REFLECTOR: Overhead NACA's (was "Rudder Pedal stops")

Wed Apr 15 09:33:04 CDT 2009

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> 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> 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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