I looked at the research on lightning for an article I did on grounding and bonding so can toss 2 cents worth in (I am also an electrical engineer if that helps). If lightning wants to hit the ground, it is going to prefer the path that goes through your mast over one that doesn't assuming you are close to the charge. I don't think it is going to matter if it is grounded. Remember that lightning is different than your 12Volt circuits in that it can make air conductive. Assuming it hits the mast, there is the question of how it will get to the water. Absent wire rigging or bonding to a keel bolt, it is likely to find some wires for at least part of the trip. I know it isn't well understood but I would assume it will find a path through the hull at some point near the bottom of the mast. Probably sink the boat. My strategy is different when it comes to lightning as California is #50 in lightning strikes so there really isn't much of a chance of a strike, my mast is shorter than the boats around me, and I stay in the slip if there is a chance of lightning. The one thing I learned from the reading is don't bond your mast to your through hulls unless you want the strike to remove them. There was a strike that instantly sunk a "well bonded" boat which had all its through hulls removed by the strike.

In the process of this research, I did a calculation that showed that a strong hit would melt my rigging. My mast is wood so the rigging is the path. If it melts, so be it. I don't expect to be hit. I am more likely to die in traffic on the freeway.

This page as links to 8 articles on the subject:
http://l-36.com/lightning.php

Allen

Valid points. If you look for a consensus in say... the last 20 years of studies, from far different sources, there is no statistical evidence that "proper grounding" increases strikes. (I'm talking about unbiased studies by university grants and the like, Not studies by some company selling their giziwonkus.) Now, if it was so close it was going to hit the boat anyway, and you have a grounded lightning rod, it IS more likely to hit the rod than the cabin, and WAY less likely to drive the mast through the hull, or "hole it" looking for ground. This is the whole idea, and there is a LOT of research that backs that up as a way to at least improve your odds. One is only trying to improve their odds...

In my case my run to the ground plate is straight, and only 2' long of "00" wire, so I don't think that side flashes are that likely anyway?

A boat that was next to me, (an F-31 tri), and hit TWICE in one year, was not grounded, but was on a metal lift at the end of a dock. It blew numerous holes in the hull each time, and I was glad to get away from it! I think the lift was a magnet. The boat on the other side was grounded, and had no structural damage, but lost ALL electronics.

The lightning damage that I have inspected aloft, seemed to be intensely hot in only the 1' radius around where it struck, usually the paint just a ways down the mast looked fine. I would think that your leather work would do the trick. The rest of the mast is such a heat sink and all.

I wasn't considering this issue a deal breaker for synthetic rigging, just genuinely curious if any synthetically supported rigs had been hit... Anybody?
Mark

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

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

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