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Lightning protection- precision 18

5K views 31 replies 15 participants last post by  smurphny 
#1 ·
I just bought a used Precision 18 and was wondering what is the simplest way to install lightning protection? I have very few electronics aboard as it's so small- VHF, am/fm radio, depth finder and gps. It's all attached thru the fuse panel directly to the battery. I really worry about the mast obviously.

Thanks
 
#3 ·
60,000,000volts discharging 60,000amps, hotter than the surface of the sun and travelling at near the speed of light is going wherever it wants no matter what you do.

Anything you do will be based on "theory" ... in "theory" everything works.
 
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#4 ·
Last I checked, nothing in this world could take a direct lightning hit. The zener is meant to snub any transient or induced current/voltage picked up by wirings. The idea is that if the positive wire get lifted above 24V, the zener would zap it down. If the negative line voltage gets lifted, the zener conducts like a diode, zapping the surge voltage. One may argue that the surge voltage slew rate is so fast that the diode may not responds fast enough, well its cheap and easy but offers no guarantee, still better than not doing anything.
 
#6 ·
great idea. co-incidentially, my new stereo got fry in a lightning storm 2 weeks ago. i fitted a vhf-fm splitter on the vhf antenna. i think the surge came thru that and fry my stereo. my boat was between two larger boats with taller mast. well i don't know if there's any damage to the other 2 boats as their owners weren't around. now i use internal antenna for the stereo. all my other electronics survived, including the vhf. i can't say the zeners saved the day. who knows. perhaps if i check each one to see if they are still working. if they still works then it doesn't confirm anything. if any zener fails, then perhaps it does its job.
 
#7 ·
#8 ·
Lightning Protection and other myths.

That should get folks talking.

I have read a few articles on this topic. Some swear by it, others scoff at it. The lightning protection industry waffles on its effectiveness as does the insurance industry. SO, the real question is "What is the likelihood that you will take a strike?" Answer that and you'll find out whether on not you should spend the money. If I recall correctly, south Florida is lightning strike alley, with 20% of the boats taking hits or near misses. Up here in Maine, I've only heard of one fellow taking a near miss that still fried his electronics. There may be more that I haven't heard about. The real problem isn't the electronics but a blow through in the hull. The lighting can burn a hole right through as it exits. If it's someplace that you can see, plug it. But if it exits in the back of the transom where you cant' see or reach, you're pretty much done. Terror tactics notwithstanding, I wouldn't worry about it. A 20' mast isn't very likely to get hit. But, again, check your location. Our mast is about 30' up and I'm not terribly concerned.

Don
 

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#12 ·
As stated by others:

a. Take the mast down.
b. Park in the trees.
c. Get next to taller boats.
d. Don't get caught on the water.

Also read this, re. disipators; basically the math doesn't work and it's all statistics.

Sailboat Lightning Protection - Inside Practical Sailor Blog Article

I've installed protection systems that have actually been hit; there is no way they can be fitted to a small boat, the power is simply too great.
 
#13 · (Edited)
I've installed protection systems that have actually been hit; there is no way they can be fitted to a small boat, the power is simply too great.
Part of my job is to repair lightning damaged boats. I get to go aboard lots of them and then work with the insurance adjusters to make sure my customer does not get screwed over.

What I see (generally)

Fuzzy disipators DO NOT prevent strikes - IMHO they are as close to snake oil as we can get today. I have plenty of boats that are hit with them one of them twice.

A shorter mast does not prevent strikes nor seem to limit them - I have plenty of small power and sailboats hit amongst hundreds of considerably taller spars with regularity. Lighting goes where it wants and the height of your mast does not seem to dictate anything.

Bonded well Earthed boats suffer less hull damage - One of the first things I look for is a path to Earth for the lightning. When it is non-existent or the wires too small and corroded there is almost always considerably more hull damage. When the mast to Earth wires are large, clean and well installed I rarely see hull damage.

