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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)
>> Homepage: http://www.flyrotary.com/
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