Hi Fred,
I use the big fan up front! The NACA inlet on the right side, originally
intended for fresh air into the cockpit, is not leading air into the cockpit
but into the panel (made a duct of bid and epoxy from the NACA to the right
underside corner of the panel, easily removable by one screw. On top of the
panel, I have made long cutouts about 1/4" wide, close to the front edge.
Leave enough un-cut material to maintain strength, ref. the bolts holding
the panel to the top of the firewall. It is surprising how tight the panel
is along the bottom, but if necessary you can put in some soft foam or other
suitable sealing material (I have not).
Soon after starting the engine, while the oil is still warming up before
starting to taxi, I can see the mist disappearing on the front window.
Heating of the air flowing through behind the panel is from the instruments
and through the firewall. This ventilation therefore also helps keeping the
instrument temps down (never has been an issue, even in southern Europe on
hot summer days).
As you well know, no air comes into the cockpit unless it also is allowed to
escape. I assume you already have made an efficient air outlet from the
cockpit, both for this de-mist air, for fresh air into the cockpit in the
summer (through the left side NACA in my case) and for cabin heating in the
cold season (I take warm air from behind the water cooler).
Regards,
Svein
LN-SKJ
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