Mac26S lightning protection

[JohnWood]

I am a new owner of a 1991 26S. I live in the Tampa bay area and will sail the boat a lot in central Florida, in salt water and fresh, basically right in the middle of the lightning capital. I am concerned that the boat has no grounding from the mast or shrouds to the water.

There is a lot of good discussion on this now 4 year old thread:
http://www.macgregorsailors.com/forum/v ... =lightning
But there does not seem to be a lot of consensus.

It seems that there are two approaches to protecting a boat from lighting:
* Provide a ground from the mast to the water. This ground may attract lightning but will safely conduct it to the water. Unfortunately, it must be very robust to handle the current of lightning and is therefore not very feasible for a trailer sailor such as a 26S or 26D.
* Isolate the mast and shrouds from the water to reduce likelihood of strike. Whether this actually reduces risk seem to depend on who you ask. Those who advocate an advantage say that a grounded mast will allow for the water to build a charge in your rigging, attracting a bolt. They point to the rarity of strikes to cars, which sit on rubber, vs the commonality of strikes to farm equipment, which are often connected to steel appurtenances such as plows that are in contact with the earth.

When I was a teen, I was sailing a regatta in Lasers in Sarasota. There was a storm approaching, but the race committee wasn't cancelling. Finally, people just started heading in quickly. Coach boats were towing sailors in as quickly as possible. A laser is a single person boat, unshrouded. The hull and deck are sealed together airtight making a hollow void. The mast sits down into a tubular step that goes through the deck down to the hull. The lower end of the aluminum mast is separated from the water by a plastic cap and maybe 1/8" of fiberglass.
A girl on our team was in tow, sitting in her cockpit, when lightning struck the top of her laser mast. The electricity went down her mast and then bypassed the plastic cap at the bottom. It went through the air space between the hull and deck, and made a couple of small holes in her hull. Unfortunately, her boat was older, and a little bit leaky. The water in the hull was heated by the electricity and turned to steam. The pressure inside the boat was enough to blow the boat up. The deck blew apart from the hull upward at the bow and stern. Floatation bags flew. Sitting in the middle of the cockpit, the skipper was unharmed, et confused as to why her boat exploded. If she had been touching her boom, however, she may have been hurt.

The 26S or 26D is similar. Its mast and shrouds are isolated from the water, which might make strikes less likely, but what happens when a strike does occur?
I'm mostly of the opinion that isolating the mast will not significantly decrease a strike risk. Disclaimer: I am a mechanical engineer, not electrical. Here's my logic. Electricity follows the path of least resistance. Let's say that there is a cloud at 150 feet above the water. That's 150ft of air with high resistance, a little bit too much resistance for the charge to break through. It's basically a big capacitor. Along comes a standard 26S. It's shrouds and stay go from 3 ft to 33ft, so offer 30 ft of very low resistance. Now the lighting only has to travel through 120ft of highly resistant air and 30 feet of low resistance stainless steel and aluminum. If the boat were well grounded, it would be 33 ft instead of 30. If the charge between the cloud and the sky was just shy of breaking the 150 ft jump, It may now be able to break the 120 foot jump, and there isn't a huge difference between the isolated boat which offs 30 feet of low resistance travel to the grounded boat that offers 33 ft of low resistance travel.

Here is my proposed solution. Build a safe path for lightening to travel down to the water, put provide an electrical break in the path, a break short enough to allow for a high voltage strike, but large enough to prevent charge buildup that might attract a strike.
Basically, run a large wire or stainless strap down to the rudder head and/or a copper plate in the water. Perhaps the copper plate could wrap around the leading edge of the rudder, doubling as a protector from logs. At the top of this wire is a stainless steel plate that is held at a distance of let's say 1 inch away from another stainless plate, in parallel, which is bolted to the backstay plate. It's not a new concept. The two parallel plates is a lightning arrestor, similar to those used in communications equipment and electric fences.
In this case, the electricity has 32 feet, 11 inches of travel along low resistance metal at the backstay, but has 30 feet at the shrouds and backstay. At the mast, is has about 29 feet of aluminum and 4 feet of wood at the compression post. My theory is that if lighting strikes the top of the mast with this design, then nearly all of the electricity will go along the back stay, jump the 1" gap, and down the 3' conductor into the water. Very little current should pass through the shrouds and forestay because of the resistance of the 3' air gap or the mast because of the 4' wood gap.

