REFLECTOR: Reflector Digest, Vol 98, Issue 29

[Dave T Nelson]

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> 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> 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/20130510/40cbe759/attachment.html>