Carbon Fiber spars are easily destroyed and EXPENSIVE - My friend Kim's boat was hit and the spar damage alone was over 80k. They had a good Earth bond and the hull was fine but the spar was still destroyed and unrepairable.

Bonded boats are hit slightly less - I see less strikes (in my data pool) of well bonded/grounded boats that are hit by lightning than I do of unbonded/ungrounded boats. The unbonded/ungrouded boats tend to get hit more. The spread however is very small and mine is about the same spread Dr. Thompson sees and pretty much inconclusive. The edge however still sides with well bonded boats being struck slightly less.

Frustrating Fact - Even large insurance companies like Boat US DO NOTHING to collect data on strikes to even begin to tell us what may or may not work to minimize damage. They HAVE this capability!!!! I have been pushing Boat US, through Beth Leonard, to come up with a form for the adjusters so that data can be compiled on a larger scale but she's been busy and I have too. Even with that I don't know what she can do to change this situation. My personal strike data seems to line up with Dr. Thompson's but these are still fairly small samples. Insurance companies have access to much more potential data.

You can not prevent a strike - You can however take steps to minimize hull damage by having a well bonded/Earthed boat.

You can not protect electronics - I've seen all kinds of cockemammy schemes drummed up, and the electronics still get fried. Even when not plugged in. A Faraday cage is your only bet but this excludes most installed gear..

Many insurance companies will try to "weasel" their way out -Do yourself a favor and hire a COMPETENT marine electrician who specializes in or is very familiar with lightning strikes. You will pay them to go over your boat ahead of time and to be there to meet with the insurance adjuster. Most of these adjuster/surveyors know squat about electronics, wiring etc.... Defend yourself, be prepared, and it will PAY YOU BACK.

I just had a claim go through on a boat for a customer hit in September. The damage claim was 90% of the "agreed value" of the vessel. Because my report was thorough and completely documented with pictures, replacement models, estimated labor with details, there was nothing denied what so ever.

The adjuster showed up and we went down the estimate list and he just checked stuff off. Done..... Owner had the check two days later. The $300.00 he paid me for my time and report was peanuts compared to what it would have cost him had he gone it alone with the adjuster.

In August I met with an adjuster who was denying the alternator, regulator, Link 2000, tachometer and 3kW inverter charger. The owner had been battling with them for six months. In a three minute meeting with the adjuster/surveyor he had signed off on all of it. Owner sent me a check for $200.00 more than I billed him for as a very nice "thank you".....

It should not have to be this way but today it very much is a fact of life that you need to defend yourself against your own insurer....
 
#14 ·
Very good info. Maine Sail. It kind of supports the old idea of attaching jumper cables to the shrouds and dangling the other end in the water during a lightning storm. The way I understand the theory is that you want to make the boat "look" the same to lightning as the surrounding sea by equalizing the potential of water and rigging. Having well bonded metal objects like rails and chainplates, attached to a ground plate makes sense. Thanks for posting your experience with this.
 
#16 ·
Not at all. The point of adequate grounding is to attempt to take the brunt of the strike directly to Earth & not allow it to divert off path and go through your hull... With well bonded boats I simply see less of this:



This does not at all mean the strike won't damage your boat, but it can help to minimize hull-sinking damage..There are no absolutes in lightning strikes all we can do is to attempt to minimize damage and the best way I know is to bond your spar/stays to external lead or an external copper lightning grounding system.

When our boat was hit the lightning exited at the dead bottom of the keel and nowhere else. I know some "lightning experts" say this can't happen but it does.... Our hull was 100% perfect but all electronics were toasted.

Our spar is grounded to the longest J bolt in the keel (our keel has the bolts installed at varying depths with the deepest right under the spar. It is bonded with 2/0 wire.

If you have internal ballast then an option like this can be a good choice if you can keep the wire bends minimal.
 
#15 ·
Yea, there is no realistic way to protect the boat from being hit by lightning. We were hit 3 years ago.

