Fuel Probe Wing Wiring

[Mike Davis]

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Date: Thu, 05 Nov 1998 10:24:48 +0400
From: "Warren T. Montgomery" <monty@emirates.net.ae>
Subject: Fuel Probe Wing Wiring
To: Murphy Rebel <murphy-rebel@dcsol.com>
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list-server wrote:

--------------------------------------------------------------------------
From: Bob Patterson <bob.patterson@canrem.com>

Most of the fellows are running a plastic tube inside the wing -
lately flexible plastic, earlier with rigid plastic water pipe. The
advantage is that even loose wires can't short out on the tube. You
can just run a piece of heavy twine through the tube for now, then
use it to pull wire through later.
The tube usually runs in front of the spar, to miss the fuel tank,
and is run through enlarged holes in the ribs, and held with tie wraps.

--

Regarding wing wiring, can/should all the wires/pitot lines be run down the
wing
strut? From what I've read this seems to be the preffered method.

I'm also installing a WESTAC fuel system. I plan to mount the sending unit
where the
top cross vent is and move the top cross vent slightly aft.
Can I cut an inspection hole out of the main rib and mount the unit to the
cover for
later removal?
If so how close to the flange can I cut? I think a 3" x 4" hole would work.
How many rows of Rivets(1or2) and what spacing?
Should the cover then be mounted from the outside (easiest) or inside
(pressure seal)?

Would it then be best to double the wiring back to the strut?
Thanks,
--------------------------------- __________ -----------____
crossvent ( x ) ( x _ x x ) II
-----___
( x ( ) x )
II Spar
Main Rib ( x ( 3"x4" ) x ) II
Nose Rib
( x ( ____ ) x ) II
( _x_x_x_x_x- ) II

II

II
Warren T. Montgomery
SR#029
<monty@emirates.net.ae>
Dubai, United Arab Emirates





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[Mike Davis]

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To: <murphy-rebel@dcsol.com> (Murphy Rebel)
From: Bob Patterson <bob.patterson@canrem.com>
Subject: Re: Fuel Probe Wing Wiring
Message-Id: <E0zcCW2-0005vY-00@mail2.toronto.istar.net>
Date: Sat, 7 Nov 1998 12:51:15 -0500


Hi, Monty !

Many builders have run the wires AND the pitot lines down the strut.
This gives a clean entry into the cockpit and easy access to the back of the
panel. If you come in at the top, you have to go AROUND the rectangular
'cage' extrusions (drilling large holes here is NOT a good idea ! ;-) )

Most use quick-connect fittings for car trailer lights on both
ends, to make strut removal easy.

I'm not familiar with WESTAC - the hole sounds HUGE !!! Is this
a float-sender type of system ?? They are mechanical, & prone to failure
sooner or later. The factory (and many others) are using a capacitance
type system which uses a thin hollow tube running diagonally from the
top front of the tank to the bottom rear. This needs only a small hole
at the top front - MUCH easier to seal well !!
NOTE - if you use the capacitance tube type - DON'T forget to drill
a small hole at the TOP of the tube to allow fuel to circulate inside
& out. Air trapped in a CLOSED tube makes it very difficult to calibrate
the guage !!

Could someone who's done this please help Monty out with
part numbers, etc. ??? Thanks !!

I'm no engineer, but I've seen the factory test stand loading wings
to failure, and I can tell you that that root rib is VERY important !!
(and so are ALL of the inner 3 or 4 ribs !!) Note that the outer Rebel
ribs have lightening holes, and are plenty strong enough - the Super Rebel
ribs, which carry almost TWICE the load of the Rebel, are ALL SOLID to
give the needed extra strength.

I sure wouldn't cut ANY extra holes in it without checking with
Darryl first !! I'm sure that <IF> they approved it, they would want a
WIDE doubler, with 2 rows of rivets, as far from the flange as possible.
Captive nuts for the cover, on the inside, with doubler plates inside and
out, would likely be best for easy removal.... <IF> ....

I'd be more inclined to make the hole in the front of the tank
than the rib - if you were really concerned about failure, you could
always put in TWO sensors, so you could connect the other easily later !
This is really overkill, as the only thing I can think of that would
destroy the capacitance tube would be metal fatigue from flexing -
likely to take MANY hours.... Especially if the tube is secured to the
tank side & bottom by generous blobs of ProSeal !

Sorry, couldn't figure out the character sketch - it came out wrapped
- see below.

Although it's a longer wire, it would likely be easier to run it
down the strut - provided that the extra length doesn't effect the
accuracy of the capacitance circuit. The instructions should detail
correct wire size, type, length, etc., and testing before closing the
tank would be a VERY good idea !!

Sounds like you're making progress !! Hang in there !!!

.....bobp

-------------------------------orig.------------------------------------
At 10:24 AM 11/5/98 +0400, you wrote:

list-server wrote:

-------------------------------------------------------------------------

-

From: Bob Patterson <bob.patterson@canrem.com>

Most of the fellows are running a plastic tube inside the wing -
lately flexible plastic, earlier with rigid plastic water pipe. The
advantage is that even loose wires can't short out on the tube. You
can just run a piece of heavy twine through the tube for now, then
use it to pull wire through later.
The tube usually runs in front of the spar, to miss the fuel tank,
and is run through enlarged holes in the ribs, and held with tie wraps.

--

Regarding wing wiring, can/should all the wires/pitot lines be run down the

wing

strut? From what I've read this seems to be the preffered method.

I'm also installing a WESTAC fuel system. I plan to mount the sending unit

where the

top cross vent is and move the top cross vent slightly aft.
Can I cut an inspection hole out of the main rib and mount the unit to the

cover for

later removal?
If so how close to the flange can I cut? I think a 3" x 4" hole would work.
How many rows of Rivets(1or2) and what spacing?
Should the cover then be mounted from the outside (easiest) or inside

(pressure seal)?

Would it then be best to double the wiring back to the strut?
Thanks,
--------------------------------- __________ -----------____
crossvent ( x ) ( x _ x x ) II
-----___
( x ( ) x )

II Spar

Main Rib ( x ( 3"x4" ) x ) II
Nose Rib
( x ( ____ ) x ) II
( _x_x_x_x_x- ) II

II
II

Warren T. Montgomery
SR#029
<monty@emirates.net.ae>
Dubai, United Arab Emirates

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