Interesting thought in the prior post below.  Any CFD/aerodynamics experts
care to comment?  

I'm just at the point of doing my wing tips (and need to add the NACA scoop
vent to one which was inadvertently left off by Lancair).  I have noticed
that the std setup seems to be to route the aluminum vent tube directly to
the back wall of the NACA.  From a novice perspective it seems like this
partially undermines the NACA pressure recovery design (i.e. more like a
plain old pitot tube - perhaps worse).  Also many of those small NACA's
don't seem to follow NACA principles (sharp edges and inverted airfoil
design on the rear edge/cuff).

I was thinking of making a small cavity/manifold behind/inside the NACA and
them routing the vent into it.  Perhaps I also need an additional pressure
neutral "leak" to keep the NACA flowing???

If it works too well, is there any chance of over-pressurizing the wing
tanks?  I've heard anecdotal stories of the tail fresh air NACA's creating
enough pressure to blow switches, lights, etc out of the overhead duct.

Rick Titsworth

p.s. JohnH, I certainly don't want anything on my Lancair sticking out 1.5
inches into the airsteam {wink}.


-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of John
Huft
Subject: [LML] Re: IO-550 fuel injection

Here is an off-the-wall theory from the RV spy....

I am suspicious of those cute little NACA vents you guys use for tank
vents. I am thinking they may not be as effective as they need to be...