Skysports Capacitive Fuel Senders: This is one of the fuel senders we're installing. They're capacitive senders from Sky Sports.
Van's offers a float type sender, but not a capacitive type (they do
for models other than the RV-10 though). Since floats have a
history of providing marginal accuracy we decided we wanted to go the
capacitive route, so we had to start looking elsewhere. Sky Sports
offers these non-aircraft specific capacitive senders. It's
basically a 1/4" diameter tube with a smaller diameter tube running
through the center of it but isolated from it. Fuel is allowed to
fill the gap between the two, and the level it falls along the length
of the two changes the voltage the sender supplies to the fuel
gauge. If you'd like the 'black science' behind how this works,
check out Sky Sports' description on their sight here.
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Sky Sports
offers their senders in many sizes, and will custom build pretty much
to any length. They even make ones with a bendable portion.
Since the RV tank senders are designed to insert from the side of the
tank, we need ours bendable to get the probe portion to span from the
top of the tank to the bottom. In order to get the most accuracy
possible we plan to have the probe portion of the sender run diagonally
from the lowest point in the tank next to the fuel drain, up and
outboard across two bays of the fuel tank. In order to get the
probe portion down to the lowest point, the first 7 inches of our
sender is bendable. Before bending the senders I plan to make a
mockup from a bent clothes hanger. I also put some marks on it...
the one at the far left marks the bendable portion of the sender
(everything to the right of the line is bendable). The next line
over is the closest I can start a bend to the head of the sender (this
is due to our bender not physically being able to get closer to the
head of the sender), and the last line just marks the end of the
aluminum portion of the tube.
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Here
is my first pass at bending the mockup. This shows the general
idea of what we're shooting for. One important point here…
the tube of the sender can't touch any metal inside the tank.
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Here…
this is what I'd like to do… However, without getting too wordy,
I'm not sure if I can have the sender start at the bottom and go up (as
opposed to starting at the top of the tank and going down), so I tried
calling Sky Sports. No answer so I sent them an email... So, I'll move on to something else for now.
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(18-5 step 6): Moving on I mixed up some proseal and started sealing up all the rivets on the ribs & J-stiffeners inside the tank.
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I also ran a bead of proseal around the end ribs.
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(18-6 step 4): Heres
a poor-man's method of torquing tubing fittings ;-) It's just a
digital fish scale and a crescent wrench. After inserting the
fitting through the end rib with some proseal it needed to be torqued
to ~50 in-lbs. So, I measured the wrench length from the center
of the fitting to the center of the hole in the handle (in).
Dividing the torque needed by the length of the "lever arm" gives me
the force I need to see on the fish scale. One thing though, I
made sure the wrench was as close to vertical as possible so it's
weight didn't help or hinder the torquing action. Anyway...
seemed to work ok.
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(18-6 step 6): Once the fitting was in place I hand bent the vent line to line up with the fitting.
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And then torqued the tube fitting in place using the fish
scale and wrench again. Although I haven't yet I'll probably dab
some proseal on this just to ensure this thing won't back off.
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(21-3 step 5):
Next I moved on to the ailerons. Here are the 8 pre-punched
sticks that make up the 32 aileron skin stiffeners. These have to
be separated and cut to their final shape (you can just barely see
I've already measured out and drawn the cut lines)
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Using the band saw I cut all the stiffeners, and then started
deburring them on the scotchbrite wheel. I only got through 9 of
them before calling it a night though.
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