REFLECTOR: Prop "suction"

[Al Gietzen]

Al just convinced me that the propeller isn't sucking much air out of the
cowl. I'll stick a fan on the drive shaft (next year when I get to the
engine installation) and let everybody know how it works. I'm going to
install the DeltaHawk diesel, so I've got one or two radiators, and like
Kurt, I'm hoping I don't need any external bulges from ram scoops. Have you
seen that big, honkin' belly scoop on DeltaHawk's Velocity?

 

Doug;

 

Don't get me wrong; the prop does provide fairly good negative pressure at
the cowl exit if the prop is within a few inches of the cowl exit - and may
be adequate for low power ground operations cooling; even with compact heat
exchangers.  No problem with the widely spaced fins of air cooled engines.
My cowl exits are 6" from the prop, and it definitely draws air from the
cowl, and I'm hoping enough for ground cooling.

 

But for high power flight operations I'm suggesting that it is basically a
non-factor compared to other aerodynamic forces.

 

The problem with a fan on the prop extension is that the shaft speed,
especially on the ground, is so low that the "fan" would probably be of
little help.  

 

Al

 

 

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