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Ed/ Tracy,
Can't say as I understand Tracy's set- up
completely, other than it's toward the lower end of Rad sizes. I was thinking to
myself how I could create a -ve pressure in the rad outlet to create a
suction on the Rad. We all know how the exhaust augmentation works and I was
wondering why we can't do the same thing with the rad outlets by running the rad
outlets inro a larger outlet fed by outside air. At idle the air is fed by the
prop air stream and at level fight it is fed by outside air stream.
The outside air could be could controlled by a
butterfly - simple enough. I know there emphasis on using shutter /flaps to
control the cowl outlet and I believe their good at restricting air flow, but I
don't know if this equates to a good -ve pressure behind the Rad. This
presupposes the Rads are completely enclosed for both inlet and outlet
air.
George ( down under)
75% of my cooling problems were solved
with the oil cooler change I did but still needed more margin for hot weather
climbs. Made the decision to not change or enlarge the cooling outlet
(that adds drag) so went ahead and butchered the pretty inlets I
made.
Ed Anderson's spreadsheet on BTUs & CFM cooling air
required was instrumental in deciding to go this way. It showed
that without negative pressure on the back side of the rads, there would never
be enough cfm to do the job during climb at full throttle. Negative
pressure is what I had when I flew without the cowl on but oh what a draggy
condition that was.
The old inlets were 4.5" diameter for the radiator
and 4.125" diameter for oil cooler.
New inlets
are 5.190" for the rad, and
4.875" dia for the oil.
This may not sound like a lot but it
represents a 36% increase in inlet area.
Results were excellent.
Oil temp went down 19 degrees at the test speed (130) and water temp dropped 9
degrees. On 80 degree day and 500 ft msl the oil temp maxed out at 194F
at 210 mph which is way faster than I would normally go at this
altitude. Temp was around 175 at 130. Oil Temp in climb
remained below redline (210) but the temperature lapse rate today made results
not very meaningful. OAT was dropping 14 degrees a minute at 3000 fpm
climb rate.
now back to that nasty composite work to pretty up the
inlets again. They look like large stubby pitot tubes now.
I
hadn't thought of a good name for the RV-8 but a friend in California recently
came up with the winning idea which fit it well. "Euphoriac" It's a term from a Sci Fi book (Vintage
Season) meaning something which induces euphoria.
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