Anyone know of a good reason NOT to do that?

Thanx,
Joe Hull

Joe, Paul and group,

There are many good reasons, "not to do that". The most telling reason

can be explained by anyone who has flown behind a variable pitch prop.

After a certain speed is acheved the fan is simply IN THE WAY of the

air.

Like a vp prop in flat pitch the air can't flow through properly. This

is a problem for high speed cars as well. Most cars capable of 100+
continiously use some kind of dump on the radiator shroud to allow
the air to route around the fan.  Bill Jepson

Also it is not good to heat the air before it goes through the rad.
My rule of thumb for a liquid cooled engine is a one degree rise in the
incoming air temp results in a 1% drop in cooling.

Paul Lamar

"Joe Hull (Pilgrim Technologies)" wrote:

Paul, etal. -
I should have given a little bit more info on my configuration.  This is
a Cozy Mark-IV - Pusher configuration.  Several people have put the
radiator under the engine and I'm not sure there is adequate space there
- unless I configure it like Perry Mick's original layout and leave the
radiator exposed on the back side - or I could make the lower cowl more
"boxy" to give the necessary clearance (can you spell drag!).

Attached is what I was thinking (forgive the simplistic drawing - I'm
CAD challenged). But it looks like there is enough room between my
firewall and the engine to slant the radiator and build a plenum to
direct the air up from the NACA and through the radiator. The space
behind 80% of the radiator is unobstructed (> 10") with the other 20%
being within 4"-5" of the radiator.

I was thinking about adding a radiator fan only because I'm worried
about extended idling on the ground.

What are other's experience with engine temperature on the ground -
especially in a pusher?

Thanx,
Joe Hull
Cozy MkIV #991 (working on Engine & Cowling)
http://www.maddyhome.com/canardpages/pages/JoeHull/index.html

Oh OK  Now I see what you are driving at.

That looks like that will work great. I marked up your sketch in red to
show the dimensions. Normally fans are driven on the water pump shaft
and you have it driven off the e-shaft. No problem there but you
will need some sort of adapter.

NACA ducts are not recommended by NACA for use feeding heat exchangers.
I recommend a P51 style duct instead.

This could be a major break through in liquid cooling pushers
if you have the required room behind the engine.

This scale 3D is how I would handle the lower motor mount. This would give
you more room for a curve in the P51 style duct and a stronger and lighter
motor mount in the bargain.

Paul Lamar

This looks very nice on clean sheet of paper, but in reality there is too
much stuff mounted on the firewall. Aileron control tubes, rudder cables,
fuel lines and much more. All that will be hard to seal for leaks and may
interfere with the controls.

Bulent

 
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