But the prop typically doesn't (can't) force much air through the cowl on
the ground:

1. The cowl opening is typically a couple inches behind the prop and is in
no way sealed or ducted to the prop, so most of the prop air just goes
around the hole.
2. The prop is relatively narrow with only a few (2-4) blades so it's time
in front of the cowl hole is relatively small.  Furthermore, given that most
cowl opening are flat, they do little to catch/scoop any of the rotational
air (spiraling slipstream) being drug around by the prop.
3. The inner portion of the prop is not very aerodynamically powerful, nor
moving very fast so that area isn't pushing much air anyway
4. Most auto fans draw (suck) air through the radiator, versus trying to
push air through.


  -----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Mark
Sletten
Sent: Monday, April 02, 2007 10:36 AM

A diesel installation with heat exchangers up front has a built in fan...
it's called a prop!