Paul or anyone.

My airplane specs. have a wet wing (leading edge D section) which are
divided into main and auxiliary long range tanks.  Total is about 110
gallons.  Holes are cut on both the middle bottom and front edge of the
D
shape ribs to allow fuel to flow down to the pickup for the mains and
another pick-up and pipe plumbed to the auxiliary.   That is four pipes
with
check valves, solenoids, side to side transfer pump for balancing the
plane
on the water. In addition the specs.  call for pieces of rubber to be
fastened over the  the ribs holes  to prevent backflow during turns.
The
rubber pieces are a joke. IMHO the design is less than admirable.

There must be a better design approach such as installing  simple
flapper
valves like those that are used in  hand fuel pumps or diving snorkels?

I would like to eliminate the four tank concept and just make the whole
leading edge into one tank thus having only two tanks to deal with.  Any
foreseeable problems with this approach?

Thanks

Doug in Japan

Can you send me a sketch jpg showing all the parts? Fuel systems
are extremely important.  Here is a picture of the metal flapper valves
used
in the Lancair IV and ES I suspect. I think they yield a certain
redundancy in a slip or uncorrodinated turn situation. The last thing
you want is an air bubble on the intake side of the high pressure pump.
The pump may fail to self prime when fuel is restored to the intake.
Particularly if the pump has cavitated in the past. If it does fail to
self prime it will rapidly over heat.

Paul Lamar

Paul,
It's not very clear from the picture, but these "Lancair flapper valves"
are fabricated from a couple pieces of sheet aluminum riveted to a short
piece of piano hinge.  They should be easy for anyone to make.  The
hinge pin should be longer than the hinge so it can be bent over to
prevent it from sliding out.  The "tab" at the top is to prevent the
flapper from getting jammed in the open position.  Once it is bolted
into place, Lancair instructs the builder to put a bead of micro around
the perimeter of the hole and then push the flapper up against it and
leave it to cure.  After cure, you pop it loose and you now have a nice
sealing surface.  Helps to put some packaging tape on the flapper before
pushing it into the micro.

Mark S.

Paul,

The system layout is identical to what you recommend ie: double deck Andair
valve with fuel return to the tank it is drawing from.  The leading edge is
divided into two tanks main inboard 38 gallons and aux. outboard 18 gals.
The D wing ribs go through the tank at regular intervals. Holes are cut into
the ribs to allow fuel to flow down towards the sump outlet and vent out
along the top towards the wing tips. There are two pumps (one in each wing)
that pump the fuel out of the auxiliary tank and downhill a few inches and
back into the main tanks. Wings have a 3 degrees dihedral and fuel is drawn
from the bottom of the inboard side of the tank only.  From there to the
header tank is straight forward design and not a design concern at the
moment

In my case with an additional ferry tank in the aft luggage area that
would mean 5 tanks to play with.  It seems the logical solution would be to
make the whole leading edge one tank. Thus I have only three tanks to deal
with.

Sloshing towards the wing tips can be handled with flapper valves and but I
think finding a long fuel sensor over four feet long might be the biggest
challenge.


Say I will be flying the C-150 to Portland and Seattle from Sept 12th
through the 19th if any of you rotary heads wouldn't mind me stopping by for
a few hours.


Doug in Japan

I changed my mind about those Andair valves. They are in dire need
of stronger detentes.

Header tank design is critical as is tank vent design.
Keep header tank tall and skinny.
EFI return flow to the header tanks is warm and full of bubbles.
Place the high pressure pump near the bottom of the header tank.

Improperly designed vents can empty a tank in minutes
at speeds over 150 MPH. Do not vent the tanks in such a way as to pick
up dynamic pressure. Vent the header tank straight up and shield it from
air currents. Use vents with four small holes drilled 90 degrees
all away around the vent tubing. Place the main tank vents in a
unpressurized (static pressure) wing tip fairing. Place the separate header
tank vent near the top of the fuselage straight up in an unpressurized area.
Keep the bugs (literally) away.

Fuel level sensors are easy to make. Concentric metal tubes open on both
ends form a capacitor with fuel as the dielectric. Hook this capacitor
to a Radio Shack 555 IC oscillator and thence into a counter. As the fuel
is burned off the capacitance changes and that changes the frequency of the
555 oscillator hence the count also changes. Counters with LCD can be
cheaply cannibalized from low cost digital VOMs.

http://www.uoguelph.ca/~antoon/gadgets/555/555.html

Paul Lamar

Thanks Paul,

Good advise.  I am afraid the SeaWind header tank vent design is on the
engine pylon facing forward, hence it might well  pressurize the header
tank.  Not advisable.

The html location would not open but I am familiar with the 555 series in
timer applications. Hadn't thought to measure capacitance in that way.
Clever.

How to keep the tubes separate? Plastic inserts?


Thanks


Doug in Japan

You make up a bunch of little Teflon spacers on a lathe.
Other types of plastic may or may not be compatible with
alcohol and gasoline.

Paul Lamar