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Old 12-07-2011, 18:01   #1
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Boat: Cheoy Lee Richards 38
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DIY Copper Lightning Ground Plate - How Thick ?

Hi All,

Currently I'm working on installing a lightning ground plate that will also serve as a ground for the 12v electrical system.

Both Nigel Caulder and Don Casey recommend not grounding to sintered bronze plates (Dynaplate).

As far as I can tell the best option seems to be buying some copper bar stock and bolting it through the hull. What I'm wondering is how thick copper stock should I use? I'm thinking about a 1/4" thick bar 6' x 2" This would cover both the 1sq ft requirement that nigel caulder cites and exceed the 4' of edge that don casey suggests.

Has anyone done this?
Thoughts on thickness of copper, bolt types, type of copper and source (I'm thinking McMaster Carr multi purpose copper alloy 110 (99.9%copper).

Thanks!
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Old 12-07-2011, 18:10   #2
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Re: DIY Copper Lightning Ground Plate - How Thick ?

1 square foot? I thought it was 4 sq feet?
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Old 12-07-2011, 18:56   #3
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Re: DIY Copper Lightning Ground Plate - How Thick ?

I obtained some copper bar stock, 18' x 4" x0.5". I had milled, at great expense, lengthwise parallel grooves 0.25" wide and deep, 0.25" apart. This gave me a lot of 'edge' which I think is more important than total area but also served to increase the area. Then I conterbored three 1/2" holes evenly spaced along the centerline. These holes were tapped to accept bronze bolts. The copper plate was attached to the hull with these bolts. But only the middle one was attached to the ground system. The outer two bolts are to keep the plate entact in the event of a lightning hit. Meaning the center bolt might vaporize but the two remaining should stay put leaving me with only one smallish hole to deal with. In my theory anyway.
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Old 12-07-2011, 19:03   #4
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Re: DIY Copper Lightning Ground Plate - How Thick ?

Thanks!

That's quite a hefty section of copper. Based on what I'm finding online, the raw copper alone would be a significant expense, especially at half an inch of thickness...

Any ideas on suppliers other than McMaster Carr?
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Old 13-07-2011, 14:46   #5
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Re: DIY Copper Lightning Ground Plate - How Thick ?

Cheaper than a low end GPS. I have a lightning ground system but no GPS. I guess it is all depends on what one feels is important. I value safety and comfort.

The machinist's charges were more than the copper, FWIW.

Online metals will seel what I got for $180
http://www.onlinemetals.com/merchant...253&top_cat=87

6 ft. x 2 inches x 0.25 inches goes for $117 plus oversize shipping. My solution yeilds much more edge
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