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FWIW, I had experience similar to Eds. I'd too heard that exit duct was
important, so fashioned a nice one for radiator exit air. It caused oil temps to
rise (I don't need oil cooler, just allow rad air to flow over pan). and had no
measurable effect on rad air flow. So I chucked it.
So I'd say test the concept, but find a way to measure the air flow in case
it has negative effect. I use barometric pressure sensor to compare pressure in
front of rad, to behind.
Yes, John, in the boest of all possible
worlds a duct exiting the cooler would undoubtedly help. In fact, I
attempted that with my two GM radiator cores - BUT, by the time I had created
the two fiberglass ducts the constraints on their flow mandated by things like
engine, mounts, exhaust, etc, adversely affected the airflow to such a degree
that they actually hurt the cooling (in my case). If you have plenty of
room and/or a location for your cooler where you could avoid the twists
and turns then it may be worthwhile. I have a nose gear, so no way could
I run a duct straight back from my cooler. Also having a "plugs up"
installation puts my exhaust on the bottom also in the way.
In the long run, the oil temps are just fine dumping the
exit air under the cowling. That said - if you can round (2-3" dia)
(fiberglass? PVC pipe?) the bottom edge of your firewall (where the air
exists) that reportedly helps considerably by making it
easier for air to exit the cowl.
Ed A
----- Original Message -----
Sent: Tuesday, December 13, 2005 9:54
AM
Subject: [FlyRotary] Re: oil cooler
opening
Ed; Thanks for the numbers. Last
night I read the article in kit planes, Oct 99, by Barnaby Wainfan on duct
work and his article entitled wind tunnel said that you need a duct behind
the coolers to offset the drag of the air in the cowling. Has anyone
done any practical applications on this (for Mazdas), or is the air from the
coolant and oil radiators just dumped into the cowling. My very
limited understanding of this, tells me that drag means more fuel
needed. Any and all comments welcome. JohnD From the
farm
----- Original Message -----
Sent: Monday, December 12, 2005 9:20
PM
Subject: [FlyRotary] Re: oil cooler
opening
John,
The area of my oil cooler opening is 22-24 sq inches
about 10" wide and 2 1/2" high. I don't have the exact dimension
handy, but its opening is approx 3-4" back of the prop flange. So
far its worked fine for about 5 RVs that I am aware of using this
approach.
Ed
----- Original Message -----
Sent: Monday, December 12, 2005
5:04 PM
Subject: [FlyRotary] oil cooler
opening
Ed; What is the opening area and the
distance behind the prop for the oil cooler inlet. I'm wondering
if the opening needs to be as near the prop as the inlets for the
radiators. Thanks in advance.
JohnD Had to cancel the insurance on
the ole Colt today and put comp. on - snowed in for the winter in
northern Michigan.
-al wick
Artificial intelligence in
cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on
engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk
assessment, Glass panel design
info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
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