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----- Original Message -----
Sent: Sunday, July 18, 2004 5:55 PM
Subject: Re: [FlyRotary] Re: New Scoop
Hi, Ed.....The statement I made regarding NACA
ducts not working for carburetors is on the page that you submitted, from
NACA....the same one that says they won't work for radiators, it also includes
carburetors in the same sentence.
I agree, Ed....we
are finding ways to "make things work" through determination (sometimes
stubborness as in my case), and refusing to take NO for an answer, just like
Columbus, Orville and Wilber, etc. Scientists also said that the bumble
bee is too heavy to fly, given it's wingspan, etc. Fortunately, no one has told
the bumblebee. We have been told that EWP's won't work, NACA ducts won't
work for radiators, etc. Fortunately, we are using them anyway. We
are fortunate to have an engineer such as yourself on this site, and one that is
willing to listen to evidence from the field as well as numbers and
formulas. A Cozy builder named Al Wick has a Subaru powered Cozy with his
radiator behind a NACA duct, and he can do full power climbs to altitude with no
cooling problems. I copied his installation. (A google search will reveal
his website). Thanks again for all of your contributions to this
site. Paul Conner
----- Original Message -----
Sent: Friday, July 16, 2004 6:50 PM
Subject: [FlyRotary] Re: New Scoop
I would not argue with your assessment,
Paul.
I mainly put it up so you folks could see
the source that many "experts" use to tell you "Dummies" why what you
have working - can't possibly work {:>). I was offering a hypothesis
as to why in some cases the results "in-the-field" might be different from
what NACA found in the wind tunnels. I had not heard about the
NACA supposedly not being good for carburetors. My impression was that
so long as there was not back pressure (such as a cooler block will produce)
anything that created a lower than ambient pressure region behind the NACA
duct (such as engine intake or duct into a cabin) would cause it to work
OK. I know that the NACA duct that feeds cooling air into my cabin
always has a tremendous rush of air coming through it. Have to keep it closed
off most of the time at altitude or freeze my butt.
Ed
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
Sent: Friday, July 16, 2004 6:45
PM
Subject: [FlyRotary] Re: New
Scoop
Hi, Ed.....I am of the opinion that the NACA
report you provided is old and out of date. Note that they also state that
the NACA duct does not provide desireable recovery characteristics for
carburetors on reciprocating engines. Tell that to the many LongEZ
builders (myself included) that found it to be very efficient in supplying
air to our carburetors in all attitudes, from cruise attitude to steep
climbouts. They came up with a very nice, low drag inlet, but I don't think
they spent as much time studying their creation or finding out it's true
potential. Just my experience, based upon a very succesful NACA duct
feeding my MS carb on my Lycoming (ugh, sorry about that) powered
LongEZ. Paul Conner
----- Original Message -----
Sent: Thursday, July 15, 2004 6:52
PM
Subject: [FlyRotary] Re: New
Scoop
Looking at John's cooling set up, it
appears that the cooler core exits are in an excellent position to
benefit from any lower pressure region that may exist at the
rear of the canard fuselage.
Its been my contention that this
is one of the reasons that at least some canard installations appear
to defy both the conventional "wisdom" and the NACA
admonishment that NACA ducts are not well suited for radiator cooling (or
other uses that produce a back pressure). That is - as in
John's case - the successful arrangement appears to
minimized the back pressure across the core and perhaps benefits from
a localized area of lower than ambient pressure.
Attached is an extract from a NACA report
which makes it clear, that at least in their opinion at the time, the NACA
ducts were not suited for radiators. But, as John and other's have
shown, they can work very effectively. So something they are doing
must be different. The only thing I can come up with is that the
canard arrangement provides the opportunity to benefit from what must be a
lower pressure area behind the fuselage as it moves through the
air.
However, in my own personal experience
in using a Naca duct in the front of my cowling (in one of my five
attempts to solve my oil cooler problem) the results were consistent with
the NACA assessment. It was not successful for me.
One of the differences is my oil
cooler was approx 10" from the firewall and did not have exit to a
negative pressure area. In fact, the pressure inside the cowl was
probably slightly positive. I don't know that would have made
a difference but seeing the success of John and others with it, I am led
to believe that having the back of your cooler cores in a lower
pressure area will enhance the probability of success in using a NACA
duct.
My 0.02 worth.
Ed
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
Sent: Thursday, July 15, 2004 6:48
PM
Subject: [FlyRotary] Re: New
Scoop
>I believe that his cowling must extend down
approximately 4-5 inches to achieve that.
Nope. The cowl is
level with the fuselage floor, then curves upwards.
It's tight, but it
can be done.
John Slade (Got my
EM2 .... manual)
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