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Old 28-09-2010, 16:02   #1
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Aluminum Keel-Stepped Mast to Iron Keel - Grounded ?

Can I assume that my type of setup is grounded for lightning strikes?

Electrical ground terminals lead to my keel bolts.

Thanks
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Old 28-09-2010, 16:59   #2
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What seems like a simple enough question is actually opening a can of worms. Lightning refuses to be understood and certainly resents efforts to manage it. But yes, you are grounded. For what purpose and how effectively is open to debate here, ad infinitum.

Are you worried about getting struck by lightning? Do a search of this Forum for that. How about galvanic corrosion? Search again. Do you have a signle side band radio and want to know about the ground plane? Search.

If you just want to stir up a hornet's nest for fun, remain unclear and fasten your seatbelt!

Anybody got popcorn?
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Old 29-09-2010, 05:13   #3
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Thank you very much, you answered my question.
Peace.
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Old 29-09-2010, 05:23   #4
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I brought the popcorn. You setup sounds excellent. And I've been waiting for a chance to tell this tale. In a Malaysian marina a lightening storm arrived. Twenty tall aluminum masts teased the clouds. Yet the lightening bolt found it's way between them all and struck the piling of the dock between two sailboats. Setting it to smoking.

Go figure
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Old 29-09-2010, 06:00   #5
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Quote:
Originally Posted by daddle View Post
I brought the popcorn. You setup sounds excellent. And I've been waiting for a chance to tell this tale. In a Malaysian marina a lightening storm arrived. Twenty tall aluminum masts teased the clouds. Yet the lightening bolt found it's way between them all and struck the piling of the dock between two sailboats. Setting it to smoking.

Go figure
Abot 10 yrs ago, while the fleet of 90ft tall racers was stern-to at the dock, lightning chose a 60ft mast right in the middle of the line-up.
20 boat units to replace electron stuff.
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Old 29-09-2010, 06:38   #6
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Originally Posted by endoftheroad View Post
Can I assume that my type of setup is grounded for lightning strikes?

It is best not to assume anything, and this is an easy thing to check. With your multi-meter on the Ohms setting, put one lead on the mast and the other on a keel bolt. (If your mast is painted make a scratch through the paint to the bare aluminum.) If the resistance is low the mast is grounded.
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Old 29-09-2010, 07:31   #7
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Yes your keel stepped mast is (intended to be) grounded. The cables (terminals?) are there to ensure that it’s a good low-resistence ground, which is essential to effective lightning mitigation.

As ShipShape indicates, it can't hurt to check.
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Old 29-09-2010, 08:46   #8
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How come one could go unearthed. I bet a copper slab between the hull and the mast will do the trick.

Then again there are those who like it all separated, so on my boat the slab would be grp.

b.
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Old 29-09-2010, 12:59   #9
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Originally Posted by endoftheroad View Post
Can I assume that my type of setup is grounded for lightning strikes?

Electrical ground terminals lead to my keel bolts.

Thanks
A lot of people here are saying "yes". But I thought that you need a bronze plate or something like it to get a good ground. If your keel is painted (guessing it is) or glassed-in, then there is no good connection between the keel and the water, so you aren't really grounded.

At least, that's how I understand it.

Regards,
Brad
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Old 29-09-2010, 15:40   #10
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Electrical ground terminals lead to my keel bolts.

It appears that many of you are making an assumption: endoftheroad does NOT say where these "ground terminals" originate from - they could be wires grounding the DC system.

See the cut green wire on the right side of this seacock?

Click image for larger version

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One would assume it was is a bonding wire, but it wasn't attached to the bonding system at all - it was grounding the AC system to this seacock! It is best not to make assumptions about boat wiring, some of it is quite, um, shocking.

Even if there IS a wire going from the mast to the keel bolt, keel bolts are frequently submerged in bilge water and the connection at the terminal may be corroded, as may the terminal at the mast. Just get out the multimeter and check.

barnakiel: aluminum and copper should never be in contact with each other. Add bilge water and the bottom of the mast would be gone pretty quick.

All this is fun stuff, but as daddle's story shows so well, lightning is gonna do what lightning is gonna do.
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Old 30-09-2010, 14:21   #11
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thanks,

the wires are grounded to the keel bolts and come from sources other than the mast.
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Old 30-09-2010, 15:47   #12
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The mast on my CS36M is keel stepped and there is a heavy guage wire going from the shoe to a keel bolt so it could be said that it's grounded. But what the heck does that mean and what does that do? When I was hit by lightning there was evidence of it throughout the boat. All the through hulls (from stem to stern) showed "treeing" that is burning in the paint as did the rudder at the gudgeon and pintle. All the electronics blew but I'll not list all the damage here. I just want to make the point that the charge went throughout the boat.
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