Subject: [FlyRotary] Evaporator Cores for slow planes?


> Good Evening...
>
> From my readings of print and posts past I thought I
> understood evaporator cores were not appropriate for
> aircraft which travel at around 130mph or less.
> However, Ed Anderson recently posted "...with the
> engine  idling at 2000 rpm, you would need the
> equivalent of a 15 mph wind through the cores to
> maintain adequate cooling. ..."  This statement starts
> me down the path( again ) of again considering evap
> cores instead of the stock radiator.
>
> Thus, with that preface what is the consensus on what
> the airspeed range is when evap cores are not the best
> choice and something like the stock radiator is more
> appropriate.
>
> Thank You.
>
> -Scott
Hi Scott,

    It all depends on how much power you are going to produce and at what
airspeed your will normally cruise at.  I do sit on the ground at idle and
have absolutly no problem with over temps using evaporator cores.  However,
they would not cool for long should I up the power even modestly to say 4000
rpm.  But at 2000 rpm you are only producing approx 24 HP so two cores and
the oil cooler will remove that much heat as long as you have some air
blowing through the cores.

   I don't have a direct answer to your question, but if you want to know
where I would start, I would consider a thinner radiator if I were going to
consistently fly under 120MPH at high power settings.  However, even if
1w0MPH were your cruise airspeed, you probably would not be producing
anywhere the power at cruise  that you will for take off.  So again its
trying to balance the cooling you need for most of your flight regime with
that needed to get you through the most adverse conditions - high power for
take off with low airspeed.

True, you can always put in enough radiator to keep it cool at high power
and slow speeds, however, you may pay a high pentalty in drag at higher
airspeeds such as curise, where you will spend most of you time flying.  So
like most other areas, cooling is one of compromise.

Ed Anderson