The Murphy Builders Site

My Rebel 049 has the old style ball-valves over the door and all fuel line
routing is as-per MAM circa early 1990's.

On trips--- I always take-off on both tanks then in level flight turn off
the passenger side and run on the left side till the engine sputters then
turn the left side off before turning the right side on so I don't have fuel
pushed back in to the left tank. With judicious leaning I can run 2.5 on ea.
side and have never run longer than 4.2 airtime (Wilkesboro NC to Lakeland
FL) . My thought is, beyond the monitored use of a functioning time-piece I
know closely how much air time/fuel is in the tanks.

I've never had a no-restart condition from this method in a Rebel.

Local flying both tanks stay on and I'm at the pumps by the time indicators
are between half and quarter.

Not recommending anything here just giving my experience and would like to
hear pro's and con's I may not have considered. .........Angus



----- Original Message -----
From: "Ron Shannon" <rshannon@cruzcom.com>
To: <rebel-builders@dcsol.com>
Sent: Tuesday, December 22, 2009 6:04 PM
Subject: Re: [rebel-builders] Fuel slector valves

I believe the tank venting design will have an influence on this switching
procedure. Not to reopen a subject that's been covered quite a bit (see
archives) I think with dual vents and full cross vent (and perhaps other
configurations) it may be possible to run one tank dry before switching as
Drew suggests -- if you're so inclined. Personally, I wouldn't
intentionally
cause an in flight shutdown except in an emergency scenario where fuel
reserves absolutely had to be managed that tightly. Your mileage may
vary --
literally. :-)

Ron
254R


On Tue, Dec 22, 2009 at 2:41 PM, Drew Dalgleish
<drewjan@cabletv.on.ca>wrote:

Hi Walter I wonder if that problem could be unique to your plane cuz I
often run the pilots side tank empty to help balance my plane and get
maximum range. I think I usually turn off the empty tank before turning
on
the one with fuel in it and I've never expreienced any delay in the
engine
restarting.
As for floor mounted valves consider where you place it so that if you
ever
install floats you will be able to easily crawl through to the other side
for docking, pumping out, refueling etc.

At 11:27 AM 22/12/2009 -0800, you wrote:

And with only the top mounted independent valves, be very careful when

running one tank dry while flying. The sequence for closing and opening
the
valves is very critical to avoid an air lock. I know this from first hand
experience and am able to replicate the issue on the ground.

We've discussed it before on the list, but here is the sequence. When
you

run one tank dry, with the other full tank closed, you must first open
the
full tank before you close the dry one. Otherwise, your engine will quit,
and you will not be able to keep it running. It will restart, but then
keep
quitting on you.

The problem is that air gets trapped when you close the empty one, and
the

full one can't flow fast enough. It flows just enough to start your
engine,
but it will keep quitting on you. If you keep the empty one open, the
locked air will vent up through it, and allow the good tank to feed down
to
the carb. Once it is feeding OK, and the air is out, then you can close
the
empty one.

It took me a while to figure this out when it happened. Luckily, I was
on

the ground when I first did it.

With floor mounted valves you avoid this problem, as the air can't get

locked in the lines above to the tanks.

Walter

Drew

-----------------------------------------------------------------
List archives located at: https://mail.dcsol.com/login
username "rebel" password "builder"
Unsubscribe: rebel-builders-unsubscribe@dcsol.com
List administrator: mike.davis@dcsol.com
-----------------------------------------------------------------

-----------------------------------------------------------------
List archives located at: https://mail.dcsol.com/login
username "rebel" password "builder"
Unsubscribe: rebel-builders-unsubscribe@dcsol.com
List administrator: mike.davis@dcsol.com
-----------------------------------------------------------------

Angus, your sequence is exactly the one I described as being susceptible to
an air lock. If the good tank line drains enough to fill with air, you would
be in trouble. With a quick change on a sputter, you may be OK, as you have
experienced. Also the fact that the good tank is full provides more head
pressure.

Consider this scenario. You are flying to a far destination, and you are
starting to run low on both tanks. You shut down one tank, to drain it first
so you know better how much is left in the other, and how much time you have
left. Let's say your good tank has 5 gal left (which is pretty low
actually). You are flying at high altitude and now it is time to do a slow
descent as you get nearer to your destination.

