| In our fuel tanks we're
installing the AE Fuel Guardians. These are simple optical
sensors that are completely independent of our fuel senders and
guages. The sensors mount in the side of the tank. They
emit an infrared beam that is dispersed in the fuel as long as fuel is
covering it. If the fuel level goes below the sensor it triggers
a light on the instrument panel indicating low fuel in that tank... so
this is our 'idiot light'! |
April 4, 2007:
First thing we wanted to do was test the system. We picked up a couple of D-cell battery holders from Radio
Shack and zipped-tied them together. This allows us to wire 8
D-cells (1.5 Volts each) in series, that gives us 12 Volts. We
then wired the system up according to its instructions and then
immersed the tip of the sensor slightly in a bowl of water (back right
of the picture). The panel light is visible just to the right of
my hand in the foreground. With the sensor covered by liquid
(simulating fuel in the tank) the light is out, as expected. In
the lower pic, the sensor is raised out of the water (simulating a low
fuel level) and the light comes on... kewl! It works!
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April 6, 2007: I had heard from a
couple of -10 owners who are using the Fuel Guardians that when the fuel level gets low
(but not low enough to trigger a warning) and they hit turbulence the
fuel sloshing in the tanks has a tendency to uncover the sensor and
trigger the warning light on the dash. It seemed to me an easy
fix could be a small box surrounding the sensor with a hole in the top
& bottom to allow fuel to enter and escape but not too quickly...
sort of a baffle system. I was a little concerned about metal
being to close to the sensor thus triggering a false alarm (or even
worse, possibly never allowing an alarm) so I contacted the
manufacturer and discussed it. They suggested at least an inch of
clearance and not having the metal normal to the sensor. So, I
took some 0.025 sheet and cut this shape. Nothing real exact...
After
bending it to shape here's what I came up with. The flanges at
the bottom are where it will attach to the rib, and I plan to proseal
all the gaps.
Here you can see the sensor temporarily installed in the rib, and the size of the 'baffle' box for reference.
And here's the 'baffle' box clecoed in place on the rib after
drilling its rivet holes. Its close to the sender mounting
flange, but there's plenty of clearance. On another note, I
originally put a #30 hole in the top and bottom, but after rigging up a
test with a plastic cup using water, that size hole didn't allow the
water to drain completely... that's not good! After messing
around with a few different sizes, I finally decided on a 1/4" hole...
it'll easily allow all the fuel to drain from the box, but not TOO
quickly... that would defeat the whole purpose!
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May 16, 2007:
The baffle boxes were alodined with the other fuel tank parts.
I prosealed them with the leftover proseal from one of my first
prosealing sessions on the tanks. I basically just sealed up the
perimeter of each of the baffle
boxes. I had to cleco
them in place on the ribs to make sure the rivet holes were in the
proper position when the proseal cured. Turned out pretty good!
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August 4, 2007: Alright,
today I'm sealing up the last few things in the left tank prior to
closing it up. First up, the AE Fuel Guardian sensor. I
wrapped a piece of masking tape around the end of it to protect it from
scratches during the install and also to keep proseal off of it.
Once I torqued the nut and sealed around it, I removed the tape.
After that we installed the baffle box over this guy. (Note:
this was done prior to the fuel sender being installed which can be
seen in the second pic below) I then sealed up all the edges
around the baffle box... I only want fuel entering & exiting the
box through the holes I drilled in the top & bottom.
(Note: the tank is inverted in this pic)
Here's a shot of the exterior of the inboard rib of the left tank showing the arrangement of fuel sender
& AE Fuel Guardian. The instructions with the Fuel Guardian state
to route the wires up so 'in the event of a fuel leak it won't migrate
down into the wires'… makes sense so I prosealed them in that direction
and then taped it to cure.
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