Over Hill Sailing Club
Join Date: Feb 2009
Location: Adirondacks NY
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Re: Lightning protection- precision 18
In theory this all sounds well and good but the existing data does not really support it other than for a very small edge to well bonded boats vs. un-bonded.
Beyond that people often lack the electrical common sense to realize that most every spar out there, with a VHF whip, is already at ground potential.
All one has to do is follow the shield of the VHF cable back to the VHF then to the ships ground which is engine/water/Earth. Take an OHM meter and put it on your mast now put it on the engine block or battery neg and you will have continuity. Why? Because the VHF shield is almost always bonded to the mast bracket which is rarely isolated from the spar. Mine is but this is a custom mount I made on my own. Most all masts are already at Earth potential whether bonded with heavy wire or not. Most boat owners simply don't understand their VHF whip is already putting their spar at Earth potential.. The heavy wire does not change the Earth potential beyond the small VHF wire but it can help to take the brunt of the strike to Earth which the small VHF wire does a horrible job at......
Just last week I was just talking with another member here who's boat was hit while on the hard. This makes it fully isolated from the Earth as in no connection at all. The lightning came down the spar into the keel and physically jumped the 12" air gap between his keel and the asphalt.... You don't even need Earth potential to be hit. However if your boats bonding wires are large enough that they can act as a "pass through" then you may just suffer less damage......
The heavy bonding wire is intended to minimize damage not prevent or minimize a strike. This is the area where I do see a large difference in damage results. Well bonded boats with heavy grounds suffer less damage, but they still get hit.
I think it's right that there is not much difference at all. Lightning is such a dangerous unknown and acts in such unpredictable and uncontrollable ways that it presents a real problem for anyone thinking they can find any real measure of protection. One thing for sure is that electronics get fried when it even comes close. Makes the idea of sailing without paper charts, as in "NOAA stops printing paper charts" seem pretty lame.
Alberg 35: With a philosophical flourish Cato throws himself upon his sword; I quietly take to the ship.