Rowland,
For the last 10 years I=99ve been putting the vent on the bottom.
I use 1/4 inch OD tube (although others have gone with larger) and
extended the tube below the fuselage some two inches minimum to be in
clean air bent forward. Typically on the Starboard side and use a break
in the cobra neck. Drill the two holes at the base of the tube as in
the Europa top mounts should mud or grass get flung into the tip. A
clogged vent will starve the engine eventually as the vacuum of the fuel
being used will be greater than the pumps capability to draw fuel...
Find a convenient place in the trigear well or on a mono it can be
behind the bulkhead or glued to the wood supports, being sure to clear
the flaps. I put it on the forward side of the bulkhead and glassed and
floxed it in. Just scuff the tube and install. It is very rugged and
light. I made my tube from stainless. It is a bit hard to drill, but
very stiff and strong. Use either rubber, tygon or polyurethane tubing
with appropriate clamps.
On my website is how I plumb the unit which is similar to Grahams. I
don=99t use AN fittings as it is a vent system and not worth the
fittings.
See photo attached and www.customflightcreations.com and hit the
techniques tab.
Regards,
Bud Yerly
From: Rowland Carson
Sent: Wednesday, May 04, 2016 11:26 AM
Subject: Europa-List: fuel vent query
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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