FUEL TANK MODIFICATIONS & SYSTEM for CHINOOK

Modifications to the Chinook Fuel System and reasons for them.

I used hole saws to cut the sheet-metal tanks. Because they were steel, I
was able to solder in my own fittings. Galvanized steel solders easily if it is
clean.
The tanks were slosh-coated with fuel tank sealant, just to be sure.
Sight gages are nothing more than a loop of clear plastic tubing.
Dye was used to spot where the filler necks should go , as they had to match
the holes in my fabric. A threaded steel ring was then soldered to the tank
for the filler-neck. Fuel cap is standard Quicksilver, MTD lawn tractor part.
Caps are vented and chained.
Gallon marks were made next to the sight gage and I found that these steel
tanks look a bit smaller, but hold 8 gallons each. Weight is about 10 pounds
more than plastic.
NOTE: If I had it to do over again, I would use nylon straps to hold tanks
in the wings.
ASAP treated me very fairly in this matter.

As I wanted a long range fuel supply for travel, I ordered my Chinook kit with the extra "in-wing" fuel tanks. On
delivery, I found I did not like the looks of the tanks, and pressure testing them at only 2 psi found an air leak in
one tank. ASAP sent a replacement tank, and while they really didn't look airworthy to me, I built my wings and
installed these plastic tanks.
The tanks lasted only about 3 hours of flight time and were never filled beyond 5 gallons of fuel. Leaks developed
at the root tube where the corners of the tank have fasteners. Leaking fuel will ruin the Lexan by clouding it, and is
really a fire hazard in the hanger. The plastic filler necks also came loose and would rotate with the fuel cap.
The wings were removed and the plastic tanks were returned to ASAP and I was given a refund.
A visit to a Taylorcraft parts supplier told me they used both steel and aluminum tanks over the years, so I elected
to have steel tanks made at a local sheet metal shop that makes heating ducts for furnaces.
( I did NOT tell them the tanks were for an airplane. I told them they were tanks for a racing go-kart.)
I chose steel tanks because of ease of repair for me as the galvanized steel is easily soldered, and I added my
fittings where I wanted them. The fittings in the sump draw fuel regardless of climbing or diving. My plane has
never suffered from fuel starvation. Cost of the blank fabricated steel tanks was less than the ASAP price for the
plastic tanks. I now have over 550 hours on the steel tanks with no problems.

I have received many questions about my fuel system and how it works.
Both steel tanks are hooked together with a "T" fitting located under the root
tube. This is the effective "bottom" of the tank. Because both tanks are
hooked together, they serve as one BIG fuel tank. All fuel is always drawn
from these "in-wing" tanks. It will flow by gravity to the engine pulse pump.
Fuel is free to move from one tank to the other, and if parked on a hill for a
long period, I notice one tank will be more full than the other. This bothers
nothing, and the weight difference cannot be noticed when flying.
Fuel level is determined by sight gages located next to the root tube as
shown here. Red pin-stripe tape marks 2 gallon increments. As the tanks are
flat and slope to center, it is not real accurate as to exact fuel level, but when
in flight, I can tell roughly how much fuel I have remaining.

The extra "football" tanks are used only when I travel, as I find the main
in-wing tanks are plenty for local flying.
Fuel is drawn from the "football" tanks through the wings to a selector
valve located right over my head on the root tube. This selector allows me
to choose which football I draw from.
From the selector the fuel goes down a fuel line to a automotive electric
12 volt fuel pump located under my seat as shown here at right. This
pump is located under my radio "U" bracket mount on my right side.
From this "transfer fuel pump" the fuel goes back along the floor to the
rear and up to a "T" fitting located on the main line, just ahead of the fuel
filter. This allows fuel to be forced "back" into the steel main tanks located
in the wings. The fuel goes in by traveling back through the fuel "outlets",
and this has the added effect of moving any debris away from the sump
outlets. Air in the main tanks then flows out of the fuel caps as the tanks
are being filled. This system is a sort of in-flight refueling.
The system is safe because fuel is always drawn from the main in-wing
tanks.
It does not rely on electricity except for transfer.
If you forget and leave the electric transfer pump running, no harm comes
from running a football tank dry. ( A red indicator light shows I am
transferring fuel as a reminder.)
The pulse pump is gravity fed.
A fuel drain valve is placed at the lowest point in the system.
Quick disconnects are fitted in the line from the football tanks to make
them easy to remove and install. Check valves were removed from the
football tanks as I have heard of the sticking all to often and are not
needed with the electric transfer pump.

Red light indicates fuel transfer is in progress

A few notes on fuel supply safety:

I have seen some really crazy fuel systems, and my advise is to keep it as
simple as possible.
Be sure to mount your pulse pump as close as possible to the crankcase
port to get the best pulse.
Use stiff or heavy walled pulse line. If the tube can flex, the pulse will
loose energy.
Mount the pulse pump so that oil will drain downhill back into the
crankcase. If the pulse pump is too low, oil or fuel can collect in the pump
or on the diaphragm and stop the pump from working. Never mount the
pump lower than the engine.
Keep any vent holes to atmosphere in the pulse pump open and free from
water or dirt.
Never rely on an electric pump for fuel supply.

Below is the drawing I gave to the sheet-metal shop.

If I did it again note:
Solder in a baffle to strengthen the steel in the long flat
tank and prevent sloshing.