REFLECTOR: Top exhaust systems

Wed Apr 15 18:45:42 CDT 2009

I've got two pipes shooting out the back of the cowl towards a 2-blade prop.
I had a lot of soot building up on the prop. Then I read that I should mount
the prop at 1 o'clock and 7 o'clock when the #1 cylinder is at TDC.  Mine
was at 11 o'clock and 5 o'clock. After I changed it, no soot at all. (I know
this doesn't help you; just thought I'd pass along the tip.)

Doug
17.2 hours of Phase I to go

On Wed, Apr 15, 2009 at 2:13 PM, Andrew Ellzey <ajlz72756 at yahoo.com> wrote:

> You are saying that you converted an up draft engine to down draft, was
> your engine originally designed for down draft cooling? Is you exhaust
> system exit the top of your cylinders or the bottom? My engine is designed
> for up draft cooling and top exhaust and I am installing the arm pit scoops
> and the NACA scoops. I intend to use the NACA scoops for engine air intake
> and second oil cooler if needed. I still haven't decided on my exhaust
> design and am curious as to how others that have top exhaust systems did
> their system. I am considering the exhaust exiting the six exhaust pipes
> straight up, or I could do a three to one aft and exhaust through the prop.
> My problem with this is that with a three blade prop you can't clock you
> prop in such a way that at least one of the blades will be in the exhaust.
> Vari-eze fliers have done this for years without any ill affects or at least
> I have been told there weren't any ill effects. Does anyone have a different
> take on the issue. I also have the option of going out each side of the
> cowling like a P51, the problem is getting the top cowling on and off of
> this configuration. The third option is a three to one routing forward and
> then down to exit the bottom of the cowling. I like this one the least
> because of the long run of hot exhaust pipes routing from top to bottom
> inside the cowling. Anyone else have a suggestion?
>
> Andy Ellzey
>
>  ------------------------------
> *From:* victor taylor <velocityoner at yahoo.com>
> *To:* Velocity Aircraft Owners and Builders list <reflector at tvbf.org>
> *Sent:* Wednesday, April 15, 2009 9:33:04 AM
> *Subject:* Re: REFLECTOR: Overhead NACA's (was "Rudder Pedal stops")
>
>   I converted my Velocity from the updraft cooling to the cut out home
> made naca vents on the top. My Velocity runs as cool as my Cessna 150 with
> temps running 310 cht and 190 oil. I had to add a small airfoil in front of
> the exhaust exit on the oil cooler after we test flew it. Also without the
> vortex generators in front of the nacas it will raise the cht by 50 degrees
> and the oil temp to 220.
>
> --- On *Wed, 4/15/09, Lawrence J. Epstein, MD <ljepstein at hotmail.com>*wrote:
>
>
> From: Lawrence J. Epstein, MD <ljepstein at hotmail.com>
> Subject: REFLECTOR: Overhead NACA's (was "Rudder Pedal stops")
> To: "'Velocity Aircraft Owners and Builders list'" <reflector at tvbf.org>
> Date: Wednesday, April 15, 2009, 7:45 AM
>
>  You guys are "fastbuild" compared to me (13 years and counting). Mine is
> so old that NACA's hadn't been invented yet (not really) ( we had to walk
> uphill to school, both ways, in the snow, no shoes………)
>
>
>
> Anyway…………..The factory sent me the templates and I cut them out myself (no
> opinion as to whether these are real NACA's or not). I cut everything except
> the forward most part and just pushed the skin down to the desired depth. I
> used 1/4" foam for the sides and covered them with bid. About 6-10 hours
> work.
>
>
>
> Larry Epstein
>
>
>
> *From:* reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] *On
> Behalf Of *jerry at jlbent.com
> *Sent:* Wednesday, April 15, 2009 8:22 AM
> *To:* Velocity Aircraft Owners and Builders list
> *Subject:* Re: REFLECTOR: Rudder Pedal stops
>
>
>
> Just to add to the challenge on the NACA ducts, you might want to consider
