MacGregorSailors.com

Hmm.. well, Moe, based upon looking at that site, I should think that the following would work nearly as well:

- Get a long automotive battery cable (the sort that they use when you mount batteries in the back)...
- Swage on a large copper battery-type ring terminal on one end of the cable (see here)...
- Strip and 'fray' out the strands on the other end of the cable, in a fan- or broom-like pattern, sharpening the points of each tip by clipping them on the bias...
- Tin each wire end as well as the attached copper ring terminal...
- Drill the mast and install a 1/4-20 'nut-sert' captive nut into the mast...
- Obtain a wing-bolt (not a wing-nut, but a bolt with a winged head) to thread into the nut-sert.

Then, simply screw the cable to the mast and pitch the other end overboard, allowing the cable to make a gentle bend away from the mast and over the side of the boat.

Sounds inexpensive but I'll bet it works nearly as well as that fancy one... what do you think?

It has been said that Tampa Bay is the lightening captial of the world. It seams like it anyway. Some research in the past has stated that the mast of a sail boat is it own lightening protection. Some people have put up lightening protection on there mast. What this does is put the same polarity to the lightening so you do not get hit. Like trying to put two magnets together. This is the same theory as lightening protection on building. The problem is that there is a lot of amps. You cannot really know where the lightening will go. One woman in Florida was washing dishes at her sink and the lightening came through her window and she got hit. No damage.

The damage done to sail boats is that the metal keel is blown out. Mac's do not have that problem. Anything electrical is toast including the motor. That is if, you get a strike. I have never heard of anybody on a sail boat damaged by lightening execpt a few burns. The problem has been damage to the boat.

If it is indeed true that the mast of a sail boat is it's own lightening protection then it is prudent that you provide the best possible ground to the mast to handle all of those amps. Most lightening strikes have many stikes per flash. Most cruisers have a big heavy chain that is attached to the standing rigging. You should disconnect all electrical equipment. That includes everything. Take in all sail an lash the rudder all the way over and get below. Keep a look out for other boats and land.
It is best to avoid. Contact other boats in the area and find the direction of the storms and head to safe shelter as fast as you can.
Good luck. Lightening is just part of the Sailing experance.
It makes the fair weather just that much better.

Sounds good, Kevin, but don't forget the adhesive heat-shrink! I guess being on freshwater gives me a little concern about sufficient discharge point.

For a discharge point in the water, I was thinking of using aluminum bar stock to make an easier stored but readily expanding version of one of those old head-grabbin' accordian baby/pet gates. Jack's comment about the expanded metal lathe (not as easily stored) gave me that idea. Perhaps rolling the lathe would store it well enough, and it would sure be a lot less work and give a lot more edge! I like that idea too, especially for freshwater.

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Moe

I've been on the ocean, in a lightning storm, the only mast in sight, and did not get hit. I sure thought I was going to though.
The only Mac that I sold, that I am aware of that got hit by lightning, was next to his two-story house, with the mast down. It fried his obm.
The closest I've been to a lightning strike, I was in my van, about half-way down a hill, when a tree about 100 feet from the road got hit. I could see, hear, and smell it at the same time.
Something as powerful and fast as lightning is going to go where it wants to go, regardless of any precautions.
Those lighning arrestors they sell, and other precautions, have about as much chance of preventing a lightning strike as an intoxicated groundhog, wearing sunglasses, seeing his shadow, on the day he wins the lottery, without a ticket, during leap-year, on the day of the full-moon, when the temperature is below freezing.
That's my opinion and I'm sticking to it.

Moe wrote:That leads me to yet another thought. Would grounding our short-masted Macs be counterproductive if they're moored in the midst of much taller-masted boats, especially those with inadequate or no grounding? Would lightning attracted by their taller masts be more likely to jump from there to our better grounded one?

Well, I'm no expert, but from that StrikeShield site there is this:

"Will the Strikeshield attract lightning?
Strikeshield will NOT attract lightning, as it is physically impossible to attract lightning."

Line losses transmitting DC over long distances is high. This is why we now use AC almost exclusivly. Mr. Edison and Mr. Westinghouse hashed this out at the turn of the century, and it wasn't pretty. But the upshot of it all, AC travels well, DC doesn't.

Actually AC isn't more efficient for a given voltage; it's actually less efficient due to losses other than just resistive losses. One big reason it is used is because it can easily be converted to a very high voltage for transmission and then back to a lower voltage for actual use by using transformers. Another reason is because of the efficiency of 3-phase motors. High voltage means lower current and thus lower losses for both AC and DC. DC has a big advantage in that it can be stored more easily.

As to lightening: The Thompson site mentioned earlier (http://www.thomson.ece.ufl.edu/lightnin ... html#intro) is pretty interesting. I see a lot of data that talks about what happens if a boat is hit. I don't remember seeing anything on how different setups affect the chance of being hit. One somewhat comforting statistic is that a person in an unprotected (no mast grounding) sailboat is probably better off than the guy in a motorboat.

I think one of the early theories of a lightening rod with a sharp point was that is dissapated the charge buildup before it reached a high enough voltage to strike. This probably means a grounded mast is better. I don't know. I'm thinking of using copper foil on my 26M centerboard.

