Reverse NACA duct

Can someone tell me where I can find more information on the design of a
reverse NACA duct?

--
Chris W

"They that can give up essential liberty
to obtain a little temporary safety
deserve neither liberty nor safety."
-- Benjamin Franklin, 1759 Historical Review of Pennsylvania

On Fri, 24 Oct 2003 13:28:54 -0500, Chris W wrote:

Can someone tell me where I can find more information on the design of a
reverse NACA duct?

--
Chris W

Chris, what's a reverse NACA duct? My understanding is that they were
designed to work in one direction only, to bring in air with a minimum
of drag.

They don't work well, or at all, when placed on the fuselage or cowl
in a negative pressure area.

Thanks, Corky Scott

Corky Scott wrote:

Chris, what's a reverse NACA duct? My understanding is that they were
designed to work in one direction only, to bring in air with a minimum
of drag.

They don't work well, or at all, when placed on the fuselage or cowl
in a negative pressure area.

I had heard once that on some planes, a reverse or backwards NACA duct would
be installed in the aft part of the cockpit to improve ventilation by helping
suck air out of the plane. I also think I remember something about the
design being somewhat different.


--
Chris W

"They that can give up essential liberty
to obtain a little temporary safety
deserve neither liberty nor safety."
-- Benjamin Franklin, 1759 Historical Review of Pennsylvania

"Chris W" wrote in message
...
Corky Scott wrote:

Chris, what's a reverse NACA duct? My understanding is that they were
designed to work in one direction only, to bring in air with a minimum
of drag.

They don't work well, or at all, when placed on the fuselage or cowl
in a negative pressure area.

I had heard once that on some planes, a reverse or backwards NACA duct
would
be installed in the aft part of the cockpit to improve ventilation by
helping
suck air out of the plane. I also think I remember something about the
design being somewhat different.


--
Chris W

As I recall, it was shaped rather like a raindrop, but with about 1/3rd of
the surface raised above the craft. The pointy end was pointed into the
wind, with the outlet in the downwind, rounded side. The object was to
create a low pressure area, then use it to get the bad air out. If only I
could remember where I read about it!
--
Jim in NC

Would a couple of NACA ducts work on the bootcowl of a Taylorcraft BC-12D to
bring in fresh cabin air? I understand a 337 would be required but would it
do the job better than have to fly with the windows slide back? Just
thinking of better ways of freezing my feet off this winter. RTL

--


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"Chris W" wrote in message
...
Can someone tell me where I can find more information on the design of a
reverse NACA duct?

--
Chris W

"They that can give up essential liberty
to obtain a little temporary safety
deserve neither liberty nor safety."
-- Benjamin Franklin, 1759 Historical Review of Pennsylvania

In article ,
(Corky Scott) writes:


Can someone tell me where I can find more information on the design of a
reverse NACA duct?

--
Chris W

Chris, what's a reverse NACA duct? My understanding is that they were
designed to work in one direction only, to bring in air with a minimum
of drag.

They don't work well, or at all, when placed on the fuselage or cowl
in a negative pressure area.

Thanks, Corky Scott


The concept is to place it in the airstream in such a way as to result in
negative pressure at the opening.




Bob Reed
www.kisbuild.r-a-reed-assoc.com (KIS Builders Site)
KIS Cruiser in progress...Slow but steady progress....

"Ladies and Gentlemen, take my advice,
pull down your pants and Slide on the Ice!"
(M.A.S.H. Sidney Freedman)

In article , Chris W writes:


Can someone tell me where I can find more information on the design of a
reverse NACA duct?

--
Chris W

"They that can give up essential liberty
to obtain a little temporary safety
deserve neither liberty nor safety."
-- Benjamin Franklin, 1759 Historical Review of Pennsylvania



I don't know of a specific design for one but I am simply mounting one on the
outside of the fuselage with the small end pointing into the airstream. The
air will flow around and over the duct and should result in a negative pressure
at the opening. Another option was one done by the guy who designed the
VISION. It was a small extending bulb with holes on the back side. Again, the
negative pressure on the down wind side results in a reverse flow.


Bob Reed
www.kisbuild.r-a-reed-assoc.com (KIS Builders Site)
KIS Cruiser in progress...Slow but steady progress....

"Ladies and Gentlemen, take my advice,
pull down your pants and Slide on the Ice!"
(M.A.S.H. Sidney Freedman)

In article , "Morgans"
writes:


I had heard once that on some planes, a reverse or backwards NACA duct
would
be installed in the aft part of the cockpit to improve ventilation by
helping
suck air out of the plane. I also think I remember something about the
design being somewhat different.


--
Chris W

As I recall, it was shaped rather like a raindrop, but with about 1/3rd of
the surface raised above the craft. The pointy end was pointed into the
wind, with the outlet in the downwind, rounded side. The object was to
create a low pressure area, then use it to get the bad air out. If only I
could remember where I read about it!
--
Jim in NC



I believe the guy who designed the Vision Aircraft did some work on this
several years ago and had some information on his web site at one time. I
don't know if it is still there or no.


Bob Reed
www.kisbuild.r-a-reed-assoc.com (KIS Builders Site)
KIS Cruiser in progress...Slow but steady progress....

"Ladies and Gentlemen, take my advice,
pull down your pants and Slide on the Ice!"
(M.A.S.H. Sidney Freedman)

"Robert Little" wrote in message
...
Would a couple of NACA ducts work on the bootcowl of a Taylorcraft BC-12D
to
bring in fresh cabin air? I understand a 337 would be required but would
it
do the job better than have to fly with the windows slide back? Just
thinking of better ways of freezing my feet off this winter. RTL


Oh, blasphemy and sacrilege! You would do that to the boot cowl of your
classic Taylorcraft?


Somebody's going to get this sooner or later and googling "inverted naca
duct" might bring something up. But my understanding is that the device
helps keep the boundary layer attached.


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"Chris W" wrote in message
...
Can someone tell me where I can find more information on the design of a
reverse NACA duct?

--
Chris W

"They that can give up essential liberty
to obtain a little temporary safety
deserve neither liberty nor safety."
-- Benjamin Franklin, 1759 Historical Review of Pennsylvania

Reverse NACA duct ... Bad Idea!
Several years ago I read about someone installing a NACA scoop, pointed end
aft, to remove air from the cabin. I thought I would do the same for my
plane but first decided to test the idea. I built a NACA scoop and ran
high speed water through it in both forward and reverse directions. In
forward the water flowed as expected. In reverse the water exited at
nearly 90 degrees to the slip stream.
I believe a NACA scoop will just add drag, especially to fast
planes....Better to just use a ramped exit.

Russell Sherwood
Houston, TX



"Chris W" wrote in message
...
Can someone tell me where I can find more information on the design of a
reverse NACA duct?

--
Chris W

"They that can give up essential liberty
to obtain a little temporary safety
deserve neither liberty nor safety."
-- Benjamin Franklin, 1759 Historical Review of Pennsylvania