Lightning Protection

[ChuckieTodd]

Here's the first part of my lightning protection system. So far, it consists of one square foot of copper below the waterline with 3/8" bolts. Next step is to bond the mast through to the plates using 4 AWG wire. Any thoughts on my progress?

[Sumner]

Were are you sailing? Fresh or salt water?

I take it the bolts now go thru the hull?

What do you have under that stip and how are the bolts sealed?. Are they stainless or galvanized?

Are you bonding from the bottom of the mast step to that plate inside the boat?

Is the strip under the ballast tank?

Do you plan on trying to bond any of the shrouds/stays to the plate?

Not sure I can answer any of your questions, but someone with knowledge that might be able to might need to know some of the above,

Sum

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Our MacGregor 26-S

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Mac-Venture Links

[Calin]

Lightning current seems to travel on the water surface. you seems to be a bit low below it. Summer asked about the waters you sail into. 1 sq foot is minimum req for salt water. For fresh water, less conductive, a larger surface is needed. In my opinion, you need ground the shrouds, lifeline/stanchions as well, essentially to get closer to a Faraday cage. Within a perfect Faraday cage you are safe regarding lightnings.
An easy area to install a plate, close to the water surface, would be the rudders, providing they are in the water. Attached to your mid section grounding, that may be a good solution for grounding the aft part of the boat. I would also have the aft stanchions attached to it.

[ChuckieTodd]

I'll be sailing salt water. The bolts go through the hull. The entire plate is sealed with 5200, holes and all. The bolts are silicon bronze. I will be bonding through a silicon bronze stud through the mast step. The mast will have a flexible copper connection to that stud to facilitate rotation. The strip is just below the waterline, 13 inches outboard the ballast tank. Ultimately, I'll have all stays and stanchions bonded to the system to protect from flashover. The rudders on my boat are completely out of the water without someone in the cockpit and the ballast tank full. The lowest portion is the zinc mounted to the bottom of the outboard bracket but it is only barely in contact with the water.

[Sumner]

I'll be sailing salt water. The bolts go through the hull. The entire plate is sealed with 5200, holes and all. The bolts are silicon bronze. I will be bonding through a silicon bronze stud through the mast step. The mast will have a flexible copper connection to that stud to facilitate rotation. The strip is just below the waterline, 13 inches outboard the ballast tank. Ultimately, I'll have all stays and stanchions bonded to the system to protect from flashover. The rudders on my boat are completely out of the water without someone in the cockpit and the ballast tank full. The lowest portion is the zinc mounted to the bottom of the outboard bracket but it is only barely in contact with the water.

Sounds like you have a thought out plan that is probably going to give you a degree of protection only found on much larger boats. Hope you never get to test it out,

Sum

===================================
Our MacGregor 26-S

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Mac-Venture Links

[Calin]

Looks great indeed. Hope you'll never get to test it!
Have I understood well that the mast is linked to the mast step/ base? Do you consider that the 1/2 bold securing the mast to the base is not sufficient? I planned a lightning protection myself and thought that it will be sufficient to link the base to the grounding system. This would allow an easier removal of the mast.

[ChuckieTodd]

Have I understood well that the mast is linked to the mast step/ base? Do you consider that the 1/2 bold securing the mast to the base is not sufficient?

Compared to aluminum, stainless is not a great conductor. In a strike, the less conductive a material, the more heat that will be generated. I had some concerns about relying on the connection through the washers/bolt/step to the deck. I've got quite a bit invested in the setup and for the little extra to connect the mast directly to the bonding system, I've got some extra piece of mind. All that said, I'm sure I'll be terrified if I ever find myself in a situation for it to be used.

[Calin]

good point. Made me curious and found the conductivity for copper is 41X higher than for stainless steel. 1.2 bold has a section 6x higher than the AWG 4 so an AWG 4 is ~7x more conductive. Sounds like a good decision.

Do you consider also grounding your battery ground (-)? It may already be groundeed through the engine and I think I would prefer a more direct path to the water than traveling through the engine electrical system.