Re: [Amel Yacht Owners] Maramu - Main Mast Grounding / Bonding
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as often, Bill has answered already the right way. He's faster than me (but I was on a business trip).
Let me add the following:
On a GRP vessel, while struck by lightning, connecting the mast/rigging to the keel will never prevent damages. The power is too high for a wire, even a big one.
When AMEL started to install electric equipments in the rigging (furlers, RADAR antennas, lights...) they (Amel and Carteau) decided not to connect the mast to the keel/bonding circuit (the yellow/green wires) because in case a wire was damaged in the mast, it would bring voltage to the bonding and therefore electrolytic corrosion.
As experience built up, there were more cases of electric leaks that caused corrosion on the deck fittings/hardware (on stanchions, guardrails, chain-plates, masts) because of leaking power and permanent salt on the deck.
This is why AMEL developped the leak detector system (on the last SMs, and every boat since). This system lets you know if a +24V or a -24V is leaking to the bonding system. This system is very good but, as the masts were not connected to the bonding system, you could not detect a leak on one of the (more and more numerous) electric equipments of the masts (spreaders'lights, motor driven satellite antennas, etc...).
This is why AMEL, then, decided to connect the masts/rigging to the bondong system (including the keel, as you know). This happened around 2009.
When I worked at AMEL, some clients absolutely wanted to have their mast connected to the water. In that case (when these people insisted a bit...) AMEL made an equipment "for lightning protection", two pieces of 10mm chain in a hose (to prevent chafing along the hull) that the captain would attach to the main mast top shroud chain-plate, in case of being caught in a thunder storm.
I've never heard people saying they had used it in a thunder storm.
I heard people saying they had been struck by lightning, directly on the vessel, or even 100 meters aside, and that all their electronics were destroyed (including alternators, battery chargers). With lightning, there is no rule...
I guess some people have better peace of mind if they know they have a means of connecting their rigging to the water...
Some other think that if they put a piece of chain between the rigging and the water, they will necessarily be struck.
The only thing I'm sure of, is that lightning strikes randomly, and even alone, with no sailing vessel around within 10 miles, you may be struck... or not...
Conclusion: having the mast connected to the keel will help you finding power leaks (if you have the leak detector system) but will for sure never protect you from damages due to a lightning.
On Saturday, May 9, 2015 3:47 PM, "Stephen Davis flyboyscd@... [amelyachtowners]" <amelyachtowners@...> wrote:
All very good questions which I would like to know the answer to. Our boat was struck by lighting in 2011 prior to our ownership, most of the electronics were destroyed, and some wiring was burned as well. It cost the previous owner who was self insured a about 25k in repairs. It would be nice to be able to avoid such problems in the future, but I've never heard of a sure way to do that. Hard to overcome the power of Mother Nature.
St Augustine, FL for a few more weeks.
On May 9, 2015, at 08:27, 'Bill & Judy Rouse' yahoogroups@... [amelyachtowners] <amelyachtowners@...> wrote: