Re: [Amel Yacht Owners] Maramu - Main Mast Grounding / Bonding

Beaute Olivier

Good evening,

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.

Happy sailing.


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. 

Steve Davis
Aloha SM72
St Augustine, FL for a few more weeks. 

On May 9, 2015, at 08:27, 'Bill & Judy Rouse' yahoogroups@... [amelyachtowners] <amelyachtowners@...> wrote:

I love this kind of question and I really like challenging Nigel Calder, who I believe is right the majority of the time.
So let me add some questions to this thought proces:
1.) Does anyone know the range of power of a lightning Strike?
2.) Does anyone know how to direct the electric power generated in a lightning strike to follow a predetermined path?
3.) If you were sure you were going to have a lightning strike and happened to know the answers to the first two questions why would you bond all of the electrical devices together to share the power of that lightning strike?
I really trust Henri Amel's decisions, especially when there are two or more possibilities....AND even when "some experts" say something else.
But, to confuse matters, I heard the rigging and masts are part of the bonding system on the 54.
Bill Rouse
BeBe Amel 53 #387
Sent from my tablet
+39 333 121 8115 Italy Mobile
+1832-380-4970 USA Voice Mail
On May 9, 2015 10:57 AM, "j.lochhead@... [amelyachtowners]" <amelyachtowners@...> wrote:
Hi,  I have read on a previous thread that the masts are not bonded on the SM. I have a Maramu and it appears to be the same.  What I am not sure is Why this is so.  Should it not be bonded?  

Further I have noticed that the forward through hulls are not bonded either.  I am sure these should be, correct?

Mahiti #147

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