REFLECTOR: Performance

[Dave Philipsen]

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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