[The area of a 1/4" id tube is about 0.05in^2, so it would take 1155 inches of tubing to hold 57.75cf, which equates to about 96 feet/minute to move that much volume.   Increasing the ID of the vent tube to 3/8" would reduce that velocity by more than 1/2 (its x-sectional area is about 0.11in^2.  <Marv> ]

Marv,

 

Verrrrry interrrrresting.  Not.

 

You calculated the 1/4" tubing speed at .95 Kts (1.1 mph or 2938 furlongs/fortnight).  I don't see water flowing against gravity with that little of a push.  I am sure some engineer can calculate those forces.

 

What, me worry?

 

I only pump 5 gallons per hour out of each wing.  But then, it is at a faster rate for a shorter duration (about 1 gal/minute) so the water has time to drip back down in between pump usage.  I have never detected water in the fuel - even after several hours in "light" rain at 170 KIAS.  I have a mini NACA vent in the belly for the header, that is drawing 10 gallons per hour (water must be lifted 2 feet), and I use 1/4" tubing with bevel cut vents for the wings (vertical run is about 5 inches).