The best protection for sailors is to have as small a gap as possible between the toerail and the dock. Then do like Brave Sir Robin and run away (preferably inside a building with beer, wine, liquor, and a barstool)
 
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#20 ·
Maine- Have a 46' boat with 63'airdraft. Fully bonded as per ABYC but has encapsulated keel and no ground plate as of yet. ? Should I install the square plate offered by Ward's Electronics or the strips offered by Dr. Thompson or nothing further? ? if ground plates are installed where should they be installed? Should they be at the heeled waterline as it appears plates near the water surface are more effective then those deeper down? Mast is keel stepped and it very difficult to avoid sharp radius. Is connection between shroud plates and ground sufficient? Dr. Thompson is in Florida is there a good local resource in R.I. area? Are you interested in providing services or referrals for New England sailors?
 
#21 ·
I've taken courses from several well respected marine electrical experts, a couple of whom are also recognized "lightning" experts (court recognized).

One word that is used repeatedly in these courses and the same word is used in all scholarly publications on the issue ...... "theory"

I've come to believe that most published information on the subject is at best either guess work or theoretical. I was involved in one case several years where a sailboat was hit twice within ten minutes (over 200 witnesses) and the same boat had been hit twice before. With the odd history of this boat and some curious issues regarding its location at time of hits and even odder damage, we could not get any of the recognized experts to testify.

So I will stick to my mantra .. 60,000,000volts, 60,000amps, hotter than the surface of the sun at near the speed of light .. get to hell out of the way :)
 
#23 · (Edited)
I've taken courses from several well respected marine electrical experts, a couple of whom are also recognized "lightning" experts (court recognized).

One word that is used repeatedly in these courses and the same word is used in all scholarly publications on the issue ...... "theory"
Amen! This is why I wish we could get the insurance companies to track strikes and collect better data as to what the boat had for systems, damage etc...

Interestingly in our strike the GPS that was in my ditch bag was wrapped in aluminum foil then inserted into a ZipLock bag with a bag of desicant to keep it dry. The "aluminum foil theory" that was purported to me to never fail, FAILED.........

As I always say lightning simply does what it wants. We can only try to minimize the damage..
 
#22 ·
The best advice on this thread seems to be coming from Maine Sail, based on my experience and technical background. I've had 2 strikes on my boat: an indirect strike while on the hard and a direct strike 10 years later while in the water. No one was aboard, but both were witnessed.

I lost all of my electronics in each case. The indirect strike took out a wheel pilot control module that was on a shelf and not electrically connected to anything. The direct strike took out my battery bank (3 month old AGMs) in addition to just about anything with semiconductors. After the first strike I conferred with a couple of lighting experts, including Dr. Ewen Thomson, in an attempt to better understand what happened and what to do in the future.

My boat has the mast and chainplates grounded through the hull to a dynaplate in close proximity to the mast step. My boat also has a counterpoise system (for the SSB radio that was taken out in the first strike) that connects to 2 sizable sintered bronze grounding plates. I believe my grounding system protected my hull from being damaged.

That said, my lightning protection plan has 2 parts:
1. place any removable electronics (handheld GPS and VHF, rangefinder, camera, phone, etc.) in a faraday cage. Aluminum foil is better than nothing and is readily available on board. Better yet, place it all in the oven.
2. maintain a proper yacht policy that provides for full replacement of electronics--less the basic policy deductible, of course. Last time I checked, the BoatUS policy premium was $200 less than my yacht policy, but did not offer this kind of coverage.

I could go further, perhaps by fully subscribing to Dr. Thomson's approach (check out Articles), but I'm willing to live with my current configuration and trust that the probability of a future strike is rather small.
 
#24 ·
Agree with Maine Sail that there are no iron clad guarantees with lighting. That would include through-hull grounds and aluminum foil wrapped electronics. Nonetheless, you improve your chances with these techniques.

That said, my in-water grounding plates are much smaller than desired by folks like Dr. Thomson, but they obviously were somewhat effective. I would agree that an aluminum foil wrap and your oven are far from ideal faraday cages for several reasons, but haven't seen evidence that they do not provide some protection--even if minimal.
 
