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Old 02-16-2011, 02:45 PM
Mark Johnson Mark Johnson is offline
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Join Date: Oct 2010
Location: New Bern NC
Posts: 21
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Allen, great link... it's like the Rosetta Stone! (My previous post was a response to Benz BTW)

I agree with you about not grounding your mast's lightning protection to your through hulls! I launched our tri 15 years ago, and after standing the rig, I had it, and ALL grounds go to the same point, per ABYC at the time. It was eating shaft zincs at an incredible rate, even though it didn't yet even have an electrical system, and was not connected to the dock. HMMMM?

After a lot of head scratching, I consulted Stan Honey about the issue. I later separated my rig & mast lightning ground system, from the bonding wire, that ran to the shaft, strut, prop, and engine. I even isolated the VHF antennae mount, etc, as the mount screw has continuity with the boat's 12v dc ground. So the lightning ground and its more galvanically active copper plate are totally separated, and my zinc consumption returned to normal.

Just for kicks, I even put a battery cable switch on the negative wire to the engine as well, (which already had a three way red)... This way, when the engine is not running, the boat's DC wiring is not in any way connected to the engine, OR therefore, the shaft, prop, etc.

Three totally separated grounding systems... the mast for lightning protection only, the boat's 12v dc system, and the bonding wire to keep underwater metal happy, and protected by the shaft zinc. (The throughhulls are Maralon)

ABYC doesn't always apply. In many cases I just do what works!

Mark
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Old 02-16-2011, 08:13 PM
allene allene is offline
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Join Date: Feb 2008
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The lightning link I posted was just a side topic for the article I wrote on bonding. You might get a kick out of it. http://l-36.com/bonding2.php I am glad you enjoyed it.

If you were eating zincs, you were probably involved in the marina ground or currents. I was surprised to find lately that many boats connect their DC boat ground to the dock green ground wire directly without an isolator. I have made measurements at our marina and that greatly increases the zinc current. I am not a fan of bonding parts of your boat together. It is generally a bad thing for the boat and should be done only for safety of the crew, not for safety of the boat (except for lightning). Metal isolated in water is not subject to galvanic action. It is the bonding that creates the galvanic problem. The standard you quote is concerned with keeping people from getting electrocuted, a good goal, but not one that should be confused with helping the boat parts last longer. Just to make the point, last year I replaced a 55 year old through hull that was not bonded. It was cut in half to get it out and it looked brand new. I think that through hulls last just fine without bonding. In fact, I contend they last longer.

Kind of off the subject of rigging. I will say, I had occasion to test some 1/8 inch Amsteel to failure and broke some 3/8 line that was part of a 3:1 pully (thus getting 1/3 the load) before the Amsteel broke. That stuff is truly amazingly strong. The 3/8 was old but still...

Btw, did you know Stan Honey did the magic lines we all love on the TV for the football games? They say he is going to do some magic stuff for the America's Cup.

Allen
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Old 02-17-2011, 06:59 AM
Mark Johnson Mark Johnson is offline
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Join Date: Oct 2010
Location: New Bern NC
Posts: 21
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Really? Interesting... Stan sure knows his stuff!

When my boat was consuming zincs (once a week!) it did not yet even HAVE a dc system or connection to the dock. It was however in a marina that was wired soo poorly that you had to wear shoes just to walk on the concrete floating piers, (because of shocks), and if I was in the water, and I reached up and touched a dock cleat, it would almost knock me out! I actually became "persona non grata" for energetically pointing this out! When forced to, they removed the dock's face boards, and found a bare spot every 20' or so on the main AC feed lines, where they rested on the main dock bolts! To solve THEIR problem, they just covered it back up, and eventually I was asked to leave.

Anyway... in this battery atmosphere, or "aquasphere"... My 8' long bonded in copper plate, which was also the CB trunk minikeel's worm shoe, was picking up more of the current than the other underwater metal, consuming the zincs. I had created a battery, in a really bad marina for it. The modifications I mentioned took care of it, as did to a degree,moving to another marina. Years later I also switched to a much smaller 2 sq ft copper plate on the side of the minikeel, as it was easier to wipe down...

When I did wire up my DC system, I tied in an isolater in the green wire, as one should. THIS is good advice!

Many ABYC dictates seem to be geared toward protecting the boat manufacturer from liability, OR only see the safety issue from the point of view of the boat's occupants. It is more complicated than that. If I did something that made me safer in a VERY unlikely situation while aboard, but it vastly increased my time spent scrubbing the bottom, or the associated danger of being in the water in a crowded marina, I sometimes did what I thought was safer for me, while in the water. I won't be specific here, but you get my drift... (Even small amounts of stray current attracts barnacles!)
Mark
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