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Yes, but they only have 22 gallons. I have 70
gallons with two forward facing vents directed into an airstream that is going
200 mph, not 90 mph like the Cessna. Seems like I should have more pressure
coming into the vents at the higher airspeeds? Paul Conner
----- Original Message -----
Sent: Thursday, February 24, 2005 10:20
PM
Subject: [FlyRotary] Re: Vapor Lock
The Cessna 152/172 have, what, 2 - 3 feet of gravity feed, you
have only one.
Anyway, here's a question. Is there a possibility that
the path from the lagging tank gets hotter than the faster draining tank? I'm
beginning to think that even a minor temp rise in fuel path to pumps produces
a much bigger effect than any of us would imagine. Just a theory not proven
yet.
Finn
Jim Sower wrote:
This problem drove me NUTS for two years. I tried
everything. For example, I checked the vents as best I could, leveled
the airplane (checked the ball to ensure it was centered - it was),
disconnected the fuel line from the engine side of the firewall and let it
drain into a bucket. I turned off one strake at a time (with manual
maintenance valve) and timed how long it took for the other strake to
gravity drain ten gal of fuel into the sump, out of the sump through the
boost pump, through the filter and then through the firewall into the
bucket(s). Then I turned it off and did the same thing with the left
tank. They both drained 10 gal each within 5% of the same
time. Then I reconnected all the plumbing, taped over the fuel caps so
there's no possible way they could leak and went flying. Right tank
drained 20 gal while the left tank maybe 2 or 3. Level balanced flight
on a cross country. All fuel lines, vent lines, etc. are as identical
as I am able to make them. To this day, I've not met anybody
who can explain what happened. I tried everything. Back
and forth on the Velocity list much longer than you've been inquiring after
your vapor lock. NOTHING. I figured out a workaround - I
installed electric shutoff valves in place of the manual maintenance valves
between the strake and the sump. Now, when one tank doesn't transfer,
I turn off the tank that does and let the "reluctant" tank catch up.
The pump sucks it through the system just fine (the head pressure of 6" of
fuel is about 0.16 psi - a problem that would inhibit that flow you can't
even MEASURE. Assymmetric transfer is common as dirt in the Velocity
community (but not nearly as persistent as mine). It was also a
problem a long time with the Vari-EZ.
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