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I am looking to ground my mast to a keel bolt and have a quick question. Is there a recommended way to attach the ground wire to a keel bolt? Nigel Calder's description is vague about this, but says something about perhaps having to custom manufacture a copper washer to use as an attachment point.
Is there a reason I couldn't just use a battery post clamp? I plan on using #4 gauge wire and don't have easy access to a crimper for this size wire. Is there a reason I can't just by a pre-made battery cable and clamp it to the keel bolt with a battery terminal?
Are you looking to ground the mast as part of a lightning grounding protection system? What kind of boat is it? Is the mast deck stepped or keel stepped—sounds like a keel-stepped mast, but still confirmation is good?
I agree that I won't find a cable with a lug sized for a keel bolt, but that is why I was thinking of a battery terminal.
However, thinking about this further, if I use a battery terminal it will damage the threads on my keel bolt. So I think I need to make up a custom lug and then put another nut on the keel bolt and tighten it down.
Answers: Yes, keel stepped and lightning grounding is what I'm looking to do. Keel is external lead keel with silicon bronze keel bolts.
One good way to attach a lightning ground to the keelbolts is to drill and tap the keelbolt with a small screw...say a #10. Most keel bolts are of sufficient diameter that this isn't an issue, especially since the tapped hole doesn't have to be very deep...say 1/4" or so. Then use a silicon bronze machine screw to attach a ring terminal to the keelbolt.
Tapping the top of the bolt would be an elegant solution, but I don't have a lot of experience using taps. My concern would be drilling the initial hole and not getting it nice and straight. Wouldn't this be difficult to do with a hand held drill?
If you ground the mast to a lead keel, you may create galvanic corrosion issues, as the lead keel is at a different potential than other underwater metals like your SS propshaft and bronze propellor. You will need to make sure that the mast is not connected to any other boat ground--a common problem is the VHF antenna mount.
sd, do you really think a #10 screw is going to still exist after a lightning strike?
I'd suggest a tin snips and a sheet of bronze or copper scrap followed by a little handwork, to make a "washer" and crimp connection that are robust enough to last a little longer.
Plumbean, I think most battery cable terminals are still lead. Again, they'd just melt apart after a first strike. The ones that aren't lead tend to corrode and not conduct terribly well. Still, if you can get a good connection with good contact area, and grease it up so it doesn't corrode....beats nothing at all, doesn't it?
Good battery cable terminals are tinned copper. Cheaper ones are plain copper. I have never seen lead lugs.
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