Who thinks I'm brilliant? Who thinks I'm paranoid and overthinking? Who thinks I'm an idiot?

[NiceAft]

You may wish to read these.

Ray

http://www.boatus.com/boattech/casey/lightning.asp

http://www.frugal-mariner.com/Lightning ... _boat.html

[RGF]

Having had my 26 X already struck by lightning, only two old things come to mind - something about you can't fool Mother Nature, and, if you want to make God laugh....tell him your plans. I applaud your efforts and eagerly wait to hear the final solution.

[mrron_tx]

Hmmm... Thinking along the lines of a wire going into the water as a path.... Don't Our Macs already have a path from the mast to the water ??? If the mast lighting plug is plugged in , that would take the jolt ( as long as #14guage wire will hold ) and carry it ( the jolt ) to the breaker panel , which if You are underway probably will have closed switches , which will give the jolt access to paths all over the boat , including the outboard motor and mounting gear which probably some part will be in the water. Whew. All I can add about RGF's post is... Thank God fuses and breakers where invented. I really did enjoy those Mother Nature commercials Ron.

[paulkayak]

I think you have thought this out well. You do not want to make an easy path for the electricity to flow you just want the easiest path to be the safest or to be more correct the path of least destruction. If you look at your boat that is already in the setup. Mind you a bit bigger gap than 1". The shrouds chainplates continue along the hull inside the fiberglass so your 3 foot estimate may be a bit generous. I believe you are correct in that if lightning was to take that path the results would not be favourable. Same thing with the forestay.
As you I believe the backstay is the path of least destruction. (And the storage area would be a bit of a barrier between people in the boat and the potential shrapnel produced.) I think you could probably even sail home with no backstay if the winds were not that strong. On my 26s the proximity of the backstay to the ladder is inches and the tiller is about a foot. I would rather have the lightning destroy the ladder (or again to be more correct destroy the part of the boat holding the ladder) than the tiller so I would try to encourage the current to go down the ladder by leaving the ladder in the water in a storm or when left for any time. But I sail in fresh water where I can do that.

[RobertB]

I consider lightning strikes one of those things beyond my control. I can figure all day long about what the most logical path to ground is but in the end, the lightning does not care what I think. The time I felt most vulnerable, out on the Chesapeake Bay near Baltimore (the time a tornado touched down about a half mile away ), I made a run for Hart Miller Island, and beached near the tallest trees I could find. I would have been in good shape except that other guy who thought it was a good idea and followed me in and put out a whole 10 feet of anchor rode on a light anchor. Oh, it did not hold, he flooded his engine, and I was leaning over the side for several minutes holding his anchor roller/bowsprit contraption a few inches from my boat for the rest of the storm

Best message in the articles referenced above - make sure your insurance is paid up.

[Catigale]

This topic has gotten a bit heated in the past - kind of like oil change intervals on auto forums.

It turns out one of our members here actually grounds antenna and metal structures for a living and I will summarize his advice here.

Doing nothing is perfectly reasonable

Doing something that is not 'expertly installed' is WORSE than doing nothing

And my contribution...

You cannot become an expert by reading posts on the internet.

[mrron_tx]

Catigale..... You mean that somethings We read on the internet aren't true Say it ain't so Sorry... I had to do that Ron.

[Russ]

I think you could probably even sail home with no backstay if the winds were not that strong..

Don't try this ever. The back stay is crucial. If you ever lose it, watch out overhead and make a temporary out of a halyard or something to keep the mast up That is if your mast doesn't come crashing down while you are trying.

This is a highly discussed topic for obvious reasons. We are traveling with a big metal stick above us. I agree with Cat, if you don't know what you are doing, it's best to not even try. Fresh water grounding becomes even more difficult.

