Anyone have any good ideas on a position for the OAT gauge probe.  My
aircraft is already built and does not have one, and I would like to
install one.

Steve,

 

Oat probes and the connecting wires are very sensitive to temperature influences - cabin heating of the wires and mounting location, sun influence (even in flight), hot air leaking out of the cowling, etc.......

 

The best location I found (LNC2) was on the pilot side, just forward of the landing gear door opening, about mid- opening.  This is the RMI "button" sensor housing.  The lower wing surface generally does not see the sun and there is nothing in the wheel well to influence the temperature.  Indeed, air is drawn into the low pressure cockpit thru the flap and aileron push rod holes.

 

On the other hand, the VM temp probe is a 1/2" long, 1/8" diameter projection and that is located in the co-pilot flap fairing fillet just forward of the hinge line.  The interior of the fairing fillet is stuffed with insulation.  This probe generally coincides with the RMI probe except when the sun hits the right side of the airplane.