BB

I read that there and on the UF lightning expert's websites (professional and commercial), Kevin. But I have to believe there's a reason for lightning traveling down a tree to leave it and sidestrike another object, or person standing under it. I'm no lightning researcher, but it seems to me the second target would present a better path to ground. Maybe not. I guess the quantity of positively charged ions on the second target would be an issue.

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Moe

[on edit] Added links

I'm with Bill. Particularly the groundhog part.

From what I've read it seems the one thing almost everyone agrees on is that a half assed lightning protection system is worse than none at all.

Further, it seems that a full blown, permanently installed system would so badly compromise the utility and particularly the trailerability of the Mac, it just doesn't seem worth it.

I'm opting for the "none at all" system. Simple, cheap, and apparently, just about as effective.

BTW, I've read and reread that UF study, and I believe the conclusions arrived at by the lightning "expert" are not supported by the statistics he presents. Maybe I'm just naturally cynical. It's possible that it's completley above board that his conclusions just happen to enhance the sale of the products he's plugging on the side.

I had the same perception after reading it myself. Here's the patent on his product.

OTOH, I felt perhaps Arlyn Stewart's critique of it sounded a bit like whistling in the dark.

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Moe

Last summer I was out on a local lake when a thunderhead showed up more than 2 miles away. When we heeled a little bit one of my shipmates hollered "Ouch!". The other two of us turned around wondering? Did she get bitten by something? Then we grabbed the lifelines, and got the same treatment. A spark about 2" long leapt across to my hand. These sparks were much more severe than the standard new carpet variety. They actually hurt. We three started crowding to the middle of the cockpit making sure we didn't touch anything, but then , of course we had to reef the main , and fire up the motor to get off the water. I think I could have run that little 9.8 mercury without a coil, but I did manage to get it going. Our solution was that someone had to drag the aluminum boathook in the water while touching the lifeline. You can bet we were scared as the storm was moving quickly in, and horizontal lightning is the norm here. Now I have a wire to drag in the dagger trunk . A temporary fix, but it works for now.

When this happens, it's time to adopt the one hand in the pocket rule. Holding on to something grounded (like a boat hook in the water or steering wheel) with one hand, and touching something charged with the other, can cause electrical current running across your heart.

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Moe

Chip Hindes wrote:I'm with Bill. Particularly the groundhog part.

From what I've read it seems the one thing almost everyone agrees on is that a half assed lightning protection system is worse than none at all.

Further, it seems that a full blown, permanently installed system would so badly compromise the utility and particularly the trailerability of the Mac, it just doesn't seem worth it.

I'm opting for the "none at all" system. Simple, cheap, and apparently, just about as effective.

What an incredible forum. What a thread! You guys are the best. Thanks!

I have followed this thread closely and have come to the same conclusion as Chip, Duane, I think Moe, and others. I'm opting for the "none at all" system. Simple, cheap, and apparently, just about as effective.

Thanks everybody for your research.

awsome, simply awsome.

hull, Moe don't know what Moe thinks at this point! But in the spirit of primum non nocere it may be awhile before he does anything.

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Moe

Let me explain that a little more. What I know of electricity would lead me to disagree with what Kevin quoted above from one of the manufacturers, the position that grounding doesn't increase the probability of a strike. In that sense, what I know would lead me to agree with Arlyn Stewart, that grounding does supply an unlimited bank for electrons and unlimited supply of positively charged ions to feed an attachemnt spark from the top of the mast. It seems to me that this superior attachment spark is what provides any "cone of protection," that is, any strike leader that would otherwise hit an attachment spark from some other part of the boat (or person) is "attracted" away from them by the grounded mast. It may not agree with the scientists, but that's the way I see it.

However, having an ungrounded mast above the cabin, or worse yet an ungrounded compression post connected to that mast IN the cabin, in the event of strike on that mast, is probably a guarantee of a large discharge in the cabin, possibly even from the chainplates. And without a "cone of protection," or preferred target at the top of the mast, the same could be said for a direct strike on the stanchions and lifelines all around the cabin.

Doing nothing could, in fact, be the worst of both worlds, if as Arlyn pointed out, the mast is "accidentally" grounded by lighting, wind instruments, or a radio antenna and cable system (through the DC electrical system to the motor or motor mount in the water). The relatively fine wiring might be sufficient to provide that unlimited stream of ions to make the mast's attachment spark most attractive, but not to carry a direct strike, leaving the mast, compression post, or chainplates discharging. That's one reason I'll have an arrestor that isolates both center conductor and sheild if I ever do mount an antenna up there.

So that's where I'm at... still undecided, but strongly leaning toward Darren's/StrikeShield's solution.
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Moe

Moe wrote:Let me explain that a little more. ...

Doing nothing could, in fact, be the worst of both worlds, if as Arlyn pointed out, the mast is "accidentally" grounded by lighting, wind instruments, or a radio antenna and cable system (through the DC electrical system to the motor or motor mount in the water). T
Moe

I agree Moe. My experience left me believing the boat was acting like a big capacitor. Before we started dragging the aluminum boat hook, we tried discharging the life lines with short water to line contact. It would only last for a few seconds before the charge built up again, and you could actually hear crackling sounds around the craft. The daggerboard trunk is the straightest line to the water for The 26M.