Message-ID: <01BF81D9.C4E595D0.ed@testelectronics.com>
From: Ed Armstrong <ed@testelectronics.com>
Reply-To: "ed@testelectronics.com" <ed@testelectronics.com>
To: "Lancair [Lancair.List@Olsusa.Com] (E-mail)" <lancair.list@olsusa.com>
Subject: Electrical bonding for static buildup
Date: Mon, 28 Feb 2000 10:51:28 -0800
Organization: Test Electronics
Mime-Version: 1.0

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I agree with Chris who says, "In Australia it seems to be accepted as good 
practise to electrically bond all the metal bits especially in the fuel 
tank area" The spam cans all do it here in the USA too.

I think the main reason for electrically bonding all metals and other 
conductive surfaces is to prevent in flight arcing which causes a lot of 
obnoxious RF interference. I'm building the carbon fiber 360, each panel is 
a conductive surface insulated from the other nearby conductive surfaces 
with a thin layer of Hysol. In flight, all these conductive surfaces are 
going to be at different charge potentials. Static charge is proportional 
to the surface area times the wind velocity squared, (same as drag). The 
way I see it is that the propeller is going to have the highest charge. 
Since this is connected to the engine which in turn is connected to all the 
wiring, all the avionics are going to be at a slightly higher potential 
than the rest of the plane. Next I think the wings, then next the body. It 
doesn't really matter which is higher or lower all that matters are that 
they are going to be different. All these different potentials are going to 
create a lot of arcing in flight, especially at high altitudes. This arcing 
will generate RF interference in the radio and Navaids. So, I am planning 
to put a tinned copper braided ground strap going to every panel and 
surface that is out in the slip stream and epoxy this with some conductive 
epoxy. This will also go to the filler cap mounts and finally bond to the 
engine block. I thought about adding carbon powder to the Hysol, but I 
don't want to get that experimental. To emphasize how important this is, 
even the aluminum spam cans have ground wires going to all the different 
panels. For example, If you look at an aileron in a spam can, they have a 
ground strap on it even though it is connected with a metal hinge, just to 
make sure there is no temporary break in ground. Since these spam cans 
ground everything and they don't even go as fast as our 360's, I figure it 
must cause enough trouble that I should probably ground everything too.

Ed Armstrong


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