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Old 17-01-2012, 09:35   #1
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Lighting Protection - From Mast or From Butt Plate ?

I have an alu mast on a BIG alu butt plate. I am replacing the wire of the lighting protection. Can I run the wire from the alu butt plate to the keel bolt (there are already # of bolts in butt plate) or is it better to drill hole in mast to connect wire directly to mast?
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Old 18-01-2012, 18:00   #2
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Re: lighting protaction: from mast or from butt plate?

I am not familiar with the Nordic 40 so I don't know if your mast is deck or keel stepped. I'll answer for both to be of the most help to everyone.

For deck stepped, likely there is some sort of gasket between your mast and step. But even if there isn't, neither the connection between the mast and step nor the connection between the step and compression post plate will be adequate.

For keel stepped, definitely ground the mast - you do not want to try to make the current go horizontally to get it to ground. Also, to be on the safe side you should ground the step.

Any bend in your wires must have a radius no smaller than eight inches.

Use the largest ALUMINUM lug you can find, be sure the manufacturer states that it is compatible with copper wire, and tap screw holes into the mast (do not rivet the lug to the mast) and fasten it with aluminum or stainless steel machine screws. I used two layers of heat shrink to protect the wire and connection from UV and corrosion. Use an aluminum-compatible anti-corrosion conductive paste between the lug and the mast, and remove the lug and clean and preserve the connection annually to keep it low resistance. Treat the connection to your keel bolt the same, but use a tinned copper lug.

If I remember correctly, ABYC recommends a minimum of 4 AWG wire for your main lightning conductor ... have you seen the size of a lightning bolt?! On my boat I used two 2/0 AWG cables to ground the mast, and also grounded all four step bolts on the compression post. Probably overkill, but that's the way I do things that matter.

There is another cable just like it on the other side:

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And inside:

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ID:	36189
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Old 18-01-2012, 18:57   #3
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Re: lighting protaction: from mast or from butt plate?

Thank you very very much! The mast is keel stepped and I will make as you said it. Thanks for your time!!
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Old 23-02-2012, 11:10   #4
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Re: Lighting Protection - From Mast or From Butt Plate ?

ok.... I am now past the reality check.
1. Unless I rip the interior out I will not be able to connect chain plates and forestay to the keel bolts; 2. There will be an almost 90' angle in the wire from the mast to the keel bolt as the space between floorboards and butt plate is very limited (I dont have space for an 8" radius). 3. I will be able to also ground the butt plate.

Now: does it still make sense to also connect the back stay to the engine? Anmnd how does that relate/interfere with the grounding of the engine?

slowly but surely....
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Old 23-02-2012, 23:11   #5
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Re: Lighting Protection - From Mast or From Butt Plate ?

Stainless chain plates should be pulled every 10 years to be inspected for crevice corrosion, so if they are stainless go ahead and rip the interior out to inspect them and then they can be grounded. (If the bolts are stainless renew them.) If your back stay has insulators because it is an SSB antenna there is no need to ground it, otherwise ground it to your main lightning ground, NOT the engine. Remember to ground all large metal items that are within six feet of your mast, including stanchions/lifelines. If you can't do it all right be ready for the consequences, and make sure your insurance has coverage for lightning strikes.

Since your bilge at your mast step is shallow you'll have to connect the ground wire up outside of the bilge. If you think that won't look so good, well this doesn't look so good either:

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This boat has a keel-stepped mast that wasn't grounded. The lightning jumped off the mast to one of the keel bolts and partly blew off the keel, and also jumped over to a thru-hull and blew it out of the hull - there is a board over the hole about the center of the keel. (Amazing they got the boat in and hauled without sinking!)

Another option is to install a separate lightning ground plate near the base of the mast, which is what I did since my keel is encapsulated. My philosophy is to keep all grounds separate, so I have four separate systems for my lightning, electrical, radio and bonding grounds. I wish I could tell you the chances of getting hit are rare, but in the past five years I've heard of about 40 boats getting struck, and only one person who has been in a car accident.
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Old 24-02-2012, 05:08   #6
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Re: Lighting Protection - From Mast or From Butt Plate ?

that is a scarry pic!!! Thank you very much for your comment, I will reexamine the chainplates. Thnx.
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Old 24-02-2012, 05:25   #7
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Re: Lighting Protection - From Mast or From Butt Plate ?

Forgot to give you this link - this guy has a different system that may interest you, plus tons of info: Marine Lightning Protection Inc.

I think that picture is from Boat US magazine, and the article also had a story about a guy steering, and on its way to ground lightning jumped off the back stay, went through his head and onto the steering pedestal. Yikes!

