jimboflying
MEMBER
This deserves more discussion of the vent system. Why are you installing a cross vent line at all?My opinion - - Every low point have a drain, and every high point be vented to the tops of the tanks. Avoid tee and elbow fittings where possible. Steve's gascolator. Tank cross-vent connected at the outboard ends of the tanks to prevent cross-flow when parked on a side incline.
Here’s another option. Cessna-style vents under the wings.
What is the best sealant to use on the pipe fittings?
Cuz it's a quick, easy, low-cost boost to flow rate that might be "just enough". That's all I can think of, anyway. In my personal opinion, those big snorkel holes are unsightly and an invitation for bugs. So bottom line, I agree.
FWIW, to determine fuel line size for the Exp I'm working on, I flowed my personal certified -12 at max rate of climb attitude and determined that 3/8 lines were sufficient (barely) for 200 HP in accordance with CAR 3 and Part 23. Somewhat surprisingly, Part 23 was a slightly easier standard to meet.
Edit: I can supply the actual flow data in spreadsheet format if anyone wants it.
It is my understanding, it is to provide a positive pressure. Because of this the flow rate will be higher.So back to the snorkel caps, are they supposed to provide positive pressure or is the snorkel just a way to enlarge the vent hole in the cap?
I can't be certain, but I seem to recall someone was certifying a larger engine and had difficulty passing the FAA's flow tests. So they installed the snorkels and they worked. End of story.Full power usually is used at slow speeds. The ram air idea never made sense to me.
Yes, this is critical. Joining at the tank level could result in a broken syphon. Either (or both) front or rear port line(s) must be entirely below the fuel surface in the tanks BEFORE they are joined.There is no front tank outlet shown on that drawing. If you use a tank with two outlets, join the two lines at or near the header tank, well below the location of the tank outlets. If you joined them up high there is the possibility of introducing air to the lines when low on fuel.
Why avoid tees?My opinion - - Every low point have a drain, and every high point be vented to the tops of the tanks. Avoid tee and elbow fittings where possible. Steve's gascolator. Tank cross-vent connected at the outboard ends of the tanks to prevent cross-flow when parked on a side incline.