Since I won't have the big fan in front, I won't have much airflow to
deliver the water spray to the radiator and cooler. My opinion is that fans
are a necessity in a pusher configuration. The choice is whether to put a
fan in the main flow and shorten its life, or find an alternative like the
side duct. As far as the fan for the water radiator, it will be behind the
rad. Since its cross section will be about 3 times that of the inlet, its
airspeed will be about a third, minus the reduction from the pressure drop
through the system. If its bearings wear out, I will just have to replace
it. That's part of the price I pay for my choice of installation. I don't
consider it a safety issue since it is only used on the ground, and my
takeoff checklist includes verification of all temperatures.

Dick Gregory

Mike Wills wrote:

Dick,

   Seems to me that the fact you dont have the "big fan in front" as you
put it isnt necessarily a problem. Because you have the big fan in back.
With proper exit ducts and the prop drawing air from the ducts it seems to
me that you should still end up with a significant pressure differential
across the core which is the key to making it work.

  Charlie Airesman got good results on his EZ by using an exhaust augmentor
to increase the pressure differential across the core. That may be another
option for you to consider.

  I'd try hard to avoid adding any extra ducting under the cowl. And I'd
also try to avoid a fan windmilling in the airflow creating an airflow
restriction and additional drag.

Mike Wills

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