[seahouse]

I think the two most important pieces of lightning protection are your noggin' and a high-horsepower motor on the back.

Check. Check. Yup most of us already have both.

OK. Your noggin' is usually enough if you don't already have the motor. (ie. check Wx beforehand and get out of the upcoming storm!)

Seriously, judging from the initial post there is a dearth of scientific fact on the topic. In such a case a person can go with what is already known and accepted; avoid the storms and head for port to reduce the odds of being hit. Maybe God does after all play dice with the universe.

-B.

ps. one of the local clubs here has a mooring field of 100- 200 boats, a fairly closely spaced mix of power and sailboats. Two years ago one of the power boats got hit and burned to the waterline. There were 40+' sailboats with high masts that did not get hit. There are just way too many unknown variables in lightning strikes to predict or control them.

[JohnWood]

At 35 years old, I've been on the water now for 30 years, and I know that there is no hope of avoiding lightning storms every time. Some of the time yes, but not every time, especially here in Florida. You have a better chance getting out of the way with a 26X or 26M, but I have a 26S with a 9.9 hp. Water spouts, fierce lightning, microburst, I've been through them. I know what to look for but I also know that these storm move faster than I do and they build up without much warning.
I was once windsurfing and had a lightning storm fast approaching. it was one of the big wide board that plane early, but if they aren't planning, they don't go anywhere fast. The wind died just enough so that I could not plane, so I just slowly schlogged through the water, trying the best I could to get to shore. Perhaps I shouldn't have been so far out, but I just could not get out of the storm's way. When it approached, I had never seen a storm with so much lighting and I was the only thing around other than smooth water, holding a nice conductive carbon fiber mas into the air. Just before the storm overtook me, I made it to a shallow area, so close to shore. I dropped the rig a got down under water. I held the bottom of the plastic board at the bow, thinking that if the board was stuck, the electricity would prefer the more conductive fin at the stern. I only stuck my lips above the water to get an occasional gulp. I rid the storm out like that, under water. Once it passed, I made haste for shore, just before another wave of lightning swept through. It's a hopeless feeling. You are completely at the mercy of chance.

I'd rather know that I can ride through a storm with my wife and four kids, with confidence. I also need to be able to anchor over night and sleep through one without fear of lightning passing through the cabin.

I know that lightning will be more attracted to my 30 feet of mast and wire than 30 feet of air. I just don't know what path that electricity will take between the water and the bottom of those wires or mast. My son will be sleeping on the port birth, right under the shroud plate.

[seahouse]

I'd rather know that I can ride through a storm with my wife and four kids, with confidence. I also need to be able to anchor over night and sleep through one without fear of lightning passing through the cabin

Assuming you mean that to be well-founded science-based confidence, that is not within the current realm of the knowledge-base of mankind. So it's not going to happen on a small sailboat.

Your story above shows the value of using your knoggin' - your actions likely improved your odds of survival. And you're here to tell us the story. The best action is the research you (and me and many others here) have already done, realize you do have control over many other things within your power. Also realize that the majority of misfortunes that happen actually were within someone's control to prevent, but weren't- I think it's better to focus on those. The number of misfortunes that are truly random, like lightning, is small compared to them (although higher in your area, and other circumstances). Those are the ones to focus on, the ones you have control over, and not the ones that you don't.

That's my attitude toward the issue, and life overall, really.

- B.

[mastreb]

I'd thought the consensus was to slip next to a boat with a taller mast.

[BOAT]

In all the years I have been sailing I have never been able to find a way to protect myself from lighting - I hear all the same stories and theories from guys in aluminum fishing boats, ski boats, sail boats, and big cabin cruisers. I have discussed it with my Power Squadron teachers, and have voiced my concerns at dozens of harbors seeing that no boat in the slips have anything I can see for lightning.

I just do not know if anyone has an answer to this.

[cptron]

I just do not know if anyone has an answer to this.

About the only answer I can come up with is have your insurance paid up and enjoy the rest of your time on the water.
Lightning is too random and cannot be second guessed.