REFLECTOR:NACA inlet shape
Rich Guerra
reflector@tvbf.org
Wed, 6 Aug 2003 22:27:57 -0600
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Jerry,
The "old-style" process (pre - premolded) for making NACA scoops is
illustrated on my web site (http://www.rguerra.com/velocity/) in the
'NACA Scoops/Final Structure' and 'More NACA scoops' section. I
also have a brief discussion on the characteristics of an optimum
NACA scoop size and shape. The section illustrates how we used the
information below to redesign the top NACA scoops to conform to the
optimum shape as derived from the original NACA research studies.
The resulting shape and size of the scoops make an interesting
contrast with the factory version as can be seen in the first photo
in the section. THus far, they seem to work extremely well on my XL,
in addition to a few others out of Hangar 18. The discussion on my
page refers to an unfortunately defunct website, but a little poking
around the internet will get the docs and perhaps a cached version
of the old site.
Airmech has kindly reposted Andy Millin's spreadsheet which uses the
info below. Also, Vlad has another spreadsheet that you can plug
your info into and generate the shape you need on his website:
http://www.n1ut.velocity-air.com/
( in NACA scoop section - direct link:
http://www.n1ut.velocity-air.com/progress/c26/index.html )
some more potentially useful links:
http://www.wisil.recumbents.com/wisil/nacaduct/naca-duct.htm
search for "A9L29" on
http://www.larc.nasa.gov
direct link to large pdf file:
http://naca.larc.nasa.gov/reports/1950/naca-rm-a9l29/naca-rm-a9l29.pdf
Some notes posted by Tony Babb summarizing from above docs:
*******
"...
In general the width-to-depth ratio should be between 3 and 5 while the
ramp angle should be between 5 and 7
degrees for optimal pressure recovery. The entrance lip at the rear of the
duct should be a blunt airfoil leading
edge shape; however, the edge formed by the duct and the surface elsewhere
should remain crisp.
The following table gives the coordinates for laying out the planform of a
"curved divergence" NACA flush inlet
where X is the longitudinal distance along the duct, L is the total
longitudinal length, Y is the width measured from
the centerline of the duct, and W is the overall width of the duct.
X/L 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Y/W .500 .497 .457 .382 .307 .233 .195 .157 .118 .080 .042
also, this info and how to turn it into a duct are available in the july '90
central states newsletter, page 2.
*****
You can also take a look at Tony Bingelis' book, The Sportplane
Builder, pages 187-188 which has a nice diagram and reiterates the
layout as above for divergent ducts
After I get back from my honeymoon, I'll try to update that section
and post a bunch of pics from the last year including a (finally!)
painted XL. Hope this helps
Rich Guerra
Velocity XL RG N724X
http://www.rguerra.com/velocity/
>The kit that I have does not have the pre-molded NACA inlets for engine
>cooling. While I could purchase them from the factory, it seems that it
>should be easy to make them by cutting the fuselage and use that to make
>the inlet. I think someone mentioned that the factory shape may not be
>quite right. I thought someone had a drawing or the NACA source
>information on the shape and proportions. If possible, I would like to get
>the details so that I can make my own.
>
>Jerry
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--></style><title>Re: REFLECTOR:NACA inlet shape</title></head><body>
<div>Jerry,</div>
<div><br></div>
<div>The "old-style" process (pre - premolded) for making
NACA scoops is illustrated on my web site
(http://www.rguerra.com/velocity/) in the 'NACA Scoops/Final
Structure' and 'More NACA scoops' section. I also have a
brief discussion on the characteristics of an optimum NACA scoop size
and shape. The section illustrates how we used the information
below to redesign the top NACA scoops to conform to the optimum shape
as derived from the original NACA research studies. The
resulting shape and size of the scoops make an interesting contrast
with the factory version as can be seen in the first photo in the
section. THus far, they seem to work extremely well on my XL, in
addition to a few others out of Hangar 18. The discussion on my
page refers to an unfortunately defunct website, but a little poking
around the internet will get the docs and perhaps a cached
version of the old site. </div>
<div><br></div>
<div><br></div>
<div>Airmech has kindly reposted Andy Millin's spreadsheet which uses
the info below. Also, Vlad has another spreadsheet that
you can plug your info into and generate the shape you need on his
website:</div>
<div>http://www.n1ut.velocity-air.com/</div>
<div><br></div>
<div>( in NACA scoop section - direct link:
http://www.n1ut.velocity-air.com/progress/c26/index.html )</div>
<div><br></div>
<div><br></div>
<div>some more potentially useful links:</div>
<div>http://www.wisil.recumbents.com/wisil/nacaduct/naca-duct.htm</div
>
<div><br></div>
<div>search for "A9L29" on</div>
<div>http://www.larc.nasa.gov</div>
<div><br></div>
<div>direct link to large pdf file:</div>
<div><font face="Helvetica" size="+2" color="#000000"><br>
</font><font face="Courier" size="+2"
color="#0000FF"
>http://naca.larc.nasa.gov/reports/1950/naca-rm-a9l29/naca-rm-a9l29.p<span
></span>df</font></div>
<div><br></div>
<div>Some notes posted by Tony Babb summarizing from above docs:</div>
<div>*******</div>
<div>"...<br>
In general the width-to-depth ratio should be between 3 and 5
while the<br>
ramp angle should be between 5 and 7<br>
degrees for optimal pressure recovery. The entrance lip at the
rear of the<br>
duct should be a blunt airfoil leading<br>
edge shape; however, the edge formed by the duct and the
surface elsewhere<br>
should remain crisp.<br>
<br>
The following table gives the coordinates for laying out the
planform of a<br>
"curved divergence" NACA flush inlet<br>
where X is the longitudinal distance along the duct, L is the
total<br>
longitudinal length, Y is the width measured from<br>
the centerline of the duct, and W is the overall width of the
duct.<br>
<br>
X/L 0.0 0.1 0.2 0.3 0.4
0.5 0.6 0.7 0.8 0.9 1.0<br>
Y/W .500 .497 .457 .382 .307 .233 .195 .157 .118 .080 .042<br>
<br>
also, this info and how to turn it into a duct are available in the
july '90</div>
<div>central states newsletter, page 2.</div>
<div>*****</div>
<div><br></div>
<div>You can also take a look at Tony Bingelis' book, The Sportplane
Builder, pages 187-188 which has a nice diagram and reiterates the
layout as above for divergent ducts</div>
<div><br></div>
<div><br></div>
<div>After I get back from my honeymoon, I'll try to update that
section and post a bunch of pics from the last year including a
(finally!) painted XL. Hope this helps</div>
<div><br></div>
<div>Rich Guerra</div>
<div>Velocity XL RG N724X</div>
<div>http://www.rguerra.com/velocity/</div>
<div><br></div>
<div><br></div>
<div><br></div>
<blockquote type="cite" cite>The kit that I have does not have the
pre-molded NACA inlets for engine<br>
cooling. While I could purchase them from the factory, it seems
that it<br>
should be easy to make them by cutting the fuselage and use that to
make<br>
the inlet. I think someone mentioned that the factory shape may
not be<br>
quite right. I thought someone had a drawing or the NACA
source<br>
information on the shape and proportions. If possible, I would
like to get<br>
the details so that I can make my own.<br>
</blockquote>
<blockquote type="cite" cite>Jerry</blockquote>
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