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rparigor(at)SUFFOLK.LIB.N
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 Posted: Tue Feb 06, 2007 9:46 am Post subject: How to connect to 2" aluminium tube? |
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I want to ground a 2" aluminium tube used below the fuel filler of a
Europa (plastic).
I suppose I could weld a tab on it, or was thinking could order a few Adel
clamps (with aluminium straps), and discard the rubber and see if I could
get proper size and connect the ground wire to mounting screw after I
cleaned off any finish on areas I want to conduct.
Any other ideas? There are hoses clamped on this elbow at both ends, I am
looking for a way to dissipate static charge. Think by sneaking a flat
thin piece of aluminium half under the clamp and attaching to this would
be an OK resolution?
Thx.
Ron Parigoris
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mprather(at)spro.net
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| Posted: Tue Feb 06, 2007 12:08 pm Post subject: How to connect to 2" aluminium tube? |
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I assume you want to connect a wire to the filler? Or a chain? Seems
like just about anything you mentioned would work. The rate at which
charge is transfered while in the fueling process is low, and the total
amount of charge that can be stored prior to the start of the fueling
operation is also low, so there's just not that much charge to dissipate.
You could drill into the filler and rivet a PIDG or similar connecter. Or
use a machine screw instead of a rivet.
But... the topic of grounding the fuel system properly in a plastic
airplane is one that has generated lots of debate in the past. Almost as
much as political discussions on aviation fora.. So, to where do you
intend to run the wire that is connected to the filler neck?
If I were designing a grounding scheme for a plastic airplane, I'd be
tempted to run a bare wire or chain such that fuel being dispensed into
the tank would flow along its length until reaching the fuel already in
the tank. That wire or chain might also be connected to whatever location
I decided that I want the fuel dispenser's ground cable attached. That
connection should be made somewhere that the concentration of fuel vapor
is low - away from the filler neck.
One other concern I have heard mentioned is how the system behaves if the
airplane were struck by lightning... A small conductor from the filler
neck connected to an airframe ground buss might act as an ignition source
if it passes through the fuel tank. Lightning may strike the fuel
cap/filler assembly directly on a plastic plane. Some people might say
that if lightning strikes a plastic airplane all is lost anyway. I'd
rather consider possible effects of the grounding scheme to give me the
best odds.. Plastic airplanes have sustained lightning strikes and flown
away with little damage. I want to be one of those guys.
Maybe a reasonable approach would be to use a section of chain attached to
the bung in the bottom of the tank (on the dry side of the bung, another
wire connects to the ground buss). To the end of the piece of chain is a
length of fuel proof non-conductive chord. Finally, the chord is tied to
the fuel cap. The chain should be long enough that it can reach from the
bung in the bottom of the tank to the filler neck. The chord is long
enough so that when the filler cap is in place the chain can sink to the
bottom of the tank. This system serves two purposes - it dissipates any
charge buildup during the fueling process, and it retains the fuel cap
should it be left ajar/unlatched.
The remaing connection I would consider making is adding a ground wire tab
(which was your question) to the filler neck. This would eliminate any
chance that you would get a spark when the chain stretches from the bottom
of the tank up to the filler. I think for best safety, whatever you
connect to this tab shouldn't pass through the fuel in the tank
(lightning), but along the outside of the tank, possibly in a fibrefrax or
other non-flamable tube.
Okay, shoot holes in this plan... I've been pondering it for a while and
would like to hear some thoughts (if that's possible).
Matt-
| Quote: |
I want to ground a 2" aluminium tube used below the fuel filler of a
Europa (plastic).
|
| Quote: |
I suppose I could weld a tab on it, or was thinking could order a few
Adel
|
| Quote: | clamps (with aluminium straps), and discard the rubber and see if I
could
|
| Quote: | get proper size and connect the ground wire to mounting screw after I
cleaned off any finish on areas I want to conduct.
|
| Quote: |
Any other ideas? There are hoses clamped on this elbow at both ends, I
am
|
| Quote: | looking for a way to dissipate static charge. Think by sneaking a flat
thin piece of aluminium half under the clamp and attaching to this would
|
be an OK resolution?
| Quote: |
Thx.
Ron Parigoris
|
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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