[VACList] Re: VACList Digest V3 #261 - Rubber Tires Insulators?

[waymark1@xxxxxxxx]

Rubber vehicle tires are not insulators. They are rather conductive. That is why 
you don't get a terrific shock every time you get out of a vehicle that has been 
rolling down the road. I sometimes get shocked when I first touch the metal of 
the car but never upon alighting onto the pavement or ground.
The carbon blacks that is mixed into the rubber compound is there primarily to 
improve the wearing characteristics of the tire but it has the added benefit of 
grounding out the static electricity charge that would be present if pure rubber 
tires were used.
I am sure that many of us remember the grounding straps that used to be popular. 
They were made with embedded wires and dragged on the road. Their use originated 
back in the days before carbon blacks (soot from burning natural gas with 
insufficient oxygen) were used in tire rubber compounding.
Yes, a metal (aluminum in the case of Airstreams and others) shell trailer is a 
pretty good protection from lightning strike. Aircraft are struck by lightning 
very frequently but rarely suffer significant damage. The occupants of aircraft 
are protected from the electric current by the fuselage.
Hopefully one is not touching any metal parts inside the trailer that are 
connected to the trailer skin.
"Dr. J" does make a good point at the last.
Al Grayson