Your engine is now running at low power, and will have low fuel flow. It
will also probably take longer to lose power, as the low tank will keep
splashing over the outlet enough to keep some flow, but not full pressure
any more. You hesitate with changing tanks on the first sputter, as you want
to get as much as possible out of the low tank before switching. Meanwhile
the other tank line (the closed one) starts to drain as well, because there
of the lower pressure downstream. If it drains (and fills with air (from the
other tank) before the engine sputters, you will be trouble if you close the
empty tank first. The air is now trapped.

This situation can be completed avoided by simply opening the good one
before closing the empty one, as I explained in my previous posts. Why take
the chance?

Walter

-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Angus
McKenzie
Sent: December 23, 2009 6:21 AM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] Fuel selector valves

My Rebel 049 has the old style ball-valves over the door and all fuel line
routing is as-per MAM circa early 1990's.

On trips--- I always take-off on both tanks then in level flight turn off
the passenger side and run on the left side till the engine sputters then
turn the left side off before turning the right side on so I don't have fuel

pushed back in to the left tank. With judicious leaning I can run 2.5 on ea.

side and have never run longer than 4.2 airtime (Wilkesboro NC to Lakeland
FL) . My thought is, beyond the monitored use of a functioning time-piece I
know closely how much air time/fuel is in the tanks.

I've never had a no-restart condition from this method in a Rebel.

Local flying both tanks stay on and I'm at the pumps by the time indicators
are between half and quarter.

Not recommending anything here just giving my experience and would like to
hear pro's and con's I may not have considered. .........Angus



----- Original Message -----
From: "Ron Shannon" <rshannon@cruzcom.com>
To: <rebel-builders@dcsol.com>
Sent: Tuesday, December 22, 2009 6:04 PM
Subject: Re: [rebel-builders] Fuel slector valves

I believe the tank venting design will have an influence on this switching
procedure. Not to reopen a subject that's been covered quite a bit (see
archives) I think with dual vents and full cross vent (and perhaps other
configurations) it may be possible to run one tank dry before switching as
Drew suggests -- if you're so inclined. Personally, I wouldn't
intentionally
cause an in flight shutdown except in an emergency scenario where fuel
reserves absolutely had to be managed that tightly. Your mileage may
vary --
literally. :-)

Ron
254R


On Tue, Dec 22, 2009 at 2:41 PM, Drew Dalgleish
<drewjan@cabletv.on.ca>wrote:

Hi Walter I wonder if that problem could be unique to your plane cuz I
often run the pilots side tank empty to help balance my plane and get
maximum range. I think I usually turn off the empty tank before turning
on
the one with fuel in it and I've never expreienced any delay in the
engine
restarting.
As for floor mounted valves consider where you place it so that if you
ever
install floats you will be able to easily crawl through to the other side
for docking, pumping out, refueling etc.

At 11:27 AM 22/12/2009 -0800, you wrote:

And with only the top mounted independent valves, be very careful when

running one tank dry while flying. The sequence for closing and opening
the
valves is very critical to avoid an air lock. I know this from first hand
experience and am able to replicate the issue on the ground.

We've discussed it before on the list, but here is the sequence. When
you

run one tank dry, with the other full tank closed, you must first open
the
full tank before you close the dry one. Otherwise, your engine will quit,
and you will not be able to keep it running. It will restart, but then
keep
quitting on you.

The problem is that air gets trapped when you close the empty one, and
the

full one can't flow fast enough. It flows just enough to start your
engine,
but it will keep quitting on you. If you keep the empty one open, the
locked air will vent up through it, and allow the good tank to feed down
to
the carb. Once it is feeding OK, and the air is out, then you can close
the
empty one.

It took me a while to figure this out when it happened. Luckily, I was
on

the ground when I first did it.

With floor mounted valves you avoid this problem, as the air can't get

locked in the lines above to the tanks.

Walter

Drew

-----------------------------------------------------------------
List archives located at: https://mail.dcsol.com/login
username "rebel" password "builder"
Unsubscribe: rebel-builders-unsubscribe@dcsol.com
List administrator: mike.davis@dcsol.com
-----------------------------------------------------------------

-----------------------------------------------------------------
List archives located at: https://mail.dcsol.com/login
username "rebel" password "builder"
Unsubscribe: rebel-builders-unsubscribe@dcsol.com
List administrator: mike.davis@dcsol.com
-----------------------------------------------------------------






-----------------------------------------------------------------
List archives located at: https://mail.dcsol.com/login
username "rebel" password "builder"
Unsubscribe: rebel-builders-unsubscribe@dcsol.com
List administrator: mike.davis@dcsol.com
-----------------------------------------------------------------