>>>>>> 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
>>> Paul,
>>> So how does 1/4" tube inside of 1/2" tube

sound? I imagine the

Teflon>>> spacers need slots to allow fuel to

travel between the

two pipes
>>> correct?
>>> Doug in Japan
>>> Correct on the slots os small holes. My guess

is the diameters

need>>> to be
>>> closer.
>>> What wall thickness for the half inch OD tube

do you have in mind?

>>> Paul Lamar
>> >> Paul
>> >> Still clue less on actual sizes. Probably

better to look at sensors

>> already
>> out there.  I have heard that if they much over

4 feet they are

hard to
>> calibrate.  Guess it depends on size and

material though.

>> >> Doug in Japan
>> >> There is a formula around for parallel plate

capacitors with

>> an air dielectric. Also the dielectric constant

for gasoline

>> and alcohol can be looked up on Google I

suspect. The differnce

>> is what you are after. Here it is one example.

Oil is 2 to 5

depending>> on type. Here is the equation in jpg form.
>> >> >> >> If you place most of the sensor along the top

of the tank and

>> gradually bend it down near the bottom or

fuselage end of the tank

>> it will be more accurate where it counts.

Namely near the end of

the>> fuel supply.
>> >> BTW the holes to pass fuel do not have to be in

or just in the

plastic>> spacers. They can be anywhere along the

outer tube.

>> >> Paul Lamar
>> >> > > Jim Weir did an article on this in Kitplanes a

while back.  Look

at the
> "Capacitive Fuel Gauge" articles.
> > http://www.rst-engr.com/kitplanes/
> > Scott Gettings
> > Yes he did but that is apples and oranges to

what I am suggesting.

> He used parallel flat plates for the capacitor

so if there is any

dihedral> in the wings it will only measure the

last half of the

fuel supply roughly.
> Another big difference is the sophistication of

the electronics.

> Use of a 555 IC as a variable frequency

oscillator  is much much

simpler> than making an oscillator out of several

op amps. The

third difference is
> the use of a low cost digital frequency counter

to indicate the

> quantity of fuel. This is inherently much much

higher resolution

than> any analog gage such as Jim Weir used in his

design.

> > Paul Lamar
>
Scott

Thanks for the intro to the web site.  A lot of

interesting info

there.  I
thought of another way to make a inexpensive fuel

sensor.  It is

based on an
idea a group of my research buddies were

commissioned to develop

for a Swiss
client about 23 years ago.  Ready for this?  It

was a rubber duck

that when
placed in water would activate the circuit and

then sqwuak when the

temperature got too hot. OK definitely not one our

more challenging

projectsbut we did develop a small sensor the

activated when

wetted.  Perhaps seven
of these epoxied into the tank  would be good

enough to indicate

1/8 of tank
increments.

Doug in Japan

Doug,

If you like this concept and have the panel room for
the LEDs, as well as access for a vertical tube the
height of the tank, you could also make a magnetic
float that rose and fell in a tube (similar to a
sight level tube).  Then place the float in
proximity to a series of magnetic switches (e.g.
reeds or door alarm switches). This allows no
exposed elements to gas, and the LED nearest the
magnet would be switched ON.  Very simple, light and
inexpensive.  My plane uses similar magnetic sensors
for its gear position lights.

Scott Gettings