I=99m installing the type of fuel vent described by Graham
Singleton and others, where the vent pipe goes up to a syphon break at
the top of the F18 filler neck then down to reach atmospheric pressure
underneath the fuselage. I=99m using 1/4=9D soft aluminium
pipe with AN fittings.
It=99s probably not very important, but I wondered if there was
any conventional wisdom on the ideal shape for the bottom end of the
vent pipe. I believe I=99ve seen vents that are chamfered like A &
B in the diagram attached below, but am not sure if that would create an
undesirable increase (A) or decrease (B) pressure in the vent pipe.
It seems desirable (to prevent accidental damage etc) that the vent
should protrude as little as possible below the fuselage, so the
diagrams show an exaggerated length for clarity. Instead of a straight
cut pipe as at C, would there be any downside to terminating the pipe in
an AN bulkhead fitting with the outer end cut off, to make it look
rather like a large static port? This seems the most robust and elegant
way to do it, but I=99m concerned that it may cause problems I
hadn=99t thought of.
Anyone have any relevant experience or knowledge of the shapes of fuel
vents?
in friendship
Rowland
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