That draftiness in the cockpit will cause varying static port pressures, which makes an external port better for reliable reading on instruments that rely on static input.
In my model 3 the static port is cabin pressure. This makes my airspeed readings vary 5+ MPH while in steady cruise.
Ralph
Kitfox 3 flying
Building Kitfox SS7 (RockFox)
915iS Engine
Building Partner Victor V
My experienced Model 5 Vixen (original owner/builder started build in the 90’s & finally flew in 2003…that I did not build), has no plumbing to a pitot static system. Yes, the airspeed reads high but I’m used to it & do not view this deficit as enough of a hazard to retrofit tubes now. If I was a builder, I would put in the optional static port & tubing for sure.
Also, if I was building today, I would figure out a way to close off the tail section, wing roots & cowl sealing (to cockpit) to keep the air calm inside the cockpit. As an example this is possible, a friend restored his dad’s Aeronca and the cabin is draft free because he closed off all the opportunities for air to flow through the cockpit un-invited.
Kitfox Vixen 912 ULS
N24V at C29