the prop
>     from the hot gas (after about 400 - 500 hours).
>     /
>     (See attached file: IMG_1042.jpg)/
>
>     Dave
>
>     Dave T. Nelson
>     T/L 553-4327, Voice 507-253-4327, Fax 507-253-3648
>     Program Director, ISC ECAT NPI & Test Engineering
>
>
>     I still don't understand the drag mechanism for normal angle of
>     exhaust being a drag.
>     Does anyone know where I can find NACA or other research on this?
>
>     On 5/9/2013 11:07 AM, Richard J. Gentil wrote:
>
>         Geoff,
>
>         If you make the exhaust change I would be very interested in
>         your results since mine currently exit straight down.
>
>         Richard
>
>         Sent from my iPhone 5
>
>         On May 8, 2013, at 10:59 PM, Geoff Gerhardt
>         <_geoff.gerhardt at gmail.com_ <mailto:geoff.gerhardt at gmail.com>>
>         wrote:
>             Scott,
>
>             Thanks - that was the insight I was looking for and what I
>             suspected.  I would actually prefer to have the normal,
>             shorter wing - I'd love the 15kts in speed and would
>             gladly live with a little higher stall speed.
>
>             Now, given that, I wonder if there's anything I could do
>             that could improve my performance.  The two things that
>             I'm considering are changing my exhaust config from
>             exiting straight down to exiting inside the cowling at the
>             prop.  I've heard some folks state they have seen
>             significant improvements with that mod.  The other was an
>             intake ram scoop - would that give me more MAP at altitude
>             and a little more power?
>
>             Thanks for all the performance comments/comparisons...keep
>             them coming.
>
>             Geoff
>             On Wed, May 8, 2013 at 8:31 PM, Scott Baker
>             <_scottb33333 at gmail.com_ <mailto:scottb33333 at gmail.com>>
>             wrote:
>             I notice that several responders are giving numbers for a
>             Velocity Standard RG, while Geoff's aircraft is a Velocity
>             173 (aka LW 'Long Wing').
>             Velocity Standard models, with their smaller wings and
>             reduced drag, are faster than their 173 brethren ... by 15
>             knots on average (with comparable engines and propellers).
>             The factory V173FG trainer is hard pressed to see 145KTAS
>             in cruise.  I think the RG version cruises between
>             155-160KTAS (about 15knots faster than the fixed gear model).
>             These numbers are pretty close to what Geoff is reporting
>             for his aircraft.
>             Scott B.
>
>
>
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