If you double the thickness of the rad that will restrict the air flow

more

and your NACA duct will work worse than it is now. The ducted fan
did a good job of sucking air into the NACA duct and through the rad.
Without the ducted fan it will not be easy to get the air to flow

through

that double thickness rad. The counter cross flow rad design is very

good

however.

Paul Lamar

I already lowered the inlet lip on the naca over an inch, probably about
a year ago, so that it is a little bit of a scoop. Noticed absolutely no
difference in cooling with the ducted fan, but it might help with this
rad. I definitely need to increase rad capacity now, and this is about
the only way to do it.

Perry

That just shows to go you how bad it is :) The high velocity air you
are looking for is nowhere near the opening. An inch is probably
inadequate for the boundary layer air bleed on a P51 ram air scoop
that is that far back on the fuselage. My guess is the boundary
layer is several inches thick all the way back there. But why guess?

I know you still have my water manometer so put a velocity rake back
by the NACA scoop consisting of an  array of pito tubes spaced an
inch apart and report back :)

Here is a picture of a velocity rake I built for testing Tracy's airplane.
I wanted to make sure I was reading the real dynamic pressure.

Paul Lamar

I might get rid of the NACA entirely and go with the original Rutan scoop,
but it will be more work, and take my plane down longer. Fortunately the
belly of my fuselage was built to the original plans, the NACA was an add-on
that can be ground off easily. This is not true I think for someone building
a Cozy IV now.

Perry

 
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