REFLECTOR: Overhead NACA's (was "Rudder Pedal stops")
Scott Derrick
scott at tnstaafl.net
Wed Apr 15 10:33:27 CDT 2009
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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