REFLECTOR: Overhead NACA's (was "Rudder Pedal stops")
Douglas Holub
douglas.holub at gmail.com
Wed Apr 15 10:59:50 CDT 2009
The oil cooler is mounted on the engine side of the firewall, and I think
the pressure is pretty low beneath the engine, but just to make sure I added
an exhaust scoop for the oil cooler. I think the pressure was already low
enough because I didn't notice any improvement with the exhaust scoop.
Doug
On Wed, Apr 15, 2009 at 10:33 AM, Scott Derrick <scott at tnstaafl.net> wrote:
> Doug, anyway to reduce the pressure on the back side of your oil cooler?
>
> Interesting about cylinder temps. I had always thought "lower was
> better".
>
> Scott
>
> Douglas Holub wrote:
> > I would remove the VGs in front of your NACAs to get the cylinder
> > temperatures up to 360. ECI recommends that the cylinder temperatures
> > be 400-425 in cruise for a parallel valve 4-cylinder Lycoming with 500
> > F redline. If you've got an angle valve Lycoming I think the redline
> > is lower, maybe 475? My friend had a sticking valve on his engine,
> > and the mechanic told him that it was because the cylinders were
> > running too cool. His temps are in the low 300s.
> >
> > Speaking of cooling, I've got a question for the collective,
> > (especially for Al if you're out there.) I need to run my engine
> > below 75% power to keep the oil temperatures below 230 degrees on a 75
> > degree day like yesterday. My redline is 245. I went from a divergent
> > wall NACA to a parallel wall NACA to a belly scoop. The oil keeps
> > getting cooler, but I need another 20 degrees to be able to fly much
> > in Texas in the summer time. My scoop has a 5 x 2 inch opening that
> > smoothly diverges to the size of the oil cooler 2 feet later. In other
> > words, it has an exansion plenum. Here's my question: I know that the
> > drag will increase if I make the entrance larger and don't have an
> > expansion plenum, but will cooling also increase? Or will the air
> > spilling out of the entrance to the scoop just make things worse?
> >
> > Doug Holub
> > Standard FG in phase I flight testing
> >
> > On Wed, Apr 15, 2009 at 9:33 AM, victor taylor <velocityoner at yahoo.com
> > <mailto:velocityoner at yahoo.com>> wrote:
> >
> > 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 <mailto:ljepstein at hotmail.com>>/* wrote:
> >
> >
> > From: Lawrence J. Epstein, MD <ljepstein at hotmail.com
> > <mailto:ljepstein at hotmail.com>>
> > Subject: REFLECTOR: Overhead NACA's (was "Rudder Pedal stops")
> > To: "'Velocity Aircraft Owners and Builders list'"
> > <reflector at tvbf.org <mailto: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>
> > [mailto:reflector-bounces at tvbf.org
> > <mailto:reflector-bounces at tvbf.org>] *On Behalf Of
> > *jerry at jlbent.com <mailto: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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> > -----Inline Attachment Follows-----
> >
> >
> >
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> >
> > ------------------------------------------------------------------------
> >
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>
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