fuel tank plumbing

On Tue, 25 Jan 2005 19:25:52 -0600, "pwm" wrote:

So far, I am down to two concepts:

1) feed header tank from either main fuselage tank or upper wing tank with a
main/aux selector valve

2) feed header tank from only the main fuselage tank; fill main fuselage
tank (only until sight gauge shows full) from the upper wing tank via a
shutoff valve

Any other suggestions? (keep 'em simple)

Monty


The simplest is to plumb the wing tank through the aux side of the
fuel selector valve directly to the gascolator and use a vented cap.
You haven't really given enough detail about how your main and header
tanks are set up and connected. Will you have a fuel pump or is
everything gravity feed?

Ed

The simplest is to plumb the wing tank through the aux side of the
fuel selector valve directly to the gascolator and use a vented cap.
You haven't really given enough detail about how your main and header
tanks are set up and connected. Will you have a fuel pump or is
everything gravity feed?
=20
Ed


Everything gravity feed is the objective. The header tank sits on the =
cockpit floorboard, directly underneath the main fuselage tank. The =
12gal main tank is plumbed directly with fittings to the aft end of this =
cylindrical header and the gascolator is mounted on the foreward end of =
it on the engine side of the firewall. The main tank has a vented filler =
cap, as does the upper wing tank. Presently, I can find no shutoff =
valves installed, but plan to install one when I figure this out.

Thanks,
Monty

Putting the wing fuel caps on backward on a Taylorcraft will not suck the fuel
out of them. It will just not let them flow into the main tank. All you have
to do is land and turn the caps around and you are good to go.

Lyman

" jls" wrote in message
...

"Corky Scott" wrote in message
...
On Tue, 25 Jan 2005 08:13:09 -0800, Ed Sullivan
wrote:

I'm not sure why you have a header tank unless it is for inverted
flight. On my Jungster the wing tank feeds into the fuel valve as does
the fuselage tank. I can then select either the wing or fuselage tank,
but not both otherwise the wing tank could overflow the fuselage tank.
I have both upright and inverted vents on the fuselage tank and
inverted tank. On the wing tank I just use a vented cap.

Ed Sullivan

Really? You can't just plumb the wing tanks into the header tank?
Thought that was done all the time. Is it necessary to vent the
header tank if the wing tanks are properly vented?

Thanks, Corky Scott

Well, maybe, but wing tanks on a Taylorcraft are vented with ram-air tubes
on the caps and so is the header tank. In flight those tubes make
positive
pressure on the 6-gallon wing tanks and the 12-gallon header tank.

I've seen a few times, too, that the wing tank gets balky emptying into
the
header tank during flight, despite the ram-air tubes.


Let me elaborate on this rather uncomplicated fuel vent system on the
Taylorcraft. The 12-gallon header tank is fixed to 4130 fuselage tubes and
sits behind the firewall and in front of the panel. Its vent --which is
merely an acute angle cut facing forward in a vertical tube rising from the
filler cap on the boot cowl just forward of the windscreen -- is also the
hole through which the fuel gauge wire moves up and down according to the
quantity of fuel in the header tank.

Obviously the positive pressure supplied by this vent tube is slightly less
than the pressure provided by either of the ram-air tubes on the wing tank
caps. Otherwise, wing tank flow into the header tank might not occur. And
I've seen that happen with Taylorcrafts other than mine.

Some people install glorified ram air tubes on their wing tank caps. They
braze onto the caps longer tubes pointed into the slipstream and bellmouth
them. The apparent fix gives them a better pressure differential to push
wing tank fuel down into the already pressurized fuselage tank. Of course,
with the valves on the wing tanks closed, the fuselage tank must have some
way of its own to maintain positive pressure to feed gasoline through the
gascolator and into the carburetor bowl, especially in a climb where
sometimes gravity alone is not enough.

C. G. Taylor, also the designer of the Cub, must have been thinking about
those steep climbs in a Taylorcraft when he designed the ram-air tubes on
the wing tanks because they are bent more than 90 degrees downward so they
face directly into the slipstream during a steep climb.

On the subject of a small header tank in addition to a fuselage tank, that
sure does sound a little like Rube Goldberg to me. It must a device to cure
a history of fuel starvation, something I have never heard of in a simple
system like the Taylorcraft's. OTOH,maybe there's a good reason for it.

