S/R Fuel Vents

[Jerry Folkerts]

We're moving the fuselage to the airport today and plan to install the wings. Then I have some final assembly stuff to accomplish over the next couple of weeks. One of those items is the fuel vent and sight guage. I've seen some, including the new Murphy Radical with the vents in the flush fuel cap. Others in the wing root off the plumbing to the sight guage. If I go with either of those, is it still necessary to have a crossover vent tube of some kind and if so, why?
Thanks,
Jerry Folkerts

[ericfo]

Hi Jerry,

Great progress.

I did fuel vent tubes into my Murphy supplied vented fuel caps. Get a little ram pressure from the tubes. I have flown through heavy rain and have had the airplane sit outside in absolute thunderstorm deluges and never had a drop of water in the fuel tanks. I first tried my own design of putting vent tubes connected to the sight gauges, but in cruise the ram pressure would push the fuel down in the sight tubes and give incorrect readings. The fuel cap tubes work great.

I did not install a cross over vent. So, I risk getting a mud dauber or bug clogged in my ram tube. Ahha, but I still have Murphy vented caps (little pin holes in the cap). So I "should" not get hydrostatic fuel lock/starvation and collapsed tank skins when descending from altitude.

It seemed to me (not an aerospace engineer), that the Murphy cross over wouldn't work very well. The vent lines need to run all the way out to the farthest uphill end corner of eachfuel tank so that they are in the air, not under water, in the fuel. This is the Cessna design. Even in the Cessna design, uneven fuel flow from each wing tank is common. It is difficult to push the fuel through the small diameter crossover tube with the low pressures inside the tanks.

Don't know if there would be any differnces with the Super Rebel vs my Elite.

Eric