<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>>
         <<  Lancair Builders' Mail List  >>
         <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>>

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

LML website:   http://www.olsusa.com/Users/Mkaye/maillist.html
Builders' Bookstore:   http://www.buildersbooks.com/lancair

Please send your photos and drawings to marvkaye@olsusa.com.