I have flown a Taylorcraft since the eighties and never had it give trouble
feeding from the wing tank to the fuselage tank, with one or two exceptions.
And never ever had a fuel starvation problem. Here are the exceptions:
You know those socks you put over a 172's pitot tube to keep bugs out while
you're sitting on the ramp? Well, those bugs, angry at the socks on 172's,
will seek out and set up housekeeping in your ram-air tubes. So you just
take a length of .016 safety wire and punch the little *******s out. When
you get one in your 172's pitot because like me you were too slack to put on
the sock, the cure is not so easy.

"Hatz Lyman C" wrote in message
...
Putting the wing fuel caps on backward on a Taylorcraft will not suck the
fuel
out of them. It will just not let them flow into the main tank. All you
have
to do is land and turn the caps around and you are good to go.

Lyman

I think you're probably right, but I've never had the experience, having
learned long ago to pre-flight. This practice was reinforced after a
line-boy gassed us up and put those lids on backwards in Kankakee.

On Wed, 26 Jan 2005 09:38:14 -0500, " jls"
wrote:

C. G. Taylor, also the designer of the Cub, must have been thinking about
those steep climbs in a Taylorcraft when he designed the ram-air tubes on
the wing tanks because they are bent more than 90 degrees downward so they
face directly into the slipstream during a steep climb.

There is another possible reason for angling the ram tubes slightly
downward: it prevents rain drops from entering the vent system while
in flight, and sitting on the ground.

Corky Scott

On Tue, 25 Jan 2005 16:25:13 -0800, Ed Sullivan
wrote:

Corky, I don't know why you need a header tank with a fuselage tank.

Sorry, this was a part of the post I missed. I did not realise that
was the situation.

I was thinking purely about wing mounted tanks plumbed into a header
tank.

Corky Scott

C. G. Taylor, also the designer of the Cub, must have been thinking
about
those steep climbs in a Taylorcraft when he designed the ram-air
tubes on
the wing tanks because they are bent more than 90 degrees downward so
they
face directly into the slipstream during a steep climb.

The down angle is to keep rain out. The airflow will be parallel
to the top of the wing in any attitude except full stall.

On the subject of a small header tank in addition to a fuselage tank,
that
sure does sound a little like Rube Goldberg to me. It must a device
to cure
a history of fuel starvation, something I have never heard of in a
simple
system like the Taylorcraft's. OTOH,maybe there's a good reason for
it.

Some airplanes had tiny header tanks to increase usable fuel.
In a slip or steep nose-down glide (especially with flaps on some
aircraft) the fuel moves away from the tank outlet and the engine might
starve if the tanks are low. The small header is intended to keep the
engine supplied while in that attitude. The Glastar had a retrofit kit
of two small headers to overcome the starvation problem, since the very
effective flaps resluted in a rather large unusable fuel quantity,
limiting range.
Other airplanes use two tank outlets, one front and another
rear, plumbed together. Citabria is a good example.

Dan

On the Champ, wing tanks drain directly into fuselage tank. There's a
valve for each wing tank. If you open that valve before the fuselage
tank has drained sufficiently, gas will spray out the filler cap vent
onto the windshield.

Corky Scott wrote:
On Tue, 25 Jan 2005 13:14:41 -0500, " jls"
wrote:


Well, maybe, but wing tanks on a Taylorcraft are vented with ram-air tubes
on the caps and so is the header tank. In flight those tubes make positive
pressure on the 6-gallon wing tanks and the 12-gallon header tank.

I've seen a few times, too, that the wing tank gets balky emptying into the
header tank during flight, despite the ram-air tubes.


Well if the header tank is below the wing tanks, and the header tank
is vented, what's preventing the wing tanks from overfilling the
header tank as Ed Sullivan suggested?

Does the header tank vent have a checkvalve?

I was picturing the header tank being downstream of the wing tanks and
not being vented. In effect, the header tank is simply a distorted
downstream fuel line.

Thanks, Corky Scott


--
John Kimmel


Naturally, these humorous remarks are all entirely my own opinion, based
solely
on rumor, supposition, innuendo and damned lies, and should be
interpreted in a
spirit of fun. My memory is faulty, also.