Jeff Spitzer wrote:

While you are on the subject, I will put forth my intended fuel
system, if anyone can shoot it down, please do it now before I
find out the hard way!

Given:  4 fuel tanks, 2 in each wing.  The outer ones pump into
the mains by dedicated small transfer pumps, and only the mains
feed the engine.

Each main will go into a filter, then into a engine delivery
pump.

I don't agree with sucking through a filter unless its a 70 micron sock
filter.

No shut-off valve, no header tank. I am assuming that the

pump will not allow any back flow when off, nor any forward
flow, either.

Most automotive style HP pumps will allow forward flow.

If there is forward flow, a check valve with a

cracking pressure of about 3psi will stop that and only needs to
be in one side.  The only reason for this check valve is to
prevent fuel flow when parked with one wing low.  It is an
amphibian and will sit in the water one wing low.  No shut-off
valves, when the pumps are off, no flow.  You select the tank by
which pump is on.

The fuel pump outputs will be tied together to the fuel rail.
The return line will go to a electric fuel valve like the
selector valve in a pickup truck with dual tanks.  If this valve
fails, you just dump all the return to the same side.

Depending on your pump capacity vs. fuel usage this could be a short term
solution when the tanks are already quite full.

Now a further requirement is to balance the load.  I've been
told it wont take off if you start off with the left sponson in
the water.  The transfer pumps will draw from the filter and
dump it at the far end of the opposite tank.  The pump will have
to have engine pump capacity in gph in case of failure of one
engine delivery pump , you have to transfer as fast as you burn
it in order to use both mains.  One advantage of this is when
mixing the oil, turn on both transfer pumps and you will
circulate from the outlet to the other end of the tank.

I don't follow, perhaps you could elaborate.  I thought the transfer pumps
pumped from the outer tanks to the main tanks.  How can they also circulate?


Jeff Spitzer

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