Flew this morning with the cowl piece removed, so I had a big
hole in the cowl.  That is the configuration that allowed me to
fly to KS.  Took pressure data from inside cowl.  Then put the
cowl piece back in to close off the hole, so only the 16 slots
1/4" x 5" for oil cooler exit.  Flew again.  Here is the data:

Open + slots:
-80mph at 80 knot climb = 0.114 psi = [-] 3.15 in. H2O
-75mph at 130 knot cruise = 0.100 psi = [-] 2.77 in. H2O

Slots only:
-55mph at 80 knot climb = 0.054 psi = [-] 1.59 in. H2O
-50mph at 130 knot cruise = 0.044 psi = [-] 1.25 in. H2O

So now I'm going to mod the cowl to put a circular hole
around the fan hub, and hopefully maintain the lower pressures.

I mean more negative pressures.

--
Perry J. Mick
Duckt N7XR
http://www.ductedfan.com

I see. You had me confused there for a minute.
That's not bad. The oil cooler should be working fine
if indeed that is the negative pressure all over the back
side of the cooler.

Where was the tap? Porous foam on end?

Could be air is going in those slots unless they are sealed
to the top of the oil cooler. In other words is the oil cooler
outlet duct sealed straight up to the cowl? Is there an outlet duct? 
There could be a dynamic pressure effect of air flowing in the slots
off setting the lower static pressure on the back side of the cooler.

Ideally the cooler should have an outlet duct going straight
up to the skin with either closely spaced louvers or venetian blind
cowl flaps. That is the simplest and most straight forward
way of handling that oil cooler position.

Try it again with the cowl piece removed and tape up the slots.

Paul Lamar
 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.
ACRE NL web site. Copyright 1998-2002 All world wide rights reserved.
http://home.earthlink.net/~rotaryeng/            http://www.linux.org