From: "Joseph Berki" <joseph.berki@grc.nasa.gov>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, November 05, 2003 9:30 AM
Subject: [FlyRotary] Cooling


> Hi everyone,
> I decided I did not like the cooling system mounting in the Limo EZ.  The
> scoop is too big and the resulting lower cowl is draggy.  Because this is
a
>  SNIP

, evaporator cores like the 81 Caprice vintage (342 cu inches) would
> fit.  I think that this system would work but do not have any experience
> with evaporator cores in pushers.  Another issue is getting sufficient
> clear area behind the rad.  Here is where a dry sump or short oil pan
would
> really help.   Any thoughts on this?  Thanks for any help.
>
> Joe Berki
> Limo EZ
>


Joe,

    The only thing that I might add to aid in your decision it that
evaporator cores work quite well in tractor applications.  Of the six flying
rotary aircraft (all RV types) at the rotary roundup at Shady Bend, five of
them employed evaporator cores.  From my limited experience, it appears that
where there is adquate dynamic pressure (such as in flight) the cores work
quite well.  If fact, I have no problem on the ground while at taxi power
levels or less. But, if there is any area where they may not provide
adequate cooling for a pusher, I would think it would be on the ground where
the dynamic pressure is,of course, much less.  I have a fairly large bottom
cowl opening (28x4 1/2) as well as cowl louvers, so that may help my
situation to stay cool.

My back of the envelope calcuations indicates that with two evaporator cores
and a pre 93 oil cooler ,with the engine  idling at 2000 rpm, you would need
the equivalent of a 15 mph wind through the cores to maintain adequate
cooling.  Admittedly this is a rough calculation.  With the tractor
installation having that big fan up in front of the cores turning at idle
rpm appears to provide adequate airflow for cooling on the ground under most
OAT conditions.  Of course, with the pusher you have a different situation,
would your exhaust augmentation provide adequate cooling air?  Guess,
someone will have to try it to find out.

Best Regards


Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
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