> the efficency of the factory design.  While they look like NACA ducts, they
> are not.  Andy Millin has spent a lot of time researching the topic and has
> a spreadsheet that does the calculations to produce the needed profile.  One
> very big difference (and maybe the most important) is that the factory
> solution does not have an airfoil on top of the opening.  Of course the
> amount of work needed to create a real NACA vs buying the factory pre-fab is
> not trivial.
>
> I too am a SLOOOW builder and have a kit that did not come with the
> pre-fab'd NACA's.  Mine did not even have the NACAs drawn on the fuselage.
> I had read Andy's information and decided to build my own.  Just let me say
> that one can get really obsessive about the details.  I would say that Brett
> and I have at least 50 hours of work on them.  Some is my learning curve.
> Some is just ! the details.  We did the extra work to make the floor of the
> ramp flat, which is not what you get if you just cut the outline, build the
> side walls and call it done.
>
> As of yet, I can not say that the true NACA will be better.  Hangar 18
> suggest NACA's and believes they are better.  I do know that those in the
> Vari community think the Velo factory NACA are just wrong and will produce
> more drag and be less efficient than a proper NACA.  For the amount of work
> involved in both hands on construction and the amount of head scratching
> needed to build true NACA's, it is very hard not to go with the factory
> pre-fabs.
>
> If you decide to go with the true NACA, let me know and we can talk
> details.  Maybe I can save you some time.
>
> Jerry Brainard
>
>
>    -------Original Message-------
> From: Richard D. Wallace, Jr.
> Subject: Re: REFLECTOR: Rudder Pedal stops
> Sent: Apr 14 '09 7:08pm
>
> Noel:
>
> I'm on the slow path also.  I got my kit for Christmas 2000.  My
> fuselage has the NACA scoops outlined on the top also.  What do you
> make the sides out of - BID?  Also what is the dimension on the
> opening in the firewall?
>
> Rick
>
> On Tue, Apr 14, 2009 at 6:28 PM,  <gattenby at tulsaconnect.com<http://mbox.jlbent.com/compose.php?to=gattenby@tulsaconnect.com>>
> wrote:
> > Rick.
> >
> > I'm taking the slow path to building an SUV as well (8 years and
> counting)
> > I've not done the pedal things as I'm missing some parts. (got my kit 2nd
> > hand)
> >
> > The NACA scoops can be bui! lt without the prefab inserts.
> > My kit predated the inserts.  They weren't that big a deal.
> > The kit had the lines drawn on the top, and I just cut them.
> >
> > If you need templates just let me know and I'll trace mine on paper.
> >
> > Noel
> >
> > On Tue, 14 Apr 2009 17:30:24 -0400
> >  "Richard D. Wallace, Jr." <rdwallace57 at gmail.com<http://mbox.jlbent.com/compose.php?to=rdwallace57@gmail.com>>
> wrote:
> >> Guys:
> >>
> >> I don't provide comments (lack of experience and I have
> >>a single door,
> >> fixed gear, dual yoke control SUV) but I do and have
> >>read all e-mails
> >> back and forth.  I seem to be just behind in
> >>construction than some
> >> and the need to ask questions is always unnecessary
> >>because the
> >> ! subject has already been discussed.  However, I have
> >>come up with two
> >> (2) questions:  1) do you need stops for the break
> >>pedals so they are
> >> not putting pressure on the master brake cylinder heads
> >>when the
> >> springs are pulling and your foot is not on the pedals?
> >>and 2)  is
> >> there a way to make the two (2) larger NACA scoops on
> >>top and in the
> >> back for the engine cooling from the existing fuselage
> >>or do you
> >> really need to buy the pre-fabricated ones from
> >>Velocity?
> >>
> >> Thanks!
> >>
> >> Rick Wallace
> >> _______________________________________________
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> >
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>
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