REFLECTOR: Performance

[Geoff Gerhardt]

Dave,

Where did you get your exhaust made?  Do you have some pics showing it with
the cowl off?  I'd like to see how it was routed back.  Is the terminus end
of the exhaust supported in any way?

Thanks a lot for your comments and picture.

Geoff

On Thu, May 9, 2013 at 5:15 PM, Dave T Nelson <dtnelson at us.ibm.com> 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*<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*<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.
>
>
>
>
> _______________________________________________
> 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/20130510/a949d51b/attachment.html>