Sunday, 22 June 2008

Like Lightning Striking Again....

Like the lines of Lou Christies smash hit, “again and again and again”, every summer I see the tragic consequences of this all to common occurrence.

The people who track these things indicate that you are more likely to be struck by lightning that win the lottery. I know trees don't by lottery tickets but plenty of them get hit by lightning.

Its is extremely rare for a mature tree to survive a lightning strike with out major damage.

In my experience large single trees on rocky out crops get hit with lightning all to often. This is the preferred habitat for oak trees and they have long been listed as the tree most likely to be struck by lightning. In fact oak is the favored tree of Zeus, the Greek god of thunder, for just that reason.

Lightning takes the path of least resistance to the ground, this may be on the wet bark on the outside of the tree, or it may penetrate into the moist cambium layer and heart wood. The tremendous energy super heats the moisture in the tree causing it to explode. This can be quite dramatic, throwing splinters and debris for great distances. The force of the explosion can even break windows and in one case blew the wall paneling off the interior walls of the house.

More often than not the lightning flashes across from the tree into the houses electrical system causing extensive damage to appliances and electronics.

The solution to this problem is a simple as Ben Franklin's kite and key experiment.

Lightning protection in trees typically consists of a thick copper conductor running from the top of the tree to a ground rod driven deep into the ground. It sounds simple and it is.

The top of the conducting wire is attached to an air tip, a conductive rod that terminates the copper lead. The lead is held to the tree with bronze stand offs that are driven into the bark. If the tree is extremely wide or has more than one main trunk several leads may branch off from the central conductor. All metallic objects in the tree must be bonded to the central lighting conductor. This includes bolts and cables used to support the structure of the tree. Specialty hardware is used to connect the system together ensuring a good electrical contact.

Lightning protection, when properly designed and installed, can reduce the risk of lighting flashing across into your home.

Does this improved grounding of the tree make it more susceptible to lightning strikes?

Probably not, but it does make it more likely to survive a direct hit. The materials are expensive and the skills needed to install the system are beyond the average home owner. Have your certified arborist inspect large trees close to your house to see if they are candidates for lightning protection. The results will pay out more reliably than the lottery.

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