When I get my deck hardware remounted I'm going with Dynema lifelines so I don't have to bother grounding them (or the forestays, I've got those isolated) - that will be much easier and less expensive than all the copper wire.
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Old 24-02-2012, 05:35   #8
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Re: Lighting Protection - From Mast or From Butt Plate ?

How did you isolate your forestay?
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Old 24-02-2012, 06:00   #9
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Re: Lighting Protection - From Mast or From Butt Plate ?

ABYC TE-4 Lightning Protection
http://www.marinesurveyorschool.org/...Protection.pdf
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Old 24-02-2012, 07:39   #10
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Re: Lighting Protection - From Mast or From Butt Plate ?

Great Job Shipshape! I have a cat and wondering if I run a few 2/0 wire like you have in the photo dropped straight in the water below the mast ,how effective would that be?
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Old 24-02-2012, 08:14   #11
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Re: Lighting Protection - From Mast or From Butt Plate ?

Quote:
Originally Posted by Ram View Post
... wondering if I run a few 2/0 wire like you have in the photo dropped straight in the water below the mast ,how effective would that be?
You’d need a lightning grounding electrode, connecting the (2/0) lightning conductor to the water.

This grounding electrode (terminal/strip/plate/electrode) must, according to ABYC TE-4, be at least 3/16" (5mm) thick, and have an area of at least 1 square ft. (0.1m2).
NFPA780 requires that a ground plate electrode be at least 0.032" thick (8mm) and have a minimum surface area of 2 square ft (0.18 m2).

See also NFPA 780: Standard for the Installation of Lightning Protection Systems (requires free registration):
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Old 24-02-2012, 09:17   #12
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Re: lighting protaction: from mast or from butt plate?

Quote:
Originally Posted by ShipShape View Post

If I remember correctly, ABYC recommends a minimum of 4 AWG wire for your main lightning conductor ... have you seen the size of a lightning bolt?! On my boat I used two 2/0 AWG cables to ground the mast, and also grounded all four step bolts on the compression post. Probably overkill, but that's the way I do things that matter.

There is another cable just like it on the other side:

Attachment 36188

And inside:

Attachment 36189
Great post and pics shipshape!
My new boat is currently enroute from W Med to Florida to upgrade its lightning protection system. Currently Ion Dissaption style. The tallest mast was struck by lightning while in port last year in the Med yet even the poor install (not run to top in conduit and the alum when spec'd copper cable) blew a hole out thru the alum mast large enough to put your fist thru due to bare scuffed wire 102' up. Mast canted over apx 60 degrees. PO replaced the rigging and the alum masts with CF but got the money not thru the Ins Co but thru the UPS/surge suppressor company which was Ins Co requirement. They paid $60,000 USD (policy max #) and replaced the 4 units N/C. NONE of the electronics downstream of the surge suppresors was hurt or damaged. All passed survey but the pair of surge units was toast. The Ins Company spec'd 00 copper wire from the masthead on the taller mast (136') and 0 copper wire on the shorter mast. (10' less) Which is what currently exists. Don't know why <#4AWG but that is the spec so that is what is there now. The masts have what many call the "witches broom" on top though one of them has many shades of Blue thruout! LOL!

Thanks for the great pics and posts again.

John & Carol
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Old 24-02-2012, 09:49   #13
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Re: Lighting Protection - From Mast or From Butt Plate ?

If the lightening reaches as far as your chainplate, it's just as likely to jump to the water as follow some longer path to your keel. BTW, the jury is definitely out on whether doing any of this helps or hurts your odds. So dont tear up your boat doing something that has not been proven to work at all!
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Old 24-02-2012, 10:01   #14
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Re: Lighting Protection - From Mast or From Butt Plate ?

Quote:
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... BTW, the jury is definitely out on whether doing any of this helps or hurts your odds. So dont tear up your boat doing something that has not been proven to work at all!
As far as I know, there is no creditable debate regarding the efficacy of Lightning Grounding Systems. They work to mitigate damage, when struck by lightning.
The only debate is if, and how much, grounding increases the odds of actually being struck. The educated consensus is not much.
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Old 24-02-2012, 10:23   #15
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Re: Lighting Protection - From Mast or From Butt Plate ?

Yeah.... maybe..... I'm not sure God wrote "you must follow the path of a little #4 wire" into the lightening bolt training guide... :>) The theory also says that electricity will follow the shortest path to ground. However, if you look at a big lightening storm... many of the bolts are traveling horizontal! IMHO it's just too big and too powerful for anyone to think they are going to direct it. But if you can... we wont have to build anymore nuclear power plants... and you are going to be a rich man!
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