#25 ·
I would really like to further investigate the Faraday Cage theory. Aluminum foil and microwave shielding sound like reasonable ideas but I wonder whether there have been any studies into the best designs/shape of portable, temporary Faraday gizmos. I always completely disconnect the SSB and VHF as a minimal action when I see a storm approaching but if some kind of temporary "tent" for components could be designed, it might be worth trying to construct something like this for individual units. Apparently, just the electrical field created by a near-miss is enough to fry semiconductors. If circuits could be somehow shielded, even minimally it might save some of the electronics, especially those needed to call for help after a strike.

Has anyone here had EPIRB damage in a strike? I would think they are just as susceptible as everything else.
 
#26 ·
I would really like to further investigate the Faraday Cage theory. Aluminum foil and microwave shielding sound like reasonable ideas but I wonder whether there have been any studies into the best designs/shape of portable, temporary Faraday gizmos. I always completely disconnect the SSB and VHF as a minimal action when I see a storm approaching but if some kind of temporary "tent" for components could be designed, it might be worth trying to construct something like this for individual units. Apparently, just the electrical field created by a near-miss is enough to fry semiconductors. If circuits could be somehow shielded, even minimally it might save some of the electronics, especially those needed to call for help after a strike.

Has anyone here had EPIRB damage in a strike? I would think they are just as susceptible as everything else.
Our ditch bag GPS was completely encased in aluminum foil & unplugged, it was fried.

Our laptop was on top of the nav-desk unplugged, it was fried

Our iPod was inside the nav-desk unplugged, it was fried

Our EPIRB was in its holder on the bulkhead unplugged, it was fried

Our GPS MAP 176 was in the nav-desk unplugged, it was fried

Our GPS 76 was in the nav-desk unplugged, it was fried

Our Ritchie steering compass on the pedestal was hit so hard it was off by a dangerous level, on all points

You'd be amazed at the number of folks who swear by paper as a back up but I then discover their steering compass compensators were tossed off in the strike. Paper won't do much good if your compass is toast and this very often happens in a good strike.. This is one major area that insurance surveyors miss almost every time.

New compensators are not in-expensive and neither is having it professionally re-swung. I wound up ordering a new compensator set for ours and then having it professionally swung. "Theory" is they will eventually get back to where they were before the strike but how are you to know when they are done getting back to normal? We now keep two hand held compasses in an Army issue metal ammunition ditch box along with other stuff we don't want fried in a strike. The "theory" being that metal works much better as a Faraday cage than aluminum does. I hope not to test that theory cause there is a lot that won't fit in there.......;)

We had a major strike but the mast is bonded to the keel with 2/0 wire and we suffered zero hull damage. Our thru-hulls are not bonded.
 
#27 · (Edited)
Aren't airplanes designed successfully to take lightning hits without destroying electronics and damaging structure?

Found this:
According to statistics published by the Royal Canadian Air Force, a plane can be struck by lightning on average every 1,000 to 3,000 flight hours. For commercial aircraft, that’s equivalent to one strike per aircraft per year. Although The Boeing Co. (Chicago, Ill.) has reported that the probability of a worst-case strike could be as infrequent as once every 10 to 15 years, aircraft designs must be able to withstand such a strike.
 
#28 ·
In doing a little research, it seems that wrapping something in aluminum foil can be effective in blocking electromagnetic waves but the aluminum (or the inside of a microwave/oven) cannot be in contact with the device. A plastic bag or some sort of insulator needs to be between the device and the Faraday shield. Even better is to do this in more than one layer:insulator-metal-insulator-metal. I think I'm going to keep my little old Garmin GPS12 handheld in such an arrangement from now on and maybe even make up a more substantial box from some aluminum sheeting. One of my computers, a Dell Mini, would also be easy to shield like this as would the EPIRB. The EPIRB and small GPS usually reside in my ditch bag, so making shields for these should be pretty easy. It's worth a try anyway. If even one device survived a hit, it might make a big difference. Anyway, don't abandon paper and DR! :)
 
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