REFLECTOR: Overhead NACA's

Douglas Holub douglas.holub at gmail.com
Wed Apr 15 12:34:14 CDT 2009


Maybe my problem is that I need two oil coolers. But before I install
another one or a bigger one, I'll check to see if I'm getting 4 inches.
Thanks.

Doug

On Wed, Apr 15, 2009 at 12:14 PM, Brent Bourgeois <bjb3013 at yahoo.com> wrote:

>  Doug,
> I have done a lot of work on my coolers and now have a system where I get
> 180-190 no matter how hard I run (or abuse) and regardless of OAT. The best
> thing you can do is a simple press study to see what you are dealing with.
> My experience has been that its almost never an inlet problem.  If you get
> the press low enough on the cooler outlet , at least 4 in/water difference,
> your oil will cool.
> Put a sense tube in front of the cooler and one behind, use an airspeed
> indicator to get mph, convert to inch/water. Get real numbers, make one mod
> at a time and make lots of notes.
> Do this for engine cooling also. You may be surprised what works and what
> is BS
> I have a STD RG with an IO-360 arm pit cooling, front and rear coolers.
> Let me know If I can help
>
> Brent
> N61VB
>
>
> --- On *Wed, 4/15/09, Douglas Holub <douglas.holub at gmail.com>* wrote:
>
> From: Douglas Holub <douglas.holub at gmail.com>
> Subject: Re: REFLECTOR: Overhead NACA's (was "Rudder Pedal stops")
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Date: Wednesday, April 15, 2009, 9:57 AM
>
> 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>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>*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
> >> _______________________________________________
> >> To change your email address, visit
> >>http://www.tvbf.org/mailman/listinfo/reflector
> >>
> >> Visi! t 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
> >
> >
> > _______________________________________________
> > 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<http://www.tvbf.%21%0d%0a%20org/archives/velocity/maillist.html>
> >
> _______________________________________________
> 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
>
> -----Inline Attachment Follows-----
>
>
> _______________________________________________
> 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
>
>
>
> _______________________________________________
> 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
>
> _______________________________________________
> To change your email address, visithttp://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
>
>
>
> _______________________________________________
> 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/20090415/67ddc7ab/attachment-0001.htm>


More information